Re: [time-nuts] Raw phase data of super-5065

[Bob kb8tq]

Hi

I would not find it at all surprising that any of the older Rb’s are running 
below
1x10^-11 / month these days ( after a good run-in). Below 1x10^-12 is pretty 
amazing. 
The FRK’s will normally hang out a bit above that point. Indeed, getting all of 
the pressure 
and temperature stuff stable enough to see the aging is a bit of a challenge. 
The only
hope for most of us is “it’ll all average out …”.

Bob

> On Jun 15, 2018, at 11:25 AM, Ralph Devoe  wrote:
> 
> Hi,
> This is not a Super-5065, but it might be interesting. Its a 12 day
> measurement of a stock 5065a against a 5071a cesium standard. There are 10K
> points at 100 second intervals. It passes through 10(-13) at about the 6000
> second mark and settles in at 5-7 x10(-14) at longer times.
>  I think this is a lucky measurement, in that during this period our
> weather was very stable (as it  often is in Northern California during the
> summer). The barometric pressure at the local airport only varied by +/- 4
> mbar during the twelve days.  If you use Corby's value of 1.4 x 10(-14) per
> mbar from May, 2016 then this seems reasonable. The temperature is also
> very stable in Leo Holberg's very quiet lab at Stanford. We're setting up
> to log pressure and temperature.
>  The other unusual thing about this 5065a is that its aging rate is
> very low, way below 10(-12) per month.  I've been tracking it since Jan
> 2018 and I can't yet get a good number. Its an old unit, made in 1975, and
> appears to have been turned off for many years. The diode board is just
> slightly singed, not brown at all. Its been turned on continuously for the
> last two years.
>   This was measured with a sine-wave fitter, but any method should
> give the same results, given the long times. I've also been comparing my
> other "newer" 5065a against the 5071a and it shows the usual warmup drift
> and has a standard aging rate.
> 
> Ralph
> <060118_01.jpg>___
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Re: [time-nuts] Affordable PoE 6-digit time displays?

[Bob kb8tq]

Hi

There are an enormous number of displays out there that will interface with the 
little boards. You can spend a little or you 
can spend a *lot*. At least in terms of size, it is a bit of a “you get what 
you pay for” sort of thing. Some of the  larger LED 
arrays look pretty impressive. Cost wise … yikes …..

You also get off into a whole variety of rabbit holes to wander down. Do you 
want to be able to use voice commands to change
what the clock shows? ….. lots of ways to soak up a lot of time ….

Bob

> On Jun 15, 2018, at 1:17 PM, David Andersen  wrote:
> 
> Thanks, all - sounds like either finding a cheap IRIG display or hacking up a 
> pi/arduino/etc. version will be the path forward.  The IRIG displays I can 
> find quickly on ebay are still priced for people building music studios, so...
> 
> RPi 3 B+ supports PoE with an extra hat, and you can get pi-powered 3.5" TFTs 
> cheaply.  This may work best.
> 
> A friend also pointed me to some networked dot-matrix displays that will do 
> NTP from timemachinescorp, which might be a fun diversion. :); -Dave
> 
> 
>   -Dave
> 
> 
> On Fri, Jun 15, 2018 at 12:52 PM Bob kb8tq  <mailto:kb...@n1k.org>> wrote:
> Hi
> 
> I suspect part of the answer is “they are cool looking stuff, grab it when 
> it’s swapped out” ….
> They are out there, but not on the surplus market.
> 
> Bob
> 
> > On Jun 15, 2018, at 12:10 PM, Martin VE3OAT  > <mailto:ve3...@storm.ca>> wrote:
> > 
> > What about the clock part of the old AN/GSQ-53A frequency/time rack?
> > 
> > It wasn't NTP of course, but ran off of 1 MHz (as I recall) and generated 
> > IRIG-B for remote displays.  The rack included a nice Sulzer crystal 
> > oscillator (plus a spare), later upgraded to HP rubidium RVFS (5061A?).
> > 
> > There must have been thousands of them made for US DoD and NASA.  We had at 
> > least a dozen in Canada that I know of (5 field sites, plus spares).
> > 
> > Where did they all go?
> > 
> > ... Martin   VE3OAT
> > 
> > 
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Re: [time-nuts] GPS Antenna Grounding/Lightning protection.

[Bob kb8tq]

Hi

If indeed a proper ground system *could* be depended on to “bleed off” and 
prevent discharge things
would be *much* simpler. Indeed I’ve been on towers and decided to exit that 
location as the bleed
process became audible. It very much does happen. It simply is not a 100% sort 
of thing.

Bob

> On Jun 19, 2018, at 12:01 PM, Scott McGrath  wrote:
> 
> Probably the easiest and most economical grounding system is the halo ground 
> with antenna grounds bonded to the halo and the house ground bonded to the 
> halo as well.
> 
> The halo conductor sizing is governed by local codes,   But really what you 
> are doing ensuring that the entire structure and earth around it is at the 
> same potential so a nearby strike does not cause ground currents to flow.
> 
> A direct strike is probably going to fry anything it hits because of the 
> gigajoules of energy concentrated within the discharge
> 
> But a proper ground system also ‘bleeds off’ the potential difference thereby 
> preventing discharge 
> 
> Content by Scott
> Typos by Siri
> 
> On Jun 19, 2018, at 11:19 AM, Bob kb8tq  wrote:
> 
> Hi
> 
> 18” down in a swamp likely is plenty for conductivity. 18” down in a sandy 
> desert (or on an ice sheet) may be way 
> short in terms of conductivity :) The real answer to any of this is “that 
> depends”. (Yes, the ice sheet grounding 
> problem is from a real case that shows up in some class notes from way back 
> ….).
> 
> Some locations get multiple  hits on a weekly basis in the summer. Other 
> locations get a close strike once every 
> few decades. What makes economic sense for one probably does not make sense 
> for the other…. A “full up” 
> protection setup can easily run into hundreds of thousands of dollars. I’d 
> much rather spend that kind of money
> on a Maser … or two …. or three :) …. this is TimeNuts after all ….
> 
> Bob
> 
> 
> 
>> On Jun 19, 2018, at 10:56 AM, Scott McGrath  wrote:
>> 
>> The 18” inch requirement is partially for damage resistance and partially to 
>> ensure adequate soil moisture for conductivity.   
>> 
>> Content by Scott
>> Typos by Siri
>> 
>> On Jun 19, 2018, at 10:50 AM, jimlux  wrote:
>> 
>> On 6/18/18 6:39 PM, Glenn Little WB4UIV wrote:
>> 
>>> To do the grounding correctly, all connections exterior to the building are 
>>> to be welded.
>>> The cable to ground rod welds are to be 18 inches below grade.
>>> The exterior cable is to be number 2 copper or larger.
>>> To bond numerous ground systems together, a number 2 copper cable is to be 
>>> buried at 18 inches and welded to each ground system.
>>> If using eight foot ground rods, a ground rod is to be driven every 16 feet 
>>> along the connecting cable and the cable welded to the rod.
>> 
>> 
>> It helps to know *why* some requirements exist - I suspect the 18" burial 
>> requirement is to avoid accidentally digging it up or damaging it. I can't 
>> think of an electrical reason for it.
>> 
>> 
>>> A lot of work, but, cheaper, in the long run, than continuing to 
>>> repair/replace equipment.
>> 
>> It depends
>> 
>> Unless you're doing geodetic or precision timing work with a 2 or 3 band 
>> GPS, replacement GPS antennas are cheap.
>> I'd worry about the receiver and related equipment, but the antenna itself 
>> might be sacrificial.
>> 
>> As always, there's a risk/budget tradeoff
>> 
>> 
>> 
>> 
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Re: [time-nuts] 1 pps Sync'ing

[Bob kb8tq]

Hi

On a Time Nut  metaphysical note - 

> On Jun 25, 2018, at 10:38 AM, Tom Van Baak  wrote:
> 
> Steve,
> 
>> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs
>> to be aligned with the GPS 1 pps (UTC) to within 1 ns.
> 
> Two comments.
> 
> 1) If you divide 100 MHz -> 10 MHz -> 1 Hz then (with careful design, 
> calibrated layout / wiring) you can have all three rising edges within 1 ns 
> *of each other*. I assume this is your goal. If you already have a 100 MHz 
> GPSDO then it would surprise me if the outputs are not already synchronized 
> with each other. I mean, almost all GPSDO give a 1PPS output that is derived 
> from the LO, by design. If your goal is 1 ns, you obviously do not want to 
> use the raw 1PPS from the receiver. What make/model GPSDO are you using?
> 
> 2) On the other hand, if your goal is that all the outputs are within 1 ns 
> *of UTC*, then you have a big problem. Not even national timing laboratories, 
> with a pile of cesium and H-maser references, can get their UTC(k) within 1 
> ns of UTC. Perhaps you can explain a bit more what you are actually doing. It 
> sounds like an interesting application. Relative timing at the 1 ns level is 
> easy. Absolute UTC timing at the ns level is much, much harder.

Does UTC exist ( real time ) at the 1 ns level? 

Bob


> 
> /tvb
> 
> - Original Message - 
> From: "Martyn Smith" 
> To: 
> Sent: Sunday, June 24, 2018 3:37 AM
> Subject: [time-nuts] 1 pps Sync'ing
> 
> 
>> Hello,
>> 
>> I am a newbie question.
>> 
>> I have an application where I have a 10 MHz and 100 MHz squarewave output 
>> from my GPS frequency standard.
>> 
>> The frequency standard uses the PRS10 rubidium.  The 100 MHz output is just 
>> a 100 MHz VCO locked to the 10 MHz.
>> 
>> These outputs are disciplined by the GPS's 1 pps (as far as frequency).  But 
>> they are not in phase with it.
>> 
>> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to 
>> be aligned with the GPS 1 pps (UTC) to within 1 ns.
>> 
>> Anyone already done this?  I'm sure I've seen a distribution amplifier that 
>> does this at 10 MHz.
>> 
>> But the 100 MHz is actually the more important one that I need to align.
>> 
>> Regards
>> 
>> Steve
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Re: [time-nuts] HP 5065A A1 replacement with DDS

[Bob kb8tq]

Hi

One of the things I’ve run into doing Rb’s this way is that the spurs out of 
the DDS
are not always the same device to device. They also change a lot with small 
tuning
changes. The result can be a very close in spur ( like << 1 Hz) that really 
rips up 
your ADEV since it passes through all the cleanup PLL’s …. It’s a rare 
occurrence, 
but it does actually happen.

Bob

> On Jun 24, 2018, at 1:21 PM,   wrote:
> 
> Hi,
> 
> I've repaired a few 5065A A1 synthesizer modules recently and lets just
> say that they are not my favorite repair!
> I decided to go back to a project I started a while back to try and
> replace the A1 module with a DDS implementation.
> I built up two different styles to evaluate. 
> 
> One I call the DDS-FE uses a synthesizer board removed from a dead
> FE5650A 
> Rubidium module. It applies the 5Mhz input to a 74HC14 schmitt trigger
> which
> drives a 570A multiplier giving a 50Mhz output. This is applies to the 
> synthesizer board (AD9830A) which is configured for the 5.31Mhz
> output. This signal is 
> sent through a one transistor buffer amp with a tuned transformer output.
> Frequency is adjusted via RS-232 (pretty much a one time adjustment) and
> after
> saving is nonvolatile.
> 
> The second I call the DDS-BJ. It is a small board that Bert and Juerg
> designed
> that has schmitt trigger gate and 570 multiplier as well as an 8 pin PIC.
> It multiplies the 5Mhz to 100Mhz. The 100Mhz is input to one of the cheap
> Chinese
> DDS (AD9850) that are available pretty much everywhere. The DDS is
> configured
> for a 21.24 Mhz square wave output and divided by 4 on the board to 
> get the 5.31 Mhz output. This is applied via series resonant LC
> to the input to the buffer amp. Frequency is adjusted by an up and a down
> 
> pushbutton and is nonvolatile. It is cleverly designed to allow the DDS
> board to
> plug right into the PIC board.
> 
> First I installed one into a 5065A that had the super mod installed and
> the 
> performance stayed the same. So that proved  DDS was not degrading the
> performance.
> 
> Then I tried both styles in a standard 5065A that was performing well.
> and then plotted the performance. I was a bit surprised that the DDS
> units 
> gave better performance than the original A1!
> 
> Either style fits easily inside the original module once the original
> circuitry is removed.
> Also you could install onto an L shaped aluminum bracket made to fit in
> the A1 position.
> 
> Attached is a combined plot showing the performance of each and also PIX 
> of the two DDS styles.
> 
> Cheers,
> 
> Corby___
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Re: [time-nuts] 1 pps Sync'ing

[Bob kb8tq]

Hi

You can indeed do this, the question is - do you *really* want to? 

Depending a bit on your GPS module, the 1 pps output can jump around a few 
nanoseconds
on a second to second basis. Keeping the 100 MH edge locked implies modulating 
the 100 MHz
by at least a few ppb at some rate faster than 1 Hz. That will degrade the 
phase noise on the
outputs more than a little ….

A deeper issue is that the GPS module really isn’t reporting “GPS time” at the 
1 second 
level. It’s reporting GPS Time + atmospheric noise. What you would be tracking 
is more the bounce
in the atmosphere than anything that GPS actually is doing. Something like an 
L1 / L2 receiver 
would help some with this.

Bob

> On Jun 24, 2018, at 6:37 AM, Martyn Smith  wrote:
> 
> Hello,
> 
> I am a newbie question.
> 
> I have an application where I have a 10 MHz and 100 MHz squarewave output 
> from my GPS frequency standard.
> 
> The frequency standard uses the PRS10 rubidium.  The 100 MHz output is just a 
> 100 MHz VCO locked to the 10 MHz.
> 
> These outputs are disciplined by the GPS's 1 pps (as far as frequency).  But 
> they are not in phase with it.
> 
> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to 
> be aligned with the GPS 1 pps (UTC) to within 1 ns.
> 
> Anyone already done this?  I'm sure I've seen a distribution amplifier that 
> does this at 10 MHz.
> 
> But the 100 MHz is actually the more important one that I need to align.
> 
> Regards
> 
> Steve
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Re: [time-nuts] Low phase noise affordable GPSDO

[Bob kb8tq]

Hi



> On Jun 20, 2018, at 10:27 AM, Ethan Waldo  wrote:
> 
> Hello time afficionados.  I've tried my best to scan through the archives to 
> see if this has already been answered, so apologies if I missed something 
> relevant.  I am going to be experimenting with >10Ghz microwave frequency 
> grounded coplanar waveguide phase combining/cancellation/detection across a 
> number of generated signals.

If you are multiplying up, even a very low phase noise 10 MHz will get you in 
trouble outside a pretty narrow region around carrier. It’s far better / easier 
to use a 
100 MHz (or higher) cleanup VCXO ( or OCXO) than to try to find a -187 dbc/ Hz 
GPSDO. 


>  That being said, I am in the market for a GPSDO that has the least amount of 
> phase noise.  A secondary factor in my choice is how many 10Mhz references 
> the GPSDO can provide to sync all my signal generators; not as concerned 
> about what amplitude is provided.

Signal generators / counters / test gear generally have pretty modest input 
requirements. They normally do an internal cleanup process on the reference 
input. 
Put another way, they expect a dirty reference. 

> 
> Most of the cheap GPSDOs on eBay seem to have only 1-2 sine outputs with no 
> understanding of expected phase noise.  A solid option seems to be the 
> TrueTime XL-AK but something tells me there might be options out there better 
> than 1x10-12.  


Assuming you are talking now about ADEV, it is highly unlikely that you will 
find a 1x10^-12 at 1 second tau GPSDO. Yes it you go out far enough ( long tau )
they all will get there some day.  Good ADEV is not an indication of good phase 
noise in the sense of doing things at microwaves. 


> Price is the right ballpark though I could justify spending a little more for 
> better phase noise specs.  I have no need to run without GPS lock so Rubidium 
> source doesn't seems as necessary compared to something with a high quality 
> (D)OXCO, but it would be nice to add that as an external source at a later 
> time.  Build vs. buy is an option, but I would like to avoid making costly 
> mistakes so would favor buy if specs are comperable.

Simple answer is to get a reasonable GPSDO. Do something simple to distribute 
the output to your test gear. There are lots of ideas in the archives. 
CMOS gate based buffers work perfectly well for a sub $20 sort of solution. 
Then take one output and run it through your cleanup chain to form 
the base of your microwave stuff.  That way each building block is easy to come 
by and none are ghastly expensive. 

Bob

> 
> I would really appreciate advice from folks around here who already have some 
> hard-earned experience on what my best options are. Whatever I get I'm likely 
> to be stuck with for a while so I would rather take the time and research 
> than to do a knee-jerk buy.  Thank you ahead of time for any replies.
> 
> Sent from my Verizon Wireless 4G LTE Droid
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Re: [time-nuts] 10 MHz 'failover' switch?

[Bob kb8tq]

Hi

One interesting subtlety making something like this:

What if the two inputs aren’t quite on the same frequency?  Purely as an 
example, say they are 1 Hz off from each other. 
If you have 60 db of isolation in your “switch” you get a 1 Hz offset spur that 
is 60 db down. Even something much further 
down is plenty to mess up the ADEV of the output.

Bob

> On Jul 26, 2018, at 4:33 PM, Scott McGrath  wrote:
> 
> Build one yourself,   Detector diode on primary RF input when output drops 
> use a rf relay or PIN diode switch to fail over to backup standard.All 
> thats needed is a crossing detector and relay / switch driver
> 
> Yes there would be a momentary hit but it would work.
> 
> Content by Scott
> Typos by Siri
> 
> On Jul 26, 2018, at 4:13 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> They are a pretty rare item. A more common approach is a disciplined 
> oscillator that 
> will do failover on it’s inputs. That’s still a rare item, but at least a 
> possible thing to find. 
> The equally big problem will be getting doc’s on one if you do find it….
> 
> Bob
> 
>> On Jul 26, 2018, at 2:45 PM, W7SLS  wrote:
>> 
>> Hello,
>> 
>> Looking for recommendation for a ‘failover’ or ‘redundant’ switch for 10 MHz 
>> distribution.
>> 
>>   Not really sure of the correct term.
>>   Something that sensed RF on primary 10 MHz, and then switched to secondary 
>> on fail of primary.
>> 
>> A brief search showed several very nice $$$ items, suitable for commercial 
>> applications,
>> but I wonder if there are some “last year’s” (but not last century) versions 
>> that would work for a home lab.
>> 
>> Context:
>> 
>> I have a GPSDO and a Rb source of 10 MHz.  
>> The power supply on the GPSDO failed (worked enough to light up the GPSDO, 
>> but not enough to lock).
>> I have a new power supply on order, but would be nice to have “insurance”.
>> 
>> Thanks in advance for the group bandwidth.
>> 
>> Scott
>> W7SLS
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Re: [time-nuts] 10 MHz 'failover' switch?

[Bob kb8tq]

Hi

90 db will not drive the ADEV nuts, but it still will be a lot worse than a 
normal standard will deliver, even at 
120 db down, if the offset is a bit above 1 Hz you will still see it in an ADEV 
plot. 

Bob

> On Jul 26, 2018, at 5:40 PM, Scott McGrath  wrote:
> 
> True but if you use a good switch or PIN 90 db of isolation is easily 
> achievable.   Yes the spur is still there but it’s 90 down and will not 
> affect ADEV as badly.
> 
> You could drive it further down with two switches with the alternate standard 
> connected to 1 port and a termination to the other.  So a switchover would 
> switch to the alternate port and the backup path would switch from 
> termination to backup source.This would easily buy you 120-130 db 
> isolation assuming use of good cabling and proper routing, grounds etc
> 
> After all this IS time-nuts after all
> 
> Content by Scott
> Typos by Siri
> 
> On Jul 26, 2018, at 6:23 PM, Van Horn, David 
>  wrote:
> 
> Not quite what you are looking for, but I implemented a pair of thunderbolts 
> with no common parts (dual antennas power etc) into a simple RF switch.
> The production manager flipped the switch on Mondays, and if either system 
> wasn't working I had a third system in a box ready to replace.
> So for any failure of the two live systems, all he had to do was flip the 
> switch and call me.
> 
> 
> -Original Message-
> From: time-nuts  On Behalf Of W7SLS
> Sent: Thursday, July 26, 2018 1:46 PM
> To: time-nuts@lists.febo.com
> Subject: [time-nuts] 10 MHz 'failover' switch?
> 
> Hello,
> 
> Looking for recommendation for a ‘failover’ or ‘redundant’ switch for 10 MHz 
> distribution.
> 
>   Not really sure of the correct term.
>   Something that sensed RF on primary 10 MHz, and then switched to secondary 
> on fail of primary.
> 
> A brief search showed several very nice $$$ items, suitable for commercial 
> applications, but I wonder if there are some “last year’s” (but not last 
> century) versions that would work for a home lab.
> 
> Context:
> 
> I have a GPSDO and a Rb source of 10 MHz.  
> The power supply on the GPSDO failed (worked enough to light up the GPSDO, 
> but not enough to lock).
> I have a new power supply on order, but would be nice to have “insurance”.
> 
> Thanks in advance for the group bandwidth.
> 
> Scott
> W7SLS
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Re: [time-nuts] 10 MHz 'failover' switch?

[Bob kb8tq]

Hi

Isolation in a carefully managed test setup can be done (with enough money to 
spend). Isolation it the real 
world with grounds and cables running here and there is likely to be a 
challenge. At least that’s been the case
on the few dozen of these systems I’ve designed and put into production ….

Bob

> On Jul 27, 2018, at 11:29 AM, ed breya  wrote:
> 
> Getting great isolation at 10 MHz is the easy part, given enough switching 
> elements and control. One question is whether the switchover needs to be 
> transparent (glitchless), without adding or losing any clock cycles, and 
> ideally with no phase shift. This would involve a much more sophisticated 
> system, with two or more redundant references locked together, at least 
> short-term.
> 
> Ed
> 
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Re: [time-nuts] High-end GPSDO's

[Bob kb8tq]

Hi

Getting into the ~2 ns region is not as hard as it once was. The real gotcha is 
needing 
a L1/L2 receiver to do it *consistently*. If you just have L1, then you can 
easily get more
than a couple of ns over a day due to various atmospheric effects. 

It’s not at all clear what sort of GPS they have in these boxes. (at least not 
with a quick Google
check). If it’s an L1 / L2 device they could probably hit 2 ns on a consistent 
basis. If it’s L1 only
it would depend a lot on conditions . Simply put - I’d look closely at the data 
sheet to see just what
is in the box. I’d ask a few questions about the conditions the testing was 
done under. 

Bob

> On Aug 16, 2018, at 2:40 PM, Ralph Devoe  wrote:
> 
> I've seen several spec sheets on high end GPSDO's that seem to have
> performance approaching a low-noise cesium standard, but only cost $3-6$K
> new. One is the SRS FS740 which appears to combine a GPSDO with the
> interpolator of the SR620 counter. This gets down below 10(-13) in one day
> and drops below 10(-14) for longer times.  The other is the EndRun
> Technology  Meridian II, which has been tested at NIST, as shown in
> https://www.endruntechnologies.com/pdf/NISTReport-EndRun-MeridianII-US-Rb.pdf
> .  This shows a TDEV <2 ns (according to NIST) and and ADEV that gets into
> the 10(-15)'s for times longer than 1 day.
>  Has anyone had any experience with these?
> 
> Ralph DeVoe
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Re: [time-nuts] Bicentennial GOES satellite clock

[Bob kb8tq]

Hi

If GPS goes down, you then have Glonass. If Glonass goes down, you have 
Galileo. If all of those go down and you are in the
right region, the Chinese and Japanese both have systems you could use. 

In terms of *system* failure, there’s a lot of redundancy out there ….. Yes, 
you *would* have to own gear that works with all 
those systems. You might also go with multi-band (quad band maybe) gear to 
eliminate various other issues. 

Widely deployed electronic navigation isn’t all that old. People got along for 
a really long time without it ….. That includes a whole
bunch of folks who had no clue how a sextant works.  

Bob

> On Aug 12, 2018, at 10:29 AM, Scott McGrath  wrote:
> 
> And with dependence on GPS we have created a serious vulnerability as too 
> many critical pieces of infrastructure are dependent on a SINGLE precision 
> timing and positioning system.
> 
> I can use a sextant and have a copy of Bowditch.But they only work on 
> clear days and nights.
> 
> if GPS goes down for any reason.   Whats the backup solution?
> 
> 
> On Aug 10, 2018, at 2:25 PM, Lester Veenstra  wrote:
> 
> Used to work with Wayne on two time transfer via satellite
> Great guy
> 
> 
> Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
> les...@veenstras.com
> 
> Physical and US Postal Addresses
> 5 Shrine Club Drive (Physical)
> HC84 452 Stable Ln (RFD USPS Mail)
> Keyser WV 26726
> GPS: 39.336826 N  78.982287 W (Google)
> GPS: 39.33682 N  78.9823741 W (GPSDO)
> 
> 
> Telephones:
> Home: +1-304-289-6057
> US cell+1-304-790-9192 
> Jamaica cell:   +1-876-456-8898 
> 
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Tom
> Van Baak
> Sent: Friday, August 10, 2018 10:19 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Bicentennial GOES satellite clock
> 
> Tim,
> 
> Thanks for posting that photo. That space age 1976 GOES clock caught our
> eyes when the paper came out in 2005 (see also pages 11, 12, 13):
> 
> https://tf.nist.gov/general/pdf/2013.pdf
> 
> There was quite a bit of traffic on time-nuts around 2005 when the GOES
> satellite time service was turned off (and back on, and off, and on, and
> finally off for good). That left many of us with piles of 468 MHz GOES
> receivers, antennae, clocks and led to efforts to re-create the RF signals
> in-home so that GOES clocks would still work. There was even a commercial
> G2G (GPS to GOES) translator.
> 
> Anyway, I asked around about that one-off bicentennial clock in the photo
> and neither the authors, NIST, or Smithsonian knows where it ended up.
> There's tons of information on the GOES satellite system and GOES clocks in
> the NIST T archives:
> 
> https://tf.nist.gov/general/publications.htm
> 
> Best to search title for GOES, or search author for Hanson. It's a
> fascinating glimpse into the recent past. Yes, it's sad that GOES (and
> Omega, and Loran-C) aren't operational anymore, but GPS does such a better
> job. Plus we now have cable, WiFi, cell phones, the internet, Iridium, etc.
> 
> If you wanted to build your own Bicentennial GOES Clock, the design was
> published, including source code -- for its i4004 (!!) CPU. If you have even
> one minute to spare, see attached image and click on these two PDF's:
> 
> "Satellite Controlled Digital Clock System (patent)"
> https://tf.nist.gov/general/pdf/1791.pdf
> 
> "A Satellite-Controlled Digital Clock (NBS TN-681)"
> https://tf.nist.gov/general/pdf/452.pdf
> 
> /tvb
> 
> 
> - Original Message - 
> From: "Tim Shoppa" 
> To: "Discussion of precise time and frequency measurement"
> 
> Sent: Wednesday, August 08, 2018 7:29 PM
> Subject: [time-nuts] Bicentennial GOES satellite clock
> 
> 
>> See the groovy picture at
>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4847573/figure/f9-j110-2lom/
>> 
>> If anyone knows the whereabouts or history of the bicentennial GOES time
>> clock display, please let me know!
>> 
>> Tim N3QE
> 
> 
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi



> On Aug 13, 2018, at 7:24 AM, Dana Whitlow  wrote:
> 
> Note to all;
> 
> Be cautious about getting time of day from consumer GPS products.  All that
> I have encountered
> (so far) exhibit T.O.D. errors up to a few tenths of a second, and the
> error is not repeatable from
> session to session.  Some do have PPS outputs, which are typically claimed
> to provide usec
> level of accuracy, but most do not.

… but there *are* modules out there for not a lot of money that do indeed give
quite good PPS (and TOD) information. Picking out the good brands / models
from the junk is part of why you have lists like this one. 

> 
> I routinely use WWV to verify correct setting of my WWVB-synced watch and
> kitchen clock.  I have
> occasionally seen severe setting errors, which I attribute to attempts at
> syncing in the face of poor
> WWVB reception conditions.
> 
> My impression is that none of the time codes currently in use by broadcast
> NIST time signals
> contain forward error correction or even error detection features.  If this
> is wrong, please somebody
> correct me!
> 

I believe you will find that the “new” PSK modulation scheme on WWVB has at 
least some error detection built into it. 

> BTW, there are a fair number of Heathkit clocks in the wild which use WWV
> (as opposed to WWVB)

There aren’t a lot of those left running these days …..

Bob


> for syncing.  An old college-era housemate with whom I keep in touch owns
> and still uses at least
> one of them.
> 
> Dana
> 
> 
> On Mon, Aug 13, 2018 at 5:25 AM, Mark Spencer 
> wrote:
> 
>> I'm trying hard to think of routine users of WWV / WWVH other than amateur
>> radio operators, time nuts, and the occasional academic / scientific study
>> that uses the transmitters as a signal source.
>> 
>> Perhaps some boaters still use the time signals to set their chronometers,
>> but WWV /WWVH probably wouldn't be my first choice for that application if
>> I had access to GPS.
>> 
>> Perhaps some other users of the radio Spectrum occasionally use the
>> signals as a basic test signal ?
>> 
>> I use the time signals for my amateur radio hobby when I already have an
>> HF receiver and don't want to mess with using GPS as a time source.  I only
>> need accuracy within perhaps a third of a second so manually setting a
>> computer clock while listening to WWV works for me.
>> 
>> For my own interest I'd be curious in knowing of other routine uses of the
>> WWV / WWVH time signals.
>> 
>> 
>> Mark S
>> VE7AFZ
>> 
>> m...@alignedsolutions.com
>> 604 762 4099
>> 
>>> On Aug 12, 2018, at 2:08 AM, Bob kb8tq  wrote:
>>> 
>>> Hi
>>> 
>>> One would *guess* that stopping WWVB (and killing mom and pop’s “atomic
>> clocks”) would not be a reasonable thing to do.
>>> It gets a lot of voters mad. I doubt that very many voters (percentage
>> wise) would notice WWV and WWVH going away ….
>>> 
>>> Bob
>>> 
>>>> On Aug 11, 2018, at 9:00 PM, jimlux  wrote:
>>>> 
>>>> On 8/10/18 12:45 PM, Robert LaJeunesse wrote:
>>>>> I'd say it does get more detailed, with the $49M in cuts described
>> generally in groups here:
>>>>> https://www.nist.gov/director/fy-2019-presidential-budget-
>> request-summary/fundamental-measurement-quantum-science-and
>>>>> One item: "-$6.3 million supporting fundamental measurement
>> dissemination, including the shutdown of NIST radio stations in Colorado
>> and Hawaii"
>>>> 
>>>> I wonder if that's WWVB, or WWV & WWVH
>>>> 
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>>> 
>>> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

Ok, this is Time Nuts. We probably have a pretty good sample of those who use 
this and that as a source of time.
We also are reasonably conscious about what we are doing. NIST’s claimed reason 
for running WWV (and WWVH) is to
distribute accurate time and frequency.

Would / does anybody on the list actually use WWV as their *primary* source of 
accurate time or accurate frequency?

Ok, so how about as a secondary source of time?

Now show of hands …. third tier backup? 

I’ll place my votes first …. rarely as a third tier backup. Why? It’s just not 
good enough any more compared to the other 
things I have easily available. 

No, I”m not debating how badly we need third or eight tier backups. The 
question is purely - what is it actually used for?

Bob

> On Aug 13, 2018, at 8:39 AM, jimlux  wrote:
> 
> On 8/12/18 8:40 AM, Craig Kirkpatrick wrote:
>> I agree with Bob that shutting down WWVB would not go over well with the 
>> voters but losing WWV and WWVH will mainly be noticed only by HAMs.
> 
> 
> WWV/WWVH also provides HF propagation forecasts, severe weather warnings for 
> mariners, etc., as well as being a propagation beacon.
> 
> I don't think HF communications is completely going away - it's unique in not 
> requiring any infrastructure to achieve world-wide communications other than 
> the two endpoints of the link.
> 
> It's probably a smaller population than radio amateurs, but there are people 
> who work with HF propagation on a day to day basis. For example, if 
> Rocketlabs ever gets their act together and launches a couple more rockets, 
> I'll have a spacecraft in LEO for which I intend to use WWV and WWVH as 
> calibration sources.
> 
> 
> 
> 
> 
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Re: [time-nuts] 1PPS for the beginner

[Bob kb8tq]

Hi

A normal GPS module generates it’s outputs off of a free running internal 
clock. Generally 
this is a TCXO in a “timing” GPS ( = one that puts out a rational PPS).  This 
is a bit counter
intuitive, since you would *think* they phase lock the local source in the 
module. They don’t
mainly because it makes the math easier. 

The gotcha with a free running clock is that the device can only generate an 
edge (like a pps)
when the clock edge(s) allow it to. For simplicity, lets just go with the 
rising edge and accept that
there could be *double edge* designs as well.  Let’s also assume a 25 MHz 
clock. That’s in the 
general range of what shows up on the surplus GPSDO modules. 

The internal fix math in the module comes up with a solution for “when should I 
send the PPS”.
The clock edges are 40 ns apart. The solution says that the “right time” is 10 
ns after an edge. 
The module sends out a PPS that is 10 ns early. Next second the math says that 
the right time
is 30 ns after an edge. The module sends out a PPS that is 10 ns late. 

As long as it keeps going early / late / early /late things will average out. 
What makes it do this 
is the local clock on the module being a bit off frequency (modulo 1 Hz). As 
the clock drifts around
(and they do) you may hit a region where it is relatively stable. It will then 
send out early /early /early…. 
( or late / late /late…..)

If the local clock is a TCXO, the “stable points” are likely to also be points 
of frequency reversal. 
The net result is that the early / early /early never gets a corresponding late 
/late / late to average
against. It will pass right through a PLL and create an offset in the output. 

I believe that NIST was the first to spot this and document it with lots of 
plots. I could be wrong about
that. It was pretty much ignored in the days before SA was turned off. The SA 
jitter masked out a lot
of issues. Most modern GPSDO’s use sawtooth correction messages to get around 
the problem. There
may be a few still in production that don’t. 

Without full doc’s on a GPSDO, you really don’t *know* where the PPS is set to 
originate. It may 
be coming from the disciplined clock on the board. It also *may* be coming 
straight from the GPS
module. There are indeed units out there that will let you do it either way 
under software control. 

Bob

> On Aug 14, 2018, at 8:15 AM, Dana Whitlow  wrote:
> 
> Could someone please define and explain the term 'hanging bridge' in this
> context?
> 
> Thanks,
> 
> Dana
> 
> 
> On Tue, Aug 14, 2018 at 7:02 AM, Azelio Boriani 
> wrote:
> 
>> Hanging bridges out of a GPSDO's PPS? Interesting... time to try to
>> setup a measurement and see the relation between the GPS's PPS hanging
>> bridges and the corresponding DO's ones.
>> On Tue, Aug 14, 2018 at 9:55 AM Mike Cook  wrote:
>>> 
>>> 
 Le 14 août 2018 à 09:29, Mike Cook  a écrit :
 
 Sorry about the previous blank mail. Finger jitter.
 
 
 
> Le 14 août 2018 à 04:29, Chris Caudle  a
>> écrit :
> 
> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote:
>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+
>> OCXO
>> that I am using to steer a PRS10 RFS. I'm a little confused on where
>> the
>> 1PPS is coming from with respect to the GPSDO.
 
 As Chris points out the 1PPS from a GPSDO will « generally » be
>> derived from the primary frequency and can show better performance than
>> directly from a GPS receiver.
 However this is becoming less and less true.
 If you look at the Oscilloquarz blurb for the Star 4+ ( I found some
>> here > star3-4/62169-330779.html#search-en-oscilloquartz-star-4> ) , you will
>> see that the phase stability (jitter) on the 1PPS output is +/- 30ns when
>> locked to GPS, an it has a timing grade GPS receiver. This is not as good
>> as other GPS modules now. 15ns is normal, with some less than half that.
 The PRS10 has outstanding PLL control already. The SRS product doc
>> gives +/- 10ns accuracy with +/-1ns resolution.
 I don’t think that you are buying much with disciplining the PRS10
>> with a GPSDO 1PPS. Do you have any TIC measurements in this config to
>> compare with a direct GPS 1PPS feed?
 
>>> 
>>> I forgot to mention one other thing which may be of interest to some.
>> The 1PPS wave form output from the PRS10 is pretty mediocre. I put the
>> details in another post here sometime back.
>>> The Star4 spec is +/- 10ns, something I can only get from my PRS10s with
>> a 74HC7001 shaper.
>>> 
>>> 
 
> 
> A GPS disciplined oscillator contains a GPS receiver which outputs
>> 1PPS
> based on receiving the GPS signals and calculating the position  +
>> time
> equation. That PPS signal is noisy in time, it jitters around
>> relative to
> the ideal 1 second period.  The GPSDO implements a long time constant
>> PLL
> to synchronize the output of the OCXO to the long 

Re: [time-nuts] Choosing a GPS IC for carrier phase measurements

[Bob kb8tq]

Hi



> On Aug 18, 2018, at 2:25 PM, Attila Kinali  wrote:
> 
> On Thu, 16 Aug 2018 17:45:30 +0200
> Nicolas Braud-Santoni  wrote:
> 
>> The main issue I'm running into is that most timing GPS modules will
>> happily give you carrier phase measurements... for their internal
>> oscillator, and the few ICs I can find that would possibly do the job, like
>> ublox's UBX-M8030-KT-FT, do not have publicly-available datasheets & docs.
>> (I tried contacting ublox to ask, and never got an answer...)
> 
> Yeah. u-blox isn't as nice as they used to be to small customers :-(
> There are two ways to proceede: 
> 
> 1) use the timing of the PPS to deduce what the phase relation between
> your clock and the internal oscillator of the LEA is.
> In principle, this is possible, but I have not worked out the math,
> so I cannot say for sure. 
> 
> 2) replace the internal oscillator with one phase locked to your OCXO.
> The internal clock of the LEA is derived from a single TCXO. You can
> easily unsolder it and feed your own signal in. It should be relatively
> easy to reverse engineer what you need. If you don't want to reverse
> engineer it and if you get hold of a u-blox representative, you can get
> the required information from them. I got the data from them a couple
> of years ago. Unfortunately, I was explicitly asked not to share this
> information :-(

If you go this route, the close in phase noise of your signal needs to be in the
“pretty good TCXO” range. There are indeed some sources out there that
are way to noisy ….

Bob


> 
> 
>> So, what are people around here using for that purpose?  Bonus points if the
>> chip can work with a differential-signal clock.  :)
> 
> The alternative is to build your own GPS receiver. If you only want
> GPS L1 C/A, then you can use the design of The Witch Navigator[1]
> with one of the VHDL/Verilog projects out there (e.g. cu-hw-gps [2])
> 
> If you want to go for L2C, L5 or Galileo, you have to do your own coding :-)
> 
>   Attila Kinali
> 
> 
> [1] http://www.witchnav.cz 
> The website seems to be down at the moment so use archive.org for now:
> https://web.archive.org/web/20161122121726/http://www.witchnav.cz/doku.php
> 
> [2] https://github.com/perfaram/cu-hw-gps
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
> 
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Re: [time-nuts] WWV, WWVB and Daylight Savings Time

[Bob kb8tq]

Hi

I think there are a lot of ways to come up with a “local” WWVB signal that has 
all the 
DST stuff in it (or not if you prefer …). There’s not a lot of code or 
development involved.
Even with the current shortage of parts, there are an ocean of dirt cheap MCU’s 
and boards
to pick between. Assuming you already have an accurate “frequency” source, 
running that into
a board is also pretty simple. 

Doing this with a closed source “black box” sort of device …. not for me. There 
simply is no reason
in this day and age to do it that way. There’s nothing crazy hard to do inside 
the device. I see no
compelling reason any of it should be “closed”. 

Nobody is going to turn off WWVB next week. The budget will go around in loops 
for months 
and months (at the very least). We seem to have a way to get boards built and 
sold, so even
that part isn’t crazy. This sort of thing should be a lot more popular than the 
buffer board that 
now is into it’s second batch.

Firing something like this up *before* WWVB goes away might get you into 
interesting issues with
the FCC. I’d wait until things are a bit more clear before building a bunch of 
boards …..

Bob 

> On Aug 24, 2018, at 12:21 PM, Graham / KE9H  wrote:
> 
> That is the problem I am trying to avoid.
> The politicians insist on messing-with/changing Daylight Savings time.
> (I'll stop there before Tom comes after me.)
> 
> Today I have a convenient bit I can look at on a WWV or WWVB signal and
> know whether to offset for DST.
> Little intelligence and no OS required.
> No software/firmware update required when someone decides to change the
> changeover weekend in the US.
> GPS doesn't tell me.
> NTP doesn't tell me.
> 
> NIST seems to be suggesting the clock makers move off of radio, and onto
> the net for accurate time.
> Is there something as simple on the net that I could query with a single
> packet and get a single packet answer?
> 
> --- Graham
> 
> ==
> 
> On Fri, Aug 24, 2018 at 9:23 AM Hal Murray  wrote:
> 
>> 
>> ke9h.gra...@gmail.com said:
>>> If both the HF and LF signals go away due to the proposed budget cuts,
>> what
>>> is the next simplest way (for something like a microprocessor based
>> clock) to
>>> get DST information?
>> 
>> "microprocessor" isn't a well defined term.
>> 
>> If you have an OS, use the time conversion package.  They all use the same
>> collection of zone info files.
>> 
>> If you don't have an OS, use a system with an OS to pre-compute the
>> switch-dates for the next N years and store them in a table.  You will
>> have to
>> update that table whenever Congress screws with things.
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> 
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Re: [time-nuts] WWV, WWVB and Daylight Savings Time

[Bob kb8tq]

Hi

> On Aug 24, 2018, at 1:18 PM, Mark Sims  wrote:
> 
> Lady Heather has DST support code in it (in file heathmsc.cpp).   It supports 
>  the current standard settings for several areas (US, Europe, Australia, New 
> Zealand) or you can specify a custom DST rule.  The code is around 200 lines 
> long... some of that is Heather-specific requirements.  It can also be 
> simplified by not parsing the ASCII rule string and using hard coded values.
> 
> Implementing and testing seamless DST adjustment is a bit of a pain...  
> particularly keeping the time correct during the hours before/after the 
> switch.

Yet another reason to avoid closed source / packaged solutions ……

Bob


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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

You can do the 14 db deep modulation with a tristate gate and a pair of 
resistors. 
Ground the input and feed the “modulation” signal to the tristate control. 

Bob

> On Aug 25, 2018, at 4:35 PM, paul swed  wrote:
> 
> From the earlier threads OOK modulation does not work for high end clocks
> like spectracoms and truetimes. Have not tried it on the cheapy clocks yet.
> 
> I added an external modulator. A dg419 analog switch and then with a few
> resistors added DC offset and anttenuation so that the carrier drops by -14
> db per the wwvb spec. The logic control is driven from the chronverter and
> it totally works. Spectracom Netclock 2 locked up in the normal time.
> There are far better modern single supply analog gates that will work. Just
> did not have any.
> 
> The 60 KHz carrier is supplied by a fluke 6060 generator. This eliminates
> any chance of being off frequency and is not the long term answer.
> 
> The chronverter actually uses a dallas semiconductor clock chip thats
> reasonably accurate.(dangerous to say on time-nuts) So that even if you do
> not add the GPS receiver it will run quite some time correctly after
> setting the time.
> 
> Chronverter draws 6 ma from a 5 V supply. I always like low power.
> 
> All in all a very nice answer to what do we do if WWVB goes away.
> As mentioned it handles timezones and DST and you can change DST if those
> silly politicians screw with it again.
> 
> Speculation
> The chronverter actually puts out carriers for the popular LF stations
> along with the time codes for them.
> 
> Though the modulator allows quality clocks to lock I speculate the
> frequency from the chronverter is not tight enough. All of these clocks
> have very sharp crystal filters in them. 10 Hz. Plan to measure the output
> of the chronverter see what the 60 KHz is actually at. Though listening on
> a HP3586 receiver it appears pretty close to frequency maybe its just not
> good enough. Or the fact is OOK modulation does not work because it gaps
> the PLL in these clocks.
> 
> Next steps
> 
>   - Determine and lay to rest the OOK/need for external modulator.
>   - Power amplifier and loopstick transmitting antenna staying at or below
>   30uv@30 meters.
>   - Integrate a neo6 GPS receiver in. (Seriously easy)
>   -
>   - Box it up.
> 
> Have my eye on one of the Truetime DC468 units and the classy panelplex
> display.
> 
> Hope this helps those of you concerned with what to do should WWVB go away.
> Regards
> Paul
> WB8TSL
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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

Well …. 1Hz at 60KHz is …. errr … (off to Google Calc …) …. 16.67 ppm. That’s 
a pretty major lock range for a TCXO. It’s likely > 10X what an OCXO will do. 
What the
bare crystal in a watch will do … who knows. 

Bob

> On Aug 26, 2018, at 5:52 PM, paul swed  wrote:
> 
> Looks like the signal has to be with in 1 hz. I new it was tight.
> Need a bit more experimentation across the several receivers though they
> all use the same approach with a sharp Xtal filter.
> 
> 
> On Sat, Aug 25, 2018 at 8:24 PM, paul swed  wrote:
> 
>> My mistake the chronverter uses a pic 12f1840.
>> 
>> On Sat, Aug 25, 2018 at 8:23 PM, paul swed  wrote:
>> 
>>> Have to look at what oscillators and crystals I have then a divide.
>>> Thats old style and most likely the junk box has everything.
>>> Have to look in my box of tricks as I built several chains for the
>>> de-psk-er experiments.
>>> Have to agree on the micro the chronverter uses a pIC 12F64 as I recall
>>> and it has quite a nice set of dividers in it. Just not an external crystal
>>> input so a better oscillator can be used. Getting lazy these days.
>>> I have some number of tcxos from a company called vectron. Several cards
>>> of each. Can't imagine how I came by those.
>>> :-) Believe the lowest freq was 12 MHz.
>>> Regards
>>> Paul.
>>> 
>>> 
>>> On Sat, Aug 25, 2018 at 8:07 PM, Bob kb8tq  wrote:
>>> 
>>>> Hi
>>>> 
>>>> A pretty simple modest Q tuned circuit on the output of a gate will turn
>>>> the square wave
>>>> into a sine. Not much to it since there are a lot of power supply
>>>> components out there that
>>>> work fine at 60 KHz. In order to get a stable 60KHz, a divider is the
>>>> way to go. I’d probably
>>>> use one that’s built into an MCU as part of a timer or something
>>>> similar.
>>>> 
>>>> Bob
>>>> 
>>>>> On Aug 25, 2018, at 7:00 PM, paul swed  wrote:
>>>>> 
>>>>> Bob The generator sig is 60 Khz sinewave.but as a I build up a divider
>>>>> chain and such your idea makes great sense.
>>>>> Then filter to 60 KHz.
>>>>> But I see the issue with the Chronverter carrier its 120-150 Hz high.
>>>>> Bounces around a fair amount.
>>>>> There could be a secondary issue in that the carrier may not actually
>>>> be
>>>>> phase stable.
>>>>> It really doesn't matter as for the Truetimes and Spectracoms its
>>>> simply
>>>>> not good enough.
>>>>> I still need to try the cheapy clocks as that is what it was intended
>>>> for.
>>>>> Not throwing stones as so much of what it does saves me a bunch of
>>>> coding
>>>>> and doing exactly what Dave did.
>>>>> Regards
>>>>> Paul
>>>>> WB8TSL
>>>>> 
>>>>> On Sat, Aug 25, 2018 at 5:31 PM, Bob kb8tq  wrote:
>>>>> 
>>>>>> Hi
>>>>>> 
>>>>>> You can do the 14 db deep modulation with a tristate gate and a pair
>>>> of
>>>>>> resistors.
>>>>>> Ground the input and feed the “modulation” signal to the tristate
>>>> control.
>>>>>> 
>>>>>> Bob
>>>>>> 
>>>>>>> On Aug 25, 2018, at 4:35 PM, paul swed  wrote:
>>>>>>> 
>>>>>>> From the earlier threads OOK modulation does not work for high end
>>>> clocks
>>>>>>> like spectracoms and truetimes. Have not tried it on the cheapy
>>>> clocks
>>>>>> yet.
>>>>>>> 
>>>>>>> I added an external modulator. A dg419 analog switch and then with a
>>>> few
>>>>>>> resistors added DC offset and anttenuation so that the carrier drops
>>>> by
>>>>>> -14
>>>>>>> db per the wwvb spec. The logic control is driven from the
>>>> chronverter
>>>>>> and
>>>>>>> it totally works. Spectracom Netclock 2 locked up in the normal time.
>>>>>>> There are far better modern single supply analog gates that will
>>>> work.
>>>>>> Just
>>>>>>> did not have any.
>>>>>>> 
>>>>>>> The 60 KHz carrier is supplied by a fluke 6060 generator. This
>>

Re: [time-nuts] Choosing a GPS IC for carrier phase measurements

[Bob kb8tq]

Hi

> On Aug 19, 2018, at 5:26 PM, Nicolas Braud-Santoni  
> wrote:
> 
> On Sat, Aug 18, 2018 at 08:25:11PM +0200, Attila Kinali wrote:
>> On Thu, 16 Aug 2018 17:45:30 +0200
>> Nicolas Braud-Santoni  wrote:
>> 
>>> The main issue I'm running into is that most timing GPS modules will
>>> happily give you carrier phase measurements... for their internal
>>> oscillator, and the few ICs I can find that would possibly do the job, like
>>> ublox's UBX-M8030-KT-FT, do not have publicly-available datasheets & docs.
>>> (I tried contacting ublox to ask, and never got an answer...)
>> 
>> Yeah. u-blox isn't as nice as they used to be to small customers :-(
> 
> Ah, that's a pity.  :(
> 
> FWIW, I'm going to try going through a ublox reseller that says they have
> that timing GNSS IC available, ask whether I can purchase in small quantities
> and whether I could have the datasheet.
> 
> 
>> 1) use the timing of the PPS to deduce what the phase relation between
>> your clock and the internal oscillator of the LEA is.
>> In principle, this is possible, but I have not worked out the math,
>> so I cannot say for sure. 
> 
> I've considered that, and it ends up being mostly equivalent to what I'm
> currently doing. Part of the issue is that I don't want to wait ~1 month
> for a PLL lock, but I also need/want an integration time about that long,
> as that's about where the GPS becomes more stable than my local XO.

If you *assume* 2 ns on the GPS ( could be better … might be worse) then at 
100,000 seconds ( = about a day) you are at 2x10^-14. That’s a pretty good LO.
A month gets you to 6.7x10^-16. A LO that is in that range is also in the “very 
expensive” range. 

Going to an L1 /L2 approach will drop the GPS errors by an order of magnitude 
or 
more. Given that you already are in the “very expensive” range, the cost of the 
receiver
should be trivial.

Bob


> 
> I was able to work around the problem in part, by dynamically adjusting the
> constants of my IIR (and so the integration time), and it works pretty OK
> despite being highly non-linear, but there is only so much one can do when
> fixing hardware deficiencies in software. :(
> 
> 
>> 2) replace the internal oscillator with one phase locked to your OCXO.
>> The internal clock of the LEA is derived from a single TCXO. You can
>> easily unsolder it and feed your own signal in.
> 
> That seems pretty much equivalent to using a “naked” GPS IC, as the part
> I care about is clocking it with my XO and getting phase measurements
> (wrt. the time-code and the carrier) out.
> 
> OTOH, it might be much easier than getting a datasheet out of u-blox, so
> I will keep that in mind, in case I cannot do it the way I wanted.
> Thanks a lot for the suggestion.
> 
>> Unfortunately, I was explicitly asked not to share this information :-(
> 
> :'(
> 
> 
>>> So, what are people around here using for that purpose?  Bonus points if the
>>> chip can work with a differential-signal clock.  :)
>> 
>> The alternative is to build your own GPS receiver. If you only want
>> GPS L1 C/A, then you can use the design of The Witch Navigator[1]
>> with one of the VHDL/Verilog projects out there (e.g. cu-hw-gps [2])
>> 
>> If you want to go for L2C, L5 or Galileo, you have to do your own coding :-)
> 
> Thanks a lot for the pointers  :)
> 
> I indeed low-key considered rolling my own GNSS receiver, as there are now
> some RFSoCs that would make it not too bad, but I decided against it as:
> 
> - Trying to make a good GPSDO is hard enough as-is  ;)
> - I would need anyway to be able to validate that the PLL works correctly
>  and gives the expected accuracy, with a known-good GNSS receiver.
> 
> 
> Best,
> 
>  nicoo
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Re: [time-nuts] Choosing a GPS IC for carrier phase measurements

[Bob kb8tq]

Hi

> On Aug 20, 2018, at 5:46 AM, Nicolas Braud-Santoni  
> wrote:
> 
> On Mon, Aug 20, 2018 at 01:15:10AM +0200, Attila Kinali wrote:
>> On Sun, 19 Aug 2018 23:26:03 +0200
>> Nicolas Braud-Santoni  wrote:
>> 
 Yeah. u-blox isn't as nice as they used to be to small customers :-(
>>> 
>>> Ah, that's a pity.  :(
>>> 
>>> FWIW, I'm going to try going through a ublox reseller that says they have
>>> that timing GNSS IC available, ask whether I can purchase in small 
>>> quantities
>>> and whether I could have the datasheet.
>> 
>> The online shop still works pretty well, as far as I am aware of.
>> If you order more than 10-20 LEA/NEO modules, I recommend going
>> through the u-blox sales. They might not resopond to you as quickly
>> as one would like but they should still give you a decent offer.
> 
> They do not have the UBX-M8030-KT-FT in the shop, but perhaps I should try
> and modify a NEO module as you suggested.
> 
 1) use the timing of the PPS to deduce what the phase relation between
 your clock and the internal oscillator of the LEA is.
 In principle, this is possible, but I have not worked out the math,
 so I cannot say for sure. 
>>> 
>>> I've considered that, and it ends up being mostly equivalent to what I'm
>>> currently doing. Part of the issue is that I don't want to wait ~1 month
>>> for a PLL lock, but I also need/want an integration time about that long,
>>> as that's about where the GPS becomes more stable than my local XO.
>> 
>> One month? If you are not using a Cs beam standard, then having
>> an integration time of a month is pretty pointless.
> 
> The issue is that I only get a measurement every second, with a fairly-large
> amount of noise, so it takes a while to get enough samples until the noise
> averages down to below the oscillator's own noise.
> (Hence why I want to move to carrier-phase measurements; a better receiver
> would definitely help, though)
> 
> I mis-spoke, though, one month was how long it took, with a particular set of
> parameters, to get a PLL lock from a cold start (i.e. without the Kalman 
> filter
> being seeded with previous measurements); I guess that what I get when writing
> late at night. :)
> 

This is why many GPSDO’s use multi stage filters. Most of the code involved is 
aimed
at getting the transitions between the filter stages to work properly. 

Bob


> 
>>> I was able to work around the problem in part, by dynamically adjusting the
>>> constants of my IIR (and so the integration time), and it works pretty OK
>>> despite being highly non-linear, but there is only so much one can do when
>>> fixing hardware deficiencies in software. :(
>> 
>> Hmm? What kind of problems?
> 
> “The problem” in question was the trade-off between precision and the time it
> takes for the PLL to lock.
> 
> 
 2) replace the internal oscillator with one phase locked to your OCXO.
 The internal clock of the LEA is derived from a single TCXO. You can
 easily unsolder it and feed your own signal in.
>>> 
>>> That seems pretty much equivalent to using a “naked” GPS IC, as the part
>>> I care about is clocking it with my XO and getting phase measurements
>>> (wrt. the time-code and the carrier) out.
>> 
>> No it's not. As you can relate the phase measurements of the GPS module
>> to your clock.
> 
> Yes, that's the goal of the whole thing.
> 
> 
>>> I indeed low-key considered rolling my own GNSS receiver, as there are now
>>> some RFSoCs that would make it not too bad, but I decided against it as:
>>> 
>>> - Trying to make a good GPSDO is hard enough as-is  ;)
>> 
>> Not really. You just need to understand what the limitations of the
>> components are and how to design a proper control loop. That's why
>> Trimble GPSDOs or the Star-4 work so well. They were designed by
>> people who know these things. 
> 
> I'm keenly aware; I was saying that I don't have the same expertise as
> Trimble's engineer, so there is a bunch of learning involved.
> 
> 
>>> - I would need anyway to be able to validate that the PLL works correctly
>>>  and gives the expected accuracy, with a known-good GNSS receiver.
>> 
>> If you build a GPSDO using a GPS module, you still have to vialidate
>> it works correctly by comparing it to stable sources. At the minimum
>> against another GPSDO of a different design and a Rb standard. 
> 
> Yes, I currently validate my design against a commercial GPSDO driving a Rb
> standard; some friends at a local university's timing lab offered to measure
> ADEV and phase noise with their equipment (they use a Cs beam as a reference,
> which is itself synced by GPS common-view measurements), but I'm holding off 
> on
> that until my design stabilises more.
> 
> 
> Best,
> 
>  nicoo
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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

One of the “interesting” things about the phase modulation on WWVB is that it 
does not get converted to 
AM (and thus mess things up) in the front end filters of the typical watches 
and clocks. The filters also do
not strip off the AM modulation sidebands of the signal. One would *guess* that 
the filters have to be at least
20Hz wide (+/- 10 Hz relative to 60,000 Hz)  to make this happen. 

Bob

> On Aug 27, 2018, at 2:26 PM, Larry McDavid  wrote:
> 
> Tim, there is indeed a consumer clock that uses only the BPSK modulation on 
> WWVB. It is an "ULTRATOMIC" clock by La Crosse and has available on Amazon 
> for over a year now. I have two of these clocks. They are *vastly* more 
> sensitive than the usual "atomic" AM clocks. My actual experience is that 
> these clocks will sync to WWVB within 10 minutes any time of day, completely 
> unlike the usual AM "atomic" clocks.
> 
> Several years ago I had radiant barrier thermal insulation installed in my 
> home attic; it forms essentially an aluminum umbrella over my home, an 
> unexpected result. I had to relocate all my AM "atomic" clocks to (the inside 
> of) outside walls for them to sync overnight. However, the ULTRATOMIC clocks 
> will sync within 10 minutes any time of day, anywhere within my home.
> 
> But, so far as I can determine, this one rather large analog-display La 
> Crosse clock is the only consumer BPSK clock available. It uses two or four 
> C-cells for power and claims up to 6 years "battery" life. I installed two 
> C-cells and they were only slightly depleted after one year. The clock can be 
> configured for time zone and to inhibit motion of the second hand between 
> midnight and 5 am. For me, one advantage is that the clock face is large 
> enough that I can read it without my glasses!
> 
> Look here:
> 
> https://www.amazon.com/Crosse-Technology-404-1235UA-SS-UltrAtomic-Stainless/dp/B01CCHXTE2/ref=sr_1_3?ie=UTF8=1535393731=8-3=la+crosse+ultratomic
> 
> or search ULTRATOMIC La Crosse on Amazon.
> 
> Tom Van Baak did a tear-down has many pictures posted on his website; look 
> here:
> 
> http://www.leapsecond.com/pages/ultratomic/
> 
> Larry
> 
> 
> On 8/27/2018 8:12 AM, Tim Shoppa wrote:
> ...
>> Now, if this is a fancy-pants consumer WWVB wall clock that also expects
>> the phase shift keying (not just amplitude keying) then I have no idea how
>> it'll respond to just plain amplitude keying for the time code. You might
>> think the WWVB BPSK chip will respond to loud and clear amplitude
>> modulation but I have no experience with this. Nor do I even know if a
>> single consumer clock was ever sold with BPSK ability.
>> Tim N3QE...
> 
> -- 
> Best wishes,
> 
> Larry McDavid W6FUB
> Anaheim, California  (SE of Los Angeles, near Disneyland)
> 
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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

One Hertz out of a million Hertz is one part out of a million parts.

One Hertz out of 100,000 Hertz is ten parts per million.

One Hz out of 10KHz is 100 PPM. 

One Hertz out of 60,000 Hertz is 16.667 parts per million.

If you are running into a device that swings it’s OCXO to lock to the incoming 
signal, 
it’s unlikely that the OCXO has a very wide tuning range. Numbers in the sub 
half ppm
range are not uncommon. 

So - what are we trying to do? If it’s just feeding the cheap wall clock, they 
aren’t phase locking 
an OCXO. The vast majority of them just want to do AM reception. If this is 
going to feed
TimeNuts gear for various purposes then indeed locking up an OCXO may be part 
of 
the deal.

Bob

> On Aug 27, 2018, at 10:19 AM, paul swed  wrote:
> 
> OK you sort of lost me here. 16 PPM would be great I might find something
> that works without a power sucking oven.
> But Bob mentioned online calculators and there are PPM calculators. Mr
> Google seems to know all.
> That said the lock range of any of the professional receivers is tight. +/-
> .6 Hz. Used a HP 3336 gen and moved up and down by .1 Hz to figure out the
> lock range. 3336 locked to GPSDO.
> I may have used the calculator wrong but at 60 KHz it seems like its .05
> PPM or was it .5ppm. Anyhow don't like the answer.
> I have numbers of 6 MHz xtals and also clock gens. The clock gens were off
> by 5Hz when divided down and out of the lock range. It is interesting that
> all 3 were of by different amounts but all negative. These are not TCXOs.
> A home brew xtal oscillator will not have temperature compensation.
> So this has presented a bit more of a challenge then hoped for.
> Regards
> Paul
> WB8TSL
> 
> 
> On Mon, Aug 27, 2018 at 7:29 AM, Mike Feher  wrote:
> 
>> Simple error. It is 1.667. 73 - Mike
>> 
>> 
>> 
>> Mike B. Feher, N4FS
>> 
>> 89 Arnold Blvd.
>> 
>> Howell NJ 07731
>> 
>> 848-245-9115
>> 
>> 
>> 
>> -Original Message-
>> From: time-nuts  On Behalf Of Bob kb8tq
>> Sent: Sunday, August 26, 2018 6:34 PM
>> To: Discussion of precise time and frequency measurement <
>> time-nuts@lists.febo.com>
>> Subject: Re: [time-nuts] WWVB Chronverter update progress
>> 
>> 
>> 
>> Hi
>> 
>> 
>> 
>> Well …. 1Hz at 60KHz is …. errr … (off to Google Calc …) …. 16.67 ppm.
>> That’s a pretty major lock range for a TCXO. It’s likely > 10X what an OCXO
>> will do. What the bare crystal in a watch will do … who knows.
>> 
>> 
>> 
>> Bob
>> 
>> 
>> 
>>> On Aug 26, 2018, at 5:52 PM, paul swed < <mailto:paulsw...@gmail.com>
>> paulsw...@gmail.com> wrote:
>> 
>>> 
>> 
>>> Looks like the signal has to be with in 1 hz. I new it was tight.
>> 
>>> Need a bit more experimentation across the several receivers though
>> 
>>> they all use the same approach with a sharp Xtal filter.
>> 
>>> 
>> 
>>> 
>> 
>>> On Sat, Aug 25, 2018 at 8:24 PM, paul swed < <mailto:paulsw...@gmail.com>
>> paulsw...@gmail.com> wrote:
>> 
>>> 
>> 
>>>> My mistake the chronverter uses a pic 12f1840.
>> 
>>>> 
>> 
>>>> On Sat, Aug 25, 2018 at 8:23 PM, paul swed < > paulsw...@gmail.com> paulsw...@gmail.com> wrote:
>> 
>>>> 
>> 
>>>>> Have to look at what oscillators and crystals I have then a divide.
>> 
>>>>> Thats old style and most likely the junk box has everything.
>> 
>>>>> Have to look in my box of tricks as I built several chains for the
>> 
>>>>> de-psk-er experiments.
>> 
>>>>> Have to agree on the micro the chronverter uses a pIC 12F64 as I
>> 
>>>>> recall and it has quite a nice set of dividers in it. Just not an
>> 
>>>>> external crystal input so a better oscillator can be used. Getting
>> lazy these days.
>> 
>>>>> I have some number of tcxos from a company called vectron. Several
>> 
>>>>> cards of each. Can't imagine how I came by those.
>> 
>>>>> :-) Believe the lowest freq was 12 MHz.
>> 
>>>>> Regards
>> 
>>>>> Paul.
>> 
>>>>> 
>> 
>>>>> 
>> 
>>>>> On Sat, Aug 25, 2018 at 8:07 PM, Bob kb8tq < <mailto:kb...@n1k.org>
>> kb...@n1k.org> wrote:
>> 
>>>>> 
>> 
>>>>>> Hi
>> 
>>>>>> 
>> 
>

Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

The temperature spec on a typical 60 KHz crystal is in the 100’s of ppm
range. The temperature coefficient can hit multiple ppm / C at fairly rational
temperatures.  That all adds on top of the set tolerance of the crystal. Simply 
to keep it passing signal while the room changes temperature would require a 
bandwidth into the 10’s of Hz. 

For reasonable loss in the filter you would want a Ql/Qu ratio of at least ten 
… 
again back into the 10’s of Hz range. 

The gotcha of course is that some of the tolerance stacks up all in one 
direction.
You might pass 20 Hz high just fine, but nuke 2 Hz low on this or that device. 

Bob

> On Aug 27, 2018, at 11:12 AM, Tim Shoppa  wrote:
> 
> The consumer WWVB wall clocks use a single 60kHz crystal as a front end
> filter (not as an oscillator).
> 
> Unloaded Q of a small tuning fork crystal is often 30,000 or so. (You can
> actually observe this order of magnitude when a 32kHz crystal used in an
> oscillator - remove power and the crystal continues vibrating for a couple
> seconds before dying off.).
> 
> This gives expected bandwidth of WWVB front end crystal filter as a more
> than a couple Hz. Well, that should be expected too, because they are
> demodulating a time code with a 1 bit per second data rate using amplitude
> modulated pulses requiring differentiating 0.2s pulses from 0.8s pulses.
> And anyway these tuning fork crystals are only specified to 20 or 30 ppm.
> 
> It's only a single pole filter so if a WWVB emulator were 10Hz off and
> "loud", I'm sure the clock will respond just fine.
> 
> Now, if this is a fancy-pants consumer WWVB wall clock that also expects
> the phase shift keying (not just amplitude keying) then I have no idea how
> it'll respond to just plain amplitude keying for the time code. You might
> think the WWVB BPSK chip will respond to loud and clear amplitude
> modulation but I have no experience with this. Nor do I even know if a
> single consumer clock was ever sold with BPSK ability.
> 
> Tim N3QE
> 
> On Mon, Aug 27, 2018 at 10:40 AM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> One Hertz out of a million Hertz is one part out of a million parts.
>> 
>> One Hertz out of 100,000 Hertz is ten parts per million.
>> 
>> One Hz out of 10KHz is 100 PPM.
>> 
>> One Hertz out of 60,000 Hertz is 16.667 parts per million.
>> 
>> If you are running into a device that swings it’s OCXO to lock to the
>> incoming signal,
>> it’s unlikely that the OCXO has a very wide tuning range. Numbers in the
>> sub half ppm
>> range are not uncommon.
>> 
>> So - what are we trying to do? If it’s just feeding the cheap wall clock,
>> they aren’t phase locking
>> an OCXO. The vast majority of them just want to do AM reception. If this
>> is going to feed
>> TimeNuts gear for various purposes then indeed locking up an OCXO may be
>> part of
>> the deal.
>> 
>> Bob
>> 
>>> On Aug 27, 2018, at 10:19 AM, paul swed  wrote:
>>> 
>>> OK you sort of lost me here. 16 PPM would be great I might find something
>>> that works without a power sucking oven.
>>> But Bob mentioned online calculators and there are PPM calculators. Mr
>>> Google seems to know all.
>>> That said the lock range of any of the professional receivers is tight.
>> +/-
>>> .6 Hz. Used a HP 3336 gen and moved up and down by .1 Hz to figure out
>> the
>>> lock range. 3336 locked to GPSDO.
>>> I may have used the calculator wrong but at 60 KHz it seems like its .05
>>> PPM or was it .5ppm. Anyhow don't like the answer.
>>> I have numbers of 6 MHz xtals and also clock gens. The clock gens were
>> off
>>> by 5Hz when divided down and out of the lock range. It is interesting
>> that
>>> all 3 were of by different amounts but all negative. These are not TCXOs.
>>> A home brew xtal oscillator will not have temperature compensation.
>>> So this has presented a bit more of a challenge then hoped for.
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>>> 
>>> On Mon, Aug 27, 2018 at 7:29 AM, Mike Feher  wrote:
>>> 
>>>> Simple error. It is 1.667. 73 - Mike
>>>> 
>>>> 
>>>> 
>>>> Mike B. Feher, N4FS
>>>> 
>>>> 89 Arnold Blvd.
>>>> 
>>>> Howell NJ 07731
>>>> 
>>>> 848-245-9115
>>>> 
>>>> 
>>>> 
>>>> -Original Message-
>>>> From: time-nuts  On Behalf Of Bob
>> kb8tq
>>>> Sent: Sunday, August 26, 2018 6:34 PM
>>>> To: Discuss

Re: [time-nuts] WWVB Signal Generator

[Bob kb8tq]

Hi

The gotcha is if you have neighbors two or three doors away that *also* put up 
one of
these devices. You then have a real problem with the neighbor(s) in the middle. 
The 
wavelength is long enough that Raleigh issues won’t get you. You still have the 
two
signals ( at slightly different frequencies) beating against each other. The 
result is
going to show up as who knows what to this or that receiver. With a precision 
receiver, 
you might even have issues from the guy two houses away …...

Bob

> On Aug 26, 2018, at 1:08 PM, paul swed  wrote:
> 
> Agree with the conversation. With respect to neighbors when the day comes
> they may ask you to boost your signal. :-)
> Granted maybe the day won't come but at least having your local clocks work
> is nice.
> Regards
> Paul
> WB8TSL
> 
> On Sat, Aug 25, 2018 at 10:29 PM, Dana Whitlow 
> wrote:
> 
>> With the watch being physically close to the faux WWVB "transmitter", one
>> is in
>> the so-called "near field" regime, where the field strength (V/m) falls as
>> the inverse
>> cube of the distance.  If one is putting the watch, say, within a few
>> inches of the
>> transmitter, reliable reception should be available yet the signal should
>> be literally
>> undetectable by any practical receiving device more than a few feet away.
>> Hence,
>> meeting the FCC field strength limit should be trivial.if the device is
>> used as pictured.
>> However, if one cranks up the power enough to reliably cover one's entire
>> house,
>> then there might be a problem depending how close the nearest neighbor
>> lives,
>> even at levels well within the FCC limit he quotes.
>> 
>> Taking the near field relationship in hand, 40 uV/m at 300m would translate
>> into
>> a whopping 0.135 V/m at 20 meters range, more than enough to feed most
>> peoples'
>> entire house.  So the pragmatic issue would again be- neighbors.  On the
>> other
>> hand, most of them would never be aware of the local signal as long as they
>> get good
>> time settings, unless they live close enough to Ft. Collins for the two
>> signals to
>> contend with each other.
>> 
>> It looks to me like the ferrite rod antenna is considerable overkill.  Even
>> with no
>> purposeful antenna I'd expect leakage to yield sufficient signal for at
>> least a few
>> inches.
>> 
>> Dana
>> 
>> 
>> On Sat, Aug 25, 2018 at 8:11 PM Wayne Holder 
>> wrote:
>> 
>>> This guy has what looks like a well thought out design using a Sirf-Based
>>> GPS and ATTiny44A chip to generate a signal to update his watch:
>>> 
>>>  https://www.anishathalye.com/2016/12/26/micro-wwvb/
>>> 
>>> Unfortunately, he doesn't seem to have published a schematic or his
>> source
>>> code.  But, he covers enough detail that I think it wouldn't be too hard
>> to
>>> replicate what he's done.  Or, perhaps he would disclose these details if
>>> contacted.
>>> 
>>> Wayne
>>> 
>>> On Sat, Aug 25, 2018 at 4:33 AM, D. Resor 
>> wrote:
>>> 
 I thought I would search in a different way for a WWVB signal generator
 design.  I found this item.  While the designer explains it isn't as
 accurate as WWVB it may be another starting point.
 
 http://www.tauntek.com/wwvbgen-low-cost-wwvb-time-signal-generator.htm
 
 
 
 Donald R. Resor Jr. T. W. & T. C. Svc. Co.
 http://hammondorganservice.com
 Hammond USA warranty service
 "Most people don't have a sense of humor. They think they do, but they
 don't." --Jonathan Winters
 
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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

HI

If you are feeding “Time Nuts” gear, a fancy filter on the output of the 
WWVB gizmo may be an issue. Temperature impacts the value of the
components and that value change impacts the phase of the signal….

Bob

> On Aug 28, 2018, at 9:33 PM, paul swed  wrote:
> 
> LPF filter added 2.2mH choke to a .0022uf cap 1K R pretty simple and
> anttenuators and isolation to drive up to 4 receivers.
> Have not looked at the power amp and loops stick antenna yet. But it really
> is time for GPS a neo.
> Looking very good.
> 
> On Tue, Aug 28, 2018 at 7:29 PM, paul swed  wrote:
> 
>> Ed appreciate the details but no intent to generally run a GPSDO in fact
>> the 5 V @ 50 ma is a serious power pig. The chronverter draws 5 ma. Clearly
>> the TTL is a heater. Chuckle. I do want to drive the chronverter with GPS
>> as its designed for.
>> Whats pretty interesting is you can adjust its offset. I just jammed time
>> into it several days and its been fairly good with power ups and down. Its
>> impressive. Though not in an ultimate time-nuts way.
>> GPS just assures it is accurate. But there is a lot of flexibility.
>> Main goal of this whole project is to replace wwvb if it goes away. If it
>> does the project doesn't even have to run 24/7. Fire up at 10 pm to 3 am
>> and power down. Thats enough to set my wall clocks for a day. Its just nice
>> to know it can also set the spectracoms and Truetimes. Icing on the cake.
>> I am impressed with what Dave did with the 8 pin pic. He has all of the LF
>> time signals in there. (No wwvb BPSK though) DSTs settings, zone offsets,
>> half zones, etc.
>> Just looking at low pass filters for the 60 KHz ttl out right now. Simple
>> LR or RC. Since this particular output feeds coax to the quality receivers
>> I don't need to be that careful. Its working great without any filtering.
>> Reality if it draws little power I will let it run 24/7 but then you just
>> have to stick a display on at that point.
>> Regards
>> Paul
>> 
>> On Tue, Aug 28, 2018 at 7:11 PM, ed breya  wrote:
>> 
>>> Paul,
>>> If you're going to reference it from a GPSDO anyway, why worry about a
>>> TCXO reference (and power too, for that matter). You can easily make the 60
>>> kHz from the 10 MHz.
>>> 
>>> For example, with two 74HC390s and a 74HC86 you can make 50 kHz and 10
>>> kHz and mix them with one EXOR section of the '86 to have 60 kHz available.
>>> Some fairly simple bandpass filtering should select and clean it up
>>> sufficiently. Two other sections of the '86 can be set up as inverters and
>>> self-biased as amplifiers - one to convert the 10 MHz sine reference to
>>> logic, and the other from the filter output to logic, if needed. And, you'd
>>> still have a divide by 5 and an EXOR left over to fool around with.
>>> 
>>> The same parts and process can be done at a higher frequency and then
>>> divided down afterward. (5+1) MHz/100, and (500+100) kHz/10 would work too.
>>> It depends on what frequency you prefer for the BPF. If you go high at 6
>>> MHz, you then have the option to make a crystal filter from readily
>>> available parts.
>>> 
>>> Going the high way also provides for higher logic frequencies that are
>>> more or less in sync, in case you want to do any I-Q modulation type stuff
>>> - you can even use synchronous counters instead, to really make sure.
>>> 
>>> Overall, I think I'd recommend going at 5+1= 6 MHz, filtering with 6 MHz
>>> crystals, then dividing down to 60 kHz, with 2f and 4f clocks available for
>>> I-Q use. I sketched out a quickie circuit that's quite simple and I think
>>> would do. It would take two HC390s for the dividing, as before. Each HC390
>>> is two divide by 10 counters, including a 1/2 and 1/5 in each, usable
>>> separately. So, with two parts, there are four 1/5s and four 1/2s available.
>>> 
>>> Here's a verbal process description: 10 MHz sine convert to logic with
>>> HC86, 10 MHz/2=5, 10 MHz/10=1 with first HC390, add 5+1=6 with EXOR, BPF 6
>>> MHz, convert to logic with HC86, 6 Mhz/25=240 kHz=4f, 240/2=120 kHz=2f,
>>> 120/2=60 kHz=f, with second HC390.
>>> 
>>> Ed
>>> 
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>>> 
>> 
>> 
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Re: [time-nuts] time-nuts Digest, Vol 168, Issue 21

[Bob kb8tq]

Hi

I think it’s just the normal summertime drop-off. Everybody is on vacation…..

Bob

> On Jul 23, 2018, at 12:41 PM, Dan Kemppainen  wrote:
> 
> FYI,
> 
> I would tend to agree about the drop in traffic. Not sure if it's just a 
> quiet period, but there are many less messages than before in the digest.
> 
> Dan
> 
> 
> On 7/23/2018 12:00 PM, time-nuts-requ...@lists.febo.com wrote:
>> Could it be that the reflector drops messages?
>> I did not get Ulrich's? NO-Message and also not that from msimon6808.
>> It has become quite silent since the move to the new server.
>> Subjectively -6 dB.
>> Cheers, Gerhard
> 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

This is not so much a GPS issue as a system design issue. GPSDO’s are used to 
“smooth over” bumps in a lot 
of systems out there. At the timing levels required by ATM or authentication 
setups, you can go a *long* time
running on a GPSDO. It’s not a matter of GPS, it’s a matter of doing things on 
the cheap ….

Bob

> On Aug 30, 2018, at 10:42 AM, Scott McGrath  wrote:
> 
> Um no
> 
> Will the internet continue to route packets without precision timing yes it 
> will,  Yes the lambdas will stay lit on fiber but the ATM transport that runs 
> on the lambdas will fail (note DSL is simply an ATM VC over copper).  and 
> other timing dependent services will fail
> 
> Will many services like authentication continue especially those based on 
> multimaster replication continue to function?
> 
> No they will not,  they are totally dependent on precision timing to ensure 
> proper replication sourcing. (Microsoft Active Directory)
> 
> Banking transactions in the same boat.
> 
> Unless you’ve actually run a large network you dont realize just how 
> dependent on precision timing the services running over the network have 
> become especially authentication And one reason for this is increased 
> security for the overall network.
> 
> On Aug 30, 2018, at 8:45 AM, Brian Lloyd  wrote:
> 
> On Thu, Aug 30, 2018 at 7:01 AM, Scott McGrath  wrote:
> 
>> 
>> 
>> 
>> Without precision timing there is no telephone network, cell phones or
>> internet.   And that only became true in the last 20 years or so as long
>> haul networks went from FDM on coaxial cable to TDM on fibre.
>> 
> 
> The Internet is largely asynchronous due to the store-and-forward nature of
> the routers. Fiber capacity is increased through the use of wavelength
> division multiplexing (WDM) which is itself a form of FDM. The Internet
> functions without any sort of central synchronization.
> 
> Yes, there are portions that run over the synchronized telco services but
> that is by convenience, not necessity.
> 
> -- 
> 
> 
> 
> Brian Lloyd
> 706 Flightline
> Spring Branch, TX 78070
> br...@lloyd.aero
> +1.210.802-8FLY (1.210.802-8359)
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[time-nuts] News

[Bob kb8tq]

Hi

Magnus … do you have some news you might want to share with the group?

Bob
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

When infastructure GPS *does* get jammed these days that source gets tracked 
down a lot faster
than a month or so. Anything that goes on for more than a day gets booted up 
pretty high
pretty fast. Indeed I’ve been in the middle of that more than I would have 
wished to be …..

The same sort of RFI issues that take out GPS from a TV preamp  can equally 
well take out WWVB or WWV.
With WWVB, there are a *lot* of 60KHz switching power supplies out there to 
create problems. There is nothing 
unique about any of these services in terms of being jam immune. 

The bigger issue with any of them is spoofing. A proper GPSDO will go into 
holdover when RFI jammed. I would
*assume* the same would be true of a fancy WWVB device. I’m not at all sure 
that’s true of a real WWVB standard, 
they haven’t been for sale new for a really long time. If your time source is 
in holdover, you can go out and track down
the issue. If it simply locks to the new signal …. not so much. 

There is a subtle distinction in some of this. Newer systems do indeed want 
time. Older systems were generally after 
frequency. The only WWVB standards I’ve seen were aimed at frequency (and 
frequency holdover) rather than time and
time holdover. Getting reasonable (1 to 10 ppb) frequency from WWVB is a very 
different task than getting the sort of time
that modern systems are after. 

Bob

> On Aug 30, 2018, at 2:46 PM, Scott McGrath  wrote:
> 
> The port of Long Beach CA was jammed wrt GPS for several months by a 
> malfunctioning 29.95 TV preamplifier on a boat.
> 
> GPS was completely unusable when this unsuspecting guy was watching TV on his 
> boat.
> 
> He had quite the surprise when the coasties with guns showed up.
> 
> The fact is civillian GPS Is trivial to jam and jammers can be bought ‘under 
> the counter’ at any truckstop along with illlegal linear amplifiers.
> 
> 
> 
> On Aug 30, 2018, at 12:58 PM, Peter Laws  wrote:
> 
> On Mon, Aug 13, 2018 at 8:52 AM Peter Laws  wrote:
> 
> 
>> I have yet to hear anyone make a case for retaining the HF system that
>> isn't backed by nostalgia.
> 
> Still looking for this.  Most of the "OMG IF WWV GOES AWAY MILLIONS
> WILL DIE" posts (elsewhere, not here ... quite ...) are the type of
> hysteria that is usually reserved for, I don't know, the EMP folks.
> :-)
> 
> 
>> As for solar flares taking out the various GNSSs ... wouldn't a solar
>> flare only take out the vehicles that were on the "sunny" side of the
>> Earth?  Wouldn't the (approximately) half of the SVs that are in the
>> Earth's shadow be unaffected?  Serious technical question - I have no
>> idea.
> 
> One of the responses to my initial message pointed out that the
> effects of solar flares and CMEs take a while to get from Sol to Sol
> III and don't arrive all at once, so potentially all GNSS spacecraft
> could be affected.
> 
> Since then, I've been poking around for papers on the effect
> (observed, potential, theoretical) of these events on the Navstar or
> other GNSS constellations but am not having much luck.  I assume it's
> because I'm not putting the right magic incantation into the google
> machine.
> 
> Anyone got some cites?  Looking for the effect of solar flares and
> CMEs on the spacecraft themselves and not how the GNSSs can be used to
> measure the effects on the ionosphere, etc (those seem plentiful).
> IOW, I'm curious about the resiliency of the systems to solar events.
> 
> I did note that at the time of the 1989 solar event that took out a
> lot of Hydro Quebec's grid, only the "Block I" experimental GPS "SVs"
> were in orbit.  Well, maybe a couple of the later ones - the
> operational constellation started launching about a month before that
> flare.
> 
> As I said initially, I'll be sad if WWV* goes away but it won't affect
> my life in any measurable way that I can see.  I mean, other than the
> mantle clock slowly losing time.
> 
> -- 
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

Well, designing jammers on a public forum is an “interesting” thing to do…..

With WWVB, you are fine with a “near field” solution. You don’t need something 
that propagates for 
miles and miles. The other thing you have in your favor is that coming up with 
a KW at 60 KHz is 
quite easy. All those 60 KHz switchers we complain about … there’s your dirt 
cheap source of parts. 

The next part of the “solution” is to feed your signal into the local power 
grid. Your switcher is happy
with a low impedance load. The power line looks fairly low impedance at 60 KHz. 
It goes the RF and 
out and about it flows. Indeed it works pretty well over a good chunk of 
ground. At least as good as your
typical GPS jammer and no more expensive. Been there end done all that, though 
not for a WWVB jammer. 

Bob

> On Aug 30, 2018, at 5:20 PM, Brooke Clarke  wrote:
> 
> Hi Bob:
> 
> I would disagree in that ease of jamming/spoofing is strongly related to 
> wavelength.  That's because antenna efficiency goes down as the size of the 
> antenna gets smaller than 1/4 wave.
> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 wavelength 
> is a few inches, something that  you can hold in your hand.
> It's harder to make a WWV jammer (.5, 5, 10, 15, 20 MHz) since a 1/4 
> wavelength in in the range of  500 to 12 feet, something that can be mounted 
> on a vehicle for the higher frequencies.
> But it's extremely hard to make a jammer for WWVB (60 kHz) where a 
> 1/4wavelength is over 4,000 feet.  This means an antenna that can be vehicle 
> mounted will be very inefficient. Note this also means that it's extremely 
> hard to make a Loran-C jammer.  Note that the WWVB and LORAN-C transmitters 
> run very high power and the antennas are massive.
> 
> This also means that if someone makes a WWVB simulator for their house the 
> signal at the next door neighbor's house is probably going to be too small to 
> effect their clocks.
> 
> PS. Some decades ago I maintained a beacon transmitter "LAH" on 175 kHz where 
> the rules for unlicensed operation limited the input power to 1 Watt and 
> total antenna length to 50 feet.  Under these conditions the effective 
> radiated power might be 2 milliwatts, orders of magnitude less if a portable 
> system.
> http://www.auroralchorus.com/pli/1750meter_antennas.pdf
> 
> -- 
> Have Fun,
> 
> Brooke Clarke, N6GCE
> https://www.PRC68.com
> https://www.end2partygovernment.com/2012Issues.html
> axioms:
> 1. The extent to which you can fix or improve something will be limited by 
> how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
> 
>  Original Message 
>> Hi
>> 
>> When infastructure GPS *does* get jammed these days that source gets tracked 
>> down a lot faster
>> than a month or so. Anything that goes on for more than a day gets booted up 
>> pretty high
>> pretty fast. Indeed I’ve been in the middle of that more than I would have 
>> wished to be …..
>> 
>> The same sort of RFI issues that take out GPS from a TV preamp  can equally 
>> well take out WWVB or WWV.
>> With WWVB, there are a *lot* of 60KHz switching power supplies out there to 
>> create problems. There is nothing
>> unique about any of these services in terms of being jam immune.
>> 
>> The bigger issue with any of them is spoofing. A proper GPSDO will go into 
>> holdover when RFI jammed. I would
>> *assume* the same would be true of a fancy WWVB device. I’m not at all sure 
>> that’s true of a real WWVB standard,
>> they haven’t been for sale new for a really long time. If your time source 
>> is in holdover, you can go out and track down
>> the issue. If it simply locks to the new signal …. not so much.
>> 
>> There is a subtle distinction in some of this. Newer systems do indeed want 
>> time. Older systems were generally after
>> frequency. The only WWVB standards I’ve seen were aimed at frequency (and 
>> frequency holdover) rather than time and
>> time holdover. Getting reasonable (1 to 10 ppb) frequency from WWVB is a 
>> very different task than getting the sort of time
>> that modern systems are after.
>> 
>> Bob
>> 
>>> On Aug 30, 2018, at 2:46 PM, Scott McGrath  wrote:
>>> 
>>> The port of Long Beach CA was jammed wrt GPS for several months by a 
>>> malfunctioning 29.95 TV preamplifier on a boat.
>>> 
>>> GPS was completely unusable when this unsuspecting guy was watching TV on 
>>> his boat.
>>> 
>>> He had quite the surprise when the coasties with guns showed up.
>>> 
>>> The fact is civillian GPS Is trivial to jam and jammers can be bought 
>>> ‘under the counter’ at any truckstop along with illlegal linear amplifiers.
>>> 
>>> 
>>> 
>>> On Aug 30, 2018, at 12:58 PM, Peter Laws  wrote:
>>> 
>>> On Mon, Aug 13, 2018 at 8:52 AM Peter Laws  wrote:
>>> 
>>> 
 I have yet to hear anyone make a case for retaining the HF system that
 isn't backed by nostalgia.
>>> Still looking for this.  Most of the "OMG IF WWV GOES AWAY MILLIONS
>>> 

Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
stable signal. As soon as
that signal hits the real world things start to degrade. Propagation between 
transmit and receive sites
is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade 
noise at 60 KHz. The receive 
signal to noise will never be as good as you might like it to be ….

60 KHz has a period of 16.667 us. GPS gives you ~10 ns sort of time quite 
quickly. Resolving the WWVB
carrier to that level is a major challenge. Identifying a single “cycle edge” 
as the magic timing ID with either
the old or new modulation formats …. yet another significant challenge. Net 
result is that you just can’t 
get the same sort of timing out of WWVB.

Bob

> On Aug 30, 2018, at 11:15 AM, Mike Bafaro  wrote:
> 
> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate 
> to the atomic standard and is considered traceable.  I remember when I was in 
> the Navy years ago I remember taking our unit's HP5245L for calibration and 
> they used a VLF tracking receiver at 60KHz to do the calibration.  If WWVB 
> goes off the air what is the replacement for the 60KHz standard?
> 
> Mike
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Perry 
> Sandeen via time-nuts
> Sent: Wednesday, August 29, 2018 6:34 PM
> To: time-nuts@lists.febo.com
> Cc: Perry Sandeen
> Subject: [time-nuts] WWV and legal issues
> 
> Yo Dudes!�
> WWV and all its variations distribute what in the USA is the legal standard 
> of time (from USNO) and frequency (NIST).
> �If one is running a freq cal service IIRC it is a legal requirement to be 
> able to have traceability to WWV.
> 
> If one was to rely on other sources, one has no guarantee that it 1. It is as 
> accurate as claimed and 2. It can't be *diddled* with accidentally or 
> deliberately.
> Although GPSDO's are very good and popular, they come from satellites that 
> are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own 
> physical territory then they stand or fail on their own.�
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors 
> of the bomb (I don't remember who) went to see US president Harry Truman and 
> essentially told him that the scientists who developed the bomb should have a 
> say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid 
> that was responsible for his schedule to "never in hell let that (or any 
> other) scientist� come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, 
> IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the 
> Russian federation tell the world quote: See, the USA can't be trusted for 
> something as important and simple as frequency and time.� However we are your 
> friends who you can trust. Unquote.
> Regards,
> 
> 
> 
> 
> 
> This is a case of practical use of WWV albeit over 50 years a go the 
> fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver 
> site.� Our base had to purposes.� to� �
> 
> 
> 
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

> On Aug 30, 2018, at 12:58 PM, Peter Laws  wrote:
> 
> On Mon, Aug 13, 2018 at 8:52 AM Peter Laws  wrote:
> 
> 
>> I have yet to hear anyone make a case for retaining the HF system that
>> isn't backed by nostalgia.
> 
> Still looking for this.  Most of the "OMG IF WWV GOES AWAY MILLIONS
> WILL DIE" posts (elsewhere, not here ... quite ...) are the type of
> hysteria that is usually reserved for, I don't know, the EMP folks.
> :-)
> 
> 
>> As for solar flares taking out the various GNSSs ... wouldn't a solar
>> flare only take out the vehicles that were on the "sunny" side of the
>> Earth?  Wouldn't the (approximately) half of the SVs that are in the
>> Earth's shadow be unaffected?  Serious technical question - I have no
>> idea.
> 
> One of the responses to my initial message pointed out that the
> effects of solar flares and CMEs take a while to get from Sol to Sol
> III and don't arrive all at once, so potentially all GNSS spacecraft
> could be affected.
> 
> Since then, I've been poking around for papers on the effect
> (observed, potential, theoretical) of these events on the Navstar or
> other GNSS constellations but am not having much luck.  I assume it's
> because I'm not putting the right magic incantation into the google
> machine.
> 
> Anyone got some cites?  Looking for the effect of solar flares and
> CMEs on the spacecraft themselves and not how the GNSSs can be used to
> measure the effects on the ionosphere, etc (those seem plentiful).
> IOW, I'm curious about the resiliency of the systems to solar events.
> 
> I did note that at the time of the 1989 solar event that took out a
> lot of Hydro Quebec's grid, only the "Block I" experimental GPS "SVs"
> were in orbit.  Well, maybe a couple of the later ones - the
> operational constellation started launching about a month before that
> flare.
> 

There most certainly was a lot of “stuff” in orbit by that time. If there was 
a mass die off of satellites, you would not have to look hard to find out about
it. 

Bob

> As I said initially, I'll be sad if WWV* goes away but it won't affect
> my life in any measurable way that I can see.  I mean, other than the
> mantle clock slowly losing time.
> 
> -- 
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
> 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

Same basic problem with WWVB. If you were using it as a reference, you timed 
your
data collection to avoid the transition periods. You got both phase shifting 
and the 
amplitude took a dive. Neither one was going to help you make a precision 
measurement.

In addition there are various weather events (terrestrial and solar) that can 
get into
the mix. You can see blips here and there that do not correlate with the 
sunrise / sunset
stuff. Again, not a big deal if you are manual evaluating the data to check 
your local
Rb standard or super duper OCXO. Not a good thing for disciplining a system 24 
hours
a day 365 days a year. 

Bob

> On Aug 30, 2018, at 1:54 PM, Attila Kinali  wrote:
> 
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq  wrote:
> 
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>> stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between 
>> transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade 
>> noise at 60 KHz. The receive 
>> signal to noise will never be as good as you might like it to be ….
> 
> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
> causes a phase shift of several 100µs at even moderate distances
> (like ~500km). Unfortunately I don't have any measurements at hand.
> 
> 
>   Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neal Stephenson
> 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

With the Loran boxes, you were doing well to get down to the 100 ns level. When 
you did, it always was a 
questionable sort of reading. More or less - is this real??? I spent a *lot* of 
time watching that data ….

Estimating what WWVB is doing over long baselines as the weather changes is not 
at all easy. To keep things
in sync you need solid data all the time. Guessing at your time source and then 
trying to discipline against it 
does not make for a rational disciplining system. Again … I spent a lot of 
years looking at those phase plots. 

Could you do pretty well for a few days with either one? Sure you could. For a 
system time source you are looking 
at 24 hours a day / 365 days a year sort of performance. We are going round and 
round talking about the sort of solar flares that 
haven’t happened in many decades (if ever …). The sort of stuff that disrupts 
WWVB or Loran (at the 10’s or 100’s of 
nanoseconds level) happens many times a year, even in a good year. Ramp up the 
sun spots and it can get really interesting.

Is it better if I can toss rocks and hit the transmit antenna? Sure it is. Not 
everybody was / is within a hundred miles of a master
for Loran-C or of Ft. Colins for WWVB. If you are going to use WWVB, it’s got 
to work in Miami, Florida and in Bangor, Maine. 
Working out carrier phase on WWVB as MSF comes in at equal strength in New 
England … yikes ….

There are good sound reasons why the WWVB disciplined systems gear got dumped a 
long time ago and replaced with GPS. 
The GPS based gear performs better and is more reliable. 

Bob

> On Aug 30, 2018, at 12:46 PM, Scott McGrath  wrote:
> 
> One does not get the same instantaneous accuracy that one gets from GPS but 
> with a long baseline the offsets to your site can be determined.With 
> eLoran you can  get similar levels of accuracy as the old Austron monitors 
> used to prove
> 
> Content by Scott
> Typos by Siri
> 
> On Aug 30, 2018, at 12:27 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
> stable signal. As soon as
> that signal hits the real world things start to degrade. Propagation between 
> transmit and receive sites
> is a big deal, even at 60 KHz. On top of that, there is a *lot* of manmade 
> noise at 60 KHz. The receive 
> signal to noise will never be as good as you might like it to be ….
> 
> 60 KHz has a period of 16.667 us. GPS gives you ~10 ns sort of time quite 
> quickly. Resolving the WWVB
> carrier to that level is a major challenge. Identifying a single “cycle edge” 
> as the magic timing ID with either
> the old or new modulation formats …. yet another significant challenge. Net 
> result is that you just can’t 
> get the same sort of timing out of WWVB.
> 
> Bob
> 
>> On Aug 30, 2018, at 11:15 AM, Mike Bafaro  wrote:
>> 
>> According to what I have heard the 60KHz WWVB carrier is guaranteed accurate 
>> to the atomic standard and is considered traceable.  I remember when I was 
>> in the Navy years ago I remember taking our unit's HP5245L for calibration 
>> and they used a VLF tracking receiver at 60KHz to do the calibration.  If 
>> WWVB goes off the air what is the replacement for the 60KHz standard?
>> 
>> Mike
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Perry 
>> Sandeen via time-nuts
>> Sent: Wednesday, August 29, 2018 6:34 PM
>> To: time-nuts@lists.febo.com
>> Cc: Perry Sandeen
>> Subject: [time-nuts] WWV and legal issues
>> 
>> Yo Dudes!�
>> WWV and all its variations distribute what in the USA is the legal standard 
>> of time (from USNO) and frequency (NIST).
>> �If one is running a freq cal service IIRC it is a legal requirement to be 
>> able to have traceability to WWV.
>> 
>> If one was to rely on other sources, one has no guarantee that it 1. It is 
>> as accurate as claimed and 2. It can't be *diddled* with accidentally or 
>> deliberately.
>> Although GPSDO's are very good and popular, they come from satellites that 
>> are vulnerable to damage from earth based resources.
>> When your time and frequency standard(s) is under control on your own 
>> physical territory then they stand or fail on their own.�
>> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors 
>> of the bomb (I don't remember who) went to see US president Harry Truman and 
>> essentially told him that the scientists who developed the bomb should have 
>> a say of how or when it should be used.
>> Truman is reported to have said for him to leave his office and told an aid 
>> that was responsible for his schedule to "never in hell let that (or

Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

I think we have a little bit of confusion here. WWVB is not going to help 
anybody navigate. 
It’s not going to help track people with ankle bracelets or trucks stopping at 
bars. Car thieves 
jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes on. 
None of this is 
a Time Nuts sort of issue. 

The only thing WWVB *might* do is provide timing. That’s very different than 
navigation. A 
mobile this or that driving by puts your GPSDO into holdover. It maintains time 
while it is in
holdover. Minutes or hours, possibly days … works the same way. The system 
keeps running
just like GPS was doing fine. If after a day or more, the GPS is still jammed, 
that single  cell tower 
shuts down. Take out one cell tower and the system keeps running. There is a 
lot of overlap on 
these systems. Towers go down a lot more often than you might think …..

Do all systems work identically in terms of timing? Of course not. If timing is 
critical to operation,
systems do use GPSDO’s. The same basic principles apply. The main question 
would be one
of overlap between elements of the system. 

The same jamming that takes out GPS for timing also takes it out for normal 
navigation. Take
it out over an entire city and everybody’s vehicle navigation system goes out. 
Do that even for
a couple of hours and it’s on the evening news. Do that for a day and there 
*is* a response. 
That’s the kind of thing needed to impact utility systems (like cell towers) in 
a significant way. 
It simply does not happen ….City wide is very hard to do from the ground.  From 
the air, you 
can get the coverage. It’s tough to keep doing it from the air for days on end. 

So, interns of “the world ends if / when WWVB turns off” … not so much.

In terms of the initial question, GPSDO’s in general are pretty good at 
handling the typical 
jamming they might run into. 

Bob



> On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
> 
> And here is one of the schematics running around the ‘net.   This one is 
> noise based
> 
> 
> 
> 
> 
> On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
> 
> 
> 
>> Am 31.08.2018 um 19:39 schrieb jimlux:
>>> On 8/31/18 10:15 AM, Bob kb8tq wrote:
>>> Hi
>>> 
>>> Having spent a lot of my life designing GPSDO’s it’s a “that depends” sort 
>>> of thing.
>>> For a simple noise jammer, yes, they pretty much all will go into holdover. 
>>> When the
>>> jammer goes away, they come out of holdover. There are a few older units 
>>> that may not
>>> do quite as well with various sorts of broadband jamming.  With a spoofing 
>>> jammer that is flying
>>> around overhead and simulating an entire constellation … you could see any 
>>> of them do odd
>>> things. An airborne jammer flying over this or that city likely gets you 
>>> into a “act of war” sort of issue.
>>> It’s something you build if you are a nation state.
>>> 
>>> The performance with noise jammers is not a guess. It’s based on field 
>>> experience and
>>> all those never ending meetings I keep referring to …..
>>> 
> IIRC, there was a truck driver who successfully jammed all those airworthy 
> GPS systems
> at SF airport trying to hide his private detours, just by passing on the 
> highway with
> El Cheapo hardware.
> 
>> 
>> In effect, a broadband jammer (or, probably, a tone jammer that overwhelms 
>> the 1 bit ADC receiver) is the same as a "loss of signal" - the receiver 
>> probably doesn't know the difference - it just drops sync and tries to 
>> unsuccessfully reacquire.
> 
> I think that Holmes wrote somewhere that the easiest way to jam was a carrier 
> quite close
> to the frequency where the suppressed carrier of the BPSK would be. It could 
> be weak because
> it would have some processing gain, even if not completely sync to the rest 
> of the signals.
> The typical 1 or 2 Bit ADC has no chance to see it separated from the rest.
> 
>> 
>> So you can test your hold over behavior with aluminum foil (or your hand) 
>> over your antenna
>> 
> OMG, I first read "with aluminium foil hat over your head"
> 
> Cheers,
> Gerhard
> 
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

> On Sep 1, 2018, at 3:06 AM, Magnus Danielson  
> wrote:
> 
> 
> 
> On 08/31/2018 03:36 PM, Bob kb8tq wrote:
>> Hi
>> 
>> “Backbone timing” gets done by boxes buried deep in systems. Those systems 
>> take years
>> to design. The boxes that go in them similarly take years to get onto the 
>> market. Once designed
>> deployment is far from instantaneous. Operators are always pressed by cost 
>> constraints. Adding
>> anything beyond the minimums … not going to happen.
>> 
>> The result is that there are no systems out there that use WWVB or WWV other 
>> than wrist watches
>> and wall clock like devices. Utilities (cell phones, internet, finance ) run 
>> with something else. Converting
>> them to a secondary “something” is a many years sort of thing, even if it is 
>> technically feasible. 
>> 
>> You can pull a bunch of spare GPS sat’s out of storage and get them in orbit 
>> *way* quicker than you can 
>> rebuild every cell tower in the country. In fact, newer designs run their 
>> timing in a way that a GPS failure 
>> is not that big a deal. How long it’ll take before that sort of design is 
>> common in the US…. years and years …
>> 
>> If you are going to come up with a time source at the ~ 10 ns level, that’s 
>> not going to happen from WWVB
>> or WWV. They never were good enough to get to that level and it’s not on the 
>> transmit end. You would need
>> a very different system. It’s been a long time since any of these services 
>> (internet, finance, cell )  were in the 
>> millisecond or even the microsecond range. The modern stuff in all theses 
>> areas  is  < 100 ns. 
> 
> The actual requirements is usually on the 1-10 us level, but they are
> happy when they have the extra precision.

Well, they are and they aren’t. The newer systems (which rapidly become the 
only system) are at the one microsecond
level after being in holder for many hours ( days?). The assumption is that 
only one tower (or chunk) goes into holdover
at a time and the rest are still at least 10X better than that. Cut them all 
loose an the numbers would have to be tighter.

In order to get them all at the 100 ns level, you need a source that is around 
5 to 10X better than that. The timing source
is not the only source of error and you need to “train” your holdover clock 
with something that is mighty good. The
holdover spec often applies after a very short period of training (a day to 
several days). Indeed, if you put a Cs standard
in every cell tower and every internet node you probably could back off a bit 
on the 10X. With quartz or Rb, you need
the accuracy in training. 

Bob



> 
>> How long would it take to change all this? Well first some random Senior 
>> Member of the IEEE would 
>> have to start writing papers about the various issues. Various organizations 
>> in various countries would 
>> need to hold meeting after meeting after meeting talking things over. 
>> Somebody eventually would have
>> to come up with funds to actually try a few things. Maybe they work in the 
>> real world / maybe they don’t
>> work. 
>> 
>> Once you prove you have a system that can do “good enough", you would need 
>> laws / regulations passed to
>> make the “new thing” part of the required designs. You also need funding 
>> bills to deploy the “source” end 
>> of things and time to get that up and running. Once it’s running, you then 
>> give manufacturers some amount of time 
>> to get it in the field ….. and extensions when that doesn’t happen. Twenty 
>> years? Thirty years? Maybe longer? 
>> This stuff does not go very fast. 
> 
> It's been done for 10+ years now. Some 15+ countries have nation wide
> networks that makes them GPS independent for some applications.
> It has been a fun system to design and deploy.
> 
> Getting more precision isn't all that hard, it just takes more effort in
> the details and hence money and time. If people need 100 ns or 10 ns
> system time, it can be done.
> 
>> Best bet on what the “new thing” would be? Something like IEEE-1588 over 
>> fiber. It cuts out a bunch of this and 
>> that in terms of experiments and testing the basic system. We know most of 
>> *how* to do it already. It’s just a matter 
>> of a  billions of dollars in tax money to get the gaps filled in and then a 
>> few tens of billions in tax money to get
>> the backbone gear in place. Once that’s done you ramp up to the really 
>> expensive part of the deal ….Is it paid
>> for by your tax return in April or by a higher price on every cell call / 
>> transaction you make? … who knows … it’s 
>

Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Time is not (ultimately) determined by an atomic clock. It’s determined by 
astronomical observations 
that evaluate the rotation of the planet. Those observations are what drive 
things like leap seconds. 
In the event that a flare takes out 99% of all life on earth and every 
electrical device …. I don’t really 
think we will be worried about it being 12:01:01 PM. What we *will* be 
concerned about is not really
a Time Nut subject. 

To answer the question of how many clocks are there - take a look at how UTC is 
determined by BIH
Paris. The answer is in the “many hundreds”. Yes, 99% of them could go along 
with all the people that 
run them. Again … not really a Time Nut subject. That still leaves quite a few 
to run off of. 

Bob

> On Aug 31, 2018, at 6:38 PM, Dana Whitlow  wrote:
> 
> I'm thinking about if/when "the big one hits" and takes out most or all of
> the GPS
> sats, cell phone systems, etc.
> 
> Then the time required to reboot up to a reasonable level of technology
> might turn
> out to be limited by our ability to determine time and freq somewhat
> accurately.  The
> better we can do from scratch, the faster the reboot.
> 
> So one question is:  how many Cs beam clocks are out there which are kept
> running
> and "on time", at least by frequent logging of errors if not by actual
> setting/tweaking?
> 
> If "the big one" is global nuclear war, of course we'll all have far more
> to worry about
> than keeping our watches accurately set.  But what if it's another
> Carrington-level
> event?  I'm sure we'd all like to get back to business as usual as quickly
> as possible.
> 
> Dana
> 
> 
> On Fri, Aug 31, 2018 at 5:23 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> I think we have a little bit of confusion here. WWVB is not going to help
>> anybody navigate.
>> It’s not going to help track people with ankle bracelets or trucks
>> stopping at bars. Car thieves
>> jamming Lojack still happens. Turn iWWVB on or off, this stuff still goes
>> on. None of this is
>> a Time Nuts sort of issue.
>> 
>> The only thing WWVB *might* do is provide timing. That’s very different
>> than navigation. A
>> mobile this or that driving by puts your GPSDO into holdover. It maintains
>> time while it is in
>> holdover. Minutes or hours, possibly days … works the same way. The system
>> keeps running
>> just like GPS was doing fine. If after a day or more, the GPS is still
>> jammed, that single  cell tower
>> shuts down. Take out one cell tower and the system keeps running. There is
>> a lot of overlap on
>> these systems. Towers go down a lot more often than you might think …..
>> 
>> Do all systems work identically in terms of timing? Of course not. If
>> timing is critical to operation,
>> systems do use GPSDO’s. The same basic principles apply. The main question
>> would be one
>> of overlap between elements of the system.
>> 
>> The same jamming that takes out GPS for timing also takes it out for
>> normal navigation. Take
>> it out over an entire city and everybody’s vehicle navigation system goes
>> out. Do that even for
>> a couple of hours and it’s on the evening news. Do that for a day and
>> there *is* a response.
>> That’s the kind of thing needed to impact utility systems (like cell
>> towers) in a significant way.
>> It simply does not happen ….City wide is very hard to do from the ground.
>> From the air, you
>> can get the coverage. It’s tough to keep doing it from the air for days on
>> end.
>> 
>> So, interns of “the world ends if / when WWVB turns off” … not so much.
>> 
>> In terms of the initial question, GPSDO’s in general are pretty good at
>> handling the typical
>> jamming they might run into.
>> 
>> Bob
>> 
>> 
>> 
>>> On Aug 31, 2018, at 3:52 PM, Scott McGrath  wrote:
>>> 
>>> And here is one of the schematics running around the ‘net.   This one is
>> noise based
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On Aug 31, 2018, at 3:41 PM, Gerhard Hoffmann  wrote:
>>> 
>>> 
>>> 
>>>> Am 31.08.2018 um 19:39 schrieb jimlux:
>>>>> On 8/31/18 10:15 AM, Bob kb8tq wrote:
>>>>> Hi
>>>>> 
>>>>> Having spent a lot of my life designing GPSDO’s it’s a “that depends”
>> sort of thing.
>>>>> For a simple noise jammer, yes, they pretty much all will go into
>> holdover. When the
>>>>> jammer goes away, they come out of holdover. There are a few older
>> units that may not
>&

Re: [time-nuts] Lots of Off Topic discussion

[Bob kb8tq]

Hi

I most certainly *have* seen an NTP server that ran off of WWVB and relayed 
the result to the internet. The fun part was that they had entered the “delay” 
number into their config file with the wrong sign on it (or there was a bug in 
the NTP code at that time). The result was that they were …. errr …. a bit 
off time.

So yes, you *can* hook NTP into WWVB, it has been done. It is a way (if you get
the signs right ….) to get into millisecond(s) level accuracy.

Bob

> On Sep 1, 2018, at 2:02 PM, Peter Laws  wrote:
> 
> On Sat, Sep 1, 2018 at 9:15 AM David G. McGaw
>  wrote:
> 
>> available methods of time dissemination.  I am very concerned that
>> factions of NIST consider that this should no longer be part of their
>> mission.
> 
> 
> 1) WWV* systems are not critical to anything I have found other than
> WWVB being used to keep "atomic clocks" in sync and updated for DST.
> I've asked in many places but other than two recent papers that used
> WWV HF signals with the Long Wavelength Array to do some ionospheric
> measurements I can't find any evidence that the signals are critical
> to anything in science.
> 
> 2) Anyone that *needs* accurate time to within a few ms of UTC uses
> NTP.  Anyone who thinks they need more precision than that can look at
> PTP (usually deciding that NTP is plenty good once they see what it
> will cost them for PTP).  All current consumer operating systems (OS
> X, iOS, Android, Windows, etc) have some form of NTP client built in.
> 
> 3) Is no one familiar with the US federal budgeting process?  Really?
> The executive branch (Commerce is a cabinet-level department therein)
> submits to the legislative branch the budget for what they claim they
> will need for the upcoming fiscal year.  This is made up from
> estimates of each cabinet member (and others) who get their numbers
> from the various institutions within their silos (e.g., NIST under
> Commerce).  Because no department head wants their budget cut, they
> ensure that items put up for "cutting" are ones that the public is
> most likely to complain (to congress) about.  A quick google didn't
> tell me when the executive branch last submitted a budget that was
> actually in balance but I'm sure it's been 35 years at least despite
> the alleged cutting.  And it doesn't matter because the executive
> budget is routinely ignored by the body that is actually in charge of
> spending, congress.
> 
> 4) I don't think I've ever seen an NTP server that used WWV* as their
> reference clock (it's listed in the output of the query command)
> because GPS is ubiquitous.  "Yeah, but Carrington!"  I am not certain,
> but given that in the US, the Navstar GPS is a US military system run
> by the US military for US military purposes (which happens to have a
> signal available to civilians) that the designers were not only aware
> of solar physics but used that awareness to make the GPS system as
> resilient as they could to the potential effects of CMEs and flares.
> So for me, the "GPS COULD FAIL!" argument does nothing.
> 
> 
> 
> I'd rather read about Earth tides affecting time measurements.  Or
> proper care and feeding of your Cs oscillator.
> 
> 
> 
> --
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

 “Backbone timing” gets done by boxes buried deep in systems. Those systems 
take years
to design. The boxes that go in them similarly take years to get onto the 
market. Once designed
deployment is far from instantaneous. Operators are always pressed by cost 
constraints. Adding
anything beyond the minimums … not going to happen.

The result is that there are no systems out there that use WWVB or WWV other 
than wrist watches
and wall clock like devices. Utilities (cell phones, internet, finance ) run 
with something else. Converting
them to a secondary “something” is a many years sort of thing, even if it is 
technically feasible. 

You can pull a bunch of spare GPS sat’s out of storage and get them in orbit 
*way* quicker than you can 
rebuild every cell tower in the country. In fact, newer designs run their 
timing in a way that a GPS failure 
is not that big a deal. How long it’ll take before that sort of design is 
common in the US…. years and years …

If you are going to come up with a time source at the ~ 10 ns level, that’s not 
going to happen from WWVB
or WWV. They never were good enough to get to that level and it’s not on the 
transmit end. You would need
a very different system. It’s been a long time since any of these services 
(internet, finance, cell )  were in the 
millisecond or even the microsecond range. The modern stuff in all theses areas 
 is  < 100 ns. 

How long would it take to change all this? Well first some random Senior Member 
of the IEEE would 
have to start writing papers about the various issues. Various organizations in 
various countries would 
need to hold meeting after meeting after meeting talking things over. Somebody 
eventually would have
to come up with funds to actually try a few things. Maybe they work in the real 
world / maybe they don’t
work. 

Once you prove you have a system that can do “good enough", you would need laws 
/ regulations passed to
make the “new thing” part of the required designs. You also need funding bills 
to deploy the “source” end 
of things and time to get that up and running. Once it’s running, you then give 
manufacturers some amount of time 
to get it in the field ….. and extensions when that doesn’t happen. Twenty 
years? Thirty years? Maybe longer? 
This stuff does not go very fast. 

Best bet on what the “new thing” would be? Something like IEEE-1588 over fiber. 
It cuts out a bunch of this and 
that in terms of experiments and testing the basic system. We know most of 
*how* to do it already. It’s just a matter 
of a  billions of dollars in tax money to get the gaps filled in and then a few 
tens of billions in tax money to get
the backbone gear in place. Once that’s done you ramp up to the really 
expensive part of the deal ….Is it paid
for by your tax return in April or by a higher price on every cell call / 
transaction you make? … who knows … it’s 
a tax that you are paying either way. 

Bob

> On Aug 30, 2018, at 2:14 PM, Peter Laws via time-nuts 
>  wrote:
> 
> On Thu, Aug 30, 2018 at 12:59 PM Bob kb8tq  wrote:
> 
>> There most certainly was a lot of “stuff” in orbit by that time. If there was
>> a mass die off of satellites, you would not have to look hard to find out 
>> about
>> it.
> 
> Probably not as many as there are 3 decades later, but of course.
> Satellite service (any type of satellite) is much more likely to be
> human-caued.
> 
> But here (and in other fora) the concern is that WWV Must Be
> Maintained in order to save us from being late for coffee if another
> event on the level of the Carrington Event takes out every single GNSS
> spacecraft in orbit.  But I can't find anything on the effect of that
> sort of solar event on satellites.  Almost as if, maybe, satellite
> operators were aware of solar physics and planned for this sort of
> event.
> 
> And I still haven't seen any coherent argument in favor of keeping WWV
> that doesn't involve nostalgia or (perhaps) unfounded fear.
> 
> -- 
> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
> 
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Re: [time-nuts] Lots of Off Topic discussion

[Bob kb8tq]

Hi

The referenced line item is $6.8 million a year. It is still very much unclear 
if that is just WWV(H)
(from the reference it must include them) or if it also includes WWWVB.  
Without any clarification, 
we are only guessing about WWVB. Given the way the budget process works, 
there’s never a
lot of clarity at this point. 

Bob

> On Sep 2, 2018, at 9:53 AM, Artek Manuals  wrote:
> 
> Does any one know what the line item $$$ amount is for the WWV/WWVB operating 
> budget?
> 
> -DC
> NR1DX
> manu...@artekmanuals.com
> 
> On 9/1/2018 11:59 PM, Peter Laws wrote:
>> On Sat, Sep 1, 2018 at 7:25 PM Bob kb8tq  wrote:
>> 
>>> I most certainly *have* seen an NTP server that ran off of WWVB and relayed
>>> the result to the internet. The fun part was that they had entered the 
>>> “delay”
>> I didn't say it COULD not -- W3HCF and his group didn't miss much in
>> the code -- but what I'm saying is that in 20+ years of dinking with
>> NTP as part of my job, I HAVE not seen any evidence of WWV being used
>> as a "refclock".  Certainly not in the last decade.  Maybe there were
>> many of them when Dr Mills first published the standards and reference
>> implementation back in the 1980s but not now.
>> 
>> I want to be outraged over this cut but until I have a coherent,
>> evidence-based argument in favor of keeping the stations, I'm going to
>> keep my powder dry.
>> 
> 
> -- 
> Dave
> manu...@artekmanuals.com
> www.ArtekManuals.com
> 
> 
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
> 
> 
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

Tidal effects can be very “non linear” as you approach a coast line. Lots of 
change
over a fairly short distance. If indeed the world decides to put in a global 
PTTI fiber
system, all of this would get into the mix on some links. It appears that the 
existing
technology would handle the issues. 

Of course there’s still some guy named Bob running that back hoe without 
checking
for buried lines …..*That* we could test for … likely no need to run the 
experiment. :)

Bob

> On Sep 2, 2018, at 10:07 AM, Tom Van Baak  wrote:
> 
>> I suspect there’s a longer list of “slow” environmental effects that are 
>> also taken 
>> care of with the compensation setup. One would guess that crossing a active  
>> fault line would be “interesting”. 
> 
> Yes, here's a back of the envelope calculation for you:
> 
> - the Pacific Northwest moves on the order of 10 cm per year [1]
> - 1 meter of time is 1/299792458 = 3.3 ns
> - 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
> - the best laboratory optical clocks are down to that level of stability [2]
> 
> On the other hand, in the real world you'd have to convince me that you've 
> found two national timing labs with 1) state-of-the-art optical clocks, 2) 
> which operate as phase (time) standards instead of as frequency standards, 3) 
> or run continuously for a year (instead of a few times per week), 4) are 
> connected by stabilized fiber, 5) that cross plate boundaries moving anywhere 
> near as much as 10 cm/year, and 6) the optical time nuts running the clocks 
> don't already factor geodetic effects like this into their clock 
> comparisons...
> 
> Unfortunately I won't be able to measure this. Even if John Miles (who also 
> lives near Seattle) and I find optical clocks on eBay some day, and we find a 
> way to run 30 miles of fiber between us without anyone noticing, we are both 
> on the same tectonic plate so the drift cancels out. Note that lunar/solar 
> tidal effects would be common mode to us as well.
> 
> /tvb
> 
> [1]
> https://pnsn.org/outreach/about-earthquakes/plate-tectonics
> https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf
> 
> [2]
> https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
> https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
> http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf
> 
> 
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Re: [time-nuts] Can eloran Backup GPS?

[Bob kb8tq]

Hi

The gotcha is the differential corrections. That’s not the way these systems 
are set up to work. They
function with no external input other than the timing signal its self. 
Providing bandwidth to do correction
signaling just isn’t part of the overall system design.  If you wanted to use 
bandwidth, you would go
with 1588. Then you have a backup and no fiddling with anything else.  

Indeed with an area wide 1588, you can do it all without even a GPS primary. 
Simply agree on a 
“something” as the master source. The man with one watch *always* knows what 
time it is ….

The 250 ns "without correction" is the number that directly compares to the ~10 
ns number for GPS. 
Stretch out the distances to “USA” sort of stuff and it does not improve things 
at all. 

Bob

> On Sep 8, 2018, at 1:40 PM, Bob Martin  wrote:
> 
> Bob,
> 
> I agree that eloran needs to be analyzed with regard to it's
> usefulness for each potential application. You are also 100% correct that 
> timing requirements get tighter and tighter as technology advances.  In some 
> ways the question isn't whether eloran can
> match GPS but rather would it suffice in a pinch were GPS to go down?
> 
> I think the 50ns accuracy is actually "as received" not "as transmitted".
> 
> The link below is an analysis of eloran in Great Britain. The 
> receiver/transmitter distance was  300 miles.
> 
> http://www.ursanav.com/wp-content/uploads/On-the-Uses-of-High-Accuracy-eLoran-Time-Frequency-and-Phase-2015.pdf
> 
> I've attached a screen capture of one of the pages that compares
> eloran  with GPS in case anyone is interested. This is where it
> appears that the 50ns is received as opposed to at the transmitter.
> 
> 
> 
> Best,
> 
> Bob Martin
> 
> On 9/8/2018 9:35 AM, Bob kb8tq wrote:
>> Hi
>> I believe the 50 ns is the “as transmitted” signal from the tower. The “as 
>> received” signal after going
>> through all the various gyrations is not that good on a  ~1 second basis.
>> 
>> One of the gotchas here is that we lump “systems” into one giant bag. That’s 
>> not a good way
>> to analyze things. One system may be quite happy with 10 ms timing another 
>> may be happy
>> with 10 us and yet another may die completely at 1 us and only run right at 
>> 100 ns. All of that
>> is on a 2 second basis for CDMA (they time every other second).
>> By far the biggest / baddest / most venerable system out the that uses GPS 
>> timing is the
>> cell tower system. They started out back in the 80’s with a 10us max timing 
>> / 1 us running
>> spec on CDMA. AFIK they were the first major system to adopt GPS time as 
>> their reference
>> (rather than UTC).
>> This worked out fine for a few decades while companies got a lot of towers 
>> built. People started
>> using those systems and they became congested. Others started streaming 
>> video over them
>> and they ran out of bandwidth. Upgrades followed. There have been a lot of 
>> them. Much of what
>> we TimeNuts buy on the surplus market comes to us as a result of older 
>> systems being scrapped
>> out.
>> The latest set of upgrades does / will / is getting them into the sub 1 us 
>> range at the end of holdover.
>> In normal operation they are spec’d at 100 ns worst case. To do that, you 
>> need a timing source in
>> the roughly 10 ns range. No you don’t see those GPSDO’s on the surplus 
>> market. You will see
>> them someday ….
>> Again, they went this way a decade ago. Rolling that all back …. not at all 
>> easy.
>> Are there other systems that have issues with sync? Of course there are. 
>> There also are a lot
>> of instances where miss-configuration ( or junk implementation) is a much 
>> bigger issue. Sorting
>> that all out requires a deep dive into the timing of each individual system 
>> / implementation.  No
>> two systems do things quite the same way. Unless you want to deal with the 
>> numbers and the
>> implementation details, simply moaning and groaning isn’t going anywhere.
>> Bob
>>> On Sep 8, 2018, at 3:23 AM, Hal Murray  wrote:
>>> 
>>> 
>>> kb...@n1k.org said:
>>>> You are not trying to run a cell system when checking your local oscillator
>>>> against LORAN.
>>> 
>>> The eLoran committee said 50 ns.  Is that good enough for cell towers?
>>> 
>>> Too bad it isn't up so we could collect some data.
>>> 
>>> 
>>> -- 
>>> These are my opinions.  I hate spam.
>>> 
>>> 
>>> 
>>> 
>>> __

Re: [time-nuts] Can eloran Backup GPS?

[Bob kb8tq]

Hi

Yup, and over something the size of a harbor, that works ok. It was done with 
the “old” 
Loran in a similar fashion and a couple of other ways as well.  Expanding any 
of  it to 
cover a country is a very different thing …..

I spent a lot of years trying to sell the designers of these systems on backup 
solutions. 
Not because I’m some kind of end of the world type. I figured selling them four 
boxes for
every tower was at least twice as good as selling them two boxes. I was far 
from the only
one making that pitch. None of us got a bite in 30 years of trying ….

Bob

> On Sep 8, 2018, at 5:16 PM, Bob Martin  wrote:
> 
> Bob,
> 
> That seems pretty conclusive to me but wait there's more..
> 
> By adding a letter to the name they are attempting to address the very issue 
> you've raised.
> 
> https://rntfnd.org/wp-content/uploads/eDLoran-Reelektronica-Paper.pdf
> 
> I'm sure after a few more prefix letters are added to Loran it will work for 
> everyone!
> 
> Time for a new house to flip or dead horse to flog,
> 
> Bob Martin
> 
> 
> 
> 
> 
> On 9/8/2018 2:44 PM, Bob kb8tq wrote:
>> Hi
>> The differential approach to eLoran involves running two local receivers. 
>> You look at the time of arrival on one
>> and use it to “calibrate" the time of arrival on the other. Put another way 
>> - you look at the difference between the
>> two arrival times. They can both “wander” over a 250 ns range, as long as 
>> they stay within 50 ns of each other
>> they meet the “differential spec”.
>> For disciplining a local reference, you really need an absolute number. The 
>> fact that both are wandering over a
>> pretty big range *does* matter if you are looking at a stable local source 
>> (and trying to make it more stable).  What
>> would / does work is having a very accurate standard at one of the locations 
>> and using the difference measure
>> to “distribute” that source. That gets into bandwidth.
>> Since the difference information is *very* local, there really isn’t a 
>> practical way to distribute it on the eLoran signal.
>> As you pile on more correction stations, your data bandwidth goes up. There 
>> are a very limited number of bits
>> available on the eLoran signal.
>> Another way to look at it: If you have a standard sitting in your basement, 
>> and don’t have a buddy in town with a
>> better standard. Does a difference measure to his house do you any good?
>> Bob
>>> On Sep 8, 2018, at 2:58 PM, Bob Martin  wrote:
>>> 
>>> Bob,
>>> 
>>> I believe that information is transmitted with the eloran signal. Way back 
>>> when, I remember there was an added pulse called the LDC pulse. I had to 
>>> modify that pulse with each transmission based on
>>> an input to the transmit timing unit from the computer.
>>> 
>>> I found the following on it:
>>> http://www-personal.umich.edu/~tmikulsk/loran/ref/eloran_ldc.pdf
>>> 
>>> Also, the article referenced previously on The Great Britain
>>> system mentions that the differential corrections are sent on the LDC pulse.
>>> 
>>> To be honest, I don't know if this addresses your "gotcha".
>>> 
>>> Best,
>>> 
>>> Bob Martin
>>> 
>>> On 9/8/2018 12:38 PM, Bob kb8tq wrote:
>>>> Hi
>>>> The gotcha is the differential corrections. That’s not the way these 
>>>> systems are set up to work. They
>>>> function with no external input other than the timing signal its self. 
>>>> Providing bandwidth to do correction
>>>> signaling just isn’t part of the overall system design.  If you wanted to 
>>>> use bandwidth, you would go
>>>> with 1588. Then you have a backup and no fiddling with anything else.
>>>> Indeed with an area wide 1588, you can do it all without even a GPS 
>>>> primary. Simply agree on a
>>>> “something” as the master source. The man with one watch *always* knows 
>>>> what time it is ….
>>>> The 250 ns "without correction" is the number that directly compares to 
>>>> the ~10 ns number for GPS.
>>>> Stretch out the distances to “USA” sort of stuff and it does not improve 
>>>> things at all.
>>>> Bob
>>>>> On Sep 8, 2018, at 1:40 PM, Bob Martin  wrote:
>>>>> 
>>>>> Bob,
>>>>> 
>>>>> I agree that eloran needs to be analyzed with regard to it's
>>>>> usefulness for each potential application. You are also 100% correct that 
>>>>&

Re: [time-nuts] Lost GPS lock or 1PPS recently?

[Bob kb8tq]

Hi

> On Sep 8, 2018, at 1:53 PM, Scott McGrath  wrote:
> 
> This is precisely the scenario even a short GPS blackout of 1-2 weeks would 
> cause.   Its not that GPS is not the finest time transfer system ever 
> devised.   Its that with the loss of legacy systems we’ve lost the ability to 
> degrade gracefully.

How will the presence of a “backup” system that in no way at all interconnects 
with a cell tower have any 
effect at all on it’s performance with loss of GPS ??? The legacy system (which 
does not even exist) 
has *zero* impact in this case. 

> 
> With a eLORAN system cell networks during a prolonged outage would probably 
> degrade to 3G,

Except that they have no way at all to do that. They simply are not designed 
that way and can not function 
that way. The systems that *could* function at lower timing tolerance all got 
scrapped out long ago. That 
of course *assumes* that eLoran can deliver < 100 ns timing. Is there any data 
to support that ? 

Do any members have data on the 1 second timing out of eLoran? We’re about as 
deep into it as any
group not working for the eLoran people. If we haven’t seen any performance 
data …. I kinda doubt 
anybody else has. 


>  but they would still be up.   No you cant stream HD video or play GTA Online 
> X,  but talk,text email and Facebook would still work Time transfer for most 
> applications would still work.  The HFT boyos on Wall St would be SOL.  Not 
> sure how to evaluate that eventuality.
> 
> 
> People like US need to educate political and business leadership on the need 
> for BACKUPS to GPS

The reason the systems are designed just with GPS is *not* because “nobody 
mentioned the need
for a backup”. There are indeed people out there who spent a lot of time 
talking about this with the
guys who designed and spec’d these systems. The very simple answer *always* 
came back:

1) There is no alternative out there

2) There is not FCC requirement to do so = cost is not justified

3) There is absolutely zero demonstrated need

That’s very much three strikes you’re out.

Bob


> mainly because things like the Carrington Event have happened before and WILL 
> happen again. 
> 
>   And having terrestrial systems mean that you can get techs onsite to repair 
> by horse if necessary unlike a space based system where some idiot retired 
> the fleet of repair trucks. So the only remaining option is to launch new 
> ones.
> 
> 
> On Sep 8, 2018, at 10:25 AM, jimlux  wrote:
> 
>> On 9/7/18 10:05 PM, John Reid wrote:
>> Hi all,
>> discussion of how to keep accurate time without access to GPS seems very
>> on topic to me.
>> These people involved in major catastrophe ('end of the world' as you
>> put it) scenarios have a wealth of experience in other ways of keeping
>> accurate time.
> 
> 
> Actually, they don't necessarily have a wealth of experience, because they 
> may have marched themselves down a path where they have a *requirement* for 
> much better timing than they realize, because it is so easy and cheap to get 
> good time today.
> 
> Imagine this scenario - you're a bank, and you batch process checks and 
> deposits in one physical location, so you don't much care about when the 
> check was written or the deposit made.  Then you move to a distributed system 
> across the US, where the reconciliation is done on the basis of the date of 
> the transaction - still probably ok, because there are no transactions during 
> non-business hours, so as long as you reconcile at 1AM, if transaction time 
> stamps are off by 5 minutes, it doesn't matter.
> 
> 
> Now say "we're going to charge you, the customer a fee, if your balance goes 
> negative" and go to 24/7 operations, where transactions are journaled 
> immediately, rather than batch processed at night  If a deposit that was made 
> at 12:00 (but timestamped 12:05)  is followed by a withdrawal made at 12:03 
> (but timestamped 12:00), you get unfairly charged the overdraft fee.
> 
> For small problems, banks have ways to "unwind" errors.  But if it becomes a 
> systemic thing that's a problem.
> 
> So the bank sets up GPSDOs at each transaction point - problem solved.
> 
> Until GPS fails.
> 
> 
> 
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Re: [time-nuts] Lost GPS lock or 1PPS recently?

[Bob kb8tq]

Hi

I believe the 50 ns is the “as transmitted” signal from the tower. The “as 
received” signal after going 
through all the various gyrations is not that good on a  ~1 second basis. 



One of the gotchas here is that we lump “systems” into one giant bag. That’s 
not a good way
to analyze things. One system may be quite happy with 10 ms timing another may 
be happy
with 10 us and yet another may die completely at 1 us and only run right at 100 
ns. All of that
is on a 2 second basis for CDMA (they time every other second). 

By far the biggest / baddest / most venerable system out the that uses GPS 
timing is the 
cell tower system. They started out back in the 80’s with a 10us max timing / 1 
us running  
spec on CDMA. AFIK they were the first major system to adopt GPS time as their 
reference 
(rather than UTC). 

This worked out fine for a few decades while companies got a lot of towers 
built. People started
using those systems and they became congested. Others started streaming video 
over them
and they ran out of bandwidth. Upgrades followed. There have been a lot of 
them. Much of what
we TimeNuts buy on the surplus market comes to us as a result of older systems 
being scrapped
out. 

The latest set of upgrades does / will / is getting them into the sub 1 us 
range at the end of holdover. 
In normal operation they are spec’d at 100 ns worst case. To do that, you need 
a timing source in 
the roughly 10 ns range. No you don’t see those GPSDO’s on the surplus market. 
You will see
them someday ….

Again, they went this way a decade ago. Rolling that all back …. not at all 
easy. 

Are there other systems that have issues with sync? Of course there are. There 
also are a lot
of instances where miss-configuration ( or junk implementation) is a much 
bigger issue. Sorting 
that all out requires a deep dive into the timing of each individual system / 
implementation.  No
two systems do things quite the same way. Unless you want to deal with the 
numbers and the
implementation details, simply moaning and groaning isn’t going anywhere. 

Bob

> On Sep 8, 2018, at 3:23 AM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> You are not trying to run a cell system when checking your local oscillator
>> against LORAN. 
> 
> The eLoran committee said 50 ns.  Is that good enough for cell towers?
> 
> Too bad it isn't up so we could collect some data.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] Can eloran Backup GPS?

[Bob kb8tq]

Hi

The differential approach to eLoran involves running two local receivers. You 
look at the time of arrival on one
and use it to “calibrate" the time of arrival on the other. Put another way - 
you look at the difference between the 
two arrival times. They can both “wander” over a 250 ns range, as long as they 
stay within 50 ns of each other 
they meet the “differential spec”. 

For disciplining a local reference, you really need an absolute number. The 
fact that both are wandering over a 
pretty big range *does* matter if you are looking at a stable local source (and 
trying to make it more stable).  What
would / does work is having a very accurate standard at one of the locations 
and using the difference measure
to “distribute” that source. That gets into bandwidth. 

Since the difference information is *very* local, there really isn’t a 
practical way to distribute it on the eLoran signal.
As you pile on more correction stations, your data bandwidth goes up. There are 
a very limited number of bits
available on the eLoran signal. 

Another way to look at it: If you have a standard sitting in your basement, and 
don’t have a buddy in town with a 
better standard. Does a difference measure to his house do you any good?

Bob

> On Sep 8, 2018, at 2:58 PM, Bob Martin  wrote:
> 
> Bob,
> 
> I believe that information is transmitted with the eloran signal. Way back 
> when, I remember there was an added pulse called the LDC pulse. I had to 
> modify that pulse with each transmission based on
> an input to the transmit timing unit from the computer.
> 
> I found the following on it:
> http://www-personal.umich.edu/~tmikulsk/loran/ref/eloran_ldc.pdf
> 
> Also, the article referenced previously on The Great Britain
> system mentions that the differential corrections are sent on the LDC pulse.
> 
> To be honest, I don't know if this addresses your "gotcha".
> 
> Best,
> 
> Bob Martin
> 
> On 9/8/2018 12:38 PM, Bob kb8tq wrote:
>> Hi
>> The gotcha is the differential corrections. That’s not the way these systems 
>> are set up to work. They
>> function with no external input other than the timing signal its self. 
>> Providing bandwidth to do correction
>> signaling just isn’t part of the overall system design.  If you wanted to 
>> use bandwidth, you would go
>> with 1588. Then you have a backup and no fiddling with anything else.
>> Indeed with an area wide 1588, you can do it all without even a GPS primary. 
>> Simply agree on a
>> “something” as the master source. The man with one watch *always* knows what 
>> time it is ….
>> The 250 ns "without correction" is the number that directly compares to the 
>> ~10 ns number for GPS.
>> Stretch out the distances to “USA” sort of stuff and it does not improve 
>> things at all.
>> Bob
>>> On Sep 8, 2018, at 1:40 PM, Bob Martin  wrote:
>>> 
>>> Bob,
>>> 
>>> I agree that eloran needs to be analyzed with regard to it's
>>> usefulness for each potential application. You are also 100% correct that 
>>> timing requirements get tighter and tighter as technology advances.  In 
>>> some ways the question isn't whether eloran can
>>> match GPS but rather would it suffice in a pinch were GPS to go down?
>>> 
>>> I think the 50ns accuracy is actually "as received" not "as transmitted".
>>> 
>>> The link below is an analysis of eloran in Great Britain. The 
>>> receiver/transmitter distance was  300 miles.
>>> 
>>> http://www.ursanav.com/wp-content/uploads/On-the-Uses-of-High-Accuracy-eLoran-Time-Frequency-and-Phase-2015.pdf
>>> 
>>> I've attached a screen capture of one of the pages that compares
>>> eloran  with GPS in case anyone is interested. This is where it
>>> appears that the 50ns is received as opposed to at the transmitter.
>>> 
>>> 
>>> 
>>> Best,
>>> 
>>> Bob Martin
>>> 
>>> On 9/8/2018 9:35 AM, Bob kb8tq wrote:
>>>> Hi
>>>> I believe the 50 ns is the “as transmitted” signal from the tower. The “as 
>>>> received” signal after going
>>>> through all the various gyrations is not that good on a  ~1 second basis.
>>>> 
>>>> One of the gotchas here is that we lump “systems” into one giant bag. 
>>>> That’s not a good way
>>>> to analyze things. One system may be quite happy with 10 ms timing another 
>>>> may be happy
>>>> with 10 us and yet another may die completely at 1 us and only run right 
>>>> at 100 ns. All of that
>>>> is on a 2 second basis for CDMA 

Re: [time-nuts] Can eloran Backup GPS?

[Bob kb8tq]

Hi

> On Sep 9, 2018, at 10:43 AM, jimlux  wrote:
> 
> On 9/8/18 4:52 PM, paul swed wrote:
>> Hello to the group I won't quote figures here but did indeed help UrsaNav
>> do testing. Hey 90 days with a HP 5071 that was a sweet deal at the cost of
>> some power.
>> They do send corrective data in the signal from reference sites and that
>> helps propagation corrections in the receive software.
>> It was impressive and even in buildings no less. Its been a while so thats
>> why I don't want to quote figures.
>> I sort of thought all of this would have been resolved by now. But nope not
>> until the S.. hits the fan and finger pointing starts.
>> I do know the other satellite system lightspeed? is trying to become an
>> alternate.
>> Regards
>> Paul
>> WB8TSL
> 
> 
> 
> But here's the problem - if "the network" is wiped out, how do you send the 
> correction information?
> 
> I suppose you could have a low rate network (i.e. not "the internet") and for 
> the most part, the propagation corrections (whether using 60kHz, Loran, 
> Omega, or GPS) can be done with "climatology" - time of day and time of year.
> 
> BUT - if we're talking about a Carrington event or similar, a series of high 
> altitude nuclear bursts

Actually, nuclear war *is* one of the things GPS is designed to withstand …. it 
still is very much a
military system. The same thing is true of the Russian system and one would 
guess, the Chinese 
as well. 

Pretty much none of the systems that use fancy timing information are designed 
to survive a nuclear
conflict. I would suggest that’s not a really big deal. Just as with super 
crazy solar events, many of us will 
not survive it either. For those who do survive, far more basic things will be 
top priorities.  Sure glad this
is on topic for TimeNuts … 

Bob


> - the propagation is going to be totally anomalous anyway.
> 
> If we're talking about a evil-doer taking down GPS AND "the network" 
> together, but not perturbing the ionosphere, there may be other things to 
> worry about - the network carrying "time" is also carrying all those high 
> value transactions, phone calls, etc. and that's probably a bigger business 
> disruption than losing network sync.
> 
> So I think GPS actually works pretty well - it will provide good sync for any 
> non-global disaster.  Likewise, a "campus" network will be able to stay 
> synchronized, because they've got wired connections.
> 
> In a local disaster (hurricane, earthquake) it's likely that business has 
> been disrupted by the disaster sufficiently that time sync is less important.
> 
> 
> 
> 
> 
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Re: [time-nuts] Can eloran Backup GPS?

[Bob kb8tq]

Hi

Back in the day, Loran was monitored and corrections were published. If you
really were “time nutty” about using Loran, you got the correction tables (in 
the
mail)  and post processed them into your measurements. 

Bob

> On Sep 9, 2018, at 11:34 AM, paul swed  wrote:
> 
> The correction stream is transmitted in the eLORAN signal and does require
> some form of reference site to transmitter connection. Just like GPS and
> lightspeed use RF to send corrections to the satellites.
> Loran C also did the same adjustments from a control site.
> But I am hearing nothing about eLORAN these days. It does not show up very
> often anymore in some of the navigation publications.
> Regards
> Paul
> WB8TSL
> 
> On Sun, Sep 9, 2018 at 11:20 AM, Poul-Henning Kamp 
> wrote:
> 
>> 
>> In message <3d2ae1be-927a-574a-e7f0-c7d2d289d...@earthlink.net>, jimlux
>> writes:
>>> On 9/8/18 4:52 PM, paul swed wrote:
>> 
>>> I suppose you could have a low rate network (i.e. not "the internet")
>>> and for the most part, the propagation corrections (whether using 60kHz,
>>> Loran, Omega, or GPS) can be done with "climatology" - time of day and
>>> time of year.
>> 
>> Transmitting real-time corrections is not the problem, coming up
>> with them in the first place is.
>> 
>> One of the reasons eLoran failed to go anywhere in europe is that
>> tests showed that modern container freighters are big enough to
>> 'relevantly disturb Loran-C'.
>> 
>> Nobody has a clue how you could possibly measure the necessary
>> real-time corrections for narrow and heavily trafficked straits
>> like as The English Channel, The Great Belt etc.
>> 
>> For big/expensive boats, INS/IMU is the goto-solution, at around
>> $20-50k a piece, depending on specs.
>> 
>> In difference from anything relying on radio signals from people
>> you can maybe trust some of the time, INS/IMU is entirely on-board,
>> which can lower your insurance premiums if you sail certain parts
>> of the world.
>> 
>> --
>> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>> p...@freebsd.org | TCP/IP since RFC 956
>> FreeBSD committer   | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
>> 
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Re: [time-nuts] Lost GPS lock or 1PPS recently?

[Bob kb8tq]

Hi

Well, we *do* have experience with that. It was called selective availability. 
Indeed it might get turned back on again. It’s impact on a properly designed 
GPSDO - not much. It takes a bit longer to get to best stability. System time 
wise, it still works “good enough”. 

A four hour long test format also does basically nothing to a GPSDO based 
system. You didn’t read anything in the papers about all cell service in three 
states going away. The devices did what they are supposed to do and everything 
did it’s boringly normal thing ….. it worked fine. 

I still don’t quite understand just what people think could replace satellite 
based timing in these systems. None of the “radio based” systems are within a 
factor many thousands to a few million of being adequate. 

=

Now, if this is headed off into a “the government is coming to break down the 
doors and take away all my toys sort of thing. That’s very much *not* a Time 
Nuts topic.

Bob

> On Sep 6, 2018, at 11:34 AM, Scott McGrath  wrote:
> 
> And there is the other significant vulnerability since GPS is a MILITARY 
> system the DoD can take it offline for any reason at any time.  
> 
> Leaving civilian users with nothing, 
> 
>  If its a national security threat its likely the other GNSS systems will be 
> unavailable as well.
> 
> 
> 
> 
> 
> On Sep 6, 2018, at 9:53 AM, John Sloan  wrote:
> 
> 
> Folks:
> 
> Well blow me down. It took some Google Maps fu on the web on my part, but
> my time and place does indeed coincide with this “GPS Interference Testing” at
> White Sands Missile Range. I just happened to be in my home office watching
> several of my GPS-disciplined NTP servers when this occurred. Thanks, Graham!
> 
> :John
> 
>> ZDV   DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV
>> GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A
>> 359NM RADIUS CENTERED AT 45N1063840W (TCS054036) FL400-UNL, 311NM
>> RADIUS AT FL250, 215NM RADIUS AT 1FT, 223NM RADIUS AT 4000FT AGL, 169NM
>> RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230
> 
> --
> J. L. SloanDigital Aggregates Corp.
> +1 303 940 9064 (O)3440 Youngfield St. #209
> +1 303 489 5178 (M)Wheat Ridge CO 80033 USA
> jsl...@diag.comhttp://www.diag.com 
> 
> 
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Re: [time-nuts] Lost GPS lock or 1PPS recently?

[Bob kb8tq]

Hi

No, eLoran *never* on it’s best day could ever deliver the kind of timing that 
the vast majority
of these systems require. It simply is not and can not do the job. The world 
has moved *way*
past the sort of timing it can actually deliver. 

Bob

> On Sep 6, 2018, at 6:35 PM, Scott McGrath  wrote:
> 
> Actually we DID have a radio based system that provided sufficient accuracy 
> it was called eLORAN but it was killed by US politicians because they did not 
> want a much more inexpensive to operate system ‘competing’ with GPS.
> Shutting down LORAN saved 32m dollars annually the NAVSTAR GPS program costs 
> billions annually.
> 
> Ironically while LORAN’s absolute accuracy is less than GPS,  repeatability 
> was much better so fishermen liked LORAN better.
> 
> Once again the empty suits won and the navigation and timing community lost.
> 
> Wrt cellsites staying operational i imagine the oscillators in holdover would 
> probably remain sufficiently synchronized for a month or so.
> 
> 
> 
> On Sep 6, 2018, at 4:56 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> Well, we *do* have experience with that. It was called selective 
> availability. Indeed it might get turned back on again. It’s impact on a 
> properly designed GPSDO - not much. It takes a bit longer to get to best 
> stability. System time wise, it still works “good enough”. 
> 
> A four hour long test format also does basically nothing to a GPSDO based 
> system. You didn’t read anything in the papers about all cell service in 
> three states going away. The devices did what they are supposed to do and 
> everything did it’s boringly normal thing ….. it worked fine. 
> 
> I still don’t quite understand just what people think could replace satellite 
> based timing in these systems. None of the “radio based” systems are within a 
> factor many thousands to a few million of being adequate. 
> 
> =
> 
> Now, if this is headed off into a “the government is coming to break down the 
> doors and take away all my toys sort of thing. That’s very much *not* a Time 
> Nuts topic.
> 
> Bob
> 
>> On Sep 6, 2018, at 11:34 AM, Scott McGrath  wrote:
>> 
>> And there is the other significant vulnerability since GPS is a MILITARY 
>> system the DoD can take it offline for any reason at any time.  
>> 
>> Leaving civilian users with nothing, 
>> 
>> If its a national security threat its likely the other GNSS systems will be 
>> unavailable as well.
>> 
>> 
>> 
>> 
>> 
>> On Sep 6, 2018, at 9:53 AM, John Sloan  wrote:
>> 
>> 
>> Folks:
>> 
>> Well blow me down. It took some Google Maps fu on the web on my part, but
>> my time and place does indeed coincide with this “GPS Interference Testing” 
>> at
>> White Sands Missile Range. I just happened to be in my home office watching
>> several of my GPS-disciplined NTP servers when this occurred. Thanks, Graham!
>> 
>> :John
>> 
>>> ZDV   DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV
>>> GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A
>>> 359NM RADIUS CENTERED AT 45N1063840W (TCS054036) FL400-UNL, 311NM
>>> RADIUS AT FL250, 215NM RADIUS AT 1FT, 223NM RADIUS AT 4000FT AGL, 169NM
>>> RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230
>> 
>> --
>> J. L. SloanDigital Aggregates Corp.
>> +1 303 940 9064 (O)3440 Youngfield St. #209
>> +1 303 489 5178 (M)Wheat Ridge CO 80033 USA
>> jsl...@diag.comhttp://www.diag.com <http://www.diag.com/>
>> 
>> 
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Re: [time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

Hi

Even when dividing from 48 MHz straight to 60 KHz, the uBlox is going to do
a pulse drop / pulse add to keep things on frequency. For a wall clock that 
probably 
is not an issue. For a phase locking receiver it’s not quite as clear. The 60 
KHz
edge is going to hop by about 21 ns every so often. If the TCXO is running at 
~0.1 ppm 
high or low, it’ll do it around 5 times a second. If the newer parts run both 
edges or
a higher counter drive frequency, you would get more steps per second, but 
smaller
steps.

Bob

> On Aug 29, 2018, at 3:42 PM, Mark Sims  wrote:
> 
> The Ublox 7 has two programmable "timepulse" outputs.  The default freqs are 
> (I think) 1 PPS and 10 MHz.I don't remember if the Ublox 6 has one or two 
> outputs...  also some of the earlier Ublox receivers have limits on the range 
> you can set the output(s) to (like 1 kHz).   Lady Heather can program the 
> outputs (start up with /rxu to force Ublox binary mode).  The pulse output 
> control commands are in the "P" menu.
> 
> You may have to bodge a wire onto the Ublox module to get access to 
> timepulse2 on those cheap Ublox7 boards.  I bought a couple that brought TP2 
> out to a pad.
> 
> --
> 
>> Mark I looked at the 7 and the pulse out wasn't obvious
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

Actually it’s pretty simple to track down that sort of jammer ….. and yes, the 
gear to do it 
is out there in quantity. 

Bob

> On Aug 30, 2018, at 6:51 PM, Scott McGrath  wrote:
> 
> As Brooke notes while low frequency jammers are possible, practicality is 
> another matter,   All it takes to jam a city scale area is a box the size of 
> a pack of cigarettes.Because the GPS signal is very, very weak.
> 
> As an intentional denial put a couple hundred on stray animals.Now track 
> those jammers down.
> 
> I doubt if any agency owns enough DF equipment to find them all in a 
> reasonable amount of time.
> 
> Thats why we need backup systems and each backup system will have less and 
> less accuracy as it increases in robustness.   The HF systems could provide 
> adequate syncing for the Market example.
> 
> 
> 
> On Aug 30, 2018, at 6:18 PM, Poul-Henning Kamp  wrote:
> 
> 
> In message <96e995c4-5ca2-af02-9738-0a6d87a9f...@pacific.net>, Brooke Clarke 
> writes:
> 
>> But it's extremely hard to make a jammer for WWVB (60 kHz) [...]
> 
> You can do it city-scale with a 18-wheeler sized loop-antenna
> and a good size diesel-generator.
> 
> However pedestrians will very likely note metalic items vibrating
> as they pass the "mystery white truck".
> 
> Sweden were much more serious about it:
> 
>   http://www.antus.org/RT02.html
> 
> Tl;drs:
> 
> They erected 9 200m tall Loran-C class antennas each driven by
> a Loran-C transmitter with an advanced degree which could jam
> Loran-C or Chayka.
> 
> They even mounted decoy parabolas on the towers them to hide their
> true purpose.
> 
> The fact that all the transmitters were on the east coast does drop
> a hint that swedens much touted neutrality had a bit of a slant.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

….. ok, so you are dealing with city wide jammers that take out all of New York 
City on a daily basis? 
Again, that was the original example tossed out. “A cigarette pack sized jammer 
that takes out an entire
city”.  A jammer with that sort of range is an easy jammer to spot. 

Somehow I find that a bit difficult to believe. What I’ve seen and gone after 
are *far* shorter range than 
that magic device.  A short rang mobile jammer aimed at an ankle bracelet takes 
out an infrastructure  device 
for minutes. That’s why those devices have holdover capabilities. 

Indeed at the point they *do* start interfering with major systems over a wide 
range…. bigger gear gets brought in. 
Jamming that actually takes utility systems down is very rare. No cell phone 
service anywhere in New York is 
something that gets noticed pretty fast. It also fires up meetings that last 
quite literally for years …..

Bob

> On Aug 30, 2018, at 8:43 PM, Scott McGrath  wrote:
> 
> Just ask the NY Port authority how ‘easy’ knocking these jammers offline is.  
>  Usually done by vehicle to vehicle inspection with a SA.
> 
> And yes the day job all too frequently searching for and identifying 
> interference sources.
> 
> One of the more interesting ones was a halogen leak detector wiping out WiFi 
> at a manufacturing plant.   So my opinions on interference location are 
> informed by leading teams of people doing just that.
> 
> Content by Scott
> Typos by Siri
> 
> On Aug 30, 2018, at 8:24 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> Since timing receivers are actually going to prefer high angle sats, an 
> antenna that rejects 
> close to the horizon is a pretty common thing. Enhancing that sort of 
> rejection doesn’t take 
> a lot of effort. 
> 
> Bob
> 
>> On Aug 30, 2018, at 7:05 PM, Gregory Maxwell  wrote:
>> 
>> On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:
>>> I would disagree in that ease of jamming/spoofing is strongly related to 
>>> wavelength.  That's because antenna efficiency
>>> goes down as the size of the antenna gets smaller than 1/4 wave.
>>> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 
>>> wavelength is a few inches, something that  you can
>>> hold in your hand.
>> 
>> However, the short wavelengths of GPS make beam forming a reasonable
>> countermeasure against jamming.
>> 
>> By having a small array of GPS antennas a receiver can digitally form
>> beams that both aim directly at the relevant satellites (so even
>> reducing intersatellite interference) while also steering a deep null
>> in the direction of the jammer.  If the jammer is powerful enough to
>> overload the front-end then this won't help, but against a
>> non-targeted area denying jammer it should be fairly effective.
>> 
>> There are many papers on GNSS beamforming. ( e.g.
>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )
>> 
>> This kind of anti-jamming solution should even be pretty inexpensive
>> -- really no more than the cost of N receivers. Except that it is
>> specialized technology and thus very expensive. :)
>> 
>> Seeing some open source software implementing beam-forming was one of
>> the things I hoped to see result from the open hardware multi-band
>> GNSS receivers like the GNSS firehose project (
>> http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
>> you're going through the trouble of running three coherent receivers
>> for three bands, stacking three more of them and locking them to the
>> same clock doesn't seem like a big engineering challenge... and the
>> rest is just DSP work.
>> 
>> Even absent fancy beam forming, for GNSS timing with a surveyed
>> position except at high latitudes it should be possible to use a
>> relatively high gain antenna pointed straight up and by doing so blind
>> yourself to terrestrial jammers at a cost of fewer SVs being
>> available. But I've never tried it.
>> 
>> In an urban area I noticed my own GPSDOs losing signal multiple times
>> per week. Monitoring with an SDR showed what appeared to be jammers.
>> 
>> As others have noted intermittent jamming is pretty benign to a GPSDO.
>> Spoofing, OTOH, can trivially mess up the timing.  It's my view that
>> if you need timing for a security critical purpose there isn't really
>> any GNSS based solution commercially available to the general public
>> right now, the best bet is a local atomic reference with a GPSDO used
>> to monitor and initially set it.
>> 
>> ___

Re: [time-nuts] NIST

[Bob kb8tq]

Hi

Since timing receivers are actually going to prefer high angle sats, an antenna 
that rejects 
close to the horizon is a pretty common thing. Enhancing that sort of rejection 
doesn’t take 
a lot of effort. 

Bob

> On Aug 30, 2018, at 7:05 PM, Gregory Maxwell  wrote:
> 
> On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:
>> I would disagree in that ease of jamming/spoofing is strongly related to 
>> wavelength.  That's because antenna efficiency
>> goes down as the size of the antenna gets smaller than 1/4 wave.
>> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 
>> wavelength is a few inches, something that  you can
>> hold in your hand.
> 
> However, the short wavelengths of GPS make beam forming a reasonable
> countermeasure against jamming.
> 
> By having a small array of GPS antennas a receiver can digitally form
> beams that both aim directly at the relevant satellites (so even
> reducing intersatellite interference) while also steering a deep null
> in the direction of the jammer.  If the jammer is powerful enough to
> overload the front-end then this won't help, but against a
> non-targeted area denying jammer it should be fairly effective.
> 
> There are many papers on GNSS beamforming. ( e.g.
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )
> 
> This kind of anti-jamming solution should even be pretty inexpensive
> -- really no more than the cost of N receivers. Except that it is
> specialized technology and thus very expensive. :)
> 
> Seeing some open source software implementing beam-forming was one of
> the things I hoped to see result from the open hardware multi-band
> GNSS receivers like the GNSS firehose project (
> http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
> you're going through the trouble of running three coherent receivers
> for three bands, stacking three more of them and locking them to the
> same clock doesn't seem like a big engineering challenge... and the
> rest is just DSP work.
> 
> Even absent fancy beam forming, for GNSS timing with a surveyed
> position except at high latitudes it should be possible to use a
> relatively high gain antenna pointed straight up and by doing so blind
> yourself to terrestrial jammers at a cost of fewer SVs being
> available. But I've never tried it.
> 
> In an urban area I noticed my own GPSDOs losing signal multiple times
> per week. Monitoring with an SDR showed what appeared to be jammers.
> 
> As others have noted intermittent jamming is pretty benign to a GPSDO.
> Spoofing, OTOH, can trivially mess up the timing.  It's my view that
> if you need timing for a security critical purpose there isn't really
> any GNSS based solution commercially available to the general public
> right now, the best bet is a local atomic reference with a GPSDO used
> to monitor and initially set it.
> 
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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

The original “we cracked GPS” paper back in the 1980’s (that unlimitedly lead 
to the end of SA) 
used a medium sized dish ( think of the good old C-band antennas) to pick out a 
single sat.

Bob

> On Aug 30, 2018, at 9:54 PM, Brooke Clarke  wrote:
> 
> Hi Gregory:
> 
> I wonder if anyone has tried using a small parabolic dish, like used for Free 
> To Air satellite TV and aimed it at a GPS satellite track or at a WAAS 
> geostationary satellite using a feed antenna with reverse polarization from a 
> normal GPS antenna?
> http://www.prc68.com/I/FTA.shtml
> 
> -- 
> Have Fun,
> 
> Brooke Clarke
> https://www.PRC68.com
> https://www.end2partygovernment.com/2012Issues.html
> axioms:
> 1. The extent to which you can fix or improve something will be limited by 
> how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
> 
>  Original Message 
>> On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:
>>> I would disagree in that ease of jamming/spoofing is strongly related to 
>>> wavelength.  That's because antenna efficiency
>>> goes down as the size of the antenna gets smaller than 1/4 wave.
>>> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 
>>> wavelength is a few inches, something that  you can
>>> hold in your hand.
>> However, the short wavelengths of GPS make beam forming a reasonable
>> countermeasure against jamming.
>> 
>> By having a small array of GPS antennas a receiver can digitally form
>> beams that both aim directly at the relevant satellites (so even
>> reducing intersatellite interference) while also steering a deep null
>> in the direction of the jammer.  If the jammer is powerful enough to
>> overload the front-end then this won't help, but against a
>> non-targeted area denying jammer it should be fairly effective.
>> 
>> There are many papers on GNSS beamforming. ( e.g.
>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )
>> 
>> This kind of anti-jamming solution should even be pretty inexpensive
>> -- really no more than the cost of N receivers. Except that it is
>> specialized technology and thus very expensive. :)
>> 
>> Seeing some open source software implementing beam-forming was one of
>> the things I hoped to see result from the open hardware multi-band
>> GNSS receivers like the GNSS firehose project (
>> http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
>> you're going through the trouble of running three coherent receivers
>> for three bands, stacking three more of them and locking them to the
>> same clock doesn't seem like a big engineering challenge... and the
>> rest is just DSP work.
>> 
>> Even absent fancy beam forming, for GNSS timing with a surveyed
>> position except at high latitudes it should be possible to use a
>> relatively high gain antenna pointed straight up and by doing so blind
>> yourself to terrestrial jammers at a cost of fewer SVs being
>> available. But I've never tried it.
>> 
>> In an urban area I noticed my own GPSDOs losing signal multiple times
>> per week. Monitoring with an SDR showed what appeared to be jammers.
>> 
>> As others have noted intermittent jamming is pretty benign to a GPSDO.
>> Spoofing, OTOH, can trivially mess up the timing.  It's my view that
>> if you need timing for a security critical purpose there isn't really
>> any GNSS based solution commercially available to the general public
>> right now, the best bet is a local atomic reference with a GPSDO used
>> to monitor and initially set it.
>> 
>> ___
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>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>> 
> 
> 
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Re: [time-nuts] WWVB Signal Generator

[Bob kb8tq]

Hi

If somebody really wanted to go crazy on this, a link just popped up in my 
inbox:

https://www.st.com/content/st_com/en/about/events/events.html/teseo-liv3f-gnss-module-webinar.html?ecmp=tt7108_us_enews_apr2018=stmDM10269=166175037=tEVjzOAFGOno6x6Htwrh8A==
 
<https://www.st.com/content/st_com/en/about/events/events.html/teseo-liv3f-gnss-module-webinar.html?ecmp=tt7108_us_enews_apr2018=stmDM10269=166175037=tEVjzOAFGOno6x6Htwrh8A==>

I know zip about the ST chips other than what’s in the link. The webinar is 
free and at least
that’s better than signing an NDA simply to look at the slides ( which some 
other vendors seem
to want you to do). 

Bob

> On Aug 29, 2018, at 4:55 AM, Dana Whitlow  wrote:
> 
> I hope that those of you who write code to generate the WWVB signals in real
> time from a GPS receiver's output will publish well documented source
> listings.
> 
> I for one want to learn how one does this kind of thing in 'C', both for
> general
> interest and for this specific application.
> 
> Thanks,
> 
> Dana
> 
> 
> 
> On Wed, Aug 29, 2018 at 3:36 AM Wayne Holder  wrote:
> 
>> As a follow up, I now have a simple WWVB simulator written in C that's now
>> running an an ATTiny85 using nothing more than the internal, 8
>> mHz oscillator and about a 6 inch length of wire connected to one of the
>> pins as an antenna.  It generates an approximate 60 kHz signal using PWM on
>> timer 1.  I tweaked the timer value a bit to correct for some variance in
>> the internal oscillator, but I' not even sure that was necessary, as my
>> target is just a  BALDR Model B0114ST, consumer grade "Atomic" clock.
>> Modulation is done by varying the duty cycle of the PWM to approximate the
>> -17 dBr drop on the carrier.  But, again, I don't think this value is
>> critical with a consumer clock chip.  I tapped the demodulated output
>> inside the clock and displayed it on my scope along with the generated
>> signal and I got good, steady demodulation with the wire antenna just
>> placed near clock.  The next step is to connect up a GPS module and add
>> code to use it to set the time.  I'm also going to change the code to use
>> the PPS signal from the GPS to drive the output timing rather than the test
>> code I have now that uses timer 0 to generate the PPS interrupt.  I'm happy
>> to share details if anyone is interested.
>> 
>> Wayne
>> 
>> 
>> 
>> On Sun, Aug 26, 2018 at 2:51 PM, paul swed  wrote:
>> 
>>> That would be a great neighbor to have but I can tell you around here its
>>> the phone. Not to concerned about someone putting up a wwvb replacement.
>>> And I can always up the power. Chickle.
>>> Regards
>>> Paul
>>> 
>>> On Sun, Aug 26, 2018 at 2:34 PM, Bob kb8tq  wrote:
>>> 
>>>> Hi
>>>> 
>>>> The gotcha is if you have neighbors two or three doors away that *also*
>>>> put up one of
>>>> these devices. You then have a real problem with the neighbor(s) in the
>>>> middle. The
>>>> wavelength is long enough that Raleigh issues won’t get you. You still
>>>> have the two
>>>> signals ( at slightly different frequencies) beating against each
>> other.
>>>> The result is
>>>> going to show up as who knows what to this or that receiver. With a
>>>> precision receiver,
>>>> you might even have issues from the guy two houses away …...
>>>> 
>>>> Bob
>>>> 
>>>>> On Aug 26, 2018, at 1:08 PM, paul swed  wrote:
>>>>> 
>>>>> Agree with the conversation. With respect to neighbors when the day
>>> comes
>>>>> they may ask you to boost your signal. :-)
>>>>> Granted maybe the day won't come but at least having your local
>> clocks
>>>> work
>>>>> is nice.
>>>>> Regards
>>>>> Paul
>>>>> WB8TSL
>>>>> 
>>>>> On Sat, Aug 25, 2018 at 10:29 PM, Dana Whitlow <
>> k8yumdoo...@gmail.com>
>>>>> wrote:
>>>>> 
>>>>>> With the watch being physically close to the faux WWVB
>> "transmitter",
>>>> one
>>>>>> is in
>>>>>> the so-called "near field" regime, where the field strength (V/m)
>>> falls
>>>> as
>>>>>> the inverse
>>>>>> cube of the distance.  If one is putting the watch, say, within a
>> few
>>>>>> inches of the
>>>>>> transmitter, reliabl

Re: [time-nuts] IQRB-1 RBXO

[Bob kb8tq]

Hi

That basic design (though maybe not this exact part) has been kicking around 
for at least the last ten 
years. Various people have popped up reselling it. There are a lot of older 
Rb’s that are in the <2x10^-11
range at 1 second:

http://www.ke5fx.com/rb.htm 

The gotcha with the part seems to have been that it’s “big and power hungry” 
for the people who are looking 
at the CSAC and it’s “expensive and not so stable” for the people who are 
playing with the LPRO-101 or FE-5680
style parts. 

Bob

> On Aug 29, 2018, at 12:35 PM, Nick Sayer via time-nuts 
>  wrote:
> 
> Got an e-mail from DigiKey this morning talking about this:
> 
> https://www.iqdfrequencyproducts.com/products/pn/LFRBXO059244Bulk.pdf
> 
> Unlike the other rubidium modules I’ve dealt with (which is to say, all FEI), 
> this one claims to have under 1E-10 stability at tau 1s (specifically, if I’m 
> doing the math right, it looks like they’re claiming 8E-11). The phase noise 
> looks to me to be… not fantastic (-67dBc/Hz @ 1 Hz) - again, unless I’m 
> misreading the spec. They’re also $1874 each (Q:1). But they are 4 cubic 
> inches(ish).
> 
> I’m not seriously thinking of anything that expensive, but I thought I’d 
> throw it out there and see what other folks think (or perhaps it’s already 
> been discussed and I’ve missed it. If so, sorry).
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Re: [time-nuts] OOPS on my wwv legal post

[Bob kb8tq]

Hi

The whole issue of who is what goes back to some very obscure laws / rules 
passed 
quite a long time ago. It’s been a matter of debate (usually with beer 
involved) for quite
a while. 

Bob

> On Aug 29, 2018, at 9:24 PM, Steve Allen  wrote:
> 
> On Wed 2018-08-29T19:49:59-0400 Bob kb8tq hath writ:
>> A few more details about “traceability”. USNO is by statute the official 
>> source of time for the US.
> 
> I suggest reading Matsakis, Levine, and Lombardi from this year's PTTI 
> meeting.
> USNO and NIST are both legal sources for the US.
> The USNO site currently has a broken SSL cert, but the paper is also here
> https://www.researchgate.net/publication/323600621_Metrological_and_legal_traceability_of_time_signals
> 
> --
> Steve Allen  WGS-84 (GPS)
> UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
> 1156 High Street   Voice: +1 831 459 3046 Lng -122.06015
> Santa Cruz, CA 95064   http://www.ucolick.org/~sla/   Hgt +250 m
> 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

The same sort of massive solar flare that fiddles with sat systems also makes a 
mess of HF and VLF
systems. You have a high level of correlation in the impact. That makes them a 
poor “backup” in this case.

Bob

> On Aug 29, 2018, at 7:52 PM, Scott McGrath  wrote:
> 
> Excellent point on LEGAL time,  The problem is as always is GPS is the new 
> shiny object.
> 
> You mentioned earth based hostile actors.   But a really large solar flare or 
> CME has the potential to take out or severely degrade ALL the GNSS systems.  
> 
> Something on the order of the ‘Carrington Event’ or the flare in 1989 which 
> took out power to much of Canada.   
> 
> Things like this are why we need terrestrial time distribution systems like 
> eLORAN which by its nature is resistant to both man made and natural 
> interference.
> 
> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Yo Dudes! 
> WWV and all its variations distribute what in the USA is the legal standard 
> of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be 
> able to have traceability to WWV.
> 
> If one was to rely on other sources, one has no guarantee that it 1. It is as 
> accurate as claimed and 2. It can't be *diddled* with accidentally or 
> deliberately.
> Although GPSDO's are very good and popular, they come from satellites that 
> are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own 
> physical territory then they stand or fail on their own. 
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors 
> of the bomb (I don't remember who) went to see US president Harry Truman and 
> essentially told him that the scientists who developed the bomb should have a 
> say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid 
> that was responsible for his schedule to "never in hell let that (or any 
> other) scientist  come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, 
> IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the 
> Russian federation tell the world quote: See, the USA can't be trusted for 
> something as important and simple as frequency and time.  However we are your 
> friends who you can trust. Unquote.
> Regards,
> 
> 
> 
> 
> 
> This is a case of practical use of WWV albeit over 50 years a go the 
> fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver 
> site.  Our base had to purposes.  to   
> 
> 
> 
> 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

One of the basic disconnects here seems to be the idea that radio was the “best 
thing” before
GPS came along. In fact that’s not really how it worked. Time was traced / 
coordinated by hauling
atomic clocks on airplanes as the “best thing” before satellite systems came 
along….That was true 
for decades...

Bob

> On Aug 29, 2018, at 7:54 PM, Scott McGrath  wrote:
> 
> A DIY radio distribution system is not secure and traceable to NIST/USNO even 
> if the source is GPS.
> 
> 
> 
> On Aug 29, 2018, at 7:52 PM, Scott McGrath  wrote:
> 
> Excellent point on LEGAL time,  The problem is as always is GPS is the new 
> shiny object.
> 
> You mentioned earth based hostile actors.   But a really large solar flare or 
> CME has the potential to take out or severely degrade ALL the GNSS systems.  
> 
> Something on the order of the ‘Carrington Event’ or the flare in 1989 which 
> took out power to much of Canada.   
> 
> Things like this are why we need terrestrial time distribution systems like 
> eLORAN which by its nature is resistant to both man made and natural 
> interference.
> 
> On Aug 29, 2018, at 7:33 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Yo Dudes! 
> WWV and all its variations distribute what in the USA is the legal standard 
> of time (from USNO) and frequency (NIST).
> If one is running a freq cal service IIRC it is a legal requirement to be 
> able to have traceability to WWV.
> 
> If one was to rely on other sources, one has no guarantee that it 1. It is as 
> accurate as claimed and 2. It can't be *diddled* with accidentally or 
> deliberately.
> Although GPSDO's are very good and popular, they come from satellites that 
> are vulnerable to damage from earth based resources.
> When your time and frequency standard(s) is under control on your own 
> physical territory then they stand or fail on their own. 
> After the atom bombing of Hiroshima and Nagasaki, one of the major inventors 
> of the bomb (I don't remember who) went to see US president Harry Truman and 
> essentially told him that the scientists who developed the bomb should have a 
> say of how or when it should be used.
> Truman is reported to have said for him to leave his office and told an aid 
> that was responsible for his schedule to "never in hell let that (or any 
> other) scientist  come to his office to influence American defense policy."
> Considering its status from both a scientific and political perspective, 
> IMNSHO it will go on as before.
> To explain the political. No government official wants to see China or the 
> Russian federation tell the world quote: See, the USA can't be trusted for 
> something as important and simple as frequency and time.  However we are your 
> friends who you can trust. Unquote.
> Regards,
> 
> 
> 
> 
> 
> This is a case of practical use of WWV albeit over 50 years a go the 
> fundamentals are still valid today.
> At Karamursel Air station TUSLOG 234 I was assigned to the base receiver 
> site.  Our base had to purposes.  to   
> 
> 
> 
> 
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Re: [time-nuts] Lost GPS lock or 1PPS recently?

[Bob kb8tq]

Hi

This is Time Nuts, not end of the world nuts …..

I most certainly did *not* design these systems. The *do* have timing 
requirements. If those requirements 
are not met, they stop working. That’s just the way it goes. Designing these 
systems at the timing level was
done a decade ago. You can object to what they did, it’s about ten years to 
late to change anything. Tight timing
gives then more capacity … tough to argue with even if you weren’t to late. 

If *you* believe there is an alternative system now in existence that will 
supply the timing these systems require … 
that *is* a Time Nuts topic. So, let’s hear about the numbers on the system you 
believe will supply what’s needed.
I think we’ve all heard plenty of “the world is ending” stuff. 

Bob

> On Sep 7, 2018, at 7:01 PM, Scott McGrath  wrote:
> 
> You are SO convinced that GPS will ALWAYS be there,   I’m NOT (Think 
> Carrington Event) and i’ve been part of a few disaster exercises where both 
> Internet and GPS were considered ‘down’ for the exercise and these exercises 
> are done in conjunction with the military so PPS was also ‘off the table’.
> 
> It was quite an eye opener to see how many networks could not keep time 
> synchronized within 5 minutes much less 5 seconds because of the cheap XO’s 
> used in servers and workstations(NTP will ALWAYS BE AVAILABLE).  Just like 
> the old Sun workstations.
> 
> It was also fun watching the multimillion dollar Harris radios drift once 
> they no longer had a 10 Mhz input from a GPSDO.   One would think the local 
> timebase would be a bit better than it was.  
> 
> The older ‘Pacer Bounce’ and Falcon series radios did much better because 
> they had good local timebases and made no assumptions of the availability of 
> a external timebase.  Whereas the new radios depend upon it.
> 
> These exercises are intended to practice restoring government communications 
> after a large scale natural disaster.And without readily available 
> precision time it aint easy.
> 
> Its also fun watching executives realizing that their phone during the 
> exercise is a paperweight useful only in weighting down stacks of Form 213’s
> 
> Its not for nothing that Symmetricom is building more 5071’s than HP/Agilent 
> ever did.
> 
> On Sep 7, 2018, at 5:18 PM, Bob kb8tq  wrote:
> 
> Hi
> 
> You are not trying to run a cell system when checking your local oscillator 
> against LORAN.
> It’s two completely different things. The timing requirements of the modern 
> systems are indeed
> way past what LORAN can deliver. We’re not talking about 1970’s state of the 
> art anymore. You
> need a time source that is in the 10 ns range to keep this stuff running. 
> Multiple microseconds of 
> error in your timing source aren’t good enough for what they have up and are 
> rolling out.  Full 
> end of holdover spec on many of them is below 2 microseconds. Normal 
> operation is under 100 ns.
> Give the cell outfits another couple years and that’s all they will have on 
> the air.
> 
> 
> Bob
> 
>> On Sep 6, 2018, at 9:08 PM, Scott McGrath  wrote:
>> 
>> 
>> As to eLORAN,  you can deny positioning but maintain timing service simply 
>> by modifying the GRI and since eLORAN is software based thats not a 
>> difficult change.
>> 
>> Navigation receivers go into fail but timing receivers only need ONE 
>> station.   As the users of SRS700’s and Austrons do when Wildwood is active.
>> 
>> With GNSS its a hell of a lot harder and without SA your only option is to 
>> turn off all the C/A signals hence denying civillian use of GNSS
>> 
>> I’m pretty sure if a non-state actor was doing weaponized drone attacks with 
>> GPS for guidance,  GPS for civilian use would be shut down in a NY minute .
>> 
>> Remember govt users would not be affected as they have access to the PPS and 
>> the ‘word of the day’ to make it active.
>> 
>> You dont need conspiracies to think of conditions where GPS would be shut 
>> down for long periods of time and where reasonable people would agree with 
>> the shutdown.
>> 
>> On Sep 6, 2018, at 8:44 PM, Scott McGrath  wrote:
>> 
>> Gee,  thats strange especially for those of us who ran the Austron 
>> comparitors to check our local standards against the LORSTA’s
>> 
>> 
>> 
>> On Sep 6, 2018, at 8:04 PM, Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> No, eLoran *never* on it’s best day could ever deliver the kind of timing 
>> that the vast majority
>> of these systems require. It simply is not and can not do the job. The world 
>> has moved *way*
>> past the sort of timing it can actually deliver. 
>> 
>> Bob
>&

Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

> On Sep 2, 2018, at 7:17 AM, Magnus Danielson  
> wrote:
> 
> Hi Gerhard,
> 
> I see that this became a separate thread.
> 
> On 09/02/2018 01:38 AM, Gerhard Hoffmann wrote:
>> 
>> 
>> Am 01.09.2018 um 20:40 schrieb Magnus Danielson:
>>> One should first know that there is a lot of papers now on frequency
>>> transfer over fiber. The stability achieved on the best ones so far
>>> greatly below that of the optical clocks that they want to compare.
>> 
>> Please, in a nutshell: what are the worst offenders:
>> 
>> - tranceivers (mechanical, temp, other misfeatures)
>> - cables ( bending, temp, mechanical stress)
>> - others?
>> 
>> In the case of transceivers: are there desirable modifications
>> that would alleviate the problems?
> 
> Acoustical sensitivity, low frequency changes.
> 
> For optical clocks and frequency transfer, just the vibration from
> traffic and other activity causes disturbances which disturbes the group
> delay. What is done for these links is to actively compensate then using
> a return path and closing the loop with a controller, very much like a
> PLL. The length of the loop limits the bandwidth and hence how high up
> the compensation can be done, so for longer stretches, this needs to be
> repeated. They have now built links from PTB to SYRTE and NPL.
> 
> Temperature shifts are slower, but also compensated though the active loop.

I suspect there’s a longer list of “slow” environmental effects that are also 
taken 
care of with the compensation setup. One would guess that crossing a active  
fault line would be “interesting”. 

Bob

> 
> Close proximity to strong power-currents have also been shown to cause
> modulations, so separate from power-cables if you can.
> 
> Remember that the end nodes have very stable clocks, so their effects
> can be taken out of the equation. For other setups, such as telco
> operation, that's a completely different ballgame.
> 
> Cheers,
> Magnus
> 
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Re: [time-nuts] Lady Heather V6.0 and RINEX files...

[Bob kb8tq]

Hi



> On Jul 2, 2018, at 6:49 PM, Michael Baker  wrote:
> 
> Time Nutters--
> 
> Mark Sims said of the latest release of Lady Heather:
> 
>> There are several cosmetic tweaks.  
> 
> A major new feature is the ability to write RINEX files for receivers that 
> can output satellite RAW observation data.   RINEX files can be processed to 
> produce very accurate positions (typically 150-250mm for L1 only receivers,  
> 10mm for L1/L2 receivers).   The recommended online processor is CSRS-PPP 
> from Natural Resources of Canada (NARCAN)... they seem to be the only service 
> that supports L1 only data.
> 
> 
> In layman's terms, what does this mean with regard to being
> able to set an *AFFORDABLE* GPS RX out in the field and use it
> to do site surveys and process the recorded RINEX data later to
> establish the geo-position of each of the sites within a precision
> of +/- a few centimeters?  I presume this may not be a simple as
> setting up my Trimble Thunderbolt and Lady Heather V6.0 in the
> field and gathering RINEX files for a few minutes??

Even with L1/L2 survey gear, “a few centimeters” is a bit more than a 
few minutes of data. So far, 24 hour records with L1 gear have given
meter level precision. 

Bob


> 
> Mike Baker
> Micanopy, FL
> *
> 
> 
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Re: [time-nuts] Need Advice on Trimble 22020 Antenna

[Bob kb8tq]

Hi

Trimble has been making GPS for a *long* time. Your antenna dates back a ways. 
You see them for $50 to $100 if you do some careful shopping. They have about
50 db of front end gain and need 12V for power. They are pretty broadband 
compared
to a timing antenna with built in filtering. All of that makes them a challenge 
to use 
with something like a Res-T or a T-Bolt.

Bob

> On Jul 13, 2018, at 4:55 PM, Patrick Murphy  wrote:
> 
>  recently picked up a Trimble 22020 L1/L2 antenna for a pretty good
> price. It is in near perfect physical condition including the ground
> plane. I Googled around a bit for technical specifications and so far
> have found nothing very useful. Is there a source out there I am just
> missing? I did briefly connect it to my Resolution-T but did not see any
> satellites.
> 
> Any assistance would be greatly appreciated. Thanks!
> 
> -Pat (KG5YPQ)
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Re: [time-nuts] 10 MHz -> 16 MHz

[Bob kb8tq]

Hi

If (as originally specified) noise and jitter are not a big deal - there are a 
lot 
of chips out there like the ICS570. They are designed to do weird ratio 
frequency
conversions so 10 to 12 or 10 to 16 are trivial for them. The Clockblock board 
was
one way to get it all put together. 

Bob

> On Sep 30, 2018, at 12:05 PM, Gerhard Hoffmann  wrote:
> 
> 
> Am 30.09.2018 um 16:49 schrieb Attila Kinali:
> 
>> The simplest way I can think of is the following:
>> Use a 74LV8154 to divide the 10MHz down to 152.587890625Hz.
>> Use the capture timer unit of the uC to measure the phase of the
>> pulse. Use any kind of DAC (internal, external, PWM,...) to steer
>> the 16MHz VCO. Depending on how fast the timer unit runs, this
>> will give you something in the order of 10-200ns dead-band.
>> By choosing the right frequency for the timer unit, one can
>> get it to "dither" a bit and then use averaging.
>> 
>> For lower jitter, use one half of a Nutt interpolator
>> to get the timing difference between the 152Hz signal
>> and the 16MHz (ie similar to what the SRS FS740 does).
>> Use something akin Nick Sayer's time-to-amplitude converter
>> for the fine measurement.
>> 
>> Same works equally well for 12MHz.
>> 
>> 
> 
> Wow. That's truly a Rube Goldberg design.
> 
> There is a simpler way.  IDT ICS570. Digikey 800-1073-5-ND
> 
> Solder time less than 10 minutes.
> I had the 3V3-Version in the parts drawers, officially it takes the 5V
> version to generate the 160 MHz, but the 3V3 version happened to work, too.
> The difference between 120 and 160 MHz is just a GND wire on pin 6 (vs. open)
> 
> Divide by 10 is left as an exercise.
> 
> regards,
> Gerhard
> 
> (But then, some like to build and tune multiplier chains and mixers.)
> 
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Re: [time-nuts] GPSDO uncertainties

[Bob kb8tq]

Hi

The question becomes very much, what confidence level are you after? Is 99%
good enough? Are you after 99.%? Obviously the stability gets worse as 
you crank on more nines.

Next layer to the onion is - how long have things been running and under what 
conditions are they running? A few days is probably the minimum for any sort of 
reasonable performance. A month or more will indeed help a bit. A stable 
temperature
environment is also going to have a direct impact on performance. 

Things like survey position and antenna location ( number of sats viewed at all 
times)
will have a more subtle impact on frequency. Solar storms and ionospheric 
stability (sun
spot cycle) eventually get into the picture if you put in enough nines. 

So simple answer: better than 2x10^-9 with any practical number of nines 
involved. Better
than 2x10^-10 with rational numbers (99.9 or 99.99). Maybe 2x10^-11 at the 99% 
level, but
probably not.  

Since this is a very non-standard measure your numbers may not match my 
numbers. ADEV 
was invented primarily because this sort of measure has so many issues. One of 
the issues 
is that you need a *lot* of data to even begin to estimate the confidence 
levels and they are
very dependent on data set size. A typical spec tends to have weird stuff like 
“99.9% 
based on 4 out of 5 runs of 100 hours”.  Statements like that tend to make a 
statistics guy
groan ….(or throw something at you).

Bob

> On Oct 7, 2018, at 9:59 PM, donald collie  wrote:
> 
> I have a GPSDO which has a Trimble receiver, and Trimble OCXO inside.[I
> think it runs Lady Heather] What I would like to know is what uncertainty
> the 10MHz output will be with a 10 second count.This presumes that the
> GPSDO is receiving satellite signals, and the OCXO is being suitably
> diciplined. Should I expect 1 part in 10E12?, 1 part in 10E10?. This device
> gives superior performance to an OCXO barefoot - but how much better? Would
> somebody in the group who knows the answer, please wax elequently.
> Thankyou,.Donald
> B. COLLIE
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Re: [time-nuts] RF isolation amplifier question

[Bob kb8tq]

Hi

What you have there is known as a cascade buffer amplifier. The common base
stage combined with the common emitter has some well known issues at high 
frequencies ( like UHF / microwave). That’s the tradeoff for having really good 
isolation at HF and usually at VHF. 

Put a sniffer loop near the circuit and look with a good wide range spectrum 
analyzer. 
Drive the circuit over a range of input levels. Try terminating the output with 
odd loads. 
Watch for birdies popping up and then fiddle things to kill them. 

As others have noted, those may not be the best parts to use for this. I would 
not replace
it with something simple, it should have a lot of isolation when it works 
correctly.

Bob

> On Oct 14, 2018, at 11:54 AM,   wrote:
> 
> Hi,
> 
> I removed this amp from the EFOS2 Maser as it was intermittent.
> 
> Of course now I can't get it to fail on the bench!
> 
> I have fabricated a new PC board to replace it and have the components on
> hand.
> 
> Note the 12pfd cap on the collector .
> 
> Some notes I have indicate is select at test and that is it a glass
> capacitor.
> 
> The as built unit has a johansen 50pf that looks to be an early version
> of surface mount with leads soldered on.
> 
> How do I determine what value to install on the new amplifier?
> 
> Cheers,
> 
> Corby___
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Re: [time-nuts] Question about the PLL of Trimble Thunderbold

[Bob kb8tq]

Hi

The Thunderbolt actually is not a real good solution if you want to synchronize 
to something other than GPS. It
depends on direct phase data from its internal GPS chip set to do the GPSDO 
magic. A board that has a PPS
signal between the GPS and “PLL” probably is a better way to go.

Even with a board that has a PPS internally, it’s not going to like an abrupt 
phase change between GPS and “something 
else”. It needs some customization of the firmware to handle this kind of 
transition. That makes your project more of a
“from scratch” kind of thing ….

Bob

> On Oct 24, 2018, at 5:02 PM, Ferran Valdés  wrote:
> 
> 
> Hello everyone ! I am new in here. I got referred to time-nuts by a 
> colleague, and after reading a bit, I think that is the right place for this 
> kind of questions :)
> 
> I have in mind a project which consists in synchronizing two or more stable 
> clocks (OCXO) disciplined by GPS.
> 
> However, would be great to have the option to disable the GPS on both sides 
> at a given time and to synchronize them in a Master-Slave or directly by 
> means of a protocol they could correct each other and synchronize themselves.
> 
> After some research, the Trimble Thunderbold board got my attention, as has 
> everything I need to get the project started.
> 
> Before getting a pair of the boards, on the datasheet is explained that one 
> can get the unit on a disconnected state and adjust the ADC which drives the 
> OCXO directly (that’s one of the desired capabilities !).
> 
> The question is: does anybody know if the phase difference (input of the PLL) 
> can be read, in order to know how to steer the ADC ??
> 
> Alternatively, could you please suggest another board that would fulfil the 
> following?
> 
> - GPS can be disabled.
> - has a serial com port, so commands can be sent to the unit and information 
> can be retrieved.
> - provides 1PPS and 10MHz signals.
> 
> Thank you very much for your attention,
> Ferran
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Re: [time-nuts] cable delay variation (was: Question about the PLL of Trimble Thunderbold)

[Bob kb8tq]

Hi


> On Oct 29, 2018, at 3:42 PM, Attila Kinali  wrote:
> 
> On Mon, 29 Oct 2018 12:03:25 -0700
> Hal Murray  wrote:
> 
>> If I go looking for good cables, do they specify temperature coefficient?  I 
>> don't remember ever seeing it when scanning specs, but I probably wasn't 
>> looking for it so I could have skimmed over something.
> 
> Yes. The key word here is "phase stable coax." If you search for that,
> several cables will pop up. They wont be cheap, though.
> 
> 
>> What determines the dispersion of a cable?  Is it as simple as bigger wire 
>> (more copper) is better?
> 
> For us, it's mostly the frequency dependence of the dielectric.
> If you go for higher frequencies, it also becomes a matter of
> the different modes a cable supports, which all have different
> velocities. The latter is the reason, why GHz cables and connectors
> are becomming thinner and thinner as we go up in frequency.
> 
> 
>> Why do I care about the dispersion as long as all cables match?
> 
> Because it degrades the slew rate of the pulse. If you have
> a very bad case of dispersion (combined with long cables),
> the rising slope will look more like a jagged mountain range
> than a step (though it's unlikely you hit that with modern
> cables, unless you go for several km of cable). Attached is
> a picture of what it might look like.
> 
> If you remember the old telegraph and telephone lines, they
> all used to have inductors placed on them every few km, to
> compensate the dispersion. As most of our communication these
> days is digital and we have relative short lengths before a
> regeneration step happens, there isn't much need for dispersion
> compensation anymore. Unless you go for submarine cables or
> optical fibers, both of which have elements with negative
> dispersion inserted.

Even worse things can happen when you have an air dielectric cable and 
evenly spaced supports. Putting a pulse into something like that can 
be *very* messy. 

Bob



> 
>   Attila Kinali
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
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Re: [time-nuts] Question about the PLL of Trimble Thunderbold

[Bob kb8tq]

Hi

Ok, let’s take a look at this is a bit more detail. Let’s say you have a 
reference oscillator ( = the source 
of sync) and a locked oscillator ( = the target of the sync). 

Both devices have jitter. Unfortunately this an ill defined term and we can go 
on almost forever about what
is or isn’t a valid measure. One way to measure it is ADEV, there are many 
others. Since ADEV data is 
commonly available ( rather than it being a perfect measure), lets use ADEV 
while understanding that it 
is not perfect. 

If 1 pps is the base timing exchange point, the jitter we are concerned with 
will be in the vicinity of 1 second. 
A good guess is that a practical control loop will need a few samples to work 
properly and that you probably 
will be still concerned past 10 seconds. 

If the net result is going to be “sync to a couple of ps”, then the ADEV on 
both sources likely needs to be 
well below the sync target. How far is going to depend a lot on the other noise 
sources in the system. A
few ps comes out to a total ADEV below 1x10^-11. If the combination needs to be 
well below, you may be in 
the 1 to 4x10*-12 range.  Coming back to the “ADEV is not ideal”, the range of 
tau may well get out to the 0.1 
second to 100 second range. 

Indeed these are all fairly hand waving sorts of arguments. They should be 
treated more as general limits 
than some sort of absolutes. If the sources involved are not at least in the 
general vicinity of these numbers,
you may  want to re-think things. One example of this is the fact that GPS is 
nowhere near as good as these 
limits. 

Simply put, you can’t sync to GPS to the “couple of ps” level. There is no 
target to hit at the “couple ps level”.
Down there,  it’s just noise.  Locking to noise and calling it “sync” makes no 
sense. If you build two devices and 
compare them, they will not track at the desired level. This is the reason a 
typical GPSDO runs very long time 
constants in it’s control loop and/or accepts a lot more time error than the 
low ps level. Indeed a many thousands 
of dollars GPS will do about 10X better than a low cost unit. Even that device 
has way more noise that your target.

Another part of the very slow time constants involved in GPSDO’s is that when 
you switch between sources, there
is a long period of time while things re-align to the new signal (your external 
pps). The external signal almost 
certainly has a time offset relative to GPS. How you handle that is up to you 
(do you re-align sync output to that
time or not). More subtly, it may have a drift rate. The control loop will need 
to be able to handle that as well. Various
telecom sync systems handle these issues in different ways. There is no single 
“right” solution. 

Yes, there are a *lot* of assumptions and more than a few simplifications 
above. 

Lots of fun !!

Bob

> On Oct 29, 2018, at 2:38 AM, Ferran Valdés  wrote:
> 
> 
> 
> Thanks everybody for your answers.
> 
> 
> 
> @ Bob kb8tq
> 
> 
> 
> Due to a development time constraint, I am looking for a board which has all 
> the implemented hardware In order to have a good starting point. My aim is to 
> let the oscillator to be disciplined by the GPS in normal operation, and at a 
> given moment, an algorithm to take over the adjusting process without 
> upsetting the PLL. My idea is to develop the control loop which will be able 
> to synchronize one oscillator to another.
> 
> 
> 
> @ ew
> 
> 
> 
> A 1 PPS will be exchanged in between nodes (each node would have a GPSDO).
> 
> 
> 
> @ Tom Van Baak
> 
> 
> 
> Yes, a GPSDO is already self adjusting, but for my project, I would like to 
> either use a GPS or to synchronize one node’s oscillator on another.
> 
> 
> 
> The synchronization goal is in the order of ps level.
> 
> 
> 
> @ Mark Sims
> 
> 
> 
> I have just taken a brief look at Lady Heater. I will go through the manual 
> and get back to it. But what this program does is similar to what I am 
> intending to do, so that’s quite nice to know that the Trimble Thunderbolt is 
> a suitable board !
> 
> 
> 
> I am searching for the time interval, but I have not seen the parameter yet.
> 
> 
> 
> This is the command to set the DAC value --> 0x8E-A0  | Set/Request DAC 
> values  | 0x8F-A0
> 
> 
> 
> Within the Report Packet 0x8F-AC, the bytes 16-19 indicate “Estimate of 
> UTC/GPS offset”, is this the time difference ?
> 
> 
> 
> 
> 
> I have seen that on eBay, there are listed some GPSDO modules, which claim to 
> have a “trimble” or “symmetricon” GPSDO inside, and they provide a hardware 
> platform to get access to the GPSDO parameters, however, it depends on the 
> board which is mounted inside if the adjustment loop can be externally 
> governed. Anybody got any experience with any of

Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

A lot of Radon and *really* poor ventilation…. 

There are a lot of ways for He to show up. In normal use, issue is hanging on 
to it. 
It tends to run away from its source very quickly. Maintaining a measurable 
concentration 
in something like a normal room …. not very easy at all. 

Bob

> On Nov 1, 2018, at 3:04 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message , "Richard 
> (Rick
> ) Karlquist" writes:
> 
>> According to Jack, radon emits alpha particles, AKA helium nuclei.
>> These capture stray electrons and become helium atoms.  So the
>> presence of helium is a marker for radon.  The fact that the half
>> life is a few days supports this hypothesis.   At least that is what
>> Jack told me.
> 
> Right, but you need a LOT of Radon before the Helium concentration
> becomes a problem, and the alphas would literally make things
> glow in the dark.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> 
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Re: [time-nuts] MEMS oscillators

[Bob kb8tq]

Hi

More than sketchy, it sounds a bit crazy. 

MEMS are not a lot different than any IC in that you can get packaging issues. 
Put them 
in a high pressure “bomb” test and you will see the same issues that you do on 
any IC. 
The gotcha is that an IC is die coated and a MEMS oscillator  likely is not. 
They should 
get packaged accordingly (= a low leakage package). 

Getting anything into a package at normal atmospheric pressure … not so much. 

Bob

> On Oct 30, 2018, at 8:44 AM, jimlux  wrote:
> 
> On 10/30/18 3:50 AM, Adrian Godwin wrote:
>> How sensitive to atmospheric environment are MEMs oscillators ?
>> https://www.reddit.com/r/sysadmin/comments/9si6r9/postmortem_mri_disables_every_ios_device_in/
>> It gets closer to time-nuts territory in the earlier discussion - see
>> captaincool's contribution some way down :
>> https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabled_every_ios_device_in_facility/
> 
> The helium leak sounds a bit sketchy, especially when you're talking about a 
> system that has large RF and magnetic fields.  Why would a MEMS resonator 
> care about what gas it is surrounded by.
> 
> That said, I recall someone telling me about problems with early MEMS RF 
> switches and needing some trace amount of water vapor to make them work - 
> work fine on the bench, but them into thermal vacuum testing and after some 
> amount of time they stop working, as the H2O diffuses out of the 
> (non-hermetic) packages.
> 
> 
> 
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Re: [time-nuts] Question about the PLL of Trimble Thunderbold

[Bob kb8tq]

Hi

The Trimble Thunderbolt does not have a 1 pps between the GPS chips and the 
OCXO. It makes the 
link between the two portions of the system in a different way than the typical 
GPSDO. It uses the 
OCXO as the clock reference for the GPS chip set. It then uses phase data on 
the received signal 
to “lock” the OCXO. The whole process is very much unique to the Trimble 
product line. 

To do a mod and extract a PPS, you would need to find a GPSDO based on 
something like a uBlox 
chip set or module. You potentially *could* cut a trace and inject a new PPS. 
For most devices, you 
would also have to generate the proper “status” messages that go from the uBox 
(or other module) 
to the control loop processor. Some of these messages are in response to 
specific queries. Others 
are generated automatically. 

Bob

> On Oct 30, 2018, at 4:22 PM, Ferran Valdés  wrote:
> 
> Thank you all for your answers,
> 
> 
> 
> I do have an additional question. Did anybody install an external 1PPS/10MHz 
> input to the Trimble Thunderbolt board ??
> 
> With the idea that, when the adjustment loop is deactivated, an external 
> signal can be supplied to the Thunderbolt, and the Time Interval circuit 
> could show the difference in between this signal and the feedback of the VCO.
> 
> 
> 
> 
> 
> @ Bob kb8tq
> 
> 
> 
> The aim of this project has no commercial purposes and the project itself is 
> to develop the algorithm which will be in charge of adjusting the clocks. 
> Also is yet to be determined the information that will be exchanged in 
> between nodes in order to achieve as accurate synchronization as possible.
> 
> 
> 
>> Hi
> 
>> Unfortunately there are no ?stock? boards to do this sort of thing. If this 
>> is a commercial
> 
>> requirement, there are companies who do this kind of thing on a custom 
>> basis. Figure on
> 
>> a few thousand dollars NRE and a minimum order of a few hundred to get 
>> somebody
> 
>> interested. At the ?couple ps? level, the NRE may be a bit above the few 
>> thousand
> 
>> level. Also expect to supply a full spec requirement when you go shopping ?.
> 
>> Bob
> 
> 
> 
> @Attila Kinali
> 
> 
> 
> 
> 
> Could you please share a link/name of the paper ? All information is welcome !
> 
> 
> 
> The method that you've developed, synchronizes 4 local clocks in reference to 
> one, or they keep a certain difference all together in between themselves ?? 
> Which FPGA are you using ?
> 
> 
> 
>> I have something ready, that can synchronize 4 independent clocks
> 
>> to eachother at the 180ps level, limited by the FPGA based TDC.
> 
>> The current incarnation does not allow for an external clock source
> 
>> to syncrhonize to, but that should be easy to add. That is, if you
> 
>> don't mind using some half-finished we-have-published-a-paper research
> 
>> tool.
> 
> 
> 
> Lets say that the objective is to reach 50ps. Of course is not an easy to 
> achieve goal, but that's the purpose of the project, to try to achieve as 
> best synchronization as possible within an strict time frame.
> 
> Part of the project will consist in taking into account the propagation delay 
> in between the medium used, be it a cable, fiber or radio link. Still to be 
> determined, but most likely it will be a cable.
> 
> 
> 
> Nice tips on the cables, I will do a documentation research to learn further.
> 
> 
> 
>> But going to ps level of synchronization, especially if you mean <10ps,
> 
>> is not going to be easy. There are not many ways to measure pulses
> 
>> with this accuracy. If you know what you are doing, about 1-3ps RMS is the
> 
>> practical limit you can achieve, more likely it'll be in the order of 
>> 10-30ps,
> 
>> for a one-off design. Also keep in mind that ~2mm of cable is already 10ps of
> 
>> phase shift. Ie you will need to calibrate your cables as well. Cables,
> 
>> which are of course low dispersion and low temperature coefficient cables.
> 
>> The dispersion is important so that your pulse remains a sharp pulse.
> 
>> through the cable and doesn't come out grabled as a weird wave packet,
> 
>> Quite counter-intuitively, limiting the slew rate might help with this.
> 
>> The low TC is important if there is any distance between the two
> 
>> oscillators. Otherwise you can get up to several ps per ?C temperature
> 
>> change and meter cable length for run of the mill cables. If you have
> 
>> PTFE cables, you also want to keep them well above 25?C or well below 15?C,
> 
>> for the same reason.
> 
>> Attila Kinali
> 
> 

Re: [time-nuts] Still looking for a schematic drawing for Oscilloquartz 8600-3 (945.860.011.03 S/N 422)

[Bob kb8tq]

Hi

One fairly real possibility - it can’t be repaired. The  tuning range of a BVA 
based oscillator is pretty 
small. It may be that the crystal has simply aged further than it can be tuned. 

Assuming the device is still operating properly, there are a lot of uses for a 
working “1Hz off” 5 MHz
OCXO …..

Bob

> On Oct 25, 2018, at 3:38 PM, Mark Goldberg  wrote:
> 
> I agree they likely won't provide a schematic and will want it back for
> repair. If it is a proprietary design for someone, they may not even repair
> it for you and certainly won't give you any info. I was at least able to
> get a little info from Wenzel about a similar oscillator I was looking at
> and they gave me hints about what the one I had was not, basically not
> telling me info but keeping me from heading down the wrong path. If you ask
> nicely via email and are understanding about their situation with
> proprietary products, maybe they will be of some help.
> 
> I have reverse engineered a couple of oscillators. You don't have to
> reverse engineer the whole thing, just the frequency adjustment section. I
> don't know anything about this oscillator but you can determine what the
> available adjustment is, a pot or a trimmer cap. If it is a pot, is there
> another resistor that sets the course adjustment? If it is a trimmer cap,
> there is usually a parallel cap that sets the course adjustment. Possibly
> those could be replaced with different values to get the adjustment range
> back. Worth a try.
> 
> If you can look at the circuit around the crystal, you likely can determine
> what the oscillator topology is.
> 
> Can you tell if the oven is working? Typically it will draw more current on
> startup and then reduce the current draw after a while when it gets to
> temperature. I've found broken heater wires before.
> 
> Regards,
> 
> Mark
> 
> 
> On Thu, Oct 25, 2018 at 11:26 AM paul swed  wrote:
> 
>> Ulf
>> I have no details. But perhaps off list we could reverse engineer it.
>> Simply a suggestion. Especially since you have it open.
>> Regards
>> Paul
>> WB8TSL
>> 
>> On Thu, Oct 25, 2018 at 2:15 PM Bob kb8tq  wrote:
>> 
>>> Hi
>>> 
>>> Even with an “account”, most oscillator companies will not supply
>> internal
>>> details on their product. That’s in part
>>> to protect their IP. It also reflects the complexity of tracing back to
>>> exactly what doc’s apply to an older unit. The
>>> normal drill is for you to send it back and they take a look at it. They
>>> then quote a repair charge and you either
>>> go ahead with it or have them send it back.
>>> 
>>> Bob
>>> 
>>>> On Oct 25, 2018, at 1:56 PM, Ulf Kylenfall via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>>> 
>>>> 
>>>> Many monts ago I approached the list regarding an Oscilloquartz
>>> 8600-3(945.860.011.03 s/n 422) 5 MHz Ovenized Crystal Oscillator. It had
>>> aged and was 1 Hz off and couldnot be braught back to 5.000.000 MHz.
>>>> Since I did not have "an account" with Oscilloquartz or what they are
>>> calledtoday, I was not able to get any help from them.
>>>> There was one answer off the list from someone who could possibly
>>> helpbut that person either forgot or did not have any relevant
>>> informationto share.
>>>> A box with the dismantled unit has been laying on my shelf for months
>>> and I am therefore asking again. If there is no information about
>> thisunit
>>> available I will scrap it. I do not know of any other forumto ask.
>>>> Best Regards
>>>> 
>>>> Ulf KylenfallSM6GXV
>>>> 
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>>> 
>>> 
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Re: [time-nuts] Still looking for a schematic drawing for Oscilloquartz 8600-3 (945.860.011.03 S/N 422)

[Bob kb8tq]

Hi

Even with an “account”, most oscillator companies will not supply internal 
details on their product. That’s in part
to protect their IP. It also reflects the complexity of tracing back to exactly 
what doc’s apply to an older unit. The 
normal drill is for you to send it back and they take a look at it. They then 
quote a repair charge and you either 
go ahead with it or have them send it back. 

Bob

> On Oct 25, 2018, at 1:56 PM, Ulf Kylenfall via time-nuts 
>  wrote:
> 
> 
> Many monts ago I approached the list regarding an Oscilloquartz 
> 8600-3(945.860.011.03 s/n 422) 5 MHz Ovenized Crystal Oscillator. It had aged 
> and was 1 Hz off and couldnot be braught back to 5.000.000 MHz.
> Since I did not have "an account" with Oscilloquartz or what they are 
> calledtoday, I was not able to get any help from them.
> There was one answer off the list from someone who could possibly helpbut 
> that person either forgot or did not have any relevant informationto share.
> A box with the dismantled unit has been laying on my shelf for months and I 
> am therefore asking again. If there is no information about thisunit 
> available I will scrap it. I do not know of any other forumto ask.
> Best Regards
> 
> Ulf KylenfallSM6GXV
> 
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Re: [time-nuts] OCXO Board

[Bob kb8tq]

Hi

Well if this turns into a major enterprise …. do a second board with a 
different set of 
footprints. Probably better to see if this one will fly first …..

Bob

> On Oct 26, 2018, at 4:19 PM, ewkehren via time-nuts 
>  wrote:
> 
> I have added OSA 8663 was not easy no more Please 
> BertSent from my Galaxy Tab® A
>  Original message From: Patrick Murphy  
> Date: 10/26/18  3:35 PM  (GMT-05:00) To: time-nuts@lists.febo.com Subject: 
> Re: [time-nuts] OCXO Board Not to be a "me too", but I think there will be 
> some interest for thisboard. Including a couple for me. :-)-Pat (KG5YPQ)>Dave 
> wrote:>Yep!! Count me in for a few also!! maybe 4 or 5...>>Dave M>Wes wrote:> 
> I'm not up to doing the whole project, but I would certain be> interested in 
> 2 or 3 boards for sure.>> Wes Stewart N7WS>> On 10/26/2018 5:51 AM, Bob 
> Martin wrote:>> Bert, That looks like a useful board. Certainly some of 
> the oscillators>> I'm giving away would fit nicely on it. Since it looks like 
> a two>> layer board, a quick check at pcbway.com puts the cost at $.79>> 
> apiece at the 100 quantity exclusive of shipping. Best, Bob 
> Martin On 10/26/2018 4:17 AM, ew via time-nuts wrote:> There 
> recently was a request for an OCXO board. I did a layout, see>>> attached and 
> had Corby do his usual QC test.> If some one is interested to make 
> boards and maybe sell to other>>> time nuts please contact me off list and I 
> will get you code and>>> possible suppliers.>> Board does not have an amp 
> but could be added, if so, please>>> advise, what should be added. Regardless 
> what the direct output>>> will remain>> Bert 
> Kehren___time-nuts mailing 
> list -- time-n...@lists.febo.comTo unsubscribe, go to 
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Re: [time-nuts] OCXO Board

[Bob kb8tq]

Hi

I think what is needed is somebody to stand up and say “ok, I’ll handle all the
ordering and shipping stuff”. No, that somebody is not me …. sorry about that. 
There are a *lot* more board designs than just this one floating around. This 
could
turn into a fairly complex little enterprise. 

If the first boards really are “well under $1 each” sort of boards (and I’m 
quite sure they are),
doing this one board at a time is going to be …. errr… nutty. I’d suggest that 
something like groups of 5 (or maybe even 10 if then are < <. $1 is likely the 
smallest rational increment to play with. When shipping is more than the 
stuff in the envelope … that’s silly. 

Since you pretty much always see people coming back a while later wondering 
if they can get more boards on anything like this, getting a few extras is never
a bad idea. 

So who has way too much time on their hands and *really* likes driving to the 
post office?
Hmmm …. not many hands raised. Probably a good idea to include the thought that 
there *should* be something in the deal for the poor person doing all the work. 
I’d say
they should get at least as much as the post office does …. just saying …..

Bob

> On Oct 26, 2018, at 3:35 PM, Patrick Murphy  wrote:
> 
> Not to be a "me too", but I think there will be some interest for this
> board. Including a couple for me. :-)
> 
> -Pat (KG5YPQ)
> 
>> Dave wrote:
>> Yep!! Count me in for a few also!! maybe 4 or 5...
>> 
>> Dave M
> 
>> Wes wrote:
>> I'm not up to doing the whole project, but I would certain be
>> interested in 2 or 3 boards for sure.
>> 
>> Wes Stewart N7WS
>> 
>> On 10/26/2018 5:51 AM, Bob Martin wrote:
>>> Bert,
>>> 
>>> That looks like a useful board. Certainly some of the oscillators
>>> I'm giving away would fit nicely on it. Since it looks like a two
>>> layer board, a quick check at pcbway.com puts the cost at $.79
>>> apiece at the 100 quantity exclusive of shipping.
>>> 
>>> Best,
>>> 
>>> Bob Martin
>>> 
>>> On 10/26/2018 4:17 AM, ew via time-nuts wrote:
 
 
 There recently was a request for an OCXO board. I did a layout, see
 attached and had Corby do his usual QC test.
 
 
 If some one is interested to make boards and maybe sell to other
 time nuts please contact me off list and I will get you code and
 possible suppliers.
 
 Board does not have an amp but could be added, if so, please
 advise, what should be added. Regardless what the direct output
 will remain
 
 Bert Kehren
 
>> 
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Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).

[Bob kb8tq]

Hi

One would *guess* that the PLL bandwidth in the 9578 is wider than what you see 
in a typical 
GPSDO. As long as they don’t both line up at the same point, noise and phase 
peaking should 
not be a big deal. Depending on how clean your GPSDO is, the 9578 might clean 
things up a bit. 

For timing / high precision, putting another PLL into things is going to add 
some delay and possibly
some temperature dependence. Since you are running normal test gear, neither of 
those issues 
should be significant enough to impact anything.  In this environment 75 ohms 
vs 50 ohms is also 
not a big deal, but it will have slightly more impact, fix it if you can, don’t 
sweat it if you can’t. 

Bob

> On Nov 4, 2018, at 5:44 AM, Dr. David Kirkby  
> wrote:
> 
> I want a distribution amplifier to distribute 10 MHz from an HP GPS
> receiver to various bits of test kit - spectrum analyzer, VNA, signal
> generators, HP 5370B time interval counters, signal generators etc.
> Currently I am using 75 ohm video amplifiers, but I suspect that is sub
> optimal. I also don't like the form factor of this amplifier - I would
> prefer a 19" rack mount unit.
> 
> Does anyone know how well the Racial 9478 performs? If my understanding is
> correct  this is not simply an amplifier, but has its own internal high
> stability reference oscillator, which then feeds 9 independent outputs, all
> of which have their own amplifier. The internal OCXO will phase lock that
> to an external reference.
> 
> Fundamentally, it does not seem a great idea to me to lock one OCXO to GPS
> then lock a second OCXO to the first  OCXO.  But maybe I am mistaken.
> 
> I have the chance to buy one for £150 (GBP) but are a bit worried the
> performance.
> 
> Any comments?
> 
> Dave.
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Re: [time-nuts] Datum PRS-50 ionizer voltage supply

[Bob kb8tq]

Hi

Just as a guess, it would be rare for a “heated wire” type of thing to have 
much over a 
10:1 ratio between hot and cold. Most have ratios that are less. (think of a 
light bulb …) 
If you suspect the ionizer, I’d suggest working out just what it’s resistance 
is. If it’s down 
below 0.1 ohms (and your 1V / 1A guess is correct) then it is shorted. Is it 
worth trying 
something crazy to unshift it? Who knows …..

Bob

> On Nov 1, 2018, at 3:56 PM, Dirk Niggemann  wrote:
> 
> Hi,
> 
> I acquired a PRS-50 Caesium beam frequency standard in more-or-less working
> order back in 2011. The manufacture date was February 2001, so the tube was
> probably exhausted by this stage, but it did still achieve lock so may have
> been in storage for some time rather than run for the whole of its 10-year
> lifespan.
> 
> I recovered it from storage a year or so ago to test and it worked,
> initially. The power supply was noisy, and the system wouldn't achieve lock
> on power-up from cold.
> 
> I suspect that  that it may have been retired from service originally for
> an intermittent PSU failure as it would not find lock on every power up,
> rather than an exhausted or failed tube.
> 
> Since then the power supply in the 4201A module failed completely. All the
> electrolytics in the SMPSU leaked.
> 
> I have managed to restore the PSU to the point that the PRS-50 boots and
> tries to find a lock, but fails after about 15 minutes with error F3
> (ioniser voltage out of spec)
> 
> When watching in monitor3, I can see the both the OCXO and the Caesium oven
> power and heat up, and i have voltages in spec on all rails, except that
> the ioniser voltage remains below 0.1V.
> 
> I also see almost no ion pump current. which is consistent with the ioniser
> remaining off.
> 
> I haven't managed to retrieve the tube constants, but i assume the ioniser
> wants about 1V at 1A like most other Caesium beam tubes.
> 
> I believe i have also identified the ioniser supply leads from the tube and
> these meter out at very low resistance (< 1 ohm), possibly too low (though
> how a hot-wire ioniser should fail short escapes me).
> 
> Does anybody know how the 4201A module generates the ioniser voltage? It's
> likely to be similar to the FTS4065C in that respect. When is the ioniser
> meant to turn on in the power-up cycle?
> 
> I suspect i'm missing the ioniser supply rail. There's at least 24
> unlabelled connections between the SMPSU board and the junction board which
> connects both the LV lines for the Cs tube, the main processor board and
> the SMPSU. I have no idea which particular connection this could be.
> 
> I don't believe Datum/Symmetricom/Microsemi ever published schematics for
> this Caesium module so I'm a little at a loss where to go next with
> troubleshooting.
> 
> I'd like to at least eliminate a failed tube as far as possible, since i
> really don't see myself acquiring a replacement tube at list price.
> 
> Unfortunately i don't have any test equipment that will work at the
> microwave frequencies needed to do a direct test of the tube.
> 
> Suggestions? Has anybody ever tried a repair like this before? I'm tempted
> to feed an external supply to the ioniser to see what happens, or at least
> disconnect the ioniser leads to see if it fails with an ioniser overvoltage
> instead.
> 
> Regards,
> 
> Dirk M0KRD
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

As much fun as this is, once it moves over to wireless charging as the likely 
issue ….. that’s getting pretty far from TimeNuts main focus…..

Bob

> On Nov 1, 2018, at 5:08 PM, David Witten  wrote:
> 
> Ok, one last try:
> 
> From AuntMinnie.com, free but subscrip[tion-based newslettter for clinical
> radiologists and related staff:
> 
> 
> November 1, 2018 -- A second imaging facility is reporting problems with
> Apple devices that appear to be related to the operation of the center's
> MRI scanner. Nearly 10 late-model Apple iPhones and Watches were
> permanently disabled at a Delaware center after it ramped down its MRI
> magnet.
> 
> CNMRI is an imaging facility in Dover, DE, that specializes in neurology
> and sleep medicine. It operates a 1.5-tesla MRI magnet and also performs
> studies such as polysomnography, nerve conduction, and home sleep studies,
> according to Dr. Robert Varipapa, a neurologist at the center.
> 
> In mid-October, field service engineers from an imaging OEM arrived and
> ramped the magnet down and then back up again. Immediately thereafter,
> staff members at the center who owned Apple devices with wireless charging
> reported that their devices were disabled. Approximately eight or nine
> devices were affected, according to Varipapa.
> 
> Only newer-model Apple products such as the iPhone 8 and iPhone 10 were
> affected, he added. Those with older models didn't experience any problems,
> nor did staff with Android phones.
> 
> The Delaware center's experience is similar to that of an Illinois hospital
> that also reported conflict
> s
> between its MRI scanner and iPhones. That site reported that nearly 40
> iPhones stopped working after the installation of a new MRI scanner. The
> problem was attributed to helium gas that may have leaked during the
> installation and found its way into the mechanical workings of the phones.
> 
> But there are also crucial differences between the Illinois incident and
> the experience at the Delaware center. For one thing, the Delaware site
> never experienced a helium leak, to Varipapa's knowledge. Also, while the
> Illinois site reported problems with Apple models at the iPhone 6 level and
> above, in Delaware the problem was restricted to newer models with wireless
> charging -- no iPhone 6 devices were affected, Varipapa told AuntMinnie.com.
> 
> Finally, at the Illinois hospital, some of the iPhones began working again
> after the helium inside the devices apparently dissipated. At CNMRI, all of
> the smartphones were permanently disabled, and staff had to get new ones.
> 
> Varipapa said CNMRI's physicist told him that the center's experience is
> not an uncommon one. The physicist has heard that some field service
> engineers tell staff members to place smartphones in their cars' glove
> boxes when MRI magnets are being serviced, he said.
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

Now, getting back to the original issue. MEMS oscillators of some types have
really tiny structures in them. They mount them as close to being in “free 
space”
as they can. The idea is no different than a crystal. A properly shape lump 
running 
in free space has higher Q. Higher Q is normally a good thing in an oscillator.

It’s not a great leap to guess that there may be magnetic materials in a 
structure 
like that. If so, a giant magnetic field could put some force on the mounting 
structure.
Put to much force (or to quick a “snap” in that force) and there goes the 
structure into 
really tiny pieces …..

Yes, there are a lot of other EMI possibilities. Last time I checked, things 
like phones 
and watches were not on the list of what you took with you for an MRI ….

Bob

> On Nov 1, 2018, at 3:05 PM, David Witten  wrote:
> 
> Please pardon my usual incompetence posting to mailing lists...
> 
> 2nd MRI center reports problems with Apple devices
> 
> 
> Aunt Minnie is a newsletter/site targeting clinical radiologists and
> technical staff.
> 
> Dave
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

If you take an IC package up to fairly high pressure for a few hours (and it’s 
defective) you can pretty well fill it with helium and have it well above 1 ATM 
internal 
pressure. It will then leak out (maybe over a few years) until it gets back 
down to one 
atmosphere internally.

 In some really rare conditions, you can pressurize it to high enough PSI to 
inflate the 
package when the pressure goes back to 1ATM. Even then the oscillators 
generally still work ok. 
This is inflation not really a function of helium. It’s just a function of what 
a lot of PSI does to 
a sealed package. You could inflate it with air and see the same thing. 

Getting helium in a properly sealed package  *without* a lot of pressure *and* 
very 
high concentrations (like 100%) …. very difficult. 

Bob

> On Nov 1, 2018, at 3:27 PM, Wayne Holder  wrote:
> 
> The oscillator mentioned in the article is a SiT1532 made by SiTime
> .  It's sold in a chip scale package that's only 1.5mm x
> .9mm, which means it'a no much more than a chip of silicon with some solder
> balls attached.  The data sheet indicates there is a "polymer" coating on
> the back side of the chip, but the working surface would be in the bottom
> where the solder balls are.  There is a rectangular protrusion shown on the
> "Dimensions and Patterns" section (page 12) that's right over where the
> MEMS mechanism would sit that might be some type of seal, but there is no
> descriptive text.
> 
> The curious thing to me is that some iPhones are said not to recover from
> exposure to helium but, as an essentially mechanical device, I can think of
> no reason that the SiT1532 would not recover from exposure to helium after
> the gas had migrated out.  I wonder off the iPhone could be damaged by an
> oscillator failure, o one that's running off frequency? The devices sell
> for about $1.25 at Mouser and I have a tank of helium in the garage, so I'm
> thinking about doing an experiment.  The only problems is finding a way to
> solder wires to such a small part?  Might have to make a PCB, instead.
> 
> Wayne
> 
> On Wed, Oct 31, 2018 at 12:51 PM Mark Sims  wrote:
> 
>> https://ifixit.org/blog/11986/iphones-are-allergic-to-helium/
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Re: [time-nuts] hp 10544A and 10811A ovenized oscillators

[Bob kb8tq]

Hi

The change is suspiciously close to the electrical tuning range of a typical HP 
OCXO. 
The answer may be a failure of the bias on the EFC line …..

Bob

> On Nov 2, 2018, at 2:51 PM, Walter Shawlee 2  wrote:
> 
> I have several of these as the -010 high stability timebase options
> in my various HP counters, and generally they work very well, with
> usual errors under 0.01Hz and very minor drift over time.
> 
> a few months ago, I had a power interruption, and black out for a few hours,
> along with the usual erratic restart from the power company. shortly 
> afterwards, I built a nice little
> homemade TM500 plug-in OCXO unit to fit on my bench, and without giving it 
> much thought, used
> my bench standard (an hp 435B-K26 power/frequency reference with an internal 
> 10544A) to cal it.  all seemed good.
> 
> soon after, I was working on an hp 5334A counter, and added a 10811A as as 
> upgrade from my
> spares and suddenly, I had a big 1.3Hz error at 10Mhz when I cross checked it 
> to my bench references AND a rubidium. I brought over my recently cal'd 
> rubidium from the upstairs lab, and yes, there was now clearly a big step 
> error. my upstairs 5335A with a 10811A had the same step effect!
> 
> these 2 units are always on for stability, so both got cycled the same way 
> during the power failure.
> 
> it seems that the power failure cycle had bumped the internal 10544A 
> oscillator inside the 435 by that amount, as well as the 10811A inside the 
> 5335A. I have never seen that effect before, both the ovenized osicllators 
> from hp have been very reliable for me, so I thought I would put that info 
> out in case anyone else has seen this effect and knows the cause.
> 
> using the rubidium (which I keep off until I need it, and wait for at least 2 
> hours for best settling), I reset everything back to a flat 10Mhz, and all 
> was well, except that the first 10811A I put in the 5334A conked out (oven 
> still fine, but the oscillator went dead, giving the dreaded "no osc" message 
> on the counter). another spare fixed that, and two days of drift testing to 
> get everything back where it belongs.  anybody want the bad 10811A?
> 
> anyway, just thought the information might be handy for others.  the EFC 
> range on the 10811A/10544A is *only 1Hz*, so such a big jump is unusual to 
> say the least. it required the main coarse adjustment to fix.
> The 435B-K26 is a pretty remarkable widget if you ever see one, it makes a 
> great 10Mhz reference and 1mW power reference in one little box, very useful 
> for an RF bench. One of hp's rare and forgotten treasures.
> 
> all the best,
> walter
> 
> -- 
> Walter Shawlee 2
> Sphere Research Corp. 3394 Sunnyside Rd.
> West Kelowna, BC, V1Z 2V4 CANADA
> Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
> We're all in one boat, no matter how it looks to you. (WS2)
> All you need is love. (John Lennon)
> But, that doesn't mean other things don't come in handy. (WS2)
> 
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Re: [time-nuts] Question about the PLL of Trimble Thunderbold

[Bob kb8tq]

Hi

Unfortunately there are no “stock” boards to do this sort of thing. If this is 
a commercial 
requirement, there are companies who do this kind of thing on a custom basis. 
Figure on 
a few thousand dollars NRE and a minimum order of a few hundred to get somebody
interested. At the “couple ps” level, the NRE may be a bit above the few 
thousand 
level. Also expect to supply a full spec requirement when you go shopping ….

Bob

> On Oct 29, 2018, at 2:38 AM, Ferran Valdés  wrote:
> 
> 
> 
> Thanks everybody for your answers.
> 
> 
> 
> @ Bob kb8tq
> 
> 
> 
> Due to a development time constraint, I am looking for a board which has all 
> the implemented hardware In order to have a good starting point. My aim is to 
> let the oscillator to be disciplined by the GPS in normal operation, and at a 
> given moment, an algorithm to take over the adjusting process without 
> upsetting the PLL. My idea is to develop the control loop which will be able 
> to synchronize one oscillator to another.
> 
> 
> 
> @ ew
> 
> 
> 
> A 1 PPS will be exchanged in between nodes (each node would have a GPSDO).
> 
> 
> 
> @ Tom Van Baak
> 
> 
> 
> Yes, a GPSDO is already self adjusting, but for my project, I would like to 
> either use a GPS or to synchronize one node’s oscillator on another.
> 
> 
> 
> The synchronization goal is in the order of ps level.
> 
> 
> 
> @ Mark Sims
> 
> 
> 
> I have just taken a brief look at Lady Heater. I will go through the manual 
> and get back to it. But what this program does is similar to what I am 
> intending to do, so that’s quite nice to know that the Trimble Thunderbolt is 
> a suitable board !
> 
> 
> 
> I am searching for the time interval, but I have not seen the parameter yet.
> 
> 
> 
> This is the command to set the DAC value --> 0x8E-A0  | Set/Request DAC 
> values  | 0x8F-A0
> 
> 
> 
> Within the Report Packet 0x8F-AC, the bytes 16-19 indicate “Estimate of 
> UTC/GPS offset”, is this the time difference ?
> 
> 
> 
> 
> 
> I have seen that on eBay, there are listed some GPSDO modules, which claim to 
> have a “trimble” or “symmetricon” GPSDO inside, and they provide a hardware 
> platform to get access to the GPSDO parameters, however, it depends on the 
> board which is mounted inside if the adjustment loop can be externally 
> governed. Anybody got any experience with any of those boards?
> 
> 
> 
> Kind regards,
> 
> Ferran
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Re: [time-nuts] hp 10544A and 10811A ovenized oscillators

[Bob kb8tq]

Hi

A failed ( = cold) oven on either a normal OCXO should give you a “tens of ppm” 
sort of frequency 
error. At 10 MHz that would be over 100 Hz.  Fractions of a ppm are less likely 
to be oven issues. 

Bob

> On Nov 5, 2018, at 1:01 PM, Dr. Frank  wrote:
> 
> Walter,
> 
> did you check on both failing oscillators, that the ovens work properly 
> afterwards, or that the cases still get warm?
> 
> I once had a failing 10811, where the NTC was defect, maybe also after a 
> longer unused time.
> 
> As the heater draw an excessive current on turning on, (about 500mA for the 
> 10811), maybe the thermal fuse blew up, but due to the peaking current, not 
> due to temperature.
> 
> I find it quite unusal, that the oscillator / XTAL itself should make a jump 
> like this.
> After 48h at most, it should return to its recent frequency trimming, within 
> < 1E-8, or less.. as these guys are really old.
> 
> That's the typical behavior of all three 10811, which I own (inside 5370B, 
> 5335A, and one external).
> 
> Frank
> 
> 
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Re: [time-nuts] Need recommendation for GPS antenna for Oncore GPS module

[Bob kb8tq]

Hi

Appears to be an Italian clone of the generic timing antenna. That is only a 
guess and it could 
easily be something very different …. Since it’s a part made for Erickson by 
somebody else, 
you would need their part number to properly track it down. If it’s a custom 
part, even that might 
be impossible. 

Bob

> On Nov 4, 2018, at 12:57 PM, Toby Riddell  wrote:
> 
> I spotted this on Ebay, the price is very attractive and I saw this model
> mentioned previously in the mailing list archives:
> 
> https://www.ebay.ca/itm/Ericsson-KRE-1012082-1-GPS-Antenna-26dBi-For-HUBER-SUHNER-Bracket-84097323/272646019498?hash=item3f7af819aa:g:US8AAOSwRUhZAIhz:rk:3:pf:0=mtr
> 
> Anyone have a manual or datasheet for it? I cannot seem to find one using
> Google.
> 
> 
> On Sun, 4 Nov 2018 at 12:41, Matthew D'Asaro  wrote:
> 
>> For what it is worth, I got a used HP/Symmetricom 58532a antenna off of
>> eBay for about $50. It needed a minor repair (broken internal coax) but
>> once that was done it has worked great for me. The other one I considered
>> was the 58504a but they were more expensive on the used market and didn't
>> seem as weather proof (a special weather proof cap was offered as an add-on
>> but most don't have it) so I went with the newer 58532a.
>> 
>> -Matthew D'Asaro
>> 
>>> On Nov 4, 2018, at 8:43 AM, Toby Riddell 
>> wrote:
>>> 
>>> Thanks Scott - I will look into getting one of those. And noted re. the
>>> roofline!
>>> 
 On Sun, 4 Nov 2018 at 07:26, Scott McGrath  wrote:
 
 For timing use ideally it should be above the roofline by at least
>> several
 feet otherwise satellites close to the horizon will be not be visible.
 
 The generally preferred antenna is the Agilent/Keysight/Symmetricom.
 58504A antenna also any outdoor antenna made by Trimble or TrueTime as
>> long
 as antenna does not use a downconverter.
 
 
 
 On Nov 3, 2018, at 5:26 PM, Toby Riddell 
>> wrote:
 
 Hi all,
 
 I want to fit a GPS antenna on our house (the attic is being renovated
>> and
 it just occurred to me that if I move fast I can get it done before the
 walls are closed up again!)
 
 I was planning on having it mounted on a south-facing wall but below the
 roofline - does this sound okay for picking up satellites? It can poke
 above the roofline if needed as long as the mounts are on the wall (not
>> the
 top of the roof).
 
 Is there a recommended antenna? I am planning on feeding it into an
>> Oncore
 GPS module which will then interface to a Soekris net4501 running
>> nanoBSD
 and ntpns.
 
 Thanks!
 
 Toby
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Re: [time-nuts] 53230A TIC and TimeLab

[Bob kb8tq]

Hi

Probably also worth mentioning:

For short tau, you are probably measuring the ADEV of the counter noise floor 
rather than the 
ADEV of the GPSDO. Yes, there are noisy GPSDO’s out there but most of what you 
run into
is not in that category. 

Bob

> On Oct 4, 2018, at 8:42 AM, Ole Petter Ronningen  
> wrote:
> 
> On Thu, Oct 4, 2018 at 1:40 PM Magnus Danielson 
> wrote:
> 
>> Who-oh! OK. This means that one should intentionally let a number of
>> samples pass before trusting it.
>> 
> 
> Precisely. But, crucially, discard 1-2 samples *since the last INIT* -
> which may not be obvious without some investigation. It is a bit
> convoluted, but the behaviour is easily observed using TimeLab: Feed the
> counter the same 10  MHz signal both on the EXTernal REFerence, and channel
> 1. Set up a frequency measurement, and collect data using timelab. Observe
> the phaseplot (taking care to NOT have the phase plot in "residual mode").
> 
> After a few minutes, a slope will be observed on the phase plot that should
> not be there - it is measuring its own reference, so the plot should be
> pretty much dead flat over a sufficiently long interval. It is because
> timelab calls READ every time it wants a sample, and the instrument returns
> a biased frequency estimate. Shorter gate-times, steeper slope.
> 
> It would be interesting to get some better qualifications of this.
> 
> 
> I have attempted to make a thorough writeup on the previously mentioned
> http://www.efos3.com/53230A/HPAK53230A-1.html Also parts 2 and 3 - in
> short, the behaviour has been observed on three separate instruments. The
> data is available for download on my website. Oh, and Keysight has
> acknowledged the issue, but not offered anything towards a solution.
> 
> Ole
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

That works fine if you are doing things manual to check a local standard. If 
you are trying to 
disipline a few thousand cell towers 24 hours a day … not so much. It also 
works for 
checking frequency. What modern systems need is time. That gets you into a 
whole 
world of resolving and identifying individual edges. The WWVB signal really was 
never
set up for this. Loran-C is an example of a signal that was designed to 
identify a specific
edge.

Bob

> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
> 
> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
> Ignore the phase at night and use only the phase records during the day when 
> an all-daylight propagation path exists.  You might have to "correct" the 
> absolute phase reading by some multiple of the RF period, but with a low rate 
> of local standard oscillator drift, this is a simple matter of arithmetic. 
> Back in the day, I managed Sulzer crystal oscillators at 5 field sites from 
> my office and could maintain phase continuity for weeks at a time, until we 
> had to diddle the dial on one or several of them to correct for crystal 
> aging.  Then it was just more arithmetic again.  Several of the oscillators 
> had such low drift rates that all I needed was one daily phase reading from 
> the VLF phase tracking receiver (Tracor 599Js) at those sites to know the 
> frequency of the Sulzers there.
> 
> ... Martin VE3OAT
> 
> On Thu, 30 Aug 2018 12:27:12 -0400
> Bob kb8tq  wrote:
> 
>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>> stable signal. As soon as
>> that signal hits the real world things start to degrade. Propagation between 
>> transmit and receive sites
>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>> noise at 60 KHz. The receive
>> signal to noise will never be as good as you might like it to be ?.
> 
> > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>> causes a phase shift of several 100?s at even moderate distances
>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>  Attila Kinali
> 
> 
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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Having spent a lot of my life designing GPSDO’s it’s a “that depends” sort of 
thing. 
For a simple noise jammer, yes, they pretty much all will go into holdover. 
When the
jammer goes away, they come out of holdover. There are a few older units that 
may not
do quite as well with various sorts of broadband jamming.  With a spoofing 
jammer that is flying
around overhead and simulating an entire constellation … you could see any of 
them do odd 
things. An airborne jammer flying over this or that city likely gets you into a 
“act of war” sort of issue. 
It’s something you build if you are a nation state. 

The performance with noise jammers is not a guess. It’s based on field 
experience and
all those never ending meetings I keep referring to …..

Bob

> On Aug 31, 2018, at 12:04 PM, Mark Spencer  wrote:
> 
> Hi:
> 
> I'm curious if anyone knows how typical GPSDO's are likely to respond to 
> simple GPS jammers ?  Could the GPSDO be reasonably expected to go into hold 
> over ?
> 
> The use case I am thinking is along the lines of:
> 
> -A commercial operation relies on a GPSDO for timing at a remote site.  
> 
> -A vehicle with a simple GPS jammer (perhaps intended by the vehicle driver 
> to defeat a GPS tracking system installed near the vehicle) parks near the 
> GPS antenna.
> 
> I'm thinking one likely outcome is the GPSDO goes into hold over and when the 
> vehicle moves away it exits hold over ?   This is all just speculation on my 
> part.
> 
> Comments ?
> 
> Thanks 
> Mark Spencer
> 
> m...@alignedsolutions.com
> 604 762 4099
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Re: [time-nuts] Effects of Simple GPS jamming on GPSDO's ?

[Bob kb8tq]

Hi

Most of them are doing CW signal detection and notch filtering. There are a 
number 
of ways for “birdies” to show up in any environment, jamming or no jamming. 
Some of
the details of who’s doing what and how well are under NDA. None of it is 100%
effective, it’s just a way to get another 10, 20 or 30 db of margin at this or 
that offset 
from carrier. 

Bob

> On Aug 31, 2018, at 1:36 PM, Mark Sims  wrote:
> 
> Several GPS receivers have a setting for enabling jamming detection and/or 
> mitigation.   The datasheets don't tend to talk about what it does.  But, if 
> the receiver supports it (Trimble and Venus devices), Lady Heather can 
> configure it.
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Re: [time-nuts] Possible End of Daylight Savings Time in Europe?

[Bob kb8tq]

Hi

Here in the US, we have been creeping along getting rid of daylight time. At 
the rate we have been 
changing the magic dates, I’d bet we have it gone in a few hundred years :)

Bob

> On Aug 31, 2018, at 8:57 AM, John Franke  wrote:
> 
> See: 
> https://www.msn.com/en-us/news/world/europe-ticks-closer-to-ending-daylight-saving-time/ar-BBMGU2d?ocid=spartandhp
> 
> John  WA4WDL


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Re: [time-nuts] NIST

[Bob kb8tq]

Hi

It’s back in the FCS archives. I don’t think it’s one of the ones you can hit 
without going through a
paywall. It was a fun paper to attend. The chatter in the room was 
“interesting” to say the least.

Bob

> On Aug 31, 2018, at 1:07 PM, Brooke Clarke  wrote:
> 
> Hi Bob:
> 
> Do you have and info on that article that would allow me to read it?
> 
> -- 
> Have Fun,
> 
> Brooke Clarke
> https://www.PRC68.com
> https://www.end2partygovernment.com/2012Issues.html
> axioms:
> 1. The extent to which you can fix or improve something will be limited by 
> how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
> 
>  Original Message 
>> Hi
>> 
>> The original “we cracked GPS” paper back in the 1980’s (that unlimitedly 
>> lead to the end of SA)
>> used a medium sized dish ( think of the good old C-band antennas) to pick 
>> out a single sat.
>> 
>> Bob
>> 
>>> On Aug 30, 2018, at 9:54 PM, Brooke Clarke  wrote:
>>> 
>>> Hi Gregory:
>>> 
>>> I wonder if anyone has tried using a small parabolic dish, like used for 
>>> Free To Air satellite TV and aimed it at a GPS satellite track or at a WAAS 
>>> geostationary satellite using a feed antenna with reverse polarization from 
>>> a normal GPS antenna?
>>> http://www.prc68.com/I/FTA.shtml
>>> 
>>> -- 
>>> Have Fun,
>>> 
>>> Brooke Clarke
>>> https://www.PRC68.com
>>> https://www.end2partygovernment.com/2012Issues.html
>>> axioms:
>>> 1. The extent to which you can fix or improve something will be limited by 
>>> how well you understand how it works.
>>> 2. Everybody, with no exceptions, holds false beliefs.
>>> 
>>>  Original Message 
 On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke  wrote:
> I would disagree in that ease of jamming/spoofing is strongly related to 
> wavelength.  That's because antenna efficiency
> goes down as the size of the antenna gets smaller than 1/4 wave.
> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 
> wavelength is a few inches, something that  you can
> hold in your hand.
 However, the short wavelengths of GPS make beam forming a reasonable
 countermeasure against jamming.
 
 By having a small array of GPS antennas a receiver can digitally form
 beams that both aim directly at the relevant satellites (so even
 reducing intersatellite interference) while also steering a deep null
 in the direction of the jammer.  If the jammer is powerful enough to
 overload the front-end then this won't help, but against a
 non-targeted area denying jammer it should be fairly effective.
 
 There are many papers on GNSS beamforming. ( e.g.
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ )
 
 This kind of anti-jamming solution should even be pretty inexpensive
 -- really no more than the cost of N receivers. Except that it is
 specialized technology and thus very expensive. :)
 
 Seeing some open source software implementing beam-forming was one of
 the things I hoped to see result from the open hardware multi-band
 GNSS receivers like the GNSS firehose project (
 http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once
 you're going through the trouble of running three coherent receivers
 for three bands, stacking three more of them and locking them to the
 same clock doesn't seem like a big engineering challenge... and the
 rest is just DSP work.
 
 Even absent fancy beam forming, for GNSS timing with a surveyed
 position except at high latitudes it should be possible to use a
 relatively high gain antenna pointed straight up and by doing so blind
 yourself to terrestrial jammers at a cost of fewer SVs being
 available. But I've never tried it.
 
 In an urban area I noticed my own GPSDOs losing signal multiple times
 per week. Monitoring with an SDR showed what appeared to be jammers.
 
 As others have noted intermittent jamming is pretty benign to a GPSDO.
 Spoofing, OTOH, can trivially mess up the timing.  It's my view that
 if you need timing for a security critical purpose there isn't really
 any GNSS based solution commercially available to the general public
 right now, the best bet is a local atomic reference with a GPSDO used
 to monitor and initially set it.
 
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Re: [time-nuts] WWV and legal issues

[Bob kb8tq]

Hi

Well if you have a magic piece of code that will do the trick, why don’t you 
share it with the 
rest of us? In …. errr …. 50+ years of looking at the problem, nobody else 
seems to have
come up with an answer. It’s not because people have not tried. They’ve been 
working on 
this sort of thing since at least the 60’s. It was at the heart of some really 
big problems the
DOD had with HF and VLF links.  They poured some massive chunks of money into 
it. 

Bob

> On Aug 31, 2018, at 12:30 PM, Scott McGrath  wrote:
> 
> Strangely enough there are these devices called ‘computers’ which are rumored 
> to be able to perform measurements and mathematical calculations.
> 
> One of these ‘computers’ might be profitably employed to perform the 
> necessary measurements calculations and deliver a useful output,   
> 
> Employing a Mentat would be expensive for this task...
> 
> 
> On Aug 31, 2018, at 11:37 AM, Tom Holmes  wrote:
> 
> Uh, folks...Would the apparently still on hiatus TVB approve of this on-going 
> Urinary Olympiad? Just asking. And hoping post this won’t start another one.
> 
> Tom Holmes, N8ZM
> 
> -----Original Message-
> From: time-nuts  On Behalf Of Bob kb8tq
> Sent: Friday, August 31, 2018 11:16 AM
> To: Martin VE3OAT ; Discussion of precise time and frequency 
> measurement 
> Subject: Re: [time-nuts] WWV and legal issues
> 
> Hi
> 
> That works fine if you are doing things manual to check a local standard. If 
> you are trying to 
> disipline a few thousand cell towers 24 hours a day … not so much. It also 
> works for 
> checking frequency. What modern systems need is time. That gets you into a 
> whole 
> world of resolving and identifying individual edges. The WWVB signal really 
> was never
> set up for this. Loran-C is an example of a signal that was designed to 
> identify a specific
> edge.
> 
> Bob
> 
>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT  wrote:
>> 
>> But the diurnal phase shifts at VLF are predictable and largely repeatable.  
>> Ignore the phase at night and use only the phase records during the day when 
>> an all-daylight propagation path exists.  You might have to "correct" the 
>> absolute phase reading by some multiple of the RF period, but with a low 
>> rate of local standard oscillator drift, this is a simple matter of 
>> arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field 
>> sites from my office and could maintain phase continuity for weeks at a 
>> time, until we had to diddle the dial on one or several of them to correct 
>> for crystal aging.  Then it was just more arithmetic again.  Several of the 
>> oscillators had such low drift rates that all I needed was one daily phase 
>> reading from the VLF phase tracking receiver (Tracor 599Js) at those sites 
>> to know the frequency of the Sulzers there.
>> 
>> ... Martin VE3OAT
>> 
>> On Thu, 30 Aug 2018 12:27:12 -0400
>> Bob kb8tq  wrote:
>> 
>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully 
>>> stable signal. As soon as
>>> that signal hits the real world things start to degrade. Propagation 
>>> between transmit and receive sites
>>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade 
>>> noise at 60 KHz. The receive
>>> signal to noise will never be as good as you might like it to be ?.
>> 
>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>> causes a phase shift of several 100?s at even moderate distances
>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>>   Attila Kinali
>> 
>> 
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Bob kb8tq]

Hi

Motion at a fault line can be a bit chaotic. As that motion stretches (or stops 
stretching)
the cable the delay is likely to change. How much does it change? no idea. If 
vibration 
messes with it, stretch should as well. 

Hopefully the fiber “spiralt” inside the outer jacket is enough to keep things 
from snapping
very quickly. Ground shifts around for a lot of reasons even if you are not on 
a fault line. 
That’s why they design a certain amount of “slack” into the structure.

Bob

> On Sep 2, 2018, at 11:07 AM, Azelio Boriani  wrote:
> 
> Why should there be a variation in the fiber's delay across an active
> fault line? The fiber could only break at the fault line, lay down
> more fiber than needed, to compensate the movement, and the delay
> doesn't change.
> On Sun, Sep 2, 2018 at 4:51 PM Bob kb8tq  wrote:
>> 
>> Hi
>> 
>> Tidal effects can be very “non linear” as you approach a coast line. Lots of 
>> change
>> over a fairly short distance. If indeed the world decides to put in a global 
>> PTTI fiber
>> system, all of this would get into the mix on some links. It appears that 
>> the existing
>> technology would handle the issues.
>> 
>> Of course there’s still some guy named Bob running that back hoe without 
>> checking
>> for buried lines …..*That* we could test for … likely no need to run the 
>> experiment. :)
>> 
>> Bob
>> 
>>> On Sep 2, 2018, at 10:07 AM, Tom Van Baak  wrote:
>>> 
>>>> I suspect there’s a longer list of “slow” environmental effects that are 
>>>> also taken
>>>> care of with the compensation setup. One would guess that crossing a active
>>>> fault line would be “interesting”.
>>> 
>>> Yes, here's a back of the envelope calculation for you:
>>> 
>>> - the Pacific Northwest moves on the order of 10 cm per year [1]
>>> - 1 meter of time is 1/299792458 = 3.3 ns
>>> - 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
>>> - the best laboratory optical clocks are down to that level of stability [2]
>>> 
>>> On the other hand, in the real world you'd have to convince me that you've 
>>> found two national timing labs with 1) state-of-the-art optical clocks, 2) 
>>> which operate as phase (time) standards instead of as frequency standards, 
>>> 3) or run continuously for a year (instead of a few times per week), 4) are 
>>> connected by stabilized fiber, 5) that cross plate boundaries moving 
>>> anywhere near as much as 10 cm/year, and 6) the optical time nuts running 
>>> the clocks don't already factor geodetic effects like this into their clock 
>>> comparisons...
>>> 
>>> Unfortunately I won't be able to measure this. Even if John Miles (who also 
>>> lives near Seattle) and I find optical clocks on eBay some day, and we find 
>>> a way to run 30 miles of fiber between us without anyone noticing, we are 
>>> both on the same tectonic plate so the drift cancels out. Note that 
>>> lunar/solar tidal effects would be common mode to us as well.
>>> 
>>> /tvb
>>> 
>>> [1]
>>> https://pnsn.org/outreach/about-earthquakes/plate-tectonics
>>> https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf
>>> 
>>> [2]
>>> https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
>>> https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
>>> http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf
>>> 
>>> 
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Re: [time-nuts] Efratom Oscillators

[Bob kb8tq]

Hi

The Efratom units looked like the “two generations back” Vectron devices.
They are roughly a 1.3” cube.  Efratom sold the line of parts to Vectron back
in the 1990’s.

Bob

> On Sep 21, 2018, at 12:32 PM, ed breya  wrote:
> 
> Do they look anything like this?
> 
> https://www.vectron.com/products/military/ocxo/EX-209.pdf
> 
> Ed
> 
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Re: [time-nuts] question about multi-way measurement

[Bob kb8tq]

Hi

There also are a lot of papers going back a ways by Jim Barnes and 
David Alan (sometimes together and sometimes separately)  related 
to multiple clocks driving a single “estimate” of what time it actually is. 

Bob

> On Dec 27, 2018, at 2:34 PM, Steve Allen  wrote:
> 
> On Wed 2018-12-26T10:30:24-0600 Chris Howard hath writ:
>> I see the different forms of deviation measurements and they are all
>> one-to-one comparisons.
>> 
>> Is there anything to be learned from doing mass data gathering?
> 
>> So, has this sort of thing been done?
>> Why is everything one-to-one only?
> 
> Doing this was the reason for the creation of the Bureau International
> de l'Heure (BIH) a century ago.  The initial announcement of their
> work invited observatories around the world to participate via
> correspondence sending the received times of radio time signals.
> http://adsbit.harvard.edu/full/1922BuBIH...11.
> 
> A few years later they presented to the 1928 General Assembly of the
> IAU a complete history of timekeeping and an inventory of their
> equipment including the clocks at l'Observatoire de Paris which were
> located down in the catacombs to maintain stable conditions
> http://adsbit.harvard.edu/full/1929BuBIH...3..255.
> 
> The progression of issues of Bulletin Horaire shows the development of
> technologies and techniques for intercomparing clocks from the age of
> pendulum clocks with constant pressure cases into the age of atomic
> chronometers.  At the retirement of two long-time staffers they
> published plots of the improvement of timekeeping from 1922 to 1964.
> https://www.ucolick.org/~sla/leapsecs/annastoyko.html
> 
> --
> Steve Allen  WGS-84 (GPS)
> UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
> 1156 High Street   Voice: +1 831 459 3046 Lng -122.06015
> Santa Cruz, CA 95064   http://www.ucolick.org/~sla/   Hgt +250 m
> 
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Re: [time-nuts] More ES100 WWVB Measurements

[Bob kb8tq]

Hi

Go indoors in the basement inside an inner room. You can at some times of day 
get WWVB. 
With a normal building, GPS isn’t going to make it. Even if it does, the 
signals will be degraded
enough that you will have a tough time using in.

Bob

> On Dec 31, 2018, at 8:47 PM, Wayne Holder  wrote:
> 
>> If you are fairly deep inside a building, GPS isn’t going to get there.
> WWVB likely
>> will make it to an internal location.
> 
> Interesting thought. I wonder if anyone has tested WWVB reception in a
> deep underground location such as a sub sub level in a building or parking
> garage?
> 
> Wayne
> 
> On Mon, Dec 31, 2018 at 5:29 PM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> If you are fairly deep inside a building, GPS isn’t going to get there.
>> WWVB likely
>> will make it to an internal location.
>> 
>> If you are convinced that WWVB is un-jamable and that GPS is easily
>> jammed, WWVB
>> would be more robust.
>> 
>> That’s about it.
>> 
>> Bob
>> 
>>> On Dec 31, 2018, at 7:56 PM, Wayne Holder 
>> wrote:
>>> 
>>> While reading this thread and pondering whether to buy and fool around
>> with
>>> an ES100-based module from Universal Solder, I suddenly found myself
>>> wondering if there was any advantage to using the time received from WWVB
>>> vs just using an inexpensive GPS receiver.  The ES100  module costs about
>>> $70, but I can get a GPS receiver, with antenna, for far less than that
>> and
>>> I've had no trouble receiving GPS signals indoors with most modern
>> receiver
>>> modules.
>>> 
>>> I suppose the low power requirements of the ES100 might be an advantage
>>> when building battery powered clocks to mount on the wall, but it seems
>>> like some of the newer, ultra low power GPS modules intended for use in
>>> smart watches could also work in a battery-powered wall clock, especially
>>> if the receiver was only powered on a few times a day to update the time.
>>> 
>>> And, finally, if GPS modules are (or will some become) a suitable
>>> replacement for WWVB receiver modules, do we really need WWVB in the
>> modern
>>> age?  Perhaps there's some critical advantage to using WWVB to get the
>> time
>>> but, offhand, I cannot think of it.  What am I missing?
>>> 
>>> Wayne
>>> 
>>> On Mon, Dec 31, 2018 at 4:30 PM Brooke Clarke 
>> wrote:
>>> 
>>>> Hi Joseph:
>>>> 
>>>> Thanks for the patent link.  I've added it to my WWVB phase modulation
>>>> info at:
>>>> https://prc68.com/I/Loop.shtml#La_Crosse_UltrAtomic
>>>> 
>>>> --
>>>> Have Fun,
>>>> 
>>>> Brooke Clarke
>>>> https://www.PRC68.com
>>>> http://www.end2partygovernment.com/2012Issues.html
>>>> axioms:
>>>> 1. The extent to which you can fix or improve something will be limited
>> by
>>>> how well you understand how it works.
>>>> 2. Everybody, with no exceptions, holds false beliefs.
>>>> 
>>>>  Original Message 
>>>>> On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-requ...@lists.febo.com
>>>>> wrote:
>>>>> 
>>>>>> time-nuts Digest, Vol 173, Issue 44
>>>>>> Message: 7
>>>>>> Date: Mon, 31 Dec 2018 04:04:22 -0800
>>>>>> From: "Tom Van Baak" 
>>>>>> To: "Discussion of precise time and frequency measurement"
>>>>>>
>>>>>> Subject: Re: [time-nuts] More ES100 WWVB Measurements
>>>>>> Message-ID: <96BB388753294278A9CDE96C1EA7D9AE@pc52>
>>>>>> Content-Type: text/plain;charset="UTF-8"
>>>>>> 
>>>>>> Hi Graham,
>>>>>> 
>>>>>> That's very nice work. And you have uncovered several unusual effects
>>>>>> in the ES100. Bugs? Features? If we time nuts keep up the good work
>>>>>> to evaluate this chip, we are likely at some point to get an
>>>>>> informative response from the guys who designed it. They read
>>>>>> time-nuts.
>>>>> I didn't see this mentioned, but I think I have found the relevant US
>>>>> patent application: US20130051184A1, Real-time clock integrated circuit
>>>>> with time code receiver, method of operation thereof and devices
>>>>> incorporating the same, Oren Eliez

Re: [time-nuts] More ES100 WWVB Measurements

[Bob kb8tq]

Hi

If you are fairly deep inside a building, GPS isn’t going to get there. WWVB 
likely 
will make it to an internal location. 

If you are convinced that WWVB is un-jamable and that GPS is easily jammed, WWVB
would be more robust. 

That’s about it.

Bob

> On Dec 31, 2018, at 7:56 PM, Wayne Holder  wrote:
> 
> While reading this thread and pondering whether to buy and fool around with
> an ES100-based module from Universal Solder, I suddenly found myself
> wondering if there was any advantage to using the time received from WWVB
> vs just using an inexpensive GPS receiver.  The ES100  module costs about
> $70, but I can get a GPS receiver, with antenna, for far less than that and
> I've had no trouble receiving GPS signals indoors with most modern receiver
> modules.
> 
> I suppose the low power requirements of the ES100 might be an advantage
> when building battery powered clocks to mount on the wall, but it seems
> like some of the newer, ultra low power GPS modules intended for use in
> smart watches could also work in a battery-powered wall clock, especially
> if the receiver was only powered on a few times a day to update the time.
> 
> And, finally, if GPS modules are (or will some become) a suitable
> replacement for WWVB receiver modules, do we really need WWVB in the modern
> age?  Perhaps there's some critical advantage to using WWVB to get the time
> but, offhand, I cannot think of it.  What am I missing?
> 
> Wayne
> 
> On Mon, Dec 31, 2018 at 4:30 PM Brooke Clarke  wrote:
> 
>> Hi Joseph:
>> 
>> Thanks for the patent link.  I've added it to my WWVB phase modulation
>> info at:
>> https://prc68.com/I/Loop.shtml#La_Crosse_UltrAtomic
>> 
>> --
>> Have Fun,
>> 
>> Brooke Clarke
>> https://www.PRC68.com
>> http://www.end2partygovernment.com/2012Issues.html
>> axioms:
>> 1. The extent to which you can fix or improve something will be limited by
>> how well you understand how it works.
>> 2. Everybody, with no exceptions, holds false beliefs.
>> 
>>  Original Message 
>>> On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-requ...@lists.febo.com
>>> wrote:
>>> 
  time-nuts Digest, Vol 173, Issue 44
 Message: 7
 Date: Mon, 31 Dec 2018 04:04:22 -0800
 From: "Tom Van Baak" 
 To: "Discussion of precise time and frequency measurement"
 
 Subject: Re: [time-nuts] More ES100 WWVB Measurements
 Message-ID: <96BB388753294278A9CDE96C1EA7D9AE@pc52>
 Content-Type: text/plain;charset="UTF-8"
 
 Hi Graham,
 
 That's very nice work. And you have uncovered several unusual effects
 in the ES100. Bugs? Features? If we time nuts keep up the good work
 to evaluate this chip, we are likely at some point to get an
 informative response from the guys who designed it. They read
 time-nuts.
>>> I didn't see this mentioned, but I think I have found the relevant US
>>> patent application: US20130051184A1, Real-time clock integrated circuit
>>> with time code receiver, method of operation thereof and devices
>>> incorporating the same, Oren Eliezer et al, Oren Eliezer et al, filed
>>> 2013-02-28.
>>> 
>>> .
>>> 
>>> Found this by chasing stuff from the EverSet website:
>>> .<
>> http://everset-tech.com/wp-content/uploads/2014/11/ReceiverRadioClocks.pdf
>>> .
>>> 
>>> Joe Gwinn
>>> 
>>> 
 So now both you and Tim have observed the off-by-one-second (or
 off-by-N-seconds) effect in the ES100. I wonder if this explains why
 some of my ES100-based La Crosse 1235UA Ultratomic wall clocks are
 off by a second sometimes.
 
 My main question: in your "Time Plot.PNG" plot, what is the cause of
 the sawtooth pattern? The points are almost all on a clear negative
 slope, though bounded by roughly +/- 75ms. Looking on the far left, I
 see a time drift of +50 ms to -25 ms over an hour, which is
 equivalent to a -20 ppm frequency offset; about -2 seconds/day.
 
 Do you think this is due to the 16 MHz onboard xtal? If so, how about
 changing the temperature of the eval board by a lot (say, several
 tens of degrees) for an extended time (say, 4 hours) and see if the
 sawtooth slope changes convincingly.
 
 Also, just to be sure, can you put a known independent timing signal
 (e.g., GPS/1PPS) into your complex BeagleBone Black / Debian 9.4 /
 ntpd time server / Python 3 / Excel stack to establish the validity
 of your measurement methodology? Very likely you did it right, but I
 always cringe when I hear "Linux" or "NTP" and "precise time" in the
 same sentence. Yes, sorry, forgive me; I grew up in the "trust, but
 verify" generation [1]. It applies pretty well to metrology also ;-)
 
 /tvb
 
 [1] https://en.wikipedia.org/wiki/Trust,_but_verify
 
 
 End of time-nuts Digest, Vol 173, Issue 44
 **
>>> ___