Re: [time-nuts] EFOS2 Maser acting up :(

[Dana Whitlow]

Corby,

What's the H flow rate control doing when the IF level goes down, or
increases, depending?

Prior to retirement, I was the "Keeper of The Clock" at my job, which
entailed riding herd on
our Symmetricom H-Maser (among other things).  At one point about five
years ago, the
IF amplitude began oscillating up and down a few percent, with a period of
around 11 days.
This behavior commenced rather abruptly.  Nothing that was visibly
disruptive to the usefulness
of the system, but definitely worrisome.  The folks at Symmetricom had no
idea what might be
going on, and all they could suggest was "watchful waiting".  I was still
waiting watchfully
when I retired some four years later.  This maser regulates the IF
amplitude via a feedback
loop which adjusts the H flow rate by adjusting power to a heater on a Pd
disk "filter" in the
H path.  I suspect that something has gone wrong in that feedback loop,
such as a capacitor
failure spoiling the loop dynamics, but could not justify shutting down the
system while I
troubleshot the problem.  So I just kept management apprised of the
situation, as well as the
guy who replaced me when I retired.

But if you have a log of internal goings on, as I did, it might well be
informative to study how
other internal parameters varied when your IF amplitude hiccups occurred.

Dana


On Mon, Aug 13, 2018 at 4:56 PM, Tom Van Baak  wrote:

> Corby,
>
> Nice detective work. Keep us posted. I had a case some years ago where my
> IF level was sputtering around. It turned out to be the dissociator. It was
> a pretty easy fix after a fax / email or two from Russia.
>
> If you suspect the L.O. you can always free-run it for a week and see if
> similar symptoms occur. That would eliminate 99% of the complexity of the
> maser as the source of the problem.
>
> /tvb
>
> - Original Message -
> From: 
> To: 
> Sent: Monday, August 13, 2018 1:07 PM
> Subject: [time-nuts] EFOS2 Maser acting up :(
>
>
> > Hi,
> >
> > The EFOS2 Maser is having an "issue", the I.F.level is intermittently
> > fluctuating and sometimes drops all the way to zero. I've always wanted
> > to see the "raw" output from the cavity so now was my chance! Installed
> > two SMA cables  bringing the output of the circulator and the input to
> > the LNA out to where I can get at them. Managed to catch it at zero and
> > hooked a Spec-A to the output of the circulator. Hooray, The Maser cavity
> > output is good, so the problem lies downstream. Installed a directional
> > coupler between the two lines looking back into the LNA. Can see a
> > healthy 1440 Mhz L.O. leakage and logged a reference level. Now just
> > waiting for it to drop again and see if it's the L.O. If not I'll have to
> > dive in again and move my monitor SMAs to look at the 19.6...Mhz I.F.
> > signal. Pix shows the cavity signal on the spec-A.
> >
> > Cheers,
> >
> > Corby
>
>
> 
> 
>
>
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Re: [time-nuts] Pressure related rubidium oscillator aging

[Dana Whitlow]

What you say makes good sense, as He does not stick around very well- it
would
tend to diffuse out through the cell walls.

I once spoke with a fellow involved in the deep sea diving business, and he
claimed
that vidicon cameras used in the deep habitats used to deteriorate in
performance in
a matter of days due to in-diffusion from the high pressure He atmosphere.
They
had to order custom vidicon tubes made of special glasses for which He
diffusion
was much lower.

Dana


On Tue, Aug 14, 2018 at 4:21 PM, Attila Kinali  wrote:

> On Tue, 14 Aug 2018 14:23:56 -0500
> Dana Whitlow  wrote:
>
> > Does the Rb cell use He as a buffer gas?
>
> AFAIK most use a Ne/N mixture these days. I am not sure whether
> I have seen He used as buffer gas for Rb cells, but I do not think so.
> Other noble gases (Ar, Xe, ...) popped up a few times, though.
>
> 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] PPS pulse length (was: 1PPS for the beginner)

[Dana Whitlow]

Arecibo did a kind of cute trick with their distributed 1PPS.   The one
second pulses were of one length
(100 ns as I recall), but the 10 sec boundaries had the pulses be about
twice that length.  One could carry
this scheme to considerable lengths as desired.

Dana


On Tue, Aug 14, 2018 at 4:00 PM, Attila Kinali  wrote:

> On Tue, 14 Aug 2018 20:52:50 +0200
> "Bernd Neubig"  wrote:
>
> > Is there any common practice for the duty cycle of the 1 PPS pulse?
>
> As short as the consumer can take. Because a long pulse means that
> you are wasting energy and heating up both the pulse generator
> and the consumer. As TvB wrote, it varies from a few µs to a few ms.
>
> 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] Question about effect of spurious frequency modulation on Allan Deviation

[Dana Whitlow]

One might also do some trials based on comparing ADEV results between a
clean carrier signal
and ones corrupted with varying degrees of FM (for example), to get a feel
for the problem.  If
nothing else, one ought to be able to get some feel for the sensitivities
involved.

Dana K8YUM


On Mon, Aug 6, 2018 at 8:17 AM, jimlux  wrote:

> On 8/5/18 11:22 PM, Poul-Henning Kamp wrote:
>
>> 
>> In message <84a802ff-88f1-5f50-1f79-71d8ba3c4...@rubidium.dyndns.org>,
>> Magnus D
>> anielson writes:
>>
>> What does exists is a formula for how a single sine spur would produce
>>> ADEV. A FM deviation with low enough modulation index creates two
>>> side-bands of opposite sign but same amplitude.
>>>
>>
>> I find the easiest way to wrap my head around this is to think
>> about measuring Adev by timing zero-crossings.
>>
> 
>
>> Depending on the modulation signal, there may be moments where the
>> zero-crossing is "where it should be", for instance if the modulation
>> is sine or triangular, but not if it is a signed square wave.
>>
>>
>
>
> What about doing some sort of fit to the measurement data before
> calculating the ADEV? Similar to removing a linear ramp.
>
> basically you'd solve for the three sine parameters (f, phase,
> amp/deviation), then remove that from the data, then run the ADEV
> calculation.
>
>
>
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Re: [time-nuts] Bicentennial GOES satellite clock

[Dana Whitlow]

How exactly does one get submillisecond time of day precision with a
sextant?
(even if sticks and pebbles are thrown into the mix)
I'd say more like ~1 sec precision on a really fine day, it the sextant is
wielded by
a skilled and practiced operator who has apriori knowledge of his location.

And what about standard frequency dissemination?

I'm also upset about the notion of time distribution and transfer by
internet.  Now
there's a fine example of a system that could be brought down by a single
competent
hacker!

And all it takes is one really good solar flare to bring down GPS (and
Glonass and
the others) semipermanently, if the reports I read are true.

I argue that instead of shutting down distribution avenues, NIST should be
making
additional ones available.

A lot has been said lately about how rapidly our technology is exploding.
But think
about how much of that is critically dependent on precision time transfer
over the
planet, and how much longer it would take mankind to recover from (insert
your favorite
disaster here) without good time and frequency transfer still up and
working.

Dana





On Sun, Aug 12, 2018 at 2:06 PM, djl  wrote:

> all you need for a once a day noon fix is a level surface, a stick, and
> some pebbles.
> Don
>
>
> On 2018-08-12 08:29, 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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>> and follow the instructions there.
>>
>> 

Re: [time-nuts] NIST

[Dana Whitlow]

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.

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!

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

[Dana Whitlow]

Craig,

The original main reason for WWVB had nothing to do with syncing our
"atomic"
wristwatches and clocks.  It was for keeping local frequency standards
honest, for
which continuous coverage throughout the day and night was desirable (if not
always achievable).  But for that application, a one-shot daily sync was
not really
good enough (for most users).  Stations that used WWVB for serious purposes
used
outdoor electrostatically-shielded loop antennas, usually up on the roof,
to get
enough signal enough of the time.

I'm curious about your fan-related interference.  Fans of the kind used for
"cooling"
living space generally use induction motors, which per se have no mechanism
for
generating RFI.  However, more modern fans sometimes have digital control
systems, which of course do include built-in RFI generators.I wonder
which variety
you're using.

My Casio watch (module 3405) seems to sync reliably at night if held in a
favorable
orientation through the exercise, but if worn on the wrist at random but
changing
orientation, it often misses.  Fortunately mine seems to drift only about 1
sec per
month when "free running", so I now leave auto-sync turned off and just do
a single
forced sync every few weeks when I decide it's getting "too far off" based
on WWV.

Dana


On Sun, Aug 12, 2018 at 10:40 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.
>
> Dana, I’m puzzled by what you wrote.  I have 8 clocks and 2 wristwatches
> that sync with WWVB.  When band conditions are poor they miss a sync for a
> day but still they are good quartz clocks so the time readout is still OK.
> When the band conditions are good again they sync up once per day usually
> around 2am (according to the manual for my wristwatch).  I can easily tell
> the sync status on all but 4 of my clocks and they sync successfully about
> 90% of the overnight times.  My wristwatches are Citizen models that charge
> by solar which is nice since I have a perfectly in sync watch that never
> needs to be opened to change a battery.
>
> I do like the idea of a GPS to WWVB timecode radio transmitter.  I think
> that would sell well to folks on the fringe of coverage for WWVB such as
> Florida, Hawaii, and Alaska or other parts of the globe.  I’ve found the
> real limitation to reception of WWVB is local 60kHz noise in the home.  For
> instance if I have a fan running to cool things in my shack then my WWVB
> clocks will not sync successfully.
>
> I hope Nick Sayer is reading this and getting the idea to make a GPS to
> WWVB timecode radio transmitter, clever gent that he is.  :-)
>
> Best Wishes,
> Craig
> KI7CRA
>
> > On Aug 11, 2018, at 7:48 PM, Dana Whitlow  wrote:
> >
> > I fear the worst.  The line in the website simply stated something like
> > "shutting down
> > the transmitters in Colorado and Hawaii", which would seem to include the
> > whole
> > enchilada.
> >
> > For the wall clocks, GPS should work well if people are willing to go to
> > battery-
> > backed AC power.  But not so good for wristwatches, where the expectation
> > is to
> > run at uW power levels.  I for one would be very irritated at having to
> > take my watch
> > off my wrist and put it on a charging stand every night.  So if this
> > shutdown comes
> > to pass, I'll be looking for an inexpensive GPS-to-WWVB converter, or at
> > least
> > plans for building one.
> >
> > Dana
> >
> >
> > On Sat, Aug 11, 2018 at 8:12 PM, Bob Albert via time-nuts <
> > time-nuts@lists.febo.com> wrote:
> >
> >> With any luck, the current administration will successfully push the USA
> >> down technically.  Denying global warming, shutting off time signals,
> and
> >> so on, is great stuff.
> >>On Saturday, August 11, 2018, 6:10:12 PM PDT, Bob kb8tq <
> kb...@n1k.org>
> >> 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-
> >&g

Re: [time-nuts] 1PPS for the beginner

[Dana Whitlow]

Thanks Bob and Azello.  Now I understand the terminology and also better the
mechanism for the sawtooth error.

I once read that the LO, at least, in some GPS receivers, was not even
crystal
controlled but was rather a ring oscillator based on a string of cascaded
logic inverters on the chip.  This always sounded improbable to me, and i've
long wondered it this claim was really true.  Can either of you shed light
on
this issue?

Thanks,

Dana


On Tue, Aug 14, 2018 at 8:04 AM, Bob kb8tq  wrote:

> 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 <
> azelio.bori...@gmail.com>
> > 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 <http://pdf.directindustry.com/pdf/oscil

Re: [time-nuts] NIST

[Dana Whitlow]

I fear the worst.  The line in the website simply stated something like
"shutting down
the transmitters in Colorado and Hawaii", which would seem to include the
whole
enchilada.

For the wall clocks, GPS should work well if people are willing to go to
battery-
backed AC power.  But not so good for wristwatches, where the expectation
is to
run at uW power levels.  I for one would be very irritated at having to
take my watch
off my wrist and put it on a charging stand every night.  So if this
shutdown comes
to pass, I'll be looking for an inexpensive GPS-to-WWVB converter, or at
least
plans for building one.

Dana


On Sat, Aug 11, 2018 at 8:12 PM, Bob Albert via time-nuts <
time-nuts@lists.febo.com> wrote:

>  With any luck, the current administration will successfully push the USA
> down technically.  Denying global warming, shutting off time signals, and
> so on, is great stuff.
> On Saturday, August 11, 2018, 6:10:12 PM PDT, 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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> > and follow the instructions there.
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Re: [time-nuts] 1PPS for the beginner

[Dana Whitlow]

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 term average
> frequency
> > >> and phase of the GPS PPS, so what you see externally is 10MHz directly
> > >> from the OCXO, 1 Hz (PPS) which is divided down from the 10MHz OCXO,
> and
> > >> those are controlled by a PLL so that long term the phase of the PPS
> > >> divided down from the OCXO follows the PPS calculated by the GPS
> receiver,
> > >> but with lower jitter.
> > >>
> > >> --
> > >> Chris Caudle
> > >>
> > >>
> > >>
> > >> ___
> > >> time-nuts mailing list -- time-nuts@lists.febo.com
> > >> To unsubscribe, go to http://lists.febo.com/mailman/
> listinfo/time-nuts_lists.febo.com
> > >> and follow the instructions there.
> > >
> > > Don’t worry about how powerful the machines are. Worry about who the
> machines are giving  power to.
> > >
> > >
> > > ___
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> >
> > Don’t worry about how powerful the machines are. Worry about who the
> machines are giving  power to.
> >
> >
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Re: [time-nuts] WWVB and Chronverter update

[Dana Whitlow]

I like Paul's idea, although there may be a risk of the LED's drive signal
not being accurately timed.  Driving that LED accurately may have had
a low priority in the programmer's mind.

This should be independently checked for critical applications.

Dana


On Fri, Aug 24, 2018 at 8:23 AM paul swed  wrote:

> Thank you for the responses.
> I have not reached out to him yet. Want to see if there are other issues
> and I can easily add an external 60 KHz source and modulator right now to
> verify the other functionality.
> There is no schematic nor source code its a 8 pin uproc chip and as such
> has almost no IO. I can easily see a very simple fix but needs a change to
> the code behavior. (The chip it self can not do the modulation function.
> Thats why its OOK).
> But if the carrier were left on there is a LED that blinks to the time code
> sequence and that can drive a 1 transistor or diode modulator.
> Regards
> Paul
> WB8TSL
>
> On Fri, Aug 24, 2018 at 3:14 AM, Dana Whitlow 
> wrote:
>
> > Is there a schematic published for the Chronverter?  I agree with Didier
> > that the
> > OOK issue *ought *to be pretty easy to fix, and I'd like to look into
> that
> > myself.
> >
> > Dana
> >
> >
> > On Thu, Aug 23, 2018 at 9:00 PM Didier Juges  wrote:
> >
> > > Have you tried to contact the manufacturer? It sounds like something
> that
> > > should be easy to fix and that he would want to fix.
> > >
> > > Didier KO4BB
> > >
> > > On Thu, Aug 23, 2018, 8:55 PM paul swed  wrote:
> > >
> > > > Hello to the group.
> > > > Had sometime to hook up the chronverter wwvb simulator.
> > > > Numbers of details.
> > > > The software and operation are clear.
> > > > Everything is easy to setup.
> > > > Bad news.
> > > > Though the system when set to wwvb puts out a signal on 60Khz its on
> > off
> > > > keying.
> > > > WWVBs signal is reduced carrier by some 14db.
> > > > As such any of the WWVB clocks of quality/phase tracking do not lock
> > and
> > > do
> > > > not decode.
> > > > I have not tried the cheap clocks yet that I suspect will work.
> > > > The actual carrier out is a healthy 0 dbm.
> > > >
> > > > Some issues with commands and the system seeming to lock up requiring
> > > power
> > > > cycles.
> > > >
> > > > With respect to the carrier. The chronverter is elegant in the fact
> > that
> > > it
> > > > can generate the 60 KHz frequency and other LF signals. But I will
> need
> > > to
> > > > add an external 6 MHz oscillator divider and modulator if I want to
> use
> > > it
> > > > with the good receivers.
> > > > Adds power and complexity.
> > > > Regards
> > > > Paul
> > > > WB8TSL
> > > > ___
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> > > >
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Re: [time-nuts] Petition to Maintain WWV, WWVH, WWVB

[Dana Whitlow]

Is there more of it?   What I see makes no reference to WWVB.

Dana


On Fri, Aug 24, 2018 at 1:10 PM Graham / KE9H  wrote:

> Here is the URL of a petition to maintain funding of WWV, WWVH, WWVB.
>
> Only currently at about 7 percent of the number required for a response
> from White House.
>
>
> https://petitions.whitehouse.gov/petition/maintain-funding-nist-stations-wwv-wwvh
>
> --- Graham
>
> ==
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Re: [time-nuts] Russian HF Timing Service ?

[Dana Whitlow]

Not having the coordinates in hand, all I can do is suggest using Google
Earth (or Maps)
and look for suitable antenna farm(s).

Dana



On Tue, Aug 21, 2018 at 12:05 PM Mark Sims  wrote:

> Lady Heather v6 has a command (SD) that estimates the propagation delay
> (and distance) between your location and a remote station/location.  The
> station location can be given as lat/lon or the station name.  I have seen
> a couple of conflicting location values for RBU.  I think I'm using the
> proper value.  Does anybody know the correct location of RBU?
> ___
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Re: [time-nuts] WWVB Signal Generator

[Dana Whitlow]

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 Signal Generator

[Dana Whitlow]

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, 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
> &g

Re: [time-nuts] TNS-BUF update

[Dana Whitlow]

Be watchful about the black epoxy.   It may just be a dyed (otherwise
clear) epoxy,
and some of the black dyes in common use pass near IR quite readily.  This
would
probably be most troublesome if the ambient light source were of the
incandescent
persuasion.

Also, small diodes in clear packages can also make photodetectors.  I once,
in
desperation at a customer's site, successfully kluged a slightly
sub-nanosecond
detector out of a 1N914 (or one of those types like that) and a 9V battery.

Dana


On Sun, Aug 19, 2018 at 8:15 AM, Didier Juges  wrote:

> That's a very good point. I have used LEDs as photocells many times, the
> first time was in 1974 when it was easier for this university student to
> get LEDs than photocells.
>
> I have also made a bi-directional optically isolated data link using a
> single fiber optic cable and two fiber optic transmitters (LEDs) in the
> HFBR-500 series.
>
> A couple coats of black paint, or a dab of black epoxy covering the LED
> should work. Include the back side of the PWB for good measure, this is
> time-nuts :)
>
> Didier KO4BB
>
>
> On Sun, Aug 19, 2018, 3:38 AM Poul-Henning Kamp 
> wrote:
>
> > 
> > In message <1818735266.3837388.1534666949...@webmail.xtra.co.nz>, Bruce
> > Griffit
> > hs writes:
> >
> > >It exploits the fact that for a RED LED at least the difference
> > >between the LED forward voltage and the transistor Vbe is ~ 1V and
> > >has a fairly low tempco and has low noise (at  least for RED LEDs).
> >
> > ... in darkness.
> >
> > When using LEDs this sort of way, they should always be totally
> > shielded from all external light.
> >
> > --
> > 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] Naked 4046 PLL chip

[Dana Whitlow]

Did the original '4046 include the anti-backlash fix?

Dana


On Saturday, July 21, 2018, Dr. Ulrich L. Rohde via time-nuts <
time-nuts@lists.febo.com> wrote:

> Obsolet by today’s standard
>
> Sent from my iPhone
>
> > On Jul 21, 2018, at 10:44 AM, Poul-Henning Kamp 
> wrote:
> >
> > Clearly not your average chip:
> >
> >https://zeptobars.com/en/read/Ti-CD4046BE-CMOS-PLL-
> Oscillator-VCO-zener
> >
> > --
> > 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] Effects of Simple GPS jamming on GPSDO's ?

[Dana Whitlow]

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
> >>> 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,
> > 

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

[Dana Whitlow]

Scott & John,

Do either of you have any activity by "Light Squared" (or whatever it's now
called) in your area.  Jamming does not always have to be in-band to be
effective.

Dana


On Tue, Sep 4, 2018 at 1:11 PM Scott McGrath  wrote:

> My TrueTime DC-XL has lost lock since yesterday as has my Z3805 and my
> car’s onboard GPS will not lock since the 2’nd.  I need to get about a mile
> from home before Car’s nav system reports ready.
>
> There has been a great deal of repair work on the local cable system so
> this is almost certainly related to that
>
> But it proves my point about the fragility of GPS
>
>
>
>
>
> On Sep 4, 2018, at 12:31 PM, John Sloan  wrote:
>
> Folks:
>
> GPS jamming and spoofing isn't really my area of expertise, but it's
> something I worry about, not just for its impact on geolocation and
> navigation applications, but also because GPS has become critical as a high
> precision timing reference in the telecommunications realm, which *is* my
> area of expertise.
>
> Yesterday (2018-09-03) afternoon (about 22:00UTC, 16:00MDT) I noticed one
> of my three home-made GPS-disciplined NTP servers had lost its GPS lock.
> After some forensics on my part, this (2018-09-04) morning (about 16:00UTC,
> 10:00MDT) I replaced the amplified antenna, and the device reacquired its
> lock. I figured it was just an antenna failures; this is an amplified
> filtered antenna so it has active electronics.
>
> Then just an hour or so later, I noticed one of my commercial
> GPS-disciplined NTP servers (TimeMachines) had lost the GPS 1PPS timing
> signal, but indicated it still had GPS lock. (I question now what this
> actually means in the context of this particular device). As a
> troubleshooting step, I power cycled the device, and it reacquired 1PPS.
> But as I did that, the second commercial GPS-disciplined NTP server
> (Uputronics) right next to it lit up with a red warning on its display,
> indicating it had lost GPS lock. A minute or so later it also reacquired
> lock and indicated 1PPS, with no action on my part.
>
> All of these devices are completely independent, have different software
> (and probably hardware), have separate amplified antennas sitting side by
> side in the window of my home office, and are not all on the same
> electrical outlet (but may be on the same household circuit).
>
> I lit up the LCD display on my little GPS monitoring tool I built that
> runs Lady Heather 24x7 and see on the graphical display sudden jumps of
> reduced timing accuracy of a factor of 10^2 (from nanoseconds to hundreds
> of nanoseconds) in the recent past. But I’m thinking this can also be
> caused just by the dynamic satellite geometry, and might be normal. It’s
> not like I watch this graph all the time (even though it does sit right in
> front of me on my desk).
>
> No clue what's going on in my suburb near Golden Colorado. But I’m a
> little freaked out. Trying to figure out which rule, [1] It’s something
> stupid I’ve done, or [2] I am not unique, to apply.
>
> :John
>
> --
> 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] wwvb antenna transmission Well harder then I might think.

[Dana Whitlow]

Paul,

You really don't want to be building an antenna that radiates energy, which
is a far-field
concept.  In your case, at 30 ft range, you're so far inside the near field
that all the
antenna articles in the world won't help, since they address radiating into
the far field.
That's what WWVB needs to do, but not you.  I think what you want to do is
use a loop
that is no larger than your house, preferably smaller, and push enough
power into it
to achieve your range goal (but not any further).

Dana


On Thu, Sep 6, 2018 at 6:21 PM paul swed  wrote:

> Working on the wwvb simulator and it works really well. On to the last
> piece. Transmission over maybe 30 ft.
> Ever notice everyone that makes a simulator has the clock on top?
> Well thats because its pretty hard to get a 60 KHz signal actually out.
> Even though I know loopsticks are not great transmit antennas that was the
> first attempt. Hey what they say is true, Bad.
> Next will be the loose wire over the distance. More likely a spare phone
> wire pair that runs all over the house.
> Just some humor.
> I have found a ton of online articles on vlf antennas and such. Heck seems
> like its time to read them.
> Regards
> Paul
> WB8TSL
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Re: [time-nuts] OOPS on my wwv legal post

[Dana Whitlow]

Since propagation issues quickly degrade both frequency stability and time
accuracy, I see little point in worrying about the difference between UTC
and UTC(NIST).

Of greater interest should be the meaningfulness of time transfer obtained
with
 NIST's TMAS service.  It is apparently referred to UTC(NIST).   See:


https://www.nist.gov/programs-projects/time-measurement-and-analysis-service-tmas

It's an interesting service; it has been in use at the Arecibo Observatory
since soon
after its inception (~5 years ago IIRC) to provide information relevant to
decisions
for  tweaking the observatory's H-maser's frequency.  TMAS revolves around
"Common
View GPS measurements".   A major down side (for most time-nuts, anyway) is
the cost
of the service, which is presently  in the neighborhood of $10k per year.

I have made inquiry regarding whether or not TMAS is also on the chopping
block;
nothing heard back so far.

Dana


Dana




On Thu, Aug 30, 2018 at 2:05 AM John Marvin  wrote:

> I was under the mistaken impression that WWV/WWVB had some type of
> direct line to NIST in Boulder. However, when I toured the facility in
> Fort Collins earlier this year, I learned otherwise.  The signals and
> carriers are derived/synced from "ordinary" HP (possibly some more
> recent Symmetricom's) cesium beam atomic clocks.  I wish I remembered
> the details, but I asked how they synced them with NIST. I believe the
> answer was that at one time they had some type of connection to Boulder,
> but now just use a GPS based solution.
>
> The WWV and WWVB stations in Fort Collins are old, and run on a fairly
> tight budget, with a very small (but dedicated) staff. They are not on
> the cutting edge of timekeeping technology.  I'm not trying to imply
> that WWV/WWVB is "inaccurate", but there is nothing special there. Many
> of the participants on this list, if they were determined, could put out
> a signal every bit as accurate as WWV or WWVB, they just wouldn't be
> able to do it at the power levels (especially WWVB) that WWV and WWVB
> signals are transmitted at. The antenna's and transmitter's are some of
> the most impressive parts of the WWV / WWVB facilities.
>
> Regards,
>
> John
>
> P.S. I was also impressed with their backup generator, although I now
> can't remember if that only provided power for the WWVB station, or for
> both WWVB and WWV (they are separate facilities, although in easy
> walking distance of each other on the same property).
>
>
> On 8/29/2018 7:24 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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>
>
>
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Re: [time-nuts] WTS: Efratom PTB-100 Precision Timebase

[Dana Whitlow]

Don, I've noticed that in general IEEE retains copyright on most stuff they
publish.
I've been a member for more than 20 years, and this galls me.  For an
organization
that purports to be for the good of mankind, they seem awfully stingy with
the
information they gather.  But if you do acquire papers from IEEE, you are
generally
*not *authorized to publish or distribute it further without getting
explicit permission
(and probably paying for it).

Sometimes I wonder why I hang onto the organizaiton- perhaps it's because,
as
a retiree, I'm unable to subscribe to all the usual "freebie" rags.  I
still very much
want to keep up with developments in my field.

Dana


On Sun, Jul 8, 2018 at 2:09 PM, djl  wrote:

> Greg et.al. IEEE stuff is just too expensive for single purchase. I have
> found, to my sorrow over 40 odd years, that they also do not contain 
> information, that is, info of actual use, because some other company or
> person might actually benefit. In other words, the papers are markers in
> the sand.
> Now, this is my own opinion, a bit harsh, admittedly. Of course the
> citations do need to be mentioned.
> BTW, any published material generated with government funds that is not
> classified belongs to the people, and is not copyrighted. I wonder if that
> includes IEEE papers? that is, if anyone buys one, it can be copied or
> distributed without restriction?
> Not being in the lawyer class, I can't say for sure...
> Thanks
> Don
>
>
> On 2018-07-08 10:39, Gregory Beat via time-nuts wrote:
>
>> Magnus -
>> When I scan/read the 1984 IEEE document, “Lifetime and Reliability of
>> Rubidium Discharge Lamps for Use in Atomic Frequency Standards”
>> by Aerospace Corp., Efraton-Ball, and EG
>> https://ieeexplore.ieee.org/document/1537723/
>> The failure of the rubidium lamps used on early NAVSTAR satellites,
>> was the reason for in-depth studies of the Rb lamp, its lifetime and
>> failure mechanism.
>>
>> greg
>>
>> Hi -
>>> I later tried that method on my R XSRM rubidium, with good progress. I
>>> have reported on that on the list way back. It took two attempts, one
>>> just to realize that I needed to keep the pinch at the top, because that
>>> is where the hot atoms go.
>>>
>>> Essentially, the thin film of rubidium will consume too much of the
>>> radiation to emit any useful amount of pumping light. Heating it has the
>>> rubidium go into gas and then collect somewhere cold, so it's just about
>>> making sure that somewhere cold isn't the glass where it is to emit
>>> light.
>>>
>>> My XSRM have however other issues that I need to attend to.
>>>
>>> Cheers,
>>> Magnus
>>>
>>
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>>
>
> --
> Dr. Don Latham
> PO Box 404, Frenchtown, MT, 59834
> VOX: 406-626-4304
>
>
>
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Re: [time-nuts] How can I measure time-delay of a cable with HP 5370B time-interval counter?

[Dana Whitlow]

If you can get access to a 2-channel 'scope, try it instead of a TIC
so you can get some clue as to what's happening.  I suspect that one
component of the problem is that the supposedly Hi-Z input of the
counter really isn't but has a stub of unterminated cable between the
input connector and where the end of said cable dumps into the internal
circuitry.

Best thing to do if anything like this is happening is to set both inputs
to 50 ohms and use an isolating splitter.  Or, failing that, put matched
attenuators in each output of the tee, using as much attenuation as
you can tolerate.

With sine waves, reflection problems just modify the amplitude and
phase, hard to tell what's going on.  But with fast-rise edges, you can
often sort these things out if you can see the waveform(s), thus the
desirability of using an oscilloscope.   And as has been pointed out,
having unequal trigger points can only make matters worse.

Dana


On Sun, Oct 28, 2018 at 11:47 PM Orin Eman  wrote:

> On Sun, Oct 28, 2018 at 8:31 PM Hal Murray 
> wrote:
>
> >
> > drkir...@kirkbymicrowave.co.uk said:
> > > I'm feeding a sine wave from a Stanford Research DS345 30 MHz function
> >
> > Are the levels set so it triggers at the same point?  It doesn't look
> like
> > it
> > in your photo.
> >
> > Looks like you are running at 1 MHz.  If the stop trigger is a little
> > lower/earlier than the start trigger, you will have to wait a whole
> cycle,
> > so
> > 950 ns is a reasonable result.
> >
>
>
> Looked like the levels were on Preset.  So, a little difference in what
> "Preset" means and as Hal says, you wait a whole cycle.
>
> One could fiddle with the stop trigger level, but the rise time of the sine
> at these frequencies is so long, that a small change in the trigger level
> is going to make a large change in the measurement.
>
> I'd try the same experiment with a square wave instead to minimize this
> effect.
>
> Once you get a stable measurement with a square wave, then experiment with
> the trigger level controls.  Going clockwise from Preset, I usually see no
> trigger, followed by a narrow band where it triggers, followed by no
> trigger.  In the band where it triggers, assuming adjusting a stop trigger
> that is set to the rising edge, as the trigger level is increased, so does
> the time interval.
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Re: [time-nuts] Tbolt GPS for sale

[Dana Whitlow]

Jerry,

Please contact me off-list.  I have questions, and might be very
interested in your T'bolt.

Dana  k8yumdoo...@gmail.com (830) 896-6712

On Tue, Oct 30, 2018 at 5:05 PM Jerry  wrote:

> Subject: Tbolt GPS for sale
> I am selling my Trimble 10 MHz Thunderbolt GPS disciplined frequency
> standard.  This is the older unit with the power connector on the top and
> labeled AA002206.G1, Rev E, 3-2-05.  It is mounted in an aluminum box
> designed for disk drives that is about 5 in. wide X 7 in. high and 10 in.
> deep.  It has a +12, -12, 5 v power supply inside and also a fan running at
> reduced speed mounted on the rear. AC Power in and the 10 MHz out,  the
> 1PPS out and the RS-232 connector are all mounted on the rear panel.  There
> is a 2 line display module mounted on the front that displays the time and
> other info from the RS-232 output from the tbolt.  The module was sold by a
> company called Fluke.1 and runs firmware from KO0BB.  The display module
> needs some attention as it is somewhat dim and has the GPS Week Rollover
> problem that confuses its date display.  I am also including the outdoor
> bullet antenna.  Other than the display module everything works fine. It
> runs both the Tboltmon and Lady Heather programs without errors and shows
> all 8 satellites in the green.  I am selling because it is a better 10 MHz
> unit than I need with my ham gear and I am now running a couple of the
> small Chinese GPS disciplined units.  I am asking $250.00 shipped and
> insured to the lower 48.  I would prefer a Bank of America Cashiers check
> or a Postal Money Order.  I have pictures and if you give me a phone number
> I will be happy to answer questions.  I am in the Phoenix AZ area and if
> you are close I would be happy to demo and of course lower the price if no
> shipping is required
> 73 Jerry
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Re: [time-nuts] Oscilloscope-based measurements of frequency stability

[Dana Whitlow]

Hello Bert,

What is the cyan-colored trace seen in these screen shots?  And is
"1 ppt" the same as 1E-12 (just to be sure)?

Are these from LH?

Thanks,

Dana




On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts 
wrote:

> We see the glitches all the time, they exist and with proper equipment are
> very visible. These are telecom timing devices and the way they correct the
> 1 pps is by changing the frequency. Even LH shows it and it is very visible
> when you eliminate the other traces.What we call the Tbolt 2, the nicely
> packaged Trimle that also was part of the fraud listing does the correction
> once an hour. It is exact an hour function of when you powered it up.In my
> case night time spikes where mostly negative Air conditioner. Recovery is a
> function of the accumulated error. Standing next to it in front of my 19
> year old M300 it did effect the recovery  since my legs where within a
> foot. One picture shows the analog trace to.Original Tbolt does it
> constantly. We have spend a couple of years on this, hoping to optimize a
> clean up loop.so far no good results.Bert Kehren
> In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time,
> tsho...@gmail.com writes:
>
> Dana, the short term few-ns jitter of the two phases, I think in a digital
> instrument is most likely data acquisition glitches.
>
> Even on a good old analog scope, jitter in the trigger circuit or jitter in
> amplitudes (with resulting changes in harmonic content and thus the shape
> of the curves) can cause the apparent zoomed in zero crossing to shift very
> similarly.
>
> In days of old the telco standards for frequency stability also included
> requirements for amplitude stability noise, directly related to making
> repeatable measurements using scopes. I'm gonna see if I can find some of
> those. I remember some crazy looking telco standard that required measuring
> amplitude noise on time scales measured in weeks.
>
> Tim N3QE
>
> On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow  wrote:
>
> > I cheered when I saw Dave B's "silly question", for
> > then I realized that I'm not the only one who likes
> > to measure things with an o'scope.
> >
> > I had purchased a GPSDO a few weeks before and
> > had  been observing its behavior relative to a free-
> > running Rb by watching 10 MHz sinewaves drift with
> > respect to each other as an aid in setting the Rb's
> > frequency.  However, I was seeing enough fairly
> > rapid random drift to limit the usefulness of this kind
> > of observation.  It dawned on me that I was sometimes
> > seeing drifts of several ns over the course of just
> > several seconds, thus implying that sometimes the
> > relative frequency error between the two sources was
> > reaching as high as roughly 1E-9.  I wanted to be able
> > to capture and plot a somewhat extended run of data
> > so I could try to understand this behavior better.
> >
> > Being TIC-less, I decided to see what I could do with
> > my o'scope, which is a Chinese-made 2-channel DSO
> > with synchronous sampling by the two channels and
> > with a respectable trace memory depth (28 MSA per
> > channel).
> >
> > I began this effort  in earnest a couple of days before I
> > saw Dave's question, and have only now brought it to
> > a sufficient state of completion to feel justified in reporting
> > some results.
> >
> > I am presently able to record about 45 minute's worth of
> > data as limited by the 'scope's trace memory, but my XP
> > computer's RAM space limits me to processing only about
> > 35 minutes of that in a seamless run.  Over that time
> > span I've seen a peak relative frequency discrepancy of
> > about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > I've also measured average frequency differences between
> > the source's a a few parts in 10E11.
> >
> > Most of the effort went into developing a C program to do
> > the processing and then correctly scaling and displaying
> > the results in a form which I considered useful to me.  This
> > processing of course had to deal with an off-frequency and
> > drifting 'scope timebase, which is *horrible* compared to the
> > quantities under measurement (as expected from the outset).
> >
> > Present indications are that at this level of GPSDO mis-
> > behavior, the results I'm viewing are about 20 dB higher
> > than the basic floor, which I am still characterizing.  I
> > believe that the floor is limited primarily by uncorrelated
> > sampling jitter between the two 'scope channels.
> >
> > If there is an expres

Re: [time-nuts] XKCD on time :)

[Dana Whitlow]

David Van Horn,

You're on the right track, but what would you do about those pesky leap
seconds?

Dana


On Fri, Sep 28, 2018 at 2:48 PM Artek Manuals 
wrote:

> H  Farce-Book hadn't considered that approach .. some sort
> of (ready for this )
>
> "subliminal millennial  mind control" !!
>
>   The gnomes and I will go to work on it immediately !
>
> -DC
>
> On 9/28/2018 3:11 PM, David Van Horn wrote:
> > By expanding facebook significantly, I plan to keep the millennials
> occupied in such a way that they are peaceful, happy, and complacent.
> > Ad revenues could support the whole program.
> >
> > Solid state electronics seems to be something we will need to tolerate,
> but we can require tubes to be allowed to participate.
> >
> > 
> >
> > -Original Message-
> > From: time-nuts  On Behalf Of Artek
> Manuals
> > Sent: Friday, September 28, 2018 12:55 PM
> > To: time-nuts@lists.febo.com >> skipp via time-nuts <
> time-nuts@lists.febo.com>
> > Subject: Re: [time-nuts] XKCD on time
> >
> > David
> >
> > 1) Before I make a donation what is your plan to control the
> millennial's ?
> >
> > 2) Could we outlaw solid state electronics (or at least custom IC's) and
> go back to vacuum tubes while we are at
> >
> > Dave
> >
> > On 9/28/2018 1:53 PM, Martin VE3OAT wrote:
> >> I love GMT.  All of this UTC stuff is ... revisionist!
> >> My cheque is in the mail.
> >> ... MartinVE3OAT
> >>
> >> David Van Horn wrote :
> >>> When I am global dictator, we will all run on GMT and all time
> >>> zones, summer time, DST and similar nonsense will be abolished.
> >>>
> >>> I am accepting campaign donations!  ?
> >>>
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go
> >> to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > --
> > Dave
> > manu...@artekmanuals.com
> > www.ArtekManuals.com
> >
> >
> > ---
> > This email has been checked for viruses by Avast antivirus software.
> > https://www.avast.com/antivirus
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
> --
> Dave
> manu...@artekmanuals.com
> www.ArtekManuals.com
>
>
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Re: [time-nuts] 10 MHz -> 16 MHz

[Dana Whitlow]

Tom,

Divide the 10 MHz down to 2 MHz in the usual way, then multiply by 8
with a cascade of three analog freq doublers separated by fairly narrow
bandpass filters.  Caveats:  Would need four filters total along the path
to get rid of unwanted frequency components, gain distributed along
the path to keep the signal level high enough to satisfy the doublers,
and might suffer excessive phase drift due to temperature changes of
the filters (and probably to a lesser extent) the doublers themselves.
You didn't mention phase stability requirements...

Freq doublers based on mixers or on full-wave rectification have the
pleasant property of having *most* of their output power in the proper
harmonic order, but require sinusoidal drives to work.  An unfiltered
digital drive signal won't suffice here.

Dana



On Sat, Sep 29, 2018 at 10:58 PM Tom Van Baak  wrote:

> What's a clever, simple, reliable (pick 2 of 3) way to get 16 MHz out of
> 10 MHz? Low phase noise isn't a big requirement and jitter doesn't need to
> be sub-nanosecond. The main requirement is perfect cycle count accuracy.
> This is for driving a 16 MHz microcontroller from a 10 MHz Rb/Cs/GPSDO. 10
> MHz input is likely sine; 16 MHz output is 3v3 or 5v CMOS.
>
> Thanks,
> /tvb
>
>
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Re: [time-nuts] Oscilloscope-based measurements of frequency stability

[Dana Whitlow]

I've done the Lissajous thing, but it takes an extra bit of effort to
work out the phase angle.   I've always gone back to the sliding
waveforms display for simplicity.

But I'll admit the Lissajous pattern is a lot prettier, and looks great
in Sci Fi movies.

Dana


On Mon, Oct 1, 2018 at 4:06 PM Richard (Rick) Karlquist <
rich...@karlquist.com> wrote:

> No one mentioned using Lissajous patterns for comparing
> frequencies if the scope has an XY mode.  Google Lissajous
> if interested.
>
> Rick N6RK
>
> On 10/1/2018 11:40 AM, Bryan _ wrote:
> > Interested as well
> >
> > -=Bryan=-
> >
> > 
> > From: time-nuts  on behalf of Chris
> Burford 
> > Sent: October 1, 2018 6:20 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency
> stability
> >
> > This sounds interesting enough and I would appreciate any notes or
> insight on doing this. I have a PRS10 and several GPSDOs that I would like
> to evaluate for performance on my scope.
> >
> > Many thanks.
> >
> >
> >  Dana Whitlow  wrote:
> >> I cheered when I saw Dave B's "silly question", for
> >> then I realized that I'm not the only one who likes
> >> to measure things with an o'scope.
> >>
> >> I had purchased a GPSDO a few weeks before and
> >> had  been observing its behavior relative to a free-
> >> running Rb by watching 10 MHz sinewaves drift with
> >> respect to each other as an aid in setting the Rb's
> >> frequency.  However, I was seeing enough fairly
> >> rapid random drift to limit the usefulness of this kind
> >> of observation.   It dawned on me that I was sometimes
> >> seeing drifts of several ns over the course of just
> >> several seconds, thus implying that sometimes the
> >> relative frequency error between the two sources was
> >> reaching as high as roughly 1E-9.  I wanted to be able
> >> to capture and plot a somewhat extended run of data
> >> so I could try to understand this behavior better.
> >>
> >> Being TIC-less, I decided to see what I could do with
> >> my o'scope, which is a Chinese-made 2-channel DSO
> >> with synchronous sampling by the two channels and
> >> with a respectable trace memory depth (28 MSA per
> >> channel).
> >>
> >> I began this effort  in earnest a couple of days before I
> >> saw Dave's question, and have only now brought it to
> >> a sufficient state of completion to feel justified in reporting
> >> some results.
> >>
> >> I am presently able to record about 45 minute's worth of
> >> data as limited by the 'scope's trace memory, but my XP
> >> computer's RAM space limits me to processing only about
> >> 35 minutes of that in a seamless run.   Over that time
> >> span I've seen a peak relative frequency discrepancy of
> >> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> >> I've also measured average frequency differences between
> >> the source's a a few parts in 10E11.
> >>
> >> Most of the effort went into developing a C program to do
> >> the processing and then correctly scaling and displaying
> >> the results in a form which I considered useful to me.  This
> >> processing of course had to deal with an off-frequency and
> >> drifting 'scope timebase, which is *horrible* compared to the
> >> quantities under measurement (as expected from the outset).
> >>
> >> Present indications are that at this level of GPSDO mis-
> >> behavior, the results I'm viewing are about 20 dB higher
> >> than the basic floor, which I am still characterizing.  I
> >> believe that the floor is limited primarily by uncorrelated
> >> sampling jitter between the two 'scope channels.
> >>
> >> If there is an expression of interest in this technique, I'll
> >> publish a detailed description of the technique and some
> >> plots showing results, probably in the form of an attachment
> >> in pdf format.
> >>
> >> Dana
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> ht

[time-nuts] Oscilloscope-based measurements of frequency stability

[Dana Whitlow]

I cheered when I saw Dave B's "silly question", for
then I realized that I'm not the only one who likes
to measure things with an o'scope.

I had purchased a GPSDO a few weeks before and
had  been observing its behavior relative to a free-
running Rb by watching 10 MHz sinewaves drift with
respect to each other as an aid in setting the Rb's
frequency.  However, I was seeing enough fairly
rapid random drift to limit the usefulness of this kind
of observation.   It dawned on me that I was sometimes
seeing drifts of several ns over the course of just
several seconds, thus implying that sometimes the
relative frequency error between the two sources was
reaching as high as roughly 1E-9.  I wanted to be able
to capture and plot a somewhat extended run of data
so I could try to understand this behavior better.

Being TIC-less, I decided to see what I could do with
my o'scope, which is a Chinese-made 2-channel DSO
with synchronous sampling by the two channels and
with a respectable trace memory depth (28 MSA per
channel).

I began this effort  in earnest a couple of days before I
saw Dave's question, and have only now brought it to
a sufficient state of completion to feel justified in reporting
some results.

I am presently able to record about 45 minute's worth of
data as limited by the 'scope's trace memory, but my XP
computer's RAM space limits me to processing only about
35 minutes of that in a seamless run.   Over that time
span I've seen a peak relative frequency discrepancy of
about 1.4E-9, with a handful reaching or exceeding 1E-9.
I've also measured average frequency differences between
the source's a a few parts in 10E11.

Most of the effort went into developing a C program to do
the processing and then correctly scaling and displaying
the results in a form which I considered useful to me.  This
processing of course had to deal with an off-frequency and
drifting 'scope timebase, which is *horrible* compared to the
quantities under measurement (as expected from the outset).

Present indications are that at this level of GPSDO mis-
behavior, the results I'm viewing are about 20 dB higher
than the basic floor, which I am still characterizing.  I
believe that the floor is limited primarily by uncorrelated
sampling jitter between the two 'scope channels.

If there is an expression of interest in this technique, I'll
publish a detailed description of the technique and some
plots showing results, probably in the form of an attachment
in pdf format.

Dana
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Re: [time-nuts] 10MHz standard for comms receivers

[Dana Whitlow]

Isn't it the case that computer clocks these days are subject to two
influences that make them worthless for timing?

1. Deliberate random FM to spectrally spread RFI leakage.

and

2, Wild variations of clock speed according to usage needs of the moment,
in order to reduce average power consumption and thermal loading.

Dana


On Mon, Oct 1, 2018 at 12:37 PM jimlux  wrote:

> On 10/1/18 9:43 AM, Bob Betts wrote:
> > Hi All. Over the years, I have experimented with WWVB and GPS and
> Rubidium timing to establish a 10MHz Standard for LO sync in communications
> receivers. My career has kept me away from the hobby for some time and,
> frankly, I am not very well versed in some of the timing techniques that I
> read here...actually I'm just a hacker. Anyhow the thought occurred to me
> that with some of these newer computer clock timing systems, that a (for
> example) a 3GHz clock could be divided down by 300 to obtain a fairly tight
> 10MHz reference. It does have an effect on SDR pgms, but I'm curious about
> analog systems as well. It would seem (to me) that whatever error there may
> be at 3GHz, that it would also decrease to a tighter tolerance during the
> "divide by" process.
>
>
> ppm scales with frequency - a 1 GHz oscillator with 1ppm will divide by
> 100 to 10 MHz with 1ppm.
>
>
> Where it gets interesting is with phase noise.  Assuming no other
> sources of noise (not generally valid, but a good starting place):
>
> If you multiply or divide a source by N, the phase noise (at a given
> offset from the carrier) changes by 20 log N.  So if phase noise at 1
> GHz is -80dBc at 10kHz away, if you divide by 100, the phase noise will
> be -120dBc at 10kHz away.
>
> In general, the quietest sources (in terms of phase noise) are crystal
> oscillators in the 5-10 MHz range - to a first approximation, it's
> because the physical "rock" is big.
>
> So, it's more likely you'd get a quieter 1 GHz source by multiplying
> 10MHz up, than the other way around.
>
> That's for close in noise...(within some kHz of the carrier)  For far
> out noise, that's not necessarily the case.  You might find that the
> microwave oscillator has better noise at 1 Mhz out than the 10 MHz
> multiplied up (and degraded by 40 dB).  Maybe, maybe not - you need to
> look at your particular oscillator.
>
> In general, the wider the tuning range, the worse the noise.
>
>
> I work a lot at 8.4 GHz - taking something like a HMC506, the phase
> noise is -50dBc at 1kHz, -105dBc at 100khz and -125 dBc at 1 MHz
>
> If I lock that to a crystal at 10 MHz.. let's take an inexpensive tiny
> OCXO with good but not special noise..
> -160 dBc at 1kHz, -165 at 10kHz, and probably the same out to 1 MHz.
>
> I'm going to need to multiply up by 845. so 20logN is 58 dB
>
> At 1kHz, the multiplied up crystal is -102dBc, which is a lot better
> than my VCO at -50.
> At 100kHz, though, my crystal is -107dBc, and my VCO is at -105 -so
> that's pretty much a wash.
>
> At 1 MHz out, my crystal is still -107, but my VCO is down at -125, so
> it's quieter.
>
> If I were building a synthesizer, I'd probably make the loop bandwidth
> right around 100kHz.
>
>
>
> > Okay, so I've been an RF and Audio products designer for 55 years and
> really (probably) shouldn't venture into territory unfamiliar to me. But
> this part is a hobby...so how's a guy supposed to learn.
> >
> > Will someone please explain the errors in my thinking? it would be
> appreciated.
> > Bob, N1KPR http://www.bobsamerica.com  http://www.youtube.com/n1kpr
> >
> > Engineering: Where Enigma meets Paradox
> > ___
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> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
>
>
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Re: [time-nuts] Frequency over fiber (was WWV and legal issues)

[Dana Whitlow]

Question:

Supposing you buy a bundle of a couple of dozen fibers inside one outer
jacket:  Can
anyone give me an idea of how well the individual fibers are likely to be
matched in
delay, and in delay tempco?

Dana


On Sun, Sep 2, 2018 at 1:46 PM Poul-Henning Kamp  wrote:

> 
>
> In message , Bob kb8tq
> writes:
>
> > That’s why they design a certain amount of “slack” into the structure.
>
> As far as I know, thermal expansion and contact losses are far
> bigger dimensioning factors, except for a few very active fault-lines.
>
> At these fault-lines and/or with very important fibers, special and
> site-specific precautions are usually taken.
>
> For terrestial faultlines, the cheapest and easiest mitigation is
> to cross the fault-line on poles with a slack messengerwire.
>
> For oceanfloor faultlines, plenty of slack and an oblique crossing
> is the best we've come up with yet.
>
> --
> 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] A silly question ...

[Dana Whitlow]

Hi,

There is one other issue that can bite you if you fail to properly
terminate the output of a source:

Depending on the source's design, an essentially unloaded output
can have a substantially higher voltage swing than expected (by
2X if the source impedance is actually 50 ohms), possibly leading
to the output stage's going into clipping, which can in turn distort
the timing, possibly even in an unstable manner.
So if you want to play the "unterminated game", at least take a
look at the waveform to be sure it's still a clean sinewave.  I've
noticed such distortion on my PRS-10, for example, although I've
seen no evidence of unstable timing results.  But in this arena,
it generally pays to be fussy.

Dana Whitlow

On Fri, Sep 28, 2018 at 7:06 AM Bill Byrom  wrote:

> On Thu, Sep 27, 2018, at 11:55 AM, Dave B via time-nuts wrote:
> > Triggering a dual beam 'scope (Tek 465) from the TB on Ch1, and having>
> the output of the OCXO on Ch2, the resulting display on Ch2 of course>
> drifts in relation to the static waveform on Ch1.  (Both nice
> > sinusoids.)
> The Tek 465 analog cathode ray oscilloscope was/is a very flexible
> instrument. But this flexibility allows you to set up the instrument in
> ways which will not allow this commonly used oscillator comparison
> technique to work correctly. Since you are interested in these
> instruments, here are some details about setting up the instrument for
> such comparisons.
> (1) The Tek 465 is not a dual beam oscilloscope. Dual beam oscilloscopes
> (such as the Tektronix 556 and 7844) use a special CRT which
> incorporates two independent electron guns. Each electron gun
> assembly has a set of vertical and horizontal deflection plates.
> There are two vertical amplifiers (one for each electron gun) and
> two horizontal sweep systems (one for each electron gun). If you had
> a dual beam oscilloscope you could compare oscillator#1 to
> oscillator#2 while  simultaneously comparing oscillator#3 with
> oscillator#4. It's like having two independent oscilloscopes sharing
> the same CRT display.
> (2) The Tek 465 single beam oscilloscope can display two  traces on the
> display using one of two methods:(a) Chopped trace display: This mode
> works well at low sweep rates (such
> as 1 ms/div) but causes trouble at fast sweep rates (such as 1
> us/div). The displayed trace is switched between Channel 1 and
> Channel 2 at a fixed rate of about 500 kHz.(b) Alternate trace
> display: This mode works well at high sweep rates
> but is hard to see at low sweep rates. The scope alternates between
> displaying one sweep of Channel 1 and one sweep of Channel 2.
> (3) The trigger source setting is crucial to using this technique to
> compare oscillators. The technique does not require you to display
> two channels. What is important is that you display one oscillator
> while triggering on the other oscillator. The trigger source can
> be set to:(a) CH 1: The Channel 2 display will drift if the two
> signals have a
> varying phase relationship.(b) CH 2: The Channel 1 display will drift
> if the two signals have a
> varying phase relationship.(c) NORM (normal): The trigger system gets
> input from the channel being
> displayed at that moment. So in chopped trace display mode the
> trigger is rapidly switched between CH1 and CH2, and in alternate
> trace display mode the trigger alternates between CH1 and CH2 on
> alternate sweeps. In all cases, you should not use NORM trigger
> source with both channels displayed when comparing oscillators!(d)
> EXT: You apply the trigger signal to the external trigger input
> connector. This works well well when comparing oscillators. If you
> use alternate trace display mode and an external trigger, you can
> compare oscillator#1 (on CH 1) to oscillator#0 (on the external
> trigger input) while you are also comparing oscillator#2 (on CH2)
> oscillator#0. So you could compare two oscillators (one on CH1 and
> the other on CH2) to a GPSDO (on the external trigger input).
> (4) When comparing oscillators, the fractional frequency difference
> (such as ppm Parts Per Million or ppb Parts Per Billion) you can
> measure depends on the oscilloscope sweep rate. What you are really
> measuring is the drift of the time delay between the edge (or zero
> crossing of a sine wave) of one signal relative to an edge or zero
> crossing of another signal. The relationship is:
> Fractional difference = (observed timing change) / (measurement
> interval)Here are some examples:
> Fractional difference in ppm = (time delay drift in us) per second of
> observation timeFractional difference in ppb = (time delay drift i

Re: [time-nuts] new op amp for distribution amplifiers

[Dana Whitlow]

Has anybody tried the AD8003 (triple video line driver amplifier) for use as
distribution amplifiers?  It looks to me like this part might be a decent
choice.

On caveat, however:  don't succumb to the temptation to reduce the circuit
bandwidth by putting a capacitor across the feedback resistor- here be
dragons!

Each section is a current feedback opamp, intended for use in a
non-inverting
2X voltage gain configuration (leading to unity gain when a back-termination
resistor equal to Zo is used).  It should be equally good for either 10 MHz
or for
PPS pulses and the like.

On concern I have is that there *might* be some difficulty with driving a
non-
terminated transmission line (by mistake, of course).

One other thing is that this part uses an "exposed paddle", which needs
to be soldered down to a well-grounded pad beneath the device for both
electrical and thermal reasons.  For those in possession of a suitably-
modified toaster oven, this should not be a big issue.

DanaK8YUM


On Sat, Dec 15, 2018 at 11:03 AM Anders Wallin 
wrote:

> Hello Gerhard, everyone,
>
> I made a test using the THS3491 on a slightly modified PCB from my "FDA"
> design [1].
>
> At first with 200 Ohm feedback/gain resistors all I got was (pulsed, in
> bursts) self-oscillation (around 150MHz or so).
> The datasheet [2] does however warn about this and suggests 976 Ohms for a
> gain of 2V/V, so I went with 1k.
> That got rid of the self-oscillation - but now I am left with severe (16 dB
> @ 230 MHz) gain-peaking! (see attached figure)
> The datasheet shows a 2V/V gain-plot with only minor peaking at >700MHz.
>
> From past simulations [3] the gain-resistors do contribute at some point to
> the noise, so increasing them further for more stability is not great for
> AM or PN.
> I did not bother with the phase-noise probe yet - better to get rid of that
> gain-peaking first (?).
> Is there anything else that can be done, besides increasing Rf/Rg for more
> stability?
> Anything obviously wrong with the layout? It does work fine with LMH6702
> and LMH6609.
>
> Thanks for any suggestions!
>
> Anders
>
> [1] https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/wiki
> [2] http://www.ti.com/lit/ds/symlink/ths3491.pdf
> [3]
>
> http://www.anderswallin.net/2015/12/frequency-distribution-amplifier-v2-simulations/
> [image: ths.jpg]
>
>
> On Sat, Nov 17, 2018 at 1:00 AM Gerhard Hoffmann  wrote:
>
> >
> > Have you seen the new THS3491 ? LMH6702 on steroids.
> >
> >
> > This one begs to be designed into new distribution amplifiers:
> >
> > Everything from DC / 1pps to a few 100 MHz into 50 Ohms, without any
> > changes.
> >
> > (the usual gain = 2,50R/50R out design)
> >
> > rise / fall 1.3 ns for 10V step
> >
> > slew rate 8V / ns
> >
> > BW 320 MHz for 10Vpp at gain of 5
> >
> > Volt. noise 1.7 nV/rt Hz
> >
> > supply max +/- 16V,  drives up to 420 mA
> >
> > SO-8 with thermal pad  or leadless
> >
> > < http://www.ti.com/lit/ds/symlink/ths3491.pdf>
> >
> >
> > regards,
> >
> > Gerhard
> >
> >
> > ___
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Re: [time-nuts] Modern signal generators

[Dana Whitlow]

Ulrich,

Is it OK for us to forward the URL for your "Noise" paper to others
outside the time-nuts group?

Thanks,

Dana   K8YUM


On Tue, Dec 11, 2018 at 9:24 AM Ulrich Rohde via time-nuts <
time-nuts@lists.febo.com> wrote:

>
> https://badw.de/fileadmin/members/R/3685/6_4_18_UNI_BW_June18-safe.pdf
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Re: [time-nuts] Scientists Build Atomic Clocks Accurate Enough to Measure Changes in Spacetime Itself

[Dana Whitlow]

I wonder if that "insult" was the inspiration for thermometers designed
around quartz resonators.

For more details on the new "accelerometer", one might want to read:

https://www.nature.com/articles/s41586-018-0738-2.epdf?referrer_access_token=xI4XbO8QUPT0oGiggqlnj9RgN0jAjWel9jnR3ZoTv0NOfvtdRGwNwsijc3L-wdrR-gN_XGjZvnhSHG8Z_GRAG2TFlrE0BhLZBwI67_QAp5OjAnEKQ4WJ4wCjk5w4vygIPUQtVEyDSwAATCo0K5MU6LufwkNUiCSha11I0_PKQaLYE9fGZ8PkVdTUdQpyGoiVbb0jP8MraWacVecZgLo2L2CMYUI4WaKOR_F4q5s8PY5IBcxvTydcNh79JRTUvUrd_referrer=www.theregister.co.uk

This can be read, but apparently not downloaded by just anybody.

Dana

On Fri, Nov 30, 2018 at 8:50 AM Richard (Rick) Karlquist <
rich...@karlquist.com> wrote:

> A little humor:
>
> This situation reminds me of an old saying we had at HP:
>
> How do you insult a clock engineer?
>
> "Hey man, that's a great thermometer you designed!"
>
> The new version of this is now:
>
> "Hey man, that's a great accelerometer you designed".  :-)
>
> Rick
>
>
> On 11/29/2018 8:06 AM, Bob kb8tq wrote:
> > Hi
> >
> > Certainly a cool clock and yes I’d love to have one in the ….errr …
> warehouse (as long as somebody else pays
> > the power bill).
> >
> > I seem to recall others as actually having measured gravity effects
> using atomic clocks …. :)
> >
> > Yes, that’s just the way the article was written and not a knock in any
> way on the *very* impressive clock.
> >
> > Bob
> >
> >> On Nov 29, 2018, at 10:39 AM, JULIAN TOPOLSKI  wrote:
> >>
> >> FYI:
> https://gizmodo.com/scientists-build-atomic-clocks-accurate-enough-to-measu-1830715349?fbclid=IwAR1H_KCZyyCpkh22YQ43zYb7KheepriKOt7S_5Fbd4bnY7b0G_zTLmU8C9M
> >> [
> https://i.kinja-img.com/gawker-media/image/upload/s--awKrmrT9--/c_fill,fl_progressive,g_center,h_900,q_80,w_1600/kueltkuo32milibvnfa0.jpg
> ]<
> https://gizmodo.com/scientists-build-atomic-clocks-accurate-enough-to-measu-1830715349?fbclid=IwAR1H_KCZyyCpkh22YQ43zYb7KheepriKOt7S_5Fbd4bnY7b0G_zTLmU8C9M
> >
> >>
> >> Scientists Build Atomic Clocks Accurate Enough to Measure Changes in
> Spacetime Itself<
> https://gizmodo.com/scientists-build-atomic-clocks-accurate-enough-to-measu-1830715349?fbclid=IwAR1H_KCZyyCpkh22YQ43zYb7KheepriKOt7S_5Fbd4bnY7b0G_zTLmU8C9M
> >
> >> Physicists have created atomic clocks so precise that they can measure
> deformations in spacetime itself, according to new research.
> >> gizmodo.com
> >>
> >>
> >> ___
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> >
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Re: [time-nuts] VLF time station, cheap sdrs

[Dana Whitlow]

I generated a spiral plot of phase and amplitude covering about 3 minutes of
WWVB last fall.  It's a good-size file, around 2MB as I recall.

Should I send it?

Dana


On Wed, Dec 5, 2018 at 8:56 AM jimlux  wrote:

> https://www.rtl-sdr.com/tag/vlf/
>
> a fair number of examples -
>
> As I speculated, the 8 bit RTL-SDR has a problem with strong broadcast
> band AM, so you need some sort of LPF.
>
> There are some examples of "amplified whip into sound card into Rpi"
> implementations.
>
> I didn't see anybody actually decoding or measuring the phase though -
> lots of waterfall plots showing the existence of a signal.
>
>
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[time-nuts] Looking for ADEV plot(s) for the SRS model SG384 sig gen

[Dana Whitlow]

I'm considering purchasing one of these units, but would like
to know just how bad/good is bad/good before I leap.  I'd get
the most useful info for the case of all modulations OFF,
"perfect" external reference, and for a reasonable assortment
of RF frequencies (or one frequency plus a statement of the
rule governing transfer to other frequencies).

Thanks,

Dana
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Re: [time-nuts] PRS10 case temperature

[Dana Whitlow]

My PRS-10 (a telecom version) runs with a heatsink temp of around 55C of
a bit less.  But some areas of the case actually run a few deg hotter than
that.

Dana


On Fri, Nov 16, 2018 at 3:49 PM Mark Sims  wrote:

> My case temp runs around 70C with the SRS heatsink installed.   If you
> don't have a heatsink (a rather bad idea) it might run 80C.  The latest SRS
> heatsinks don't seem to be as good as the earlier units which had a lot
> more metal to them...  my heatsink is the later model.
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[time-nuts] RF isolation requirements for multiple GPS receivers

[Dana Whitlow]

I want to run about 4 separate GPS units of disparate
manufacture from a single antenna.  My plan is to
provide power for the antenna via a bias tee (power
inserter) at the bottom end of the antenna's cable, then
use an isolating splitter on the receiver side of the bias
tee to split to the various receivers.

My question is: how much isolation between receivers
is likely to be necessary?  Real life splitters are only
so-so in isolation performance (15-25 dB), and may
e significantly worse if the antenna's LNA's output is
a poor match.  So I'm wondering if I'm going to need
more amplifiers in the splitter's outputs just for the sake
of adequate isolation between the GPS receivers.

Thanks,

DanaK8YUM
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

[Dana Whitlow]

I was moved to check on the terms "decimate" and "downsample" to see what
their
relative meanings are, and was disappointed to see that they are virtually
the same.

Perhaps Tom would be willing to discuss this point and suggest meanings to
be used
in this group.

Dana


On Thu, Jan 10, 2019 at 6:13 AM Adrian Godwin  wrote:

> Truncate, to me at least, means to shorten : ie to remove some precision by
> rounding off lower bits.
>
> I agree that the source of the word 'decimate' is unclear, but I think,
> within the field of DSP, it has a reasonably precise definition whether or
> not that corresponds with wider usage or derivation.
>
>
>
> On Thu, Jan 10, 2019 at 12:02 PM Peter Vince 
> wrote:
>
> > In his comment below, Mark has used the word "decimate".  There is much
> > debate about what this word means (presently, and/or in the past), but
> > common explanations refer back to Roman times when they apparently killed
> > one person in ten as a punishment, and similarly "tithes" - or taxes,
> where
> > one in ten was taken.  Now OK, you can argue this until the cows come
> home,
> > but the result is that the meaning isn't crystal clear, and particularly
> on
> > a technical forum where precision is paramount, and the entire reason we
> > are here, I believe accuracy and clarity of expression is also important.
> > In this instance, I believe "truncate" would be a better word.
> >
> >   :-)
> >
> >  Regards,
> >
> >   Peter Vince
> >
> > On Wed, 9 Jan 2019 at 23:56, Mark Sims  wrote:
> > > ...
> > > And as far as decimating the TICC output values in firmware... please
> > don't.   Let the user decimate the values if they want to.
> > ___
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Re: [time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)

[Dana Whitlow]

I'm confused...

I see two separate cases here:

Case A:  you simply throw away samples, keeping only every nth sample,
without
regard for the frequency content of the original signal.

Case B:  you first perform appropriate anti-aliasing filtering on the
original signal, and
 only then throw away all but every nth sample>

Which casee are we talking about when we use the word "decimate"?   And
then what
is the correct terminology for the other case?   Inquiring minds really
want to know...

Dana


On Thu, Jan 10, 2019 at 11:49 AM Gerhard Hoffmann  wrote:

>
> Am 10.01.19 um 17:33 schrieb Bob Martin:
> >
> >
> > Back in those same seventies, I was working for an army lab (Harry
> > Diamond Labs) as a summer student. I saw a picture in a lab supply
> > catalog of a (ein) stein of beer. I tore it out and taped it over a
> > picture off Albert Einstein that a German physicist, Howard Brandt,
> > had on the wall over his desk.  This was a bad idea. Howard was so
> > incensed that he called the whole department together, hauled out the
> > Websters Unabridged Dictionary, and forced me to read the definition
> > of the word philistine in front of the group. Fortunately, there were
> > many entries under the word and I chose "a native of Philistia" to
> > read out loud. The moral is words can have many meanings and, more
> > importantly, don't make fun of Einstein
> > around German Physicists.
> >
> I wonder if Howard even understood the intended pun.
>
>
> Stein means stone, nothing else. I have seen/heard it used in the
>
> sense of a "mug for beer" only by Americans. The closest
>
> German word would be Steinkrug, but only if you want to
>
> emphasize that the Krug is made of ceramics and not of glass.
>
>
> Decimation apart of the Roman sense for me is  only throwing away samples,
>
> and the need for filtering goes with it even without explicitly saying.
>
>
> Cheers, Gerhard
>
>
>
>
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Re: [time-nuts] Programmable clock for BFO use....noise

[Dana Whitlow]

Frequency dividers can be pretty low noise, if you choose the right class
of logic.  I remember that
at one time in the distant past, LSTTL was considered king.  Unfortunately
I've been out of touch
with frequency dividers long enough to be ignorant of what works well today.

i'd suggest trying something with either HC-series or AC-series CMOS,
chances are fair that you'd
be happy.  Write me off list and I'll tell you which well-known distributor
still has an excellent
selection of HC and AC parts in stock.

Dana


On Fri, Sep 14, 2018 at 11:14 AM,  wrote:

> Off topic for this list, but you guys are experts in oscillator noise!
>
> Playing with some mechanical filters.  Need USB and LSB crystals for the
> BFO.  No one seems to make crystals anymore, especially in the 253 KHz
> range!
>
> Looking at the DigiKey Cardinal programmable oscillators.  Cheap and
> available: CPPC1LZ A5B6
>
> Anyone have an idea how noisy these would be after a division by 4 to get
> them in range?
>
> Thanks,
>
> N0UU
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Re: [time-nuts] Noise of digital frequency circuits (was: Programmable clock for BFO use....noise)

[Dana Whitlow]

I'd been thinking, in an admittedly non-rigorous sort of way, about this
matter for some years.

As I see it, it is certainly true that the phase of an oscillator's output
is a continuous funciton
of time.  It could be described as a continuous ramp, whose slope
corresponds to the frequency,
and with a little bit of non-flat random noise superimposed on it.

Now if you square up the waveform and do digital things with it (such as
freq dividing, digital
phase detection, etc), you are really only glimpsing the phase noise at
transition times, and
are blind in between.  Thus the very process amounts to sampling the phase
noise waveform
with a sampling phase detector.  This view suggests that all the phase
noise power is aliased
and folded  back into the band ranging from DC to Fsamp / 2, where Fsamp is
the frequency
of the waveform after frequency division.  This is why the time domain
jitter of the oscillator's
waveform is unchanged by "perfect" frequency division (or multiplication).

It is why I wonder about the wisdom of doing phase comparison at
unnecessarily low frequency-
all that noise would seem to be scrunched down into a bandwidth of half the
comparison frequency.

Does this explanation help, and how does it sit with those of  you who have
more expertise
than I?

Dana




On Sun, Sep 16, 2018 at 4:06 PM, Attila Kinali  wrote:

> Moin,
>
> On Sat, 15 Sep 2018 08:38:55 -0700
> "Richard (Rick) Karlquist"  wrote:
>
> > On 9/15/2018 3:26 AM, Attila Kinali wrote:
> >
> > > possible logic family for the task. Otherwise the harmonics of the
> > > switching of the FF will down-mix high frequency white noise down
> > > to the signal band (this is the reason for the 10*log(N) noise scaling
> > > of digital divider that Egan[1] and Calosso/Rubiola[2] and a few others
> > > mentioned).
> >
> > Wow, I never knew this in 45 years of designing synthesizers!
> > I do remember that some of the frequency counter engineers at HP
> > talked about noise aliasing.  I think this is another way of
> > describing the same problem.
>
> Yes. This effect has been known for a few decades at least.
> What kind of puzzles me is, that I have not seen a mathematically
> sound explanation of it, so far. People talk of aliasing and sampling,
> but do not describe where the sampling happens in the first place.
> After all, it's a time-continuous system and as such, there is no
> sampling. One could look at it as a (sub-harmonic) mixing system,
> but even that analogy falls short, as there is no second input.
> It also fails at describing why there is not infinite energy being
> down-mixed, as the resulting harmonic sum does not converge.
>
> If someone knows of a description that goes beyond handwavy arguments,
> I would very much appreciate hearing of them.
>
> The only way to explain the effect in a rigorous way, that I could
> figure out, is to apply Hajimiri and Lee's Impulse Sensitivity Function[1],
> and adapt from the oscillators they discribed to general periodic systems.
> (The step, as one can guess, is small, but hic sunt dracones)
> Doing this, it becomes obvious that the down-mixing is an inherent
> property of all systems that use or generate non-sinusoidal waveforms.
> It is this ISF that is the source of the down-mixing/aliasing effect,
> as it has a periodic waveform of sharp spikes.
>
> As the ISF is probably (this is my intuition and I have, unfortunately,
> no proof of this) related to the derivative of the produced output
> waveform,
> it becomes important to limit the slew rate of the output, to introduce
> a second pole in the ISF and thus limit the number of harmonics.
> Yet, it is also important to keep the input slew rate high, in order to
> keep the width/height of the ISF pulses low.
>
> A partial discussion of this can be found in the paper I presented
> at IFCS earlier this year[2]. Unfortunately, the write-up is not
> nice and I only realized after the deadline that I should have
> all written it using a different approach. Sorry for that.
> If something is not clear, do not hesitate to send me an email.
>
> > About 10 years ago, the frequency synthesizer chip vendors started
> > talking about a Figure of Merit (FOM) that predicted phase noise floor,
> > and it also included the 10 LOG N noise scaling.  An application
> > engineer at ADI told me this was a characteristic of the sampling phase
> > detector that all these chips used.  But I always wondered if the
> > frequency divider could come into play.  The way FOM is defined,
> > it doesn't distinguish between phase detector and divider noise.
>
> The 10*log(N) also applies to the phase detector in PLL chips,
> where N becomes the ratio of the phase detector bandwidth divided
> by the phase detector input frequency.
>
> Given that the phase noise is dominated by the input source' phase
> noise, there will be no appreciatable difference in whether the
> down-mixing happens in the divider or the phase detector, as long
> as the bandwidth of all 

Re: [time-nuts] Noise of digital frequency circuits (was: Programmable clock for BFO use....noise)

[Dana Whitlow]

The act of squaring up the waveform alone might not do much harm, depending
on the extent
to which the phase noise on said waveform has already been filtered off.
But it's mainly when
the signal gets divided down by large ratios that the difference would
become really noticeable.

For example, take the case of 10 MHz starting frequency; the phase noise
several MHz out
is likely to be nil.  But divide the 10 MHz down to, say, 1 Hz; then
there's likely to be quite a
lot of phase noise within "folding range" of many Nyquist bands about 1 Hz.

This, again, is why I wonder so much about our efforts in re-synthesizing
higher frequencies from
the 1PPS from GPS receivers.  I don't know much the architecture of GPS
receivers, but it seems
to me it would sure be nice if there were some convenient way to extract a
clean signal at the
chipping rate, for use in generating standard reference frequencies.

Dana




On Sun, Sep 16, 2018 at 9:15 PM, Bob kb8tq  wrote:

> Hi
>
> It’s pretty easy to demonstrate that squaring up a sine wave, even with
> fairly simple
> circuits does not create crazy phase noise issues. People have been doing
> it successfully
> for a lot of years. In general faster saturated logic produces lower noise
> floors than slower
> logic.
>
> Bob
>
> > On Sep 16, 2018, at 4:33 PM, Dana Whitlow  wrote:
> >
> > I'd been thinking, in an admittedly non-rigorous sort of way, about this
> > matter for some years.
> >
> > As I see it, it is certainly true that the phase of an oscillator's
> output
> > is a continuous funciton
> > of time.  It could be described as a continuous ramp, whose slope
> > corresponds to the frequency,
> > and with a little bit of non-flat random noise superimposed on it.
> >
> > Now if you square up the waveform and do digital things with it (such as
> > freq dividing, digital
> > phase detection, etc), you are really only glimpsing the phase noise at
> > transition times, and
> > are blind in between.  Thus the very process amounts to sampling the
> phase
> > noise waveform
> > with a sampling phase detector.  This view suggests that all the phase
> > noise power is aliased
> > and folded  back into the band ranging from DC to Fsamp / 2, where Fsamp
> is
> > the frequency
> > of the waveform after frequency division.  This is why the time domain
> > jitter of the oscillator's
> > waveform is unchanged by "perfect" frequency division (or
> multiplication).
> >
> > It is why I wonder about the wisdom of doing phase comparison at
> > unnecessarily low frequency-
> > all that noise would seem to be scrunched down into a bandwidth of half
> the
> > comparison frequency.
> >
> > Does this explanation help, and how does it sit with those of  you who
> have
> > more expertise
> > than I?
> >
> > Dana
> >
> >
> >
> >
> > On Sun, Sep 16, 2018 at 4:06 PM, Attila Kinali  wrote:
> >
> >> Moin,
> >>
> >> On Sat, 15 Sep 2018 08:38:55 -0700
> >> "Richard (Rick) Karlquist"  wrote:
> >>
> >>> On 9/15/2018 3:26 AM, Attila Kinali wrote:
> >>>
> >>>> possible logic family for the task. Otherwise the harmonics of the
> >>>> switching of the FF will down-mix high frequency white noise down
> >>>> to the signal band (this is the reason for the 10*log(N) noise scaling
> >>>> of digital divider that Egan[1] and Calosso/Rubiola[2] and a few
> others
> >>>> mentioned).
> >>>
> >>> Wow, I never knew this in 45 years of designing synthesizers!
> >>> I do remember that some of the frequency counter engineers at HP
> >>> talked about noise aliasing.  I think this is another way of
> >>> describing the same problem.
> >>
> >> Yes. This effect has been known for a few decades at least.
> >> What kind of puzzles me is, that I have not seen a mathematically
> >> sound explanation of it, so far. People talk of aliasing and sampling,
> >> but do not describe where the sampling happens in the first place.
> >> After all, it's a time-continuous system and as such, there is no
> >> sampling. One could look at it as a (sub-harmonic) mixing system,
> >> but even that analogy falls short, as there is no second input.
> >> It also fails at describing why there is not infinite energy being
> >> down-mixed, as the resulting harmonic sum does not converge.
> >>
> >> If someone knows of a description that goes beyond handwavy arguments,
> >> I would very much appreciate hearing of t

Re: [time-nuts] 4.19 MHz xtal

[Dana Whitlow]

Could it really be  4.194304 MHz  (2^22 Hz)?

Dana


On Sun, Mar 31, 2019 at 5:03 PM Neville Michie  wrote:

> Hi,
> I have a Philips quartz clock that runs on 4.19 MHz.
> In spite of the high frequency it still runs for years
> on a C cell.
> Can any of the quartz crystal gurus explain why this
> frequency was chosen? I believe that this clock was
> supposed to have better than usual accuracy.
> Philips always had a high level of engineering excellence.
>
> cheers,
> Neville Michie
>
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Re: [time-nuts] reply re Harrison's timing method - #13 in Vol 176, Issue 44 digest

[Dana Whitlow]

Relative to Harrison's method of star position measurement and timing, and
the
possible effects of diffraction thereof:

Hanbury Brown's book "The Intensity Interferometer" may provide some useful
insight about various error sources, even though in a different context,
that of
measurement of a star's angular size.

The opening chapter discusses some early attempts at angular size.  Galileo
apparently made the first really serious attempt, based on how far behind a
cord of known diameter one must stand so that the cord *barely* blockes the
star's image in the eye.  He found a size of 5 arcseconds for Vega, for
example.
Evidently previous estimates were in the two arc minute range.

Hanbury Brown mentions that a pretty detailed description of Galilieo's
methods
and attention to detail were given in Galileo's "Dialogue Concerning the Two
Chief World Systems".

It is interesting to note that Galileo's method still yielded a figure some
3 orders of
magnitude larger than Vega's currently accepted (as of 1974) angular size
of about
3 milli-arc seconds.  Hanbury Brown attributed the discrepancy largely to
angular
scintillation from the Earth's atmosphere.  It seems to me that this has to
be a noisy
factor in the Harrison method, too, and it would be interesting to see more
research
done on this point.  It also seems to me that the diffraction issue would
be complicated
by the different distances to the two obstacles necessitated by Harrison's
approach.

Right now I'm beginning to think about whether I have the smarts and
computational
resources to do some simulations of this situation.

Hanbury Brown's book is basically about his invention of the Intensity
Interferometer,
which is an attempt to go beyond the capability of Michelson's stellar
interferometer.
The tale spans from HB's original late-night inspiration until the eventual
construction
and successful operation of a special telescope in Narrabri, Australia.  It
is a fascinating
story winding through HB's own initial self doubts, scientific criticism of
the validity of
the concept, technical hurdles, bureaucratic hurdles like getting funding,
more technical
hurdles, etc.

Dana


On Wed, Mar 27, 2019 at 5:00 AM Brooke Clarke  wrote:

> Hi Bruce:
>
> Would the David White 60 Degree Pendulum Astrolabe also work?
> https://prc68.com/I/PendulumAstrolabe.shtml
>
> --
> 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 
> > The Danjon impersonal astrolabe is perhaps better suited to accurate
> measurements:
> > https://www.nzmuseums.co.nz/collections/3267/objects/3380/astrolabe
> >
> > Bruce
> >> On 27 March 2019 at 15:48 Tom Van Baak  wrote:
> >>
> >>
> >> BobH wrote:
>  This would be an excellent project for time-nuts to verify.  First, a
>  better explanation of John Harrison’s method is in order.  A vertical
>  window edge is not sufficient - a second vertical reference at a
>  distance is required - Harrison used a chimney on a neighbor's house.
> >> Agreed! The project is the perfect intersection of amateur astronomy
> and amateur timekeeping. Surely, a couple of people on the list could 1)
> attempt to verify the Harrison method, and 2) determine what the limits of
> its accuracy are, say, with little effort vs. with hard work vs. with
> extreme dedication.
> >>
> >> JimL wrote:
> >>> To get 1 second accuracy, you need 360/86400 = 0.004 degree
> >>> measurements. That's 0.073 milliradian - 1 cm  at 140 meter distance.
> >>>
> >>> I'm not sure an "edge" is sharp enough (diffraction, etc.), although
> >>> your eye is pretty good at "deconvolving" the linear equivalent of an
> >>> Airy disk/rings.
> >> Keep in mind too that one can take more than one star reading per
> night. Any identifiable star that crosses your edge is a recordable timing
> event that evening. So, in theory, if you measure N stars you get sqrt(N)
> improvement in accuracy per day.
> >>
> >> I want to encourage anyone to study the problem and help solve the
> riddle, either by uncovering existing professional or amateur literature or
> by actually trying this at home. It boils down to how accurately can you
> measure earth rotation using the Harrison method.
> >>
> >> To put this in time nuts context, precision timekeeping prior to the
> middle of the 20th century was always a form of "Earth Disciplined
> Oscillator". Not unlike a GPSDO, your observatory's pendulum clock kept
> accurate time short-term and star tracking (earth rotation) kept accurate
> time long-term. The ADEV's crossed just like a GPSDO.
> >>
> >> The short-term ADEV of a really good pendulum clock is here:
> >>
> >> http://leapsecond.com/pend/shortt/
> >>
> >> The long-term ADEV of earth rotation is here:
> >>
> >> 

Re: [time-nuts] HP Stories: An architectural view of the HP 5060/5061 and awkward oscillator adjustments.

[Dana Whitlow]

I remember often reading that if you run a 'lyt at a voltage much reduced
from its rating,
the oxide layer would get thinner over time so that in the end, the
effective rating of the
capacitor was about what you had been running it at.  This would seem to
imply that
purposely overrating a 'lyt is pretty pointless.

Any comments on this notion?

Dana


On Sun, Feb 24, 2019 at 7:01 PM Gerhard Hoffmann  wrote:

>
> Am 24.02.19 um 14:39 schrieb Richard (Rick) Karlquist:
> >
> > yet they got a pass and became SOP.  The R lab manager
> > at Santa Clara Division famously said "no customer chooses
> > HP products because they have great power supplies."
> >
> G..  My HP16500C has a defective PS and my 4274A RLC bridge
>
> had a major explosion inside. OMG, WHAT A MESS! All that black magic smoke!
>
> I re-caped the bridge, it took me a day on the DIgikey site to find
> replacements.
>
> I had to use substantially larger voltages to make them fit mechanically.
>
> But that is a good thing.
>
> cheers, Gerhard
>
>
>
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Re: [time-nuts] injection locking crystal oscillator

[Dana Whitlow]

Hello Thomas,

What you ask is possible, but only if the native crystal oscillator
frequency is close enough to the signal from the GPSDO.  You
may have to tune the oscillator yourself to get it to lock, and you
may or may not find that the result is predictable from day to day.
This would depend on how much signal you inject from the GPSDO,
and other, largely imponderable factors.

I think all you can do is try it, understanding that there is also some
risk of damaging the chip if you try to inject too much in search of
success.

If you have a signal gen that you can fine tune around 10 MHz, it
would probably be worth setting it to the same output level as your
GPSDOs output and using it at first.  That way you can explore the
parameters more rapidly without (initially) bothering to retune the
oscillator on the chip.

Dana



On Thu, Feb 28, 2019 at 6:00 PM Thomas S. Knutsen  wrote:

> Hello.
>
> I have a device that consists of a PLL, that has as its reference a
> 10MHz crystal.
> What I would like to do, is to inject this with 10MHz from a GPSDO,
> when that is available, and to use the internal crystal when that is
> not available.
>
> Would it be feasible to just connect it to one leg of the crystal
> oscillator with a small capacitor, and with that get injection
> locking?
> The crystal oscillator is on chip, there is a couple capacitors that
> allow for frequecy adjustments, other than that, I know nothing about
> what is on the chip. The PLL is SP5769.
>
> Br.
>
> Thomas
>
> --
> With Best regards, Thomas S. Knutsen.
>
>  Please  avoid sending  me  Word  or  PowerPoint  attachments.
>
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Re: [time-nuts] Bricked Garmin GPS 18x LVC

[Dana Whitlow]

If you open it up, then simply connect a load resistor, perhaps
in the neighborhood of 100 ohms (but definitely not a direct short!)
across the super cap to drain it faster.

Dana


On Sat, Feb 23, 2019 at 8:00 AM Jason Rabel via time-nuts <
time-nuts@lists.febo.com> wrote:

> That page you linked to says:
>
> "I am reminded by Dave Hart that it was due to a firmware bug that bricks
> the unit until it's left off power long enough to drain the capacitor that
> retains its settings, sort of a poor-man's NVRAM.  This can take some
> weeks."
>
> Or I suppose if you are impatient you could open it up and de-solder the
> super-cap if you don't want to wait weeks for it to drain on its own.
> *Maybe* you will get lucky and that's all it will take?
>
>
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Re: [time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron

[Dana Whitlow]

Keep in mind that the 7 min "warmup time" of the PRS-10 is jut the time for
the
unit to get the physics package close enough to final temperature for the
dithering
loop to lock to the atomic transition. But based on measurements of current
drawn
by the oven(s), it takes more like an hour for the ovens to settle down
very well.

My own experiments with a well-used "telecom mod" PRS-10 suggest that it
takes
my unit more like 3 or 4 days to really settle down to its background
frequency drift
rate.  This rate is specified as something like "< 5E-11 per month", which
is frankly
pretty awful.  Mine seems to be better than spec, more like 2E-11 per month
(frequency
increasing over time).  The point here is that there are apparently a
number of warm
up drift mechanisms operating, some of which take days to sensibly settle
down.

I've been wondering about the issue of whether it's best to operate a
PRS-10 only
at times of need, or continuously, with respect to life.  I posed the
question direct;y
to SRS, and they claim that it is better to leave it running all the time.
My own
"algorithm" has become "leave it on all the time" when I'm around and even
remotely
active with time-nuttery, but shut it down when I'm away on vacation.  This
is mostly
out of concern for something going wrong with the power supply and burning
the
house down.  Lightning storms are one such risk, for example.

DanaK8YUM

On Fri, Mar 8, 2019 at 3:00 AM Forrest Christian (List Account) <
li...@packetflux.com> wrote:

> Hopefully you'll all grace me with a few answers to a beginner
> time-nut question or two.
>
> I have a PRS-10 I've never used other than to power it on with a
> recently-acquired heatsink and verify that it seems to operate
> correctly and that the operational parameters don't seem out of
> tolerance.   I would like to use this in the near future as a 10Mhz
> reference for a TAPR TICC which I'd like to use to measure the jitter
> performance of the PPS output of various consumer GPS receivers, the
> goal being to end up with a jitter histogram.
>
> So three interrelated questions:
>
> 1) Assuming the PRS-10 has been off for a long time, how long should I
> plan on leaving this on for the 10Mhz to stabilize?   I see the
> longest warmup time on the spec-sheet is 7 minutes -  although this
> seems a lot shorter than I'd likely use in real life,  I'm also not
> sure if there's much benefit to an excessively longer warmup time
> (like days), would like opinions on this.
>
> 2)  Longer-term I'd like to use the 1PPS output from a Trimble
> Thunderbolt to calibrate the PRS10 and adjust if necessary just to
> trim out any aging drift on the PRS10.  Initially I thought I was
> going to discipline the PRS10 on a continual basis with the
> Thunderbolt using the PPS input on the PRS10, but I've recently
> realized that leaving the PRS10 on permanently might not be the best
> option (see Question 3).   So I'm looking for opinions on how to keep
> the PRS10 calibrated/adjusted.  I.E. trim with the trimmer, adjust
> using digital commands, etc.
>
> 3) As implied in #2, I was originally planning on leaving the PRS10 on
> a continuous basis.   I've read a couple of things which imply that
> there is little benefit to doing so, and that every hour it's on
> consumes the lamp life.   Assuming I only need the highly stable PRS10
> source every few months for things like jitter measurements on 1PPS
> sources, is there any benefit to leaving the PRS10 on?
>
> --
> - Forrest
>
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Re: [time-nuts] Examples of noise processes

[Dana Whitlow]

Folks,

Please be careful about definitions in this discussion.

To some people, "phase noise" refers to sideband noise, away from the
carrier, arising from some form of random phase modulation of the carrier.

To others, the same term refers to the underlying phase modulation itself.

While intimately related, the two meanings refer to different manifestations
of the same root cause, and casual (unqualified) use of the term "phase
noise"
can lead to considerable confusion.

Thanks,

Dana


On Fri, Mar 15, 2019 at 12:01 PM Attila Kinali  wrote:

>
> Did someone say "noise processes"? :-)
>
> On Fri, 15 Mar 2019 10:03:11 -0400
> John Ackermann N8UR  wrote:
>
> > For a presentation on basic time-nuttery, I'd like to find
> > non-oscillator examples of the various noise processes -- white PM,
> > flicker PM, white FM, flicker FM, random walk.  (I'm not sure if FM and
> > PM have any relevance outside oscillators, though.)
>
> First you have to define what you mean by FM outside of oscillators.
> If you look at frequency just as integral of phase, then there is
> a very straight forward relation. Ie frequency noises are just
> phase noises with the exponent going up by two.
>
> white noise (~white phase):
> The most important white noise source is thermal noise, ie movement
> of atoms that disturb(scatter) the flow of electrons due to thermal energy.
> The second most important noise is shot noise in semiconductors.
> This is mediated by the fact that the current carriers (e.g. electrons)
> are discrete objects that pass through a potential barrier.
> There is also avalanche noise which is present in p-n junctions with
> high electric fields where electrons are accelerated to the point where
> they gather enough energy to knock out secondary electrons from atoms
> in the lattice before leaving the active zone. Avalanche photo diodes
> and zener diodes with voltages over 6V are the most common devices that
> exhibit
> predominantly avalanche noise.
>
> 1/f noise (~flicker phase):
> This noise comes mainly from defects in conductors or other structures
> that trapp or scatter the electrons (or phonons in crystal resonators).
> This type of noise is very common and can be found in almost all physical
> systems (even weather patterns), but it's exact source is not well
> understood.
>
> 1/f^2 noise (~white frequency):
> There are two types of noise here:
> 1) Popcorn noise: Like 1/f noise, this is not well understood, but
> is also related to the activity of single traps in regions of high
> current density. It was more a problem back in the vacuum tube and
> germanium semiconductor times. Current silicon semiconductors show,
> if any, only very low levels of popcorn noise.
> 2) generation-recombination noise: when electron-hole pairs form or
> get recombine, the carrier density changes localy. Above the frequency
> that is inversly proportional to the recombination time, this type
> of noise shows a 1/f^2 characteristic (below it's white)
> Additionally to those two real noise sources, you also have the
> integration of white noise. This can either happen due to a real
> integrator or by a device that has integrative properties within
> the circuit (e.g. the Q of the resonator in Leeson's formula)
>
> higher order noises (~flicker frequency and above):
> From what I've read in the last years, I have formed the hypothesis
> that most (all?) noises with higher exponents are formed either due
> to integration of the above noise sources[1] or are mediated
> through environmental effects that make it look like noise sources[2]
> when analysing them with our tools, but in reality are not truly
> random and/or not Gauss distributed. E.g. in Enrico's paper[3]
> you can see that thermal effects lead to a 1/f^5 type noise.
> I still need to figure out a way to prove/disprove this hypothesis
> and I do not think this way of thinking is generally accepted (I have
> not seen anyone else formulating this), so please take this with a
> grain of salt.
>
> HTH
>
> Attila Kinali
>
>
> [1] Eg. Leesons formula for oscillators. Similarly, passive frequency
> standards which do a frequency detection that exhibits white and 1/f noise,
> which thus turns the output noise in into white frequency noise and
> flicker frequency noise.
>
> [2] I use here a somewhat more strict definiton of noise surces.
> Namely sources which generate random, Gauss distributed values
> with an 1/f^a, a >= 0 power spectral density. While for practical
> purposes using this strict definition does not make sense (if it
> looks like noise, then it is noise), but from a theoretical point
> of view it is important to distinguish other effects that can be
> explained and thus potentially removed (e.g. by measuring temperature
> of the device itself very accurately) from "real" noise sources.
>
> [3] "Low Flicker-Noise DC Amplifier for 50Ω Sources", by Enrico Rubiola
> and Franck Lardet-Vieurdrin, 2004
>
> 

Re: [time-nuts] OCXO PLL gains?

[Dana Whitlow]

I learned a useful rule of thumb design procedure for 2nd degree PLLs some
time ago
(I'll speak in the context of using an inverting op-amp in the loop
gain/filter stage):

Step 1: Short the capacitor in the opamp's FB loop, then set the resistor
so that
the PLL has the desired loop bandwidth.  This is the gain part of the
adjustment.

2. Then set the capacitor value so that its reactance at the frequency of
the loop BW
is about 1/5th the resistance that you set in step 1.  This is the damping
setting step.

3. Then examine the overall loop behavior for its damping behavior.  If
there are no
"hidden poles" somewhere, the above should yield pretty good results right
off that
bat, but a little tweaking is always fair game if you want.

However, there *are* often "hidden rolloffs" (poles) somewhere, and damping
behavior will be degraded.  Such poles are most likely to arise in two
areas-
the VCO itself, or the opamp you're using.  Be sure that the opamp's gain-
bandwidth is much larger than required, said requirement being the product
of the gain being called for in the opamp stage and the desired PLL
bandwidth.
And VCOs always introduce hidden poles into the loop, which are not usually
well documented in the oscillator's specsheet (if at all).

But with luck you won't run into either problem area for the low loop
bandwidths
typically desired in oscillator-cleanup PLL applications.

Dana  K8YUM





On Fri, Feb 1, 2019 at 11:04 PM Magnus Danielson  wrote:

> Hej Anders,
>
> On 2019-02-01 19:11, Anders Wallin wrote:
> > Hi all, is there are rule-of-thumb or simple paper/presentation of how to
> > choose PLL-gains?
> >
> > I have a phase-detector that gives out a slope of roughly 1 V/rad,
> followed
> > by an op-amp circuit with proportional, integral, and double-integral
> gains
> > summed into one voltage [0, 3.3V] on the tune-pine of the OCXO ( +/- 0.6
> > ppm pull-range, from datasheet).
> >
> > So far it locks with only P-gain, but the phase-noise (and ADEV) shows a
> > 'bump' somewhere between 10 and 100 Hz offset from the carrier.
> > I tried the integrator with a time-constant of 1/16Hz using R 100k  C
> 100n,
> > but it wouldn't lock.
> > The thinking was to put the integrator time-constant about where the
> > free-running ADEV turns upwards from a 1/tau slope.
> >
> > So far I didn't enable the double-integrator - not sure if it's worth the
> > trouble or not..
>
> OK, I can give you a more in-depth overview, but I just crash this quickly.
>
> Now, let's assume you have a pure phase-detector (such as a mixer), a
> PI-regulator and an oscillator.
>
> This represents a second-degree PLL, which has two key properties:
> natural frequency and damping factor.
>
> The natural frequency depends on the loop bandwidth as it goes though
> the integrator path and the I factor.
>
> The I factor is proportional to the natural frequency in square.
>
> The damping factor depents on the balance between the I and P factors,
> in fact the P factor is proportional to the natural frequency and
> damping factor multiplied.
>
> I've derived the formulas multiple times here on time-nuts, but if you
> need further details, please let me know. Happy to discuss off-list.
>
> The loop-gain, as it goes through the integrator path, will decide the
> bandwidh of the PLL and thus the time-constants of the PLL.
>
> The loop-gain, as it goes through the proportional path, decides the
> damping factor and hence the bump of the PLL.
>
> In general, you want to make sure your damping constant is high enough
> and thus avoid the bump, and then dimension the filter bandwidth to
> bring the best balance between the reference oscillators phase-noise and
> the locked oscillators phase-noise. Essentially you overlay the
> phase-plots of reference and locked oscillator, and where they cross you
> put your cross-over bandwidth, as the PLL will low-pass filtet the
> reference oscillator phase-noise and high-pass filter the
> locked-oscillator phase-noise. The resonance due to lack of damping will
> exagerate the response at the cross-over frequency.
>
> Uhm, this may sound a bit uncoherently, but it all fits together if you
> play around.
>
> For the double-integration path, you need to be careful as the
> root-locus does not guarantee a stable system, as the complex pole-pair
> can move over to the right-hand side and hence severely unstable.
>
> I can make a few recommended readings. The TI application note
> referenced isn't bad, but there is a few books to look at. The TI
> app-note does however cover some of the field the following references
> miss out on.
>
> The Best book may be a good crash-coarse, but ends up not being good at
> teach the basics. It may be good for crashing into the field of PLLs,
> and for some things it's a very handy reference, but for others... not
> so much.
>
> The Gardner book is the one book I recommend. Few books has core
> knowledge so well compressed. If one only gets one book, this would be
> the one I 

Re: [time-nuts] Rollover : Thunderbolt

[Dana Whitlow]

My ancient T'bolt (purchased well-used several months ago) also went from
1023 to
1024.  A quick look at IQ phase data I was recording (referred to a
free-running PRS-10)
shows no discernible glitch at the moment of rollover.

This old T'bolt has been living in 1999 for as long as I've had it.  So
tonight it went from
Aug 21, 1999 to Aug 22, 1999.  I'll be interested in seeing what that date
does over the
next several months.

I also have a CNS Clock II, which went smoothly to week 2048, and it  shows
the
correct UTC date.  I confess that I forgot to see what week # it showed
before the
big event, but suspect it was 2047 (not 1023).  Shame on me!

Dana


On Sat, Apr 6, 2019 at 9:01 PM paul swed  wrote:

> HP 3801 locked after the rollover. Thats all I have checked so far.
> Regards
> Paul
>
> On Sat, Apr 6, 2019 at 9:01 PM Martin VE3OAT  wrote:
>
> > Well!  I must have misunderstood something.  At 23:59:42 on 06 April,
> > LadyHeather informed me that my Thunderbolt changed from week number
> > 1023 to 1024.
> >
> > Drama!  Suspense!  Excitement!  I had expected a reset from 1023 to
> > 0.  But that isn't what happened.  Maybe in another 20 years ...
> >
> > 73,
> >
> > ... Martin   VE3OAT
> >
> >
> >
> >
> >
> > ___
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> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Updating the unit of,time: the second.

[Dana Whitlow]

Well, I once had a nutty idea which was to detect earthquakes by looking
for the phase
variation of DTV station pilot carriers due to seismic waves propagating
around, thereby
changing the physical distance between transmitter and receiver in a cyclic
manner
until the 'quake calmed down.   Doing so would require that the phase
stability of both
transmitter and receiver, expressed as length units, be within a fairly
small fraction of
an inch.

I've since figured out that even with a Rb at both ends, this would not
work out- something
more like an H-maser would be required.  And one other thing- I had
completely
forgotten about Doppler-shifted reflections off aircraft, which often fall
right in the frequency
range of seismic waves and persist for durations similar to those of
earthquakes.  But that's
what got me interested in time-nuttery.  I still intend to do the
experiment, just to see what I
can learn about what other factors might exist which cause propagation
phase variations.

Dana


On Mon, May 27, 2019 at 11:27 AM Bob Albert via time-nuts <
time-nuts@lists.febo.com> wrote:

>  Well I have enjoyed time and frequency measurement for many years.  I
> have no equipment (nor do I expect to get any) that can tell the difference
> between the current second and the proposed standard.  And at one point I
> asked if there was a limit on the smallest time interval that could be
> discerned.
> I do remember being impressed with the Collins gear in the 1950s, and
> wanting one of those 7 foot racks of time standards made by General Radio,
> the one with the big clock on top.
> As the years passed I obtained more and more accurate frequency
> measurement equipment, including a home made heterodyne frequency meter
> that outdid the Collins radios.  Then the lousy radio propagation ended my
> dependence on WWV and I luckily obtained a rubidium oscillator.
> But that's about as far as I want to go.  My HP 8657B resolves 1 Hz at
> more than 2 GHz and it can be set to within a very small error with respect
> to the rubidium standard.  At this point I see no reason to improve my time
> and frequency measurement accuracy.
> Of course it can be an end in itself, hence the name Time Nuts.  So I
> propose the question, how many out there have interest in this topic for
> academic and psychological reasons, and how many actually have a concrete
> reason to be this precise?  One part per billion isn't a lot.  And some
> systems require iron clad synchronism such as space exploration and long
> range communication.  But the average tinkerer probably doesn't need it.
> Bob
> On Monday, May 27, 2019, 3:20:24 AM PDT, Dave B via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>  Hi.
>
> This from the recent ShortWave Radiogram broadcast, may be of interest.
>
> ~ ~ ~
>
> (Snipped stuff about other SI units undergoing a revamp...)
>
> Scientists now have their sights set on updating the unit of
> time: the second.
>
> Currently, the second is defined by atomic clocks made of cesium
> atoms. Those atoms absorb a certain frequency of light. The
> wiggling of the light's electromagnetic waves functions like the
> pendulum on a grandfather clock, rhythmically keeping time. One
> second is defined as 9,192,631,770 oscillations of the light.
>
> But a new generation of atomic clocks, known as optical atomic
> clocks, outdo the cesium clocks. "Their performance is a lot
> better than what currently defines the second," says physicist
> Andrew Ludlow of the National Institute of Standards and
> Technology in Boulder, Colo. Because those optical atomic clocks
> operate at a higher frequency, their "ticks" are more closely
> spaced, making them about 100 times more precise than cesium
> clocks.
>
> Ideally, the length of a second should be defined using the most
> precise timepieces available. A switch might happen in the late
> 2020s, Ludlow says.
>
> The change to the kilogram's definition was carefully
> orchestrated so that it wouldn't affect normal people: A kilogram
> of flour still makes the same number of biscuits. Any change to
> the second will be similarly coordinated.
>
> So, sorry, there'll be no chance to squeeze any extra seconds
> into a day.
>
>
> https://www.sciencenews.org/article/kilogram-just-got-revamp-unit-time-might-be-next
>
> ~ ~ ~
>
> So, perhaps a host of surplus cesium clocks on the market at some point?
>
> 73
>
> Dave B G0WBX.
>
> --
> Created on and sent from a Unix like PC running and using free and open
> source software:
>
>
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Re: [time-nuts] The forbidden question

[Dana Whitlow]

In answer to the question about radio astronomers, consider VLBI (Very Long
Baseline Interferometry).

VLBI is a mapping (imaging) process in which signals are *simultaneously*
received from
a small sky region of interest by a collection of radio telescopes
scattered about the world.
In order for the process to work, ultimately it is necessary for all the
signals to be lined up
in time (think phase) to a small fraction of a period of the microwave
frequency being used.
Suppose the frequency is around 5 GHz, then the period is just 200 psec,
and a small
enough fraction thereof is maybe 10 psec or less.

Now present day clocks and time transfer schemes are not good enough to
accomplish
that feat "open loop" across a collection of observatories spanning
thousands of miles.
Fortunately, radio astronomers have developed a set of magical techniques
collectively
called "self calibration" by which, with extreme care, the job can still be
done provided
that the data sets from each observatory are initially lined up to within
around 100 nsec.

However, another requirement is that the LOs for the different
observatories' receivers maintain
that constant phase relationship I mentioned above during the course of an
observation.  In
practice this condition can typically only be held for a few minutes at a
time, and the only
atomic clock in commercial production that can do that is the hydrogen
maser.  Cs beam
clocks are simply not stable enough in that time frame to get the job
done.  But I'm quite sure
that much more stable clocks yet would relieve the overall problem of
making much longer
continuous observations.  Not solve all aspects of the problem by itself,
but it would sure
help.

Another use for such observations is earthbound geodesy, used to track
continental drift
and the like.  Here the preferred radio source is a bright point source
such as a quasar,
and the point is monitoring the position of each observatory.   In this
application it's
important to accurately know the position of the selected source, and one
of the applications
of VLBI is also to measure source locations.  So if you're an
astrophysicist you want to know
the precise locations of all the telescopes, and uncertainty in this is
"noise".  But the person
wanting geodesic information want to measure drift in telescope positions,
and needs to
know where the source is located in the sky.  So one man's signal is the
other man's noise,
and vice versa.  In any case, anything that can be done to improve phase
coherence between
all the receivers in the network can only help.

Dana

Previous "Keeper of The Clock" at the Arecibo Observatory in Puerto Rico

On Tue, Jun 4, 2019 at 6:01 PM Poul-Henning Kamp  wrote:

> 
> In message  7bl...@mail.gmail.com>
> , "William H. Fite" writes:
>
> >What I am asking is not the validity of the quest for better timing
> >but rather its tangible applications.
>
> Tangible for who ?
>
> For the average pedestrian there are no *current* tangible applications
> where cesium level time-keeping isn't plenty.
>
> However, the same would have been said about chronometers and quartz
> clocks at various times in the past.
>
> To answer your question we would need to look about 20-30 years
> into the future, which seems to be the median time for better
> timekeeping to break through to the wider public, even if they do
> not know it has happened, (ie: longitude navigation, digital telephone
> networks, GPS.
>
> Peeking 20-30 years into the future is an unsolved problem, so I
> would argue that your question is unanswerable at this time.
>
> --
> 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] Si5351A harmonics question

[Dana Whitlow]

Chris,

In general I'd say that the rather high level sidebands on your
signal are not reasonable at all, but I think I see what's *really*
wrong: your SA settings.  It looks to me like the tall signal
is the DC spur, (a.k.a. "start spur") of you analyzer, and
the signal very near center screen is the actual signal of
interest.  Try setting the CF and span of the analyzer so
that the left end is at higher than zero freq, and I think
you'll feel a lot happier.

BTW, It's important to avoid any DC component on the
signals that you feed into the SA, as DC could severely
overload the mixer in the SA with all manner of bad results
depending on the front end design of the SA.  Many SAs
already have a DC blocking capacitor built-in, but not all.

The output of the SN74AHCT125N will certainly have a strong
DC component, so do pay heed to the comment immediately
above.

Also, it you want to filter the output of the SN74AHCT125N, be
sure that the filter is not putting a DC short on the output of
the logic device.  If the filter does show a DC short at its input,
add a DC blocking capacitor in series.  A LPF should never do
so, but once you get into BPSs or HPFs anything is possible
depending on the filter's particular design.

It may be that your class-D amplifier is objecting to a DC
component on its input- yet another place where a blocking
cap could be needed.

Good luck!

Dana


On Wed, Jun 5, 2019 at 11:01 AM Chris Wilson  wrote:

>
>
>   05/06/2019 16:24
>
> I am using a small transmitter called a U3S by QRP Labs as an exciter
> for a high power Class D amp. I take the output at circa 951kHz direct
> from CLK0 (it has no output stage built, I go direct from CLK0 on the
> Si5351A and input it to a level converter based on a SN74AHCT125N IC.
> The Class D amp needs a frequency input of X2 the desired output
> frequency. I have experienced terrible gate and drain waveforms on two
> Class d amps driven by this, so I put my SA on the output of the
> SN74AHCT125N via a switchable 50 Ohm attenuator. I see the trace in
> the first photo in the link below. Now I am the first to admit that
> apart from a fear of blowing the SA front end, I am a total novice
> with an SA. Are the high level additional frequencies away from the
> centre frequency to be expected, and do LPF's work on square waves? I
> di try a big high power 475 kHz LPF between the output of the
> SN74AHCT125N and the SA and the second shot was the result. Obviously
> that LPF is far from ideal though, but it was sat on the bench so I
> trie it Thanks please keep the answers at a novice level :)
>
> http://www.chriswilson.tv/mf.zip
>
> https://www.qrp-labs.com/ultimate3/u3s.html
>
> --
>Best Regards,
>Chris Wilson.
> mailto: ch...@chriswilson.tv
>
>
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Re: [time-nuts] Updating the unit of,time: the second.

[Dana Whitlow]

Ole,

Is it when all 5 conditions are met, or just any one of them?

Thanks,

Dana


On Wed, May 29, 2019 at 11:00 AM Ole Petter Rønningen 
wrote:

> As supporting material; BIPM is considering when a redefinition would be
> appropriate:
> https://www.bipm.org/utils/common/pdf/CGPM-2018/CGPM-2018-Time-2-LD.pdf
>
> And
> https://www.bipm.org/utils/en/pdf/CCTF-strategy-document.pdf annex 1 (and
> a few other places)
>
> Extract:
> The time for a new definition is right when ...
>
> 1. ... at least three different optical clocks (either in different
> laboratories, or of different species) have demonstrated validated
> uncertainties of about two orders of magnitude better than the best Cs
> atomic clocks at that time.
>
> 2. ... at least three independent measurements of at least one optical
> clock of milestone 1 were compared in different institutes (e.g. Df/f < 5 x
> 10-18) either by transportable clocks, advanced links, or frequency ratio
> closures.
>
> 3. ... there are three independent measurements of the optical frequency
> standards listed in milestone 1 with three independent Cs primary clocks,
> where the measurements are limited essentially by the uncertainty of these
> Cs fountain
> clocks (e.g. Df/f< 3 x 10-16).
>
> 4. ... optical clocks (secondary representations of the second) contribute
> regularly to TAI.
>
> 5. ... optical frequency ratios between a few (at least 5) other optical
> frequency standards have been performed; each ratio measured at least twice
> by independent laboratories and agreement was found (with e.g. Df/f <
> 5x10-18).
>
> Br,
> Ole
>
> > 29. mai 2019 kl. 15:16 skrev Attila Kinali :
> >
> > On Tue, 28 May 2019 22:56:35 +0200
> > Mike Cook  wrote:
> >
> >> a. There is no need for a new definition.
> >
> > There is. Current optical clocks deliver a lower uncertainty than
> > Cs fountain clocks. Ie the reference we have is less precise than
> > the measurement tools we have. Hence a redefinition of the second
> > is needed.
> >
> >> b. Any new definition would have to be realizable and easily
> verifiable.
> >
> > That's one of the main concerns and this is also the main reason why
> > nobody is actively pursuing a redefinition just yet. But there are people
> > out there who are already working on this topic and gathering all the
> > requirements to a successful redefinition of the second. My guess,
> > based on the current speed of things, is that we will have a new
> > definition of the second within 10-15 years.
> >
> >> c. The first commercial cesium clocks were available in 1956, but the
> second did not get redefined until 1967.  There is no rush.
> >
> > Which caesium beam standards were available in 1956? AFAIK the first one
> > was the HP5061 and that came much later. Essen and Parry built their
> > clock in the 1950s and published the results in 1955. The picture of the
> > beam tube is only a small fraction of the clock itself. There are
> multiple
> > racks full of RF equipment not shown. I would be very surprised if there
> > was any company that was able to commercialize this contraption within
> > only a year. Even in this large size.
> >
> >>I believe that commercial optical clocks are available but:
> >
> > No. As far as I am aware of, there are no commercial optical clocks
> > available. There are a few optically pumped microwave clocks out there
> > (e.g. by Oscilloquartz) and even cold atom clocks (by Muquans and SDI)
> > but no optical clocks.
> >
> > The main problem with optical clocks is the frequency division of the
> > optical signal down to something that can be used in electronics.
> > This is usually done using an optical comb. But the commercially
> > available ones are big, and according to Michael Wouters also quite
> > expensive. There are efforts to use non-linear optical rings to
> > generate these combs, but there is no commercial version available
> > yet (it's a very new technique, which has been around just a few years)
> >
> > The closest I know to a commercial product is what NIST reported
> > in Optica just a few days ago[1] (based on two-photon absorption
> > in a Rb vapor cell and using two optical combs to divide the
> > 778nm down to 22GHz).
> >
> >> d. There are too many flavors of optical clocks around on lab benches.
> So despite their increased precision and stability which flavor would get
> the vote?
> >
> > This is another issue. Of course, a redefinition will use one atomic
> species
> > only (with the others probably becoming secondary definitions). So far
> > the jury is still out which of the atoms and which method is the best
> one.
> > As there are not yet enough optical clocks out there, we don't have
> enough
> > data to decide yet. And it doesn't help that an optical atomic clock
> takes
> > several years and a quite large team to build.
> >
> >Attila Kinali
> >
> > [1] "Architecture for the photonic integration of an optical atomic
> clock",
> > by Newman et al., 2019
> > 

Re: [time-nuts] Truetime XLi sat signal levels (dBW to dBc/SNR conversion question)

[Dana Whitlow]

Mark,

When you refer to "30 dBc", what is that?   Is it the eb/n0 value?  If so,
with the XLi's
behavior as you report it, your scheme would fail over most of the useful
signal range.
And, it will probably differ from setup to setup of the HW, depending on
all the parameters
that have already been discussed.

Dana



On Fri, Jun 14, 2019 at 9:00 PM Mark Sims  wrote:

> I have figured out an empirical formula for mapping between the TrueTime
> dBW values and the more traditionally reported signal level values.
>
> I ran a Ublox F9T and the TrueTime in parallel off the same antenna.  By
> comparing the TrueTime and Ublox sig levels a rather trivial mapping
> function popped out.   Basically you divide the dBW level by the (max
> dBW)(=145) -min dBW(=196) values) to get a value in the range of 0..1
>  Multiply that by 50 and add a 3dB fudge factor).   The two values match
> within 1 dB.
>
> My XLi uses a Motorola M12 GPS receiver.  The XLi reports signal levels
> less that around 30 dBc as -196 dBW,
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Re: [time-nuts] GPSDO 10MHZ Splitter

[Dana Whitlow]

One can reduce the gulp factor mentioned by Scott quite a bit by buying
one of the non-connectorized versions from Mini-Circuits and wiring up
one's own BNC connectors.

One thing to keep in mind with these isolating splitters is that the
isolation
between outputs is good only if the impedance of the driving source is
pretty
accurately 50 ohms resistive.  This will not generally be true if the
source is
logic gate of some kind, although a parallel combination of several HCMOS
or ACMOS inverters combined with a series output resistor to bring the
output impedance up to 50 ohms will probably work well.

Dana   (K8YUM)

On Fri, Jun 21, 2019 at 12:18 PM W7SLS  wrote:

> A couple of ideas:
>
> Make one:
>
> Several hours and a few $  (cheap if you value your time as free)
> agree, not a lot of isolation between the outputs
> Case, connector, and three 16.67 ohm resistors
> in —> 16.67 ohms —> 16.67 ohms to output 1
>—> 16.67 ohms to output 2
>
> Ref:
> https://www.markimicrowave.com/blog/how-to-make-an-n-way-power-splitter/
>
> Perhaps free (may or may not work):
>
> Television 75 ohm splitter
> agree, mismatch between 75 ohms and 50 ohms
> agree, ugh to F connectors
>
> Ref: I don’t know if this just occurred to me, or if I read it
> (e.g., on this group)
>
> Buy one:
>
> Example: Mini-Circuits ZSC-2-1+, about $50 new
>
> https://www.minicircuits.com/WebStore/dashboard.html?model=ZSC-2-1%2B <
> https://www.minicircuits.com/WebStore/dashboard.html?model=ZSC-2-1+>
>
> Gulp:
>
> Your mileage may vary
> BNC-T connector
>
> As mentioned elsewhere:
>
> Legacy RGB distribution boxes (e.g. Extron), about $40 on auction
> sites
> Yes, they are 75 ohms, but may be fine, or you can change the
> internal resistors to move to 50 ohms.
>
> And of course there are other ($$$) solutions.
>
> (Obviously) I defer to the wisdom of the group (and perhaps groans and eye
> rolls).
>
> Best of luck, whatever you choose.
>
> Scott
> W7SLS
>
>
>
>
> > On Jun 21, 2019, at 7:27 AM, Don Meadows  wrote:
> >
> > Is there an easy, and cheap way to add a splitter the 10Mhz signal
> > from GPSDO, without going to a distribution amplifier to
> > feed two different devices?
> >
> > I really don’t want to build a complicated project, or
> > spend $200.00 dollars for an 8 output distribution amp
> > off the net.  One output would be dedicated for my
> > counter time base, and the other would be an ‘extra’
> > 10MHZ source for another counter, or just to display on the scope.
> >
> > I don’t have a GPSDO yet, I just can’t decide on one.
> > I am leaning to the Trimble, but it’s still undecided.
> >
> > Could anyone comment on buying a “Refurbished by Seller”
> > GPSDO on E-bay. They are a few dollars cheaper, but I really
> > want one I can have trust and confidence in.
> >
> > Sorry for the long post.
> > Thanks, Don
> >
> >
> >
> > Sent from Mail for Windows 10
> >
> > ___
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Re: [time-nuts] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design

[Dana Whitlow]

Correction from Dana:

I meant "... without accumulation of phase error during normal times ...".

Sorry about that.

Dana


On Sun, Jun 23, 2019 at 11:45 AM Dana Whitlow  wrote:

> Leo,
>
> Are you saying that you want to abandon phase lock altogether in favor of
> freq
> lock?  Or just during the reacquisition following loss of and restoration
> of the
> reference?
>
> By me definition of pure freq lock, there will generally be some permanent
> (but varying)
> frequency error, so that phase error could accumulate without limit;
> clearly an undesirable
> thing in most applications.
>
> My interest lies in having a stable LO for receiving, without accumulating
> phase error (at least
> during times of missing reference).  When the reference goes away, I'll
> accept some phase
> error accumulation.  So for me, I think the best approach is phase lock
> under normal
> circumstances, but switch to freq lock during reacquisition of phase lock.
>
> DanaK8YUM
>
> On Sun, Jun 23, 2019 at 9:01 AM Leo Bodnar  wrote:
>
>> I have to draw your attention to practical aspects of why some designs
>> use FLL rather than PLL.
>>
>> Consider a GPS locked OCXO outputting GPS synced 10MHz signal.
>>
>> Properly designed control loop will not produce much (if any) difference
>> when the reference (GPS signal) is present.  In the end, integral of zero
>> is zero.
>>
>> When reference (GPS lock) is lost the things are very similar too,
>> holdover is just flying blind in the rough direction you were facing last.
>> Accumulating frequency and phase offset on the way.
>>
>> However, when reference is restored the things are much different.
>> After regaining the reference (which in case of GPS signal has
>> unambiguous absolute time embedded into its phase) *proper* PLL loop will
>> try to correct for slipped phase at the highest slew rate.  This can be
>> huge.  If phase has drifted 1ms apart the loop will have to slew the phase
>> all the way until it gets those 10,000 cycles out of the way.  This usually
>> looks ugly in frequency domain and is very disrupting if you are using the
>> device as frequency reference rather than an absolute time reference.
>>
>> Proper FLL loop will just gently (and reasonably quickly) get your
>> frequency back and forget about all the lost phase.  Which is what a lot of
>> users want.
>>
>> Initially, I have used PLL mode on GPS clocks that I am making, but
>> switched over to FLL during the last few years.
>>
>> Cheers
>> Leo
>> ___
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>>
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Re: [time-nuts] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design

[Dana Whitlow]

Leo,

Are you saying that you want to abandon phase lock altogether in favor of
freq
lock?  Or just during the reacquisition following loss of and restoration
of the
reference?

By me definition of pure freq lock, there will generally be some permanent
(but varying)
frequency error, so that phase error could accumulate without limit;
clearly an undesirable
thing in most applications.

My interest lies in having a stable LO for receiving, without accumulating
phase error (at least
during times of missing reference).  When the reference goes away, I'll
accept some phase
error accumulation.  So for me, I think the best approach is phase lock
under normal
circumstances, but switch to freq lock during reacquisition of phase lock.

DanaK8YUM

On Sun, Jun 23, 2019 at 9:01 AM Leo Bodnar  wrote:

> I have to draw your attention to practical aspects of why some designs use
> FLL rather than PLL.
>
> Consider a GPS locked OCXO outputting GPS synced 10MHz signal.
>
> Properly designed control loop will not produce much (if any) difference
> when the reference (GPS signal) is present.  In the end, integral of zero
> is zero.
>
> When reference (GPS lock) is lost the things are very similar too,
> holdover is just flying blind in the rough direction you were facing last.
> Accumulating frequency and phase offset on the way.
>
> However, when reference is restored the things are much different.
> After regaining the reference (which in case of GPS signal has unambiguous
> absolute time embedded into its phase) *proper* PLL loop will try to
> correct for slipped phase at the highest slew rate.  This can be huge.  If
> phase has drifted 1ms apart the loop will have to slew the phase all the
> way until it gets those 10,000 cycles out of the way.  This usually looks
> ugly in frequency domain and is very disrupting if you are using the device
> as frequency reference rather than an absolute time reference.
>
> Proper FLL loop will just gently (and reasonably quickly) get your
> frequency back and forget about all the lost phase.  Which is what a lot of
> users want.
>
> Initially, I have used PLL mode on GPS clocks that I am making, but
> switched over to FLL during the last few years.
>
> Cheers
> Leo
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Re: [time-nuts] Slightly OT - Magellan Car navigation displays wrong time

[Dana Whitlow]

Glen,

This sounds like it might be one of those latent problems arising from the
GPS
week rollover that we've been warned about.

Dana


On Sat, May 18, 2019 at 4:00 PM Glenn Little WB4UIV <
glennmaill...@bellsouth.net> wrote:

> Did anything happen in the last 24 hours that would affect the time
> displayed on a gps receiver?
> I have a Magellan RoadMate RM9612T-LM that started displaying time that
> is one hour and 40 minute in the future.
> I have verified that the correct time zone is selected.
> I changed the time zone and it displayed time for that zone with the
> same offset.
> I am in eastern zone and have set receiver back to auto with same results.
>
> Thanks
> Glenn
>
> --
> --
> Glenn LittleARRL Technical Specialist   QCWA  LM 28417
> Amateur Callsign:  WB4UIVwb4...@arrl.netAMSAT LM 2178
> QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
> "It is not the class of license that the Amateur holds but the class
> of the Amateur that holds the license"
>
>
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Re: [time-nuts] Rooftop antenna and splitter

[Dana Whitlow]

Denny,

That is certainly a large difference.  But I'm not clear on one point that
could
easily be very important:

Were the two antennas for the separate antenna test indoors, or on the roof?
If indoor, I kind of suspect that the difference might mostly be attributed
to the
change in antenna locations more than anything else.  If this is what's
going on,
you've made very strong case for outdoor antennas for GPS timing.

Also, it's possible that the two receivers with their antennas in such close
proximity might have been interfering with each other.

Dana


On Mon, Apr 29, 2019 at 8:07 PM Denny Page via time-nuts <
time-nuts@lists.febo.com> wrote:

> I don’t seem to be able to attach the pics to the emails correctly to
> allow the mailing list software to process them. Rather than bombard
> everyone with any more attempts, I put them up on Dropbox.
>
> You can find the pics here:
> https://www.dropbox.com/sh/fbbfuydqac5qqql/AAADkwrcVL8u5nkHvi8ecMe3a
>
> Thank you to Tom and John for trying to help!
>
> Denny
>
>
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Re: [time-nuts] PRS-10 with 1 PPS IN goes nuts - 40 million degrees!

[Dana Whitlow]

Taka,

What happens to the timing of the PPS output and/or the phase of the 10 MHz
output during these wonky times?

This inquiring mind wants to know, as it is getting pretty close to
ordering a
PRS-10 for its own use.

Dana


On Thu, Apr 18, 2019 at 3:45 PM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> Has ANYONE have a Rubidium module by Stanford Research, PRS-10, use 1 PPS
> IN, and have watched it for extensive period using LadyHeather?  I have 2
> GPS, and they are different models.  It does the same thing with either one.
>
> I have, and every time, usually within 24 hours, it send one or more wonky
> data.  LH interprets as super high temperature and displays it.  Today, it
> has been running for about 18 hours and just today, it told me it was 40
> million degrees.  (did it go super nova?)  It does this periodically.  Then
> goes right back to normal operations.
>
> I know when PRS-10 starts up, it sends garbage data, so I have to turn on
> PRS-10 first, then fire LH.  I also know when power is interrupted, it does
> this as well.  I have upgraded the connection method and verified all
> components are securely attached.
> I've at this for more than few weeks and I don't know what else could be
> wrong.  I used two separate PRS-10 and they all behave this way.
>
> Calling technical support at SR, I was told when PPS IN is used to control
> it via GPS, for example, extra CPU cycle is used.  But they have not seen
> corrupted data.  (which could be a lie - but I'm just guessing here)
>
> ---
> (Mr.) Taka Kamiya
> I'm stuck in a wormhole  Hello, worms!
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Re: [time-nuts] It is possible to "recharge" a hydrogen maser?

[Dana Whitlow]

My experience is limited to the MHM-2010 at the Arecibo observatory, but I
suspect they all
handle the H2 supply in pretty much the same way.

Th hydrogen comes from a reservoir, in the case of the MHM-2010 from a small
"lecture" bottle of H2 under pressure.  I assume that this is isotopically
rather pure,
and also fairly pure of other gaseous contaminants.

In principle this should be field replaceable; however special procedures
including
a good vacuum pump and probably some special fittings would likely be
required.
You should consult the mfr of your maser about the availability of a new
bottle of
H2 as well as correct procedures for making the changeover.

We at Arecibo had to replace one of the vacion pumps in our maser about 6
or 7
years ago. and we decided to get help from Symmetricom in the form of a
field
service call, to the tune of $12k.   The guy who came was a physicist at
heart, and
was the very guy who had put together the physics package in our very maser.
This included replacement of the still-working pump as well, done the
following
day.  So on the first day, he replaced the failed pump while I asked
questions and
took copious notes.  Then on the 2nd day, I replaced the 2nd pump while he
kibitzed and stood ready to stop me before I did anything stupid.

In both cases there was some difficulty getting the pumps "started up",
arising
because they had been open to the atmosphere for some time beforehand.  They
both required a lot of teasing of the voltage in little steps, while
intently watching
the current to be sure not to exceed ratings.  IIRC, they each required
more than
an hour of vigilance before we could safely stand down.

The interesting thing was that this maser could (and did) run quite well
with only
one pump working, for over a year.   The delay was on our part, shuffling
stuff
around in the clock room to clear generous working space around the maser.
The
job involved a lot of "on-the-floor" work, much like working under a car
without
benefit of a lift.

But the maser was well thought out in that subsystems could be isolated with
high-vacuum valves and switches, with the result that we kept the maser
operating
throughout the two procedures, with only a subtle glitch in timing accuracy
visible in the records when I checked after the fact.   The observatory
continued
to operate with no disturbance the whole time.

Dana Whitlow

On Fri, Jul 5, 2019 at 12:01 PM Luiz Paulo Damaceno <
luizpauloeletric...@gmail.com> wrote:

> Hi friends,
>
> We have a hydrogen maser here at the university that i work. It seems the
> hydrogen is over. This is possible? If yes, It is possible to recharge It?
>
> Best regards,
>
> Luiz.
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Re: [time-nuts] Used Hydrogen Maser

[Dana Whitlow]

Perry,

The only H-maser with which I've had direct experience (the MHM-2010) costs
around $250,000 new.  But there are some other brands, mostly foreign.

The immediate operating cost is that of AC power.  IIRC, the '2010 uses
about
100W or maybe 125W, *all the time*.  The H-maser is *not* the kind of thing
one
turns on when needed and back off in between uses.

The hydrogen supply is usually large enough to last about 15 years or more.

A sort of hidden cost is that the unit must be operated in a
temperature-controllled
environment for best stability- hence there is also the purchase and
operating costs
of a suitable A/C system.

Also note that H-masers *do* drift in frequency over time.  The one we had
at Arecibo
typically needed frequency correction of about 3.5E-14 about every 4 months
on average,
to keep the observatory's master clock on time within 25-50 nsec as needed
for certain
types of radio astronomy situations.  We used the H-maser because it has
the best
stability (over the range of seconds to hours) of anything commercially
available.

The maser operated without difficulty for about the first 8 years before it
lost one of
its two vacion pumps.  We had to pay $12k for an engineer from Symmetricom
to
bring down a pair of new pumps and oversee the installation.  He replaced
the failed
one on one day while I took notes; then the next day I replaced the 2nd one
under
his close supervision and scrutiny.  Because the maser was well designed
with vacuum
isolation valves, both pump replacements were accomplished without shutting
down
the maser and with no disturbance to observations.

A few years later the maser's internal log data showed that the hydrogen
pressure
was oscillating, along with synchronized fluctuations in drive to the Pd Pd
"valve",
with a period of about 11 days.   At this point there was no noticeable
effect on timing
accuracy.  A series of calls to Symmetricom customer service indicated that
they had
no idea what was going on, and they counseled "watchful waiting".  We did
that for
several more years up until I retired in Dec 2016, with the only change
being a very
gradual drift in oscillation period and amplitude.  The in late Dec 2018,
the maser
basically died outright, and Symmetricom (then part of Micro-Semi) was
unable to
provide a definite diagnosis- just a couple of theories.  But they advised
against
trying to fully diagnose and repair the unit, considering its advanced age
(approx
15 years at the time).

Hope this helps ...

Dana




On Wed, Jul 10, 2019 at 7:00 AM Perry Sandeen via time-nuts <
time-nuts@lists.febo.com> wrote:

> Yo Bubba Dudes!,
> OK, I'll finally ask the question that probably a lot of list members
> wanted to know but were reticent to ask.
> First, what is the price of one of a new Hydrogen Maser? (This is
> important if I win the lottery.)
> Second, what would be prices for used Hydrogen Maser in *reasonable*
> working condition and what might be the long term costs to keep it running?
> Thirdly, what are the chances of finding a used one?
> Then again, might it be better, money wise just to limp along with used HP
> Cs?
> Regards,
> Perrier
>
>
>
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Re: [time-nuts] Galileo service currently degraded

[Dana Whitlow]

I wonder if a case could be made for multi-GNSS reception in the case of a
poorly-
located GPS antenna at the reception site.  That is, could the benefits of
having a lot
more sats in the sky outweigh poorer performance of some of the systems with
respect to other systems?

Dana


On Sat, Jul 13, 2019 at 1:02 AM Kevin Croissant 
wrote:

> Hi Luciano,
>
> Yes this is typically the case. GPS is the most reliably good system
> currently. When the Galileo system is working nominally and the geometry
> over our antenna is good (remember, the constellation is not yet complete),
> the single frequency performance easily rivals GPS. BeiDou will likely be
> similar once the constellation is finished, assuming they don't
> intentionally degrade the civilian signals over non-Chinese regions.
> GLONASS, well that's another case altogether.
>
> Keep in mind the limitations of the website's data collection - single
> frequency "professional grade" receivers which do not perform carrier-phase
> or any kind of satellite based corrections/augmentations (SBAS, etc). If
> the receivers were more sophisticated and in another region, the story may
> be different. If anyone wants to set up a similar monitoring system in
> another part of the world, let me know, I would be very interested in that.
>
> Kevin
>
> On Sat, Jul 13, 2019 at 1:05 AM tim...@timeok.it  wrote:
>
> >
> >Looking at the data it seems that GPS is the best system among the
> > four, correct?
> >
> >Luciano
> >
> >
> >Da "time-nuts" time-nuts-boun...@lists.febo.com
> >A "Discussion of precise time and frequency measurement"
> > time-nuts@lists.febo.com
> >Cc
> >Data Fri, 12 Jul 2019 18:29:10 -0400
> >Oggetto Re: [time-nuts] Galileo service currently degraded
> >I built this website as my senior design project last year,
> > unfortunately
> >there's no timing data (except for tdop) being logged but you can see
> > the
> >impact. Data is collected with four ublox m8n receivers, one per
> >constellation.
> >
> >Galileo data from last 1 week:
> >https://gnssperformancemonitor.com/viewdata.php?constellation=2×pan=1
> >
> >Kevin
> >
> >On Fri, Jul 12, 2019, 4:06 PM Hal Murray 
> > wrote:
> >
> >>
> >>
> >> > Galileo service is currently degraded, see:
> > https://www.gsc-europa.eu/
> >> > notice-advisory-to-galileo-users-nagu-2019025
> >>
> >> Thanks.
> >>
> >> Is anybody monitoring a Galileo-only setup to see how far off the
> > timing
> >> drifts?
> >>
> >>
> >> --
> >> These are my opinions. I hate spam.
> >>
> >>
> >>
> >>
> >> ___
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>
>
> --
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Re: [time-nuts] GPDSO Distribution amp that does not radiate ?

[Dana Whitlow]

Sure sounds to me like the distribution amp does have some sort of shielding
problem, in effect.

Are the power connections (whether AC or DC) properly filtered?   Are all
the
coax connectors' bodies well-bonded to the metallic enclosure?

You might want to try sniffing with a small diameter (~1 inch) loop on the
end
of a flexible coax cable going to the SA.  Sniff connectors, power input(s),
seams on the case, any other penetrations in the case (like a display?),
etc.

Dana


On Sat, Jul 13, 2019 at 12:00 PM Jerry O. Stern  wrote:

> I have been using a Tbolt and TAPR TADD-1 for a few years, mainly as an
> external reference source for my workbench equipment.  Just got a SDR radio
> kit (Ubitx) and trying to calibrate the local oscillators found this
> annoying substantial 10MHz signal heterodyning with the LO's (45MHz and
> 12MHz).   Taking a look on my SA with just a broad band telescopic antenna
> in the SA input, I see a 10MHZ at about -55 dBm and no other signals > -120
> dBm.  The Tbolt is about 4-5' away from the workbench BUT I disconnected
> everything and it is only connected to the TADD-1 distribution amplifier
> The TADD has no distribution coaxes attached, it is in the TAPR metal
> cabinet which I always thought was well shielded and every port has been
> terminated with 50 Ohm  dummy load plugs.  When I take the TADD-1 out of
> the
> equation and just run the Tbolt into a 50 ohm termination plug, the 10MHz
> signal on my SA drops down to  > -90 dBM. I duplicated this with a
> Lucent RFTGm-Xo/Rb pair and the TADD-1 with similar results.Has anyone
> else seen this with their distribution amp?
>
>
>
> Jerry
>
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Re: [time-nuts] Advantages of GNSS ???

[Dana Whitlow]

One what?  I see that it is a Ublox unit, but see no reference to the
interesting
modern units like the 9 series.  Also, I note that the only reference on
the board
to "ant" is on the lower right corner, while what I suppose to be the
actual antenna
connector appears to be an SMA near the upper right corner.

And why does it look like several of the components have been resoldered
or replaced or something?

Dana


On Mon, Jul 8, 2019 at 8:00 PM ew via time-nuts 
wrote:

> Well now you can see one
> Bert Kehren
>
>
> In a message dated 7/8/2019 7:02:07 PM Eastern Standard Time,
> hol...@hotmail.com writes:
>
> A big issue with using the sawtooth correction message from a GPS
> receivers is the issue of just what that sawtooth value is related to and
> how to apply it to the measured PPS value / phase.
> I added the ability to Lady Heather to calculate a sawtooth corrected
> "paper clock" by applying the sawtooth correction message value to the PPS
> output measured by an external counter like the TAPR TICC.
>
> There are around a dozen different combinations of sawtooth value and PPS
> measurements...  only one of which minimizes the PPS error.  Do you add or
> subtract the sawtooth value to the PPS measurement?  Do you apply the
> sawtooth value to the previous/current/next PPS measurement?  Do you apply
> the sawtooth correction to the PPS itself or the accumulated phase of the
> PPS?
> I don't think that I have ever seen what to do  with the sawtooth value
> documented in any receiver documentation...  Heather has default receiver
> dependent correction strategies or lets you specify the correction
> strategy to use.___time-nuts
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Re: [time-nuts] A Research Proposal

[Dana Whitlow]

I'm surprised that the VF of HV transmission lines is noticeably less than
unity, given
that the dielectric is just air.  Or does the distributed resistance do all
the damage?

Dana


On Mon, Jul 8, 2019 at 8:00 PM jimlux  wrote:

> On 7/8/19 3:11 PM, Hal Murray wrote:
> >
> > glenl...@pacificmedia.com.au said:
> >> I think  people getting confused with the phase of measured current to
> the
> >> voltage .
> >
> > No, we have been discussion the phase angle between 2 geographically
> separated
> > locations connected by a power line.
> >
> > Consider the simple case of a generator, 100 miles of line, and then a
> light
> > bulb.  The voltage at the light bulb will be delayed by the speed of
> light.
> > That delay can be expressed as a fraction of a cycle and converted to a
> phase
> > angle.
>
> >
> > It gets much more complicated if you have multiple generators, multiple
> loads,
> > and various transmission lines, and even more complicated when you turn
> things
> > on and off.
>
>
> The transmission line is decidedly not Velocity Factor =1.0
>
> A typical propagation constant might be j0.0018/mile
>
> about 5500 km/wavelength at 60 Hz.
>
> Free space propgation delay for 5500 m is 18.5 milliseconds - compared
> to 16.67 millisecond period of 60Hz.  A velocity factor of about 90%
>
> (that's for an example I found for 765 kV, using Tern conductors, in
> bundles of 6
>
> http://home.engineering.iastate.edu/~jdm/ee552/Transmission.pdf
> )
>
>
> >
> >
>
>
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Re: [time-nuts] TimeLab phase difference (slope sec/sec)

[Dana Whitlow]

Chris,

Ok, one source is a PRS-10.  Is it the DUT or the reference?  And if it's
the DUT, what
is the reference source?

Dana


On Tue, Jul 2, 2019 at 8:00 PM Chris Burford 
wrote:

> Hi Bob,
>
> I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab
> phase difference plot. Is that telling me that my DUT is within +4.22ps
> / sec from my reference 1PPS for the 24 hour measurement duration?
>
> I have attached a screen capture that will hopefully make its way
> through for viewing.
>
> Thanks,
>
> Chris
>
> On 07/02/19 11:50:10, Bob kb8tq wrote:
> > Hi
> >
> > The difference in seconds between the start phase and the end phase
> divided by the number
> > of seconds duration gives you the parts in whatever of the error.
> >
> > If you see 1us ( = 1x10^-6 seconds)  of change in a second, you are off
> by 1 ppm (or 1x10^-6).
> > If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or
> 1x10^-9). At a bit over 10
> > days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12).
> >
> > Bob
> >
> >> On Jul 2, 2019, at 10:17 AM, Chris Burford
> wrote:
> >>
> >> Is the slope value for the phase difference shown in TimeLab an average
> of the overall data sample duration? The reason I ask is that my service
> manual for my RFS says:
> >>
> >> /"//A faster way to make the comparison between the reference frequency
> and the DUT is to use the time interval measurement mode of the counters.
> In this case, the time intervals between the 10MHz zero crossings of the
> reference frequency and the DUT are measured and averaged. If this time
> interval changes by less than 10ps per second, then the DUT is within 1
> part in //10^11 of the frequency reference."/
> >>
> >> I'm just curious if the phase difference slope value can be plugged in
> to this equation.
> >>
> >> Regards,
> >>
> >> Chris
> >>
> >>
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Re: [time-nuts] 60 Hz frequency and phase measurement

[Dana Whitlow]

I've always noted that casual attempts to pick up 60 Hz with small antennas
etc see more harmonics and other trash than actual line frequency.  But if
you're in an office environment, why not plug something in?  It's quite easy
to build a simple passive diode clipper/filter that will plug into a wall
outlet and
which will provide a sort of soft (but clean) squarewave at a voltage level
convenient for lab instruments and with good protection against big spikes
and
other trash riding on the line.

If you're willing to do this and need help with a design, contact me
off-list at
k8yumdoo...@gmail.com.

Dana

On Tue, Jul 2, 2019 at 6:00 PM jimlux  wrote:

> There's some designs on the list (using a PICPET, for instance) to
> measure the local line frequency and phase..
>
> but the schemes we've discussed require connecting to the power line in
> some way.
>
> What about a non-contact sensing approach?  Something you could put in a
> box and it would pick up the electric or magnetic field as the input?
>
> Just how strong is the field anyway?  I've always been trying to cancel
> or shield it or reduce it in some way, so I've never actually measured
> it in a calibrated way.  A 10cm antenna on a 1Meg scope probe looks like
> about 40 mV peak to peak (for the 60 Hz component) along with lots of
> other high frequency stuff (40 kHz and a few hundred kHz in my office)
> from switching power supplies.
>
> I realize that in a office/industrial area you'll probably pick up all
> three phases in some way.
>
> What about using a small loop? or a magnetoresistive sensor (like the
> compasses in phones)?
>
> Has anyone tried any of these?
>
>
>
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Re: [time-nuts] verifying synchronization with PPS

[Dana Whitlow]

Steve,

I'm curious: in the absence of a PPS or other electrical output from your
"computer",
what is the nature of the time "output "?  If it's just visual via a
display, why not  view
the light output of the seconds digit with a photocell.  Most of the
transitions should
produce an easily-detectable step or glitch in the light.

Dana


On Mon, Jul 8, 2019 at 9:03 AM Steve Summit  wrote:

> This is a different sort of question than what seems to be
> discussed here usually, and I apologize if it's wholly off-topic,
> but I'm guessing there are some time nuts here who might be able
> to give me some pointers.
>
> If I have two boxes with clocks that are supposed to be perfectly
> synchronized, and I need to verify this, and they're physically
> right next to each other, and they both have PPS outputs, one
> way to verify the synchronization would be to compare the two PPS
> outputs with a 'scope.  (I'm guessing there's probably a dedicated
> instrument out there specialized for the task of comparing two
> such PPS signals for frequency, phase and jitter, and if I were
> a proper time nut myself I guess I'd know that.)
>
> My specific question concerns the case that one of the boxes is
> a computer, for example, a Linux box with time kept using ntpd
> or chrony (perhaps also listening to a PPS signal coming in on a
> serial port).  But I've never seen a computer with a PPS *output*.
>
> Is this a reasonable thing to be thinking about, or am I going
> about it wrong?  How would *you* positively verify synchronization
> of such a system?  Me, I'm pursuing this idea because too much
> of the time (at least in my own, perhaps parochial experience)
> synchronization seems to be "verified" either by saying "Yes,
> we configured it properly", or by observing a status output
> from ntpd or chrony claiming the requisite synchronization
> has been achieved, but in neither case by making a definitive,
> independent, external, empirical determination.
>
> (Perhaps PPS is overkill for this situation; perhaps it's the
> case that given the inherent inaccuracies of software-based
> timekeeping, a software-based query mechanism -- perhaps using
> ordinary NTP or PTP protocols -- would be sufficient for
> externally assessing synchronization.)
>
> I guess it's not a *completely* unreasonable thing to be thinking
> about, because I've found a couple of web pages (for example
> https://www.raspberrypi.org/forums/viewtopic.php?t=115554 and
> https://github.com/jsln/pps-gen-gpio) describing how to implement
> a PPS output under Linux.  And I do realize that trying to
> minimize the jitter and latency in this situation (given that
> the principal drivers for the hypothetical output are inherently
> software-based) presents considerable difficulties.  But taking
> all of that into consideration, I'm wondering what others think
> of the approach.  Thanks for any comments.
>
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Re: [time-nuts] TCXO improvement

[Dana Whitlow]

Question:

Do you stabilize the oscillator inside the dewar, or do you stabilize the
temperature of
the dewar's outside environment?

This may boil down to a slightly different expression:  Where do you *sense*
the temperature for
the stabilization loop?  On the crystal itself, or on the outside wall of
the dewar?

Thanks,

Dana


On Fri, Aug 2, 2019 at 4:00 AM Bill Slade  wrote:

> Hello!
> I have done this and can attest that it works well.  I did not use a TCXO,
> though.  I used a 48 MHz, third-overtone AT-cut crystal in a Colpitts
> oscillator configuration.  The vacuum flask was ovenized to maintain
> temperature near the stationary point of the temp characteristic (near 50
> deg C).   The oscillator could be phase locked to an external atomic
> reference (in our case, a rubidium) or 10 MHz from a GPS receiver.
>
> The inspiration was a couple of excellent NASA reports from some years
> ago, which I have attached (as links because files are large) for
> convenience.
> Cheers,
> Bill
> Nasa Precision Quartz 1<
> https://onedrive.live.com/embed?cid=3CBCA1CF8AB21FE1=3CBCA1CF8AB21FE1%213504=AA4EqyT05-Iz2nU=2
> >
> Nasa Precision Quartz 2<
> https://onedrive.live.com/embed?cid=3CBCA1CF8AB21FE1=3CBCA1CF8AB21FE1%213505=AEG_NqxtMFVIE_o=2
> >
>
> On 02/08/19 01:35, Perry Sandeen via time-nuts wrote:
>
> Yo Bubba Dudes!,
> If one has the space, a simple cure might be to get one of the wide mouth
> thermos containers that they sell in large variety stores such as Wal-Mart
> for being able to eat something like stew or some semi-solid hot food out
> of the container itself.
> Regards,
> Perrier
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Re: [time-nuts] PRS-10 Missing SP values in Appendix A.

[Dana Whitlow]

Thanks Forrest,

I've added this to my documentation packed for my own PRS-10; I suspect
that I'm
only a year or two from (possibly) needing it myself.

Dana


On Fri, Sep 13, 2019 at 3:00 AM Forrest Christian (List Account) <
li...@packetflux.com> wrote:

> Mainly wanting to post this to the list so it will end up in the archives.
>
> So I decided to give calibration/adjustment of my bench PRS-10 a go.
>
> What I discovered is that on my particular unit, the frequency was enough
> off that in order to bring it close to spec, I had to adjust the Mag Offset
> to the lower end of it's range (2300), and even then the set frequency was
> lower than I would have liked.
>
> According to the section of the manual under the SP command, if the Mag
> Offset is at the end of it's range, you can change the frequency
> synthesizer's parameters by querying the existing SP? settings, finding the
> row in Appendix A which corresponds to those values, then changing the SP
> value up or down a step (by using the values in the table row just above or
> below the value).
>
> In my unit, the SP value set (6114,3436,29) were not anywhere to be found
> in Appendix A.
>
> After some digging, and reading the manual, I discovered that these values
> are used to configure the  MC145193 inside the PRS-10.   Specifically the
> first value (R) is used to divide the 10Mhz output.   The second two values
> (N, A) are used to divide 359.72Mhz (which is related to the Rb
> frequency).   This second divisor is calculated by (N*64+A).  The resulting
> two divided down signals will be very close in frequency, and the
> difference is used to stabilize the oscillator.
>
> After some more work, I discovered that the divisor values currently in my
> oscillator were actually exactly 3 times the value of row 52, that is
> 6114/3=2038 and (3436*64+29)/3=(2038*64+31).   Since it's only the ratio
> between the divisors which matter, I'm assuming someone at some point
> decided to use the higher division ratio for some reason.  Not sure if this
> was at SRS or in the field.
>
> After discovering this, I followed the procedure to move the SP values by
> one row in the table, and everything seems to have re-centered itself.
>
> Hope this helps someone...  Even if it's me in the future if I have to do
> this again.
>
> --
> - Forrest
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Re: [time-nuts] Cheap GPSDO with OCXO from aliexpress

[Dana Whitlow]

I'd say that for the low price, the critical component (OCXO) can't be a
very good one.
It's too bad that the seller offers no real specifications (and that he/she
doesn't write
very good English).

I'll be "listening" with interest.

Dana


On Tue, Sep 10, 2019 at 7:32 AM Adam Kumiszcza  wrote:

> Hi!
>
> I've found an interesting product on aliexpress:
>
> https://www.aliexpress.com/i/33055900193.html?spm=2114.12057483.0.0.1f6e7820MBFZQZ
>
>
> GPSDO allegedly with OCXO, 1PPS and 10MHz BNC output, RS232 output of NMEA
> and PPS, LCD screen.
> I see that there are many similar devices there.
>
> Did anybody test something of this kind?
>
> Best regards,
> Adam Kumiszcza
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Re: [time-nuts] Beginner's Atomic Clock

[Dana Whitlow]

Dr. Kirby, et al,

Remember that a GPS-disciplined Rb has two loops, hence two time constants,
to
consider:

a) the loop which locks the Rb's internal OCXO to the atomic transition, and
b) the GPS disciplining loop.

I surmise that the internal loop (a) is fast enough to thoroughly suppress
drifts of
the unit's internal OCXO in the face of local temperature variations etc.

But the other loop (b) can be, and should be, pretty slow (time constant of
hours
or more), so as to prevent the disciplined source being jerked around by
GPS "noise".
This is why the Rb can advantageous over the OCXO- the Rb is inherently
stable enough to permit using a very slow loop for disciplining by GPS.

In my own experience to date, the one GPSDO I have with user-adjustable loop
bandwidth suffers greatly from ambient temperature variations when I make
the
disciplining loop TC large enough to effectively remove GPS noise.  I can
easily
see HVAC cycling, for example, when I use a long time constant.  I've played
with numbers ranging from 5 sec up to 500 sec, and think the best compromise
is around 40 sec.  This with an old Trimble T'Bolt which was apparently
built
around 2004 or thereabouts.

My other GPSDO is a CNS Clock II, purchased new about a year ago.  It does
*not* have provisions for user adjustment of the disciplining loop, which
is fixed
at some rather short time constant (I'm estimating roughly 5 sec).  So its
OCXO
is kept pretty honest in the face of ambient temperature variations; however
GPS noise jerks it around very considerably. in the short term.  I'm
finding this
device's greatest utility in looking at phase drift in my Rb sources over a
period
of several hours at a time, mainly for purposes of frequency setting.

My two Rb's are an old (telecom-modded) PRS-10 and an old L-PRO, neither
of which has GPS disciplining capability.   I continue to agonize over
whether or
not I should buy new (standard-featured) PRS-10- I've been trying to make
this
decision for about 2.5 years so far :-)

I do not have access to the revered HP 10811A, so can't speak to its value
for my interests.  I'd dearly love to borrow one, as it would undoubtedly
provide
a good learning experience for me.

Dana



On Tue, Sep 17, 2019 at 3:11 AM Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:

> On Tue, 17 Sep 2019 at 04:00, Dana Whitlow  wrote:
>
> > The nice thing about a Rb is that its short term stability (seconds to
> > minutes and perhaps
> > even longer) is much better than that of a GPS timing receiver.  The bad
> > news is that Rb
> > standards exhibit long term frequency drift in the neighborhood of a few
> > parts in 10^11
> > per month.  A pretty fair compromise is to use an Rb standard that is
> > disciplined by GPS
> > PPS pulses with a loop time constant on the order of a day or so.
> >
> > Dana   (K8YUM)
>
>
> Is  there any advantage in using a GPS Rb disciplined oscillator vs a GPS
> disciplined high quality OCXO like the HP 10811A? I can’t understand why
> there should be, as a Rb source would use an OCCO in its output stage
> Therefore in each case
>
> * Short term stability depends upon the quality of the OCXO
> * Long term stability depends upon GPS.
>
> Perhaps there’s is period over which the the overall stability can be
> improved by adding a rubidium oscillator. I would be interested to know if
> that is the case or not.
>
> Dave
>
> > --
> Dr. David Kirkby,
> Kirkby Microwave Ltd,
> drkir...@kirkbymicrowave.co.uk
> https://www.kirkbymicrowave.co.uk/
> Telephone 01621-680100./ +44 1621 680100
>
> Registered in England & Wales.
> Company number 08914892.
> Registered office:
> Stokes Hall Lodge,
> Burnham Rd,
> Althorne,
> Chelmsford,
> Essex,
> CM3 6DT,
> United Kingdom
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Re: [time-nuts] Sawtooth Error Correction, WAS: Capturing NMEA and TICC timestamp data in time-correlated way?

[Dana Whitlow]

Assuming that the T'bird works as you stated, you might still want to know
where in that
sawtooth the supposedly "fixed" error falls.  Maybe this is unimportant if
all you want is a
stable reference frequency source, or very important if you actually want
to know what
time it is.  However, the always somewhat noisy phase lock means that the
"fixed" error
is not constant, merely less variable than otherwise.  What I don't know is
whether or
not the hardware can even be aware of this variability- I kind of suspect
not.

Dana


On Sun, Sep 15, 2019 at 11:03 AM Alberto di Bene  wrote:

> On 2019-09-15 14:12, Forrest Christian (List Account) wrote:
>
> > Most GPS receivers with 1PPS outputs are only able to align the 1PPS to
> the
> > nearest edge of some internal clock.   In addition, in most GPS
> receivers,
> > that internal clock is not synchronized to the 1PPS signal in any way.
>
> Am I right in saying that the Trimble Thunderbolt should not require any
> sawtooth error correction, as the processor
> clock is the same 10 MHz crystal that is disciplined by the GPS signal ?
> Or something is escaping me (it happened
> before...) ?
>
> 73  Alberto  I2PHD
>
>
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[time-nuts] Is the lifetime of a Rb standard dependent on operating orientations/

[Dana Whitlow]

It seems to me that the basic operation of the Rb cell and/or the filter
cell
and lamp must all involve the presence of some liquid Rb at normal
operating temperatures.  Otherwise, temperature regulation would not
be a viable means of controlling the Rb concentration on the vapor mix.

If I'm right about this, is there a concern that operating the device in an
inappropriate orientation might lead to liquid "puddling" in some area
that is harmful to either operating stability or operating lifetime?

Or is it that the amount is so small (~100 ug according to what I've
read) that it just doesn't matter?

Thanks,

DanaK8YUM
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Re: [time-nuts] Even Seconds Pulse option (1PP2S), HP 58503B

[Dana Whitlow]

I can't speak for 1/2PPS, but at the Arecibo Observatory we distributed
1PPS with every
10th second's pulse stretched to about twice the duration of the others.  I
did find that to
be kind of handy every now and then, when troubleshooting things.

Dana


On Sun, Sep 29, 2019 at 8:36 AM Gregory Beat via time-nuts <
time-nuts@lists.febo.com> wrote:

> A new resident arrived at the “Time Cave” this weekend, the HP/Symmetricom
> 58503B.  Just the plain front panel (4 LEDs) model, without Option 1 (VFD
> clock display).
> Acquired in USA, cheaper than current Asian exporter.
> https://accusrc.com/uploads/datasheets/4975_58503b.pdf
>
> Supposedly stored in a closet since 2010 (verified by its diagnostic
> logs), the unit only had 2,000 hours of operation.
> Today, it happily has a GPS Lock and is currently “re-learning” where the
> 1 PPS and 10 MHz outputs wandered (taming Lazarus).
> —
> One surprise, it has Option 2 (1PP2S) installed on its Rear Panel.
>
> Option 002 : 1 PP2S (One-Pulse-Per-Two-Seconds) connector for outputting a
> pulse every other second, synchronized to the even seconds in GPS time.
> Pulses occur on even-numbered seconds (i.e., 2 seconds, 4 seconds, etc.).
> ===
> QUESTION:
> What Specific Applications would use this 1PP2S output regularly??
>
> greg
>
> Sent from iPhone 6s
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Re: [time-nuts] time-nuts Digest, Vol 184, Issue 13

[Dana Whitlow]

It looks to me like one might be able to exploit a resonance of the
A-frame.  Instead of
whacking it with a mallet, vibrate the tube in the appropriate direction at
the appropriate
frequency and run up the amplitude until (hopefully) the ribbon ends touch
on each
cycle as indicated by electrical means, then connect a charged capacitor to
effect a
weld.

Unfortunately, I have no idea how to find the resonant frequency.

Dana


On Thu, Nov 14, 2019 at 7:24 PM Dan Kemppainen 
wrote:

> Paul,
>
> To me it appears that "A" frame supporting half of the wire is a spring.
> It only makes sense the designers would want some axial tension. The "A"
> frame shape would supply axial load while providing excellent radial
> stability in all directions. (If this isn't the case, why is that
> support so thin???)
>
> If you look close here, I think you'll see what I'm talking about:
> http://www.rdrelectronics.com/skip/CS-tube/cstube7.jpg
> Look close at the wire, both halves are no longer in the same plane, and
> are no longer parallel.
>
> Again, most likely not repairable due to the spring tension (or missing
> wire!). That said, If it were my tube I'd have a hard time not wasting a
> few hours with a capacitor and mallet. Nothing to loose but a little time!
>
> Dan
>
>
>
> On 11/14/2019 12:00 PM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 1
> > Date: Wed, 13 Nov 2019 10:05:32 -0500
> > From: paul swed
> > To: Discussion of precise time and frequency measurement
> >   
> > Subject: Re: [time-nuts] time-nuts Digest, Vol 184, Issue 13
> > Message-ID:
> >f2mgtzb...@mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > Hi Dan at least the pictures I have seen are that the ionizer is a thin
> > ribbon. I have not seen a filament style ionizer for cesium beam tubes.
> > Regards
> > Paul
> > WB8TSL
>
>
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Re: [time-nuts] Antique pendulum clocks

[Dana Whitlow]

Somewhere, a few years ago, I saw a video in which a fairly large number of
metronomes
were mounted on a common base and exhibited some interesting injection
locking
behavior.

Personally I keep thinking of phase locking a G'father clock to a Rb
standard.   The trick
will be to do so in a manner that requires no modification to the clock
proper.  And
remembering to wind it at appropriate intervals- I'm too spoiled by watches
and clocks
that run for years at a time off a battery.

Dana


On Wed, Nov 20, 2019 at 9:00 PM jimlux  wrote:

> On 11/20/19 5:51 PM, Bill Beam wrote:
> > On Tue, 19 Nov 2019 20:10:14 -0500, Philip Gladstone wrote:
> >
> >> I've started to monitor the individual ticks on a grandfather clock from
> >> the 1790s. Essentially I timestamp whenever the pendulum
> breaks/restores a
> >> light beam.
> >
> >> The data that I get is surprising in that the pendulum swing varies
> >> according to the position of the hands on the clock. It appears that the
>
> > Most people interested in this problem have been dead for about 200
> years.
> > Also note that as the clock gets old and dirty it will begin to stop at
> 8:45.
> >
> > Now if you want to see another old interesting clock problem look up the
> > 'Thursday afternoon effect'.
> >
>
> Now this time-geek-y stuff is why this list is interesting.
>
> I'm waiting for someone to have hooked up a bunch of cheap metronomes on
> a common base to an array of TICCs...
>
>
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Re: [time-nuts] Difference in antennas

[Dana Whitlow]

Most modern GPS receivers are very quiet even barefoot.  So, one could
argue that one should
not have much more LNA gain in the antenna than required to make up for
feedline loss, which
should be easily calculable.  While excess gain  in the antenna can improve
overall system noise
figure a small amount, it will degrade intermod performance, which is
likely to be a worse problem
than simple weak signals.  It's likely that the cure is worse than the
disease, as my doctor likes to
say.

Dana



On Thu, Nov 21, 2019 at 4:00 PM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> So concensus is, 50dB gain antenna is too much gain, unless feed line
> is too long, reception is poor, or there are other circumstances extra gain
> is desired?
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Thursday, November 21, 2019, 3:00:14 PM EST, Bob kb8tq <
> kb...@n1k.org> wrote:
>
>  Hi
>
> That is indeed the gotcha. Once you get past a certain amount of gain in
> the
> preamp, the C/N levels don’t change enough to notice. Looking today vs
> looking
> tomorrow is unlikely to be of any help if you are after a fraction of a
> db.
>
> About the only way to check would be to fast switch an attenuator in and
> out of
> the signal path. Watch things for a minute at one setting and then do the
> same at
> another setting. Run for a while and log all the deltas. If you see a
> degradation of
> more than a few tenths of a db, you are getting towards the minimum gain
> point.
>
> Indeed there are some receivers that have an AGC built in. *IF* your
> receiver has one
> and *IF* you can get at it, that would be a great way to work this out.
> Indeed anybody
> who makes it past both of those constraints has a pretty unique device.
>
> 
>
> Simple answer for a 50 db antenna is to put an attenuator in after the DC
> has
> been eliminated from the circuit. It’s not idea, but it’s the best you can
> do. Running
> a great big splitter is one great way to come up with attenuation …..
>
> Bob
>
>
> > On Nov 21, 2019, at 10:29 AM, John Ackermann N8UR  wrote:
> >
> > Bob, this is a great summary, thanks!
> >
> > One related question, especially with mixed systems -- how do you tell
> > if you have optimum signal level at the receiver?
> >
> > Most show some sort of SNR or Cn value.  What should we look for?  What
> > are the indication of *too much* signal?  One issue in particular is how
> > to handle a modern GPS that expects modest antenna gain when it's
> > plugged into a system with a 50dB gain antenna at the top.
> >
> > Thanks!
> > John
> > 
> >
> > On 11/21/19 8:00 AM, Bob kb8tq wrote:
> >> Hi
> >>
> >> Way back in time, the first gear out there to use what we now look at
> as “normal” antennas
> >> was survey gear. For various reasons they decided on a 12V power supply
> and 40 to 50 db
> >> of gain in the preamp mounted in the antenna. They also got into L1 /
> L2 pretty quickly.
> >>
> >> A bit later the cell phone (and later broadcast) guys got into this. In
> a location with a lot of
> >> RF (like a cell site) having a lot of gain at the antenna didn’t work
> all that well. IMD issues
> >> got into the act pretty quickly. In addition, front end filtering was
> required to reduce overload
> >> issues. The focus was on L1 only so filtering was relatively easy.
> >>
> >> There is a whole separate set of antennas that put a big chunk of the
> RF portion of the radio
> >> in the antenna. Those still survive here and there. I have one of them
> and probably a couple
> >> of dozen of the more “normal” antennas.
> >>
> >> As time marched on, supplying 12V to antennas became a bit less
> popular. Most of the cell
> >> guys went over to a 5V antenna supply. The net result was 12V 50 db
> survey antennas that did
> >> L1/L2 and much smaller 5V 25 db antennas for “timing”. The timing
> antennas didn’t do L1/L2 so
> >> not going to work for survey. The survey antennas had way to much gain
> and no filtering so
> >> not going to work for a cell site.
> >>
> >> Indeed things did and do get crossed up in various pro and basement
> systems. With care and
> >> the right set of circumstances things may work. In other cases the
> result can be an ongoing set
> >> of systems issues over an entire network of stations.
> >>
> >> Prices for a good new survey antenna are up in the many thousands of
> dollars range. They have
> >> very stable phase centers and (usually) test results to allow
> correction of any residual phase
> >> issues. This is part of what lets you get into the “couple of mm” range
> on a survey.
> >>
> >> For timing, you have to dig a bit and answer a few questions. Is your
> concern how close you
> >> are to BIH? If so you will need to know all the delays in your system.
> This includes the delays
> >> in the antenna filters and the preamp. Is your concern (or measure) the
> ADEV at 1 second?
> >> If so the delays are not a concern. Your antenna choice may be a 

Re: [time-nuts] USB over optical fiber

[Dana Whitlow]

Even without any funny business with boost converters (or whatever). those
copper wires
make a nice antenna for coupling noise from both ends (PC and USB
accessory) into
the environment inside the chamber.  Unless, of course, the cable is
well-shielded, which
you did not mention.

I suppose it's too late to ask, but did you perhance try adding some
clamp-on ferrite chokes
to the cable?

Dana


On Fri, Dec 6, 2019 at 10:05 AM David Van Horn via time-nuts <
time-nuts@lists.febo.com> wrote:

> This is my backup plan:
> https://industrialcomponent.com/opticis/opm210003.html
>
> The docs are a bit chinglish, but I'm encouraged by the fact that the
> distal end needs external power.   I was hoping the corning one was
> powering the distal end by CW laser of maybe 200mW with data carried on
> other wavelengths, or modulation of the power laser, but NOPE, just copper
> wires.   That one's packed up and ready to go back right now.
>
> --
> David VanHorn
> Lead Hardware Engineer
>
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345  x110
> email: david.vanh...@backcountryaccess.com
>
> -Original Message-
> From: Scott McGrath 
> Sent: Friday, December 6, 2019 6:29 AM
> To: David Van Horn 
> Cc: Discussion of precise time and frequency measurement <
> time-nuts@lists.febo.com>
> Subject: Re: [time-nuts] USB over optical fiber
>
> Wow,  cost cutting at work I have the corning one but its 3 years old
> Remember when FCC certification meant something for EMC
>
>
>
>
>
> > On Dec 6, 2019, at 3:21 PM, David Van Horn <
> david.vanh...@backcountryaccess.com> wrote:
> >
>
> Well, it arrived, and it is NOISY.  ☹
> It's pushing out longitudinal noise along the cable, and it's deafening my
> receiver.
>
> After doing some research this morning, it appears that they do the DATA
> optically but power is taken on copper wires, and I'm betting a boost
> switcher to compensate for the voltage drop in the 28 ga wire.
>
> https://www.corning.com/microsites/coc/ocbc/Documents/CNT-075-AEN.pdf
>
>
>
> I have another candidate arriving today which will require a 5V supply
> inside the cage, but I can do that with batteries and a linear regulator,
> much quieter.
>
>
> --
> David VanHorn
> Lead Hardware Engineer
>
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345  x110
> email: david.vanh...@backcountryaccess.com
>
> -Original Message-
> From: time-nuts  On Behalf Of David Van
> Horn via time-nuts
> Sent: Thursday, December 5, 2019 6:15 AM
> To: Scott McGrath ; Discussion of precise time and
> frequency measurement 
> Cc: David Van Horn 
> Subject: Re: [time-nuts] USB over optical fiber
>
> Ok, thanks for the info.  My unit should be arriving today or tomorrow.
>
> --
> David VanHorn
> Lead Hardware Engineer
>
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345  x110
> email: david.vanh...@backcountryaccess.com
>
> -Original Message-
> From: Scott McGrath 
> Sent: Wednesday, December 4, 2019 9:16 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts@lists.febo.com>
> Cc: David Van Horn 
> Subject: Re: [time-nuts] USB over optical fiber
>
> You may still have a problem,  That said most of your noise power is going
> to come from your USB device itself and perhaps the power supply
>
> That said ive never really had a problem doing similar testing using small
> chambers from ETS-Lindgren and similar vendors using the Corning
> interface.
>
> That said i’d recommend you go a step up to the Newnex and similar devices
> they are 3x the price but the fiber interlink is just a standard fiber
> LC-LC patch cord.
>
> With the low cost interface crimp its cable once accidentally you are
> buying a new one.
>
> With the newnex you are buying a 20-30 dollar patch cord.
>
> All that said performance is the same in the end but the newnex and
> similar have an advantage in an open lab.   For permanent installation in
> raceway the cost advantage is with the one piece units.
>
> Content by Scott
> Typos by Siri
>
> > On Dec 4, 2019, at 10:07 PM, Davida  Van Horn via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
>
> I'm not too worried up there, my receivers are working at 457 kHz.
>
> -Original Message-
> From: Scott McGrath 
> Sent: Wednesday, December 4, 2019 12:14 AM
> To: Discussion of precise time and frequency measurement <
> time-nuts@lists.febo.com>
> Cc: David Van Horn 
> Subject: Re: [time-nuts] USB over optical fiber
>
> Its not so much the noise from the interface its the USB device itself i’d
> worry about as USB 3.0 generates RF signals up to 3 GHz.   And also has
> fairly strong signals in the 2.4 GHz ISM band.
>
> Content by Scott
> Typos by Siri
>
> > On Dec 4, 2019, at 12:07 AM, David Van Horn via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
>
> I suppose this is vaguely time-nutty. 
>
> I have an application where I 

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Dana Whitlow]

Hello Taka,

As long as you stick to CW sinewaves *and* the distribution amp specs are
honest when they say "buffered out puts", the problem is fairly simple.  If
you're not seeing distortion under your operating load and signal
amplitudes,
it's OK and I'd not bother to change anything.

By "honest ..." I  mean that each output has its own independent output
amplifier.  However, this device looks to be fairly inexpensive and it's
possible that the mfr uses a single amplifier with a low output impedance
and distributes that through three 75-ohm resistors.  In this event there is
a possibility that with lower than 75-ohm loads, the amplifier's drive
current
capability might be exceeded, leading to distortion.

So, I'd suggest that you keep an eye on distortion levels on each output,
especially after making any system changes.  And, I'd take care to load
any unused outputs with a termination whose resistance equals the
impedance of the cable you're using for distribution.  If you fail to do
this,
and the *electrical* length of any *unterminated* cable is anywhere near
1/4 wavelength at 10 MHz, the impedance seen by the afflicted distro
amp output could be much lower than the intended 75 ohms, again
leading to risk of significant distortion.

I'd try to avoid distributing non-sinusoidal signals unless you're
careful to make sure that the cable impedance matches the output
impedance of the distro amp *and* the input impedance of whatever
your load is.  Otherwise the situation can get more complicated in
a hurry, with the prospect of both nonlinear distortion and edge
distortion due to reflections bouncing around in the cable.  But if
you must, the key is again to check the waveforms at the far ends
of the cables with the intended loads attached.  If the waveforms
look just like what you're expecting (with clean transitions at the
leading and falling edges), you should be OK.

One other issue with a poorly-buffered distro amp is that something
about a given output (like it's phase and/or amplitude) might change
depending on what loads are connected to the other outputs (and the
cable lengths involved).  If this is a concern to you, then you should
check for this effect to establish the viability of your system.

I hope this helps.  Sorry to say, nothing is ever really simple.

Dana



On Fri, Oct 18, 2019 at 3:17 AM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> I am using Extron MDA 3V for distributing 10MHz at several places in my
> lab.  MDA3V is a one port in - 3 port out device made for VIDEO market and
> rather low end at that.  Input and output is 75 ohm and bandwidth extend to
> 150MHz or so.  Looking at 10MHz sine wave through it, it looks good.  No
> visible distortions.  Gain is unity between input and one of the ports.
>
> I also have distribution Amps from Spectracom.  These, of course, are made
> for clock distribution purpose and I don't question usage for the purpose.
> The level of "accuracy" of distribution is that I need frequency stability,
> but time delay in coax, slight phase shift in coax, and other small nuances
> are not my concern.  (should they be?)  I'm not running a competitive
> service to NIST and this is not for commercial purpose.  I'm just a junior
> time nuts.
> Couple of questions though.  This device is 75ohm.  It's easy to add
> 150ohm in parallel to a matching resister and make it 50ohm.  However, I'm
> guessing 50 ohm / 75 ohm mismatch is not really a big deal that I'm not
> doing anything about it.  Input and output cables are RG58 (50 ohm)  VSWR
> is 1.5, For external sync port, many equipment is not exactly spec'd for 50
> ohm, but often only spec'd for voltage or at db level without any specific
> impedance mentioned.  Recommended cable is 50 ohm though.  I typically shy
> away from consumer grade gear but looking inside, it's just an op-amp and
> registers.  If I use square wave which contains higher frequency
> components, would this be inadequate?
> There are many web pages by people doing exactly what I'm doing with
> usually bigger Extron devices.  I'd like to consult the Time-Nut community
> of sanity in what I am doing.  Is this really not an issue, or "it's not
> simple as THAT" type situation?
> Thank you very much
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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[time-nuts] Do ordinary clouds adversely affect GPS reception?

[Dana Whitlow]

A friend of mine living in SE lower Michigan recently bought
a Geppetto GPS clock, and swears that it tends to lose
satellite lock on cloudy days but does OK on sunny days.

He is admittedly using a very poorly-sited antenna,
placed in a window because his house has aluminum
siding.  He reports that his Garmin handheld GPS
has much less trouble acquiring and maintaining lock
on cloudy days than does the Geppetto, but still tends
to show higher levels of probable position error on
cloudy days.  I don't yet know if he takes the Garmin
outside for these comparisons.

Is this a real phenomenon, or is my friend just imagining
things?

Meanwhile I think I have finally persuaded him to install
the antenna outside on the roof.

Dana(K8YUM)
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Re: [time-nuts] 10MHz dist amps

[Dana Whitlow]

If you're doing beam forming, the "one amp driving multiple
loads" approach is probably going to do the best and most
stable job of getting what you need.  And all your loads should
be identical, not some mix of different makes/models.

But you will need to find an amplifier that can deliver the goods
(low output Z and adequate power level) with fairly low distortion
as well.  Perhaps a good fast opamp with a buffer on its output
to help supply the high current needed to drive multiple loads at
once.

Dana


On Wed, Oct 23, 2019 at 12:01 PM Bill Dailey, MD, MSEng, MSMI <
docdai...@gmail.com> wrote:

> I am working in a project that requires me to have very similarly phased
> 10mhz references (beamforming).
>
> Previously I just used splitters for 10MHz but now I am graduating to a
> distribution amplifier.  Looking for suggestions/recommendations and what I
> should consider.  Distributing a Fury or a manually set a (May have the
> numbers wrong on this) oscillator.
>
> 1. TADD-1 x 2
> 2. 5087A
> 3. 58502A
>
> 2&3 are from the usual auction site and may have problems now or in the
> future.
> --
> Doc
>
> Bill Dailey
> KXØO
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Re: [time-nuts] Do ordinary clouds adversely affect GPS reception?

[Dana Whitlow]

Andy,

Isn't DirecTV downlinking around 12 GHz?   Yet GPS L1 is at only ~1575
MHz.  That's
a huge difference with regard to scattering losses, and probably a fair
amount of
difference for water absorption losses as well.

I've recommended that my old friend try putting his GPS antenna up in the
attic as
close to the peak of the roof as he can do.

Thanks,

Dana


On Wed, Oct 23, 2019 at 12:01 PM Andy  wrote:

> Having had DirecTV on the roof for a few years, and having experienced
> regular significant signal loss events during heavy rain and snow (loss of
> reception was a rather good predictor that "the skies were about to open
> up" with rain), I can confirm that signal strength deteriorates noticeably
> during these events.  They are in the same general frequency range.  There
> are distinct frequencies where the loss is even more significant.
>
> DirecTV probably tells you that this doesn't happen, but they are wrong;
> but that's their salesmen speaking.  Experience shows that it's real.  When
> it rains, I could watch the signal levels drop on their meters, then watch
> the channel banks disappear.
>
> If someone had reasonably good GPS reception, then the signal loss might be
> small enough to go unnoticed by the majority of users.  If your friend's
> reception was already near borderline, then it should be obvious that any
> little bit can put it over the top.  I think your friend did not imagine
> it.  I think the loss is more than a few dBs when it's raining, not
> trivial.  It's probably small when it is just cloudy, but like I say, under
> the right conditions even a small change can put it over the top.
>
> Andy
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Re: [time-nuts] Do ordinary clouds adversely affect GPS reception?

[Dana Whitlow]

As far as I know, my friend's GPS dropout problems have been associated with
simple clouds with no rain (at least no rain reaching the surface).

Dana


On Wed, Oct 23, 2019 at 2:00 PM Tim Shoppa  wrote:

> I don't think clouds is the direct cause, but of course clouds in the sky
> can be correlated with wet foliage.
>
> Especially if the GPS Field Of View has a lot of angle taken up by tree
> canopy, wet foliage can substantially degrade not just GPS reception but
> other VHF and UHF signals.
>
> I notice this the most in the fall when the leaves are large and mature and
> are start losing their waxy coat, but have not yet fallen.
>
> Even after all the leaves have fallen, wet branches have attenuation
> ability as well.
>
> Some research papers have connected windy conditions with UHF attenuation
> especially deep fading as well (
> https://ieeexplore.ieee.org/document/1337081
> ).
>
> Tim N3QE
>
> On Tue, Oct 22, 2019 at 2:01 AM Dana Whitlow 
> wrote:
>
> > A friend of mine living in SE lower Michigan recently bought
> > a Geppetto GPS clock, and swears that it tends to lose
> > satellite lock on cloudy days but does OK on sunny days.
> >
> > He is admittedly using a very poorly-sited antenna,
> > placed in a window because his house has aluminum
> > siding.  He reports that his Garmin handheld GPS
> > has much less trouble acquiring and maintaining lock
> > on cloudy days than does the Geppetto, but still tends
> > to show higher levels of probable position error on
> > cloudy days.  I don't yet know if he takes the Garmin
> > outside for these comparisons.
> >
> > Is this a real phenomenon, or is my friend just imagining
> > things?
> >
> > Meanwhile I think I have finally persuaded him to install
> > the antenna outside on the roof.
> >
> > Dana(K8YUM)
> > ___
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> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Rubidium cell or lamp rejuvenation. WAS-HP 5065A owners, a question!

[Dana Whitlow]

Corby, I have a question to add regarding the HP units:  is the tip
temperature hot
enough to melt Rb in addition to providing vapor?  If so, doesn't the
orientation of
the physics package in earth's gravity have to be about correct in order to
keep
the excess Rb in the tip?

Thanks,

Dana


On Sat, Oct 26, 2019 at 4:01 PM  wrote:

> JF, Reference your statement:
>
> "Sorry, but I don't agree with your first statement about the 5065A :
> after long use, the rubidium plates on the inner envelope of the lamp
> (like silver on a mirror) and years after years the Rb light and photo I
> decreases."
>
> After working on the 5065A for over 40 years and across the full range of
> Serial numbers and ages of instruments (somewhere over 70 units) I have
> only seen Rubidium plated on the inside of the bulb twice. All the other
> lamps provided performance that met the HP specifications. The design of
> the lamp assy causes the tip of the lamp to be cold compared to the bulb
> causing the majority of the Rubidium to condense into the tip.
>
> The two bulbs were in units where the lamp oven winding shorted and
> "cooked" the lamp Assy.
> Those two bulbs were recovered using a heat gun.
> I suppose if the unit was stored for years in a very hot environment the
> Rubidium could get out of the tip but as long as the lamps starts you can
> just let it run for a week or so and it will condense back into the tip.
>
> If a you have a bulb that exhibits the plating I would recommend that you
> measure the lamp oven temperature to make sure it is not too hot. Also
> the two nuts on the lamp assy. rod that protrudes out of the cover should
> clamp the outer cover firmly between them. The outer cover is a heat sink
> for the lamp assy. and maintains the Rubidium in the tip. Operating for
> years without this clamping might cause what you saw.
>
> Other units specifically the Efratom FRS were poorly designed and are
> known for this problem.
>
> Cheers,
>
> Corby
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Re: [time-nuts] Are minutes more important in astronomy than seconds and hours ?

[Dana Whitlow]

My idea is that for the time this was built and used, there was little or
no need for really
accurate time keeping in most astronomy work.  The high accuracy/precision
needs
really didn't arise until the beginning of what I'll call "modern
astronomy", which I'll loosely
define as the discovery of the first pulsar, or the first use of VLBI
(whichever came first).

I took the "Astronomy 101" course during my freshman year at UMich in
1965.  I just
now realized that I was basically 2+ years too early.  At the time I took
the course, the
text used was 10 years old, and it didn't seem to me that much was going on
in the field.
Little did I know what was soon to come ...

Dana


On Sat, Nov 23, 2019 at 6:12 AM Jean-Louis Rault  wrote:

> Hi all
>
> A friend of mine offered me a secondary electric clock that was in use
> at Observatoire Royal de Belgique, in Brussels, at the end of the 19th
> century.
>
> The manufacturer is Peyer Favarger & Co, Neuchatel, Switzerland.
>
> I'm wondering why the largest hand is used for minutes, and the smaller
> hands for hours and seconds
>
> Any idea ?
>
> Jean-Louis
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Re: [time-nuts] Are minutes more important in astronomy than seconds and hours ?

[Dana Whitlow]

Celestial navigation users might object to the notion that seconds are not
important.
That is, if you can find anybody still exercising that art.  In that arena,
folks are
taught to read seconds first, then minutes, then hours.

Depending on the latitude, one second can lead to something like 1/4 mile
position error.  So, realistically, one *might* tolerate a very few seconds
error
without exceeding reasonable error expectations, but certainly no more.

Dana


On Sat, Nov 23, 2019 at 9:03 AM Matt Osborn  wrote:

> Pretty nice, I've always wondered why clocks weren't designed this
> way.  Hours last too long and estimating minutes from the hour hand is
> minimally useful while seconds are too fast and mostly irrelevant for
> human use.
>
> Reading the time as so many minutes past whichever hour is very
> natural and informative.
>
> On Sat, 23 Nov 2019 09:29:09 +0100, Jean-Louis Rault 
> wrote:
>
> >Hi all
> >
> >A friend of mine offered me a secondary electric clock that was in use
> >at Observatoire Royal de Belgique, in Brussels, at the end of the 19th
> >century.
> >
> >The manufacturer is Peyer Favarger & Co, Neuchatel, Switzerland.
> >
> >I'm wondering why the largest hand is used for minutes, and the smaller
> >hands for hours and seconds
> >
> >Any idea ?
> >
> >Jean-Louis
>
> -- kc0ukk at msosborn dot com
>
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Re: [time-nuts] Distributing GPS L1 signal to many GPS devices

[Dana Whitlow]

You could minimize problems with accumulated differential delays by *not*
daisy chaining- rather arrange the splitters in a hierarchical fashion
so that all your outputs have an equal number of splitters in the path.

I think your problem is that you started with more than one GPSDO.
You need to learn to live with just one.  Why not instead split its outputs
(1PPS and 10 MHz) with splitters?  The resulting system should be less
expensive, and all your references would track in their delays.  With
separate GPSDOs, you cannot be sure that they will always do the
same thing in the face of GPS signal impairments as well as just
plain ordinary noise.

Dana


On Tue, Sep 24, 2019 at 2:03 PM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> Currently, I have a symetricom antenna outside that feeds an HP58536A (4
> port).  One of the output port daisy chains to another HP58536A's antenna
> port.  That gives me 7 ports total. Well, I need more.  I can simply daisy
> chain another one but it doesn't look like an elegant solution.  Besides,
> if I only turn on GPS on the last port, it will end up driving all of the
> active distributor amps.  Also, signal delay would be a concern.
>
> I KNOW there are many folks here who has more than dozen GPSDOs.  How do
> you do it?  Obviously, buying an 8 port version is one of the solutions but
> what if I need to expand that?  My goal is like 20 ports for future
> craziness.
>
> GPSDOs tend to grow during my sleep.  It must be because I started with
> just two.
>
>
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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Re: [time-nuts] HP105B HP 105B 1 amp fuse blowing

[Dana Whitlow]

I once read that Supercapacitors come up short in handling really short
spikes,
and that this is not due to physical inductance arising from the
structure.  Rather,
the issue was of a subtle (to me) electrochemical nature.

Can anyone either confirm or refute this?  Inquiring minds want to know.

Dana

On Fri, Oct 11, 2019 at 2:01 PM Bob kb8tq  wrote:

> Hi
>
> Indeed, the unit seems to work fine without batteries.
>
> ---
>
> If filtering and short duration spikes are the concern, one could
> replace the batteries with super capacitors. One would *hope* they
> are a bit less likely to create problems. ……
>
> -
>
> While it is a good idea to keep OCXO’s on power, a half hour or
> couple hour outage is not that big a deal. They will settle back down
> pretty fast after that sort of interruption. Unless the rest of the lab is
> on backup power, there may not be a major need for the 105 to stay
> up and running ….
>
> Bob
>
> > On Oct 11, 2019, at 11:59 AM, Jeremy Nichols  wrote:
> >
> > The 105A was built without a battery. The 105B has a battery and charger.
> >
> > I have a 105B that had the failed battery removed before I bought it. It
> > works fine. I have it on a UPS; it survived our just-finished NorCal
> power
> > shutdown just fine.
> >
> > Jeremy
> >
> >
> > On Fri, Oct 11, 2019 at 7:01 AM Scott McGrath 
> wrote:
> >
> >> As one who owns a 105 i had the battery properly rebuilt and basically
> >> have it on low rate charge and periodically discharge the battery
> >>
> >> When rebuilding a 105 battery it’s important to replicate its
> >> characteristics
> >>
> >> Remember HP also intended I believe that the battery would also serve
> as a
> >> filter for the power supply.   As I dont recall any version of the 105
> >> without a battery.
> >>
> >>
> >>
> >> On Oct 10, 2019, at 4:50 PM, Taka Kamiya via time-nuts <
> >> time-nuts@lists.febo.com> wrote:
> >>
> >> The fact that 25V supply is dropping to 23.4V shows it is drawing far
> more
> >> current than it is rated.  I am assuming this is a regulated power
> supply.
> >> Does the power brick actually shuts down at 500mA or does it let the the
> >> voltage drop and try to supply what it can?  Maybe one or more Nicad
> has an
> >> internal short?  That will cause and over-voltage situation per battery
> and
> >> thus over-current.  I've recently seen a brick power supply go into
> >> oscillation and produce 3x rated voltage when too much current was
> drawn.
> >> (and blew the circuit)
> >>
> >> Also, different batteries has different charging rates.  As far as 105B
> >> document goes, it says 24V 0.5Amp supply but that is for default
> >> configuration. Designed charge rate is 390mA (page 3-4) and is current
> >> controlled by A5Q3.
> >>
> >> I would actually measure how much current is drawn there.  Since the
> fuse
> >> is already blown, just put an am-meter across the fuse and see
> >>
> >> ---
> >> (Mr.) Taka Kamiya
> >> KB4EMF / ex JF2DKG
> >>
> >>
> >>   On Thursday, October 10, 2019, 4:00:41 PM EDT, Roy Thistle <
> >> roy.this...@mail.utoronto.ca> wrote:
> >>
> >> Hi All:
> >> A 105B (quartz oscillator) is blowing the 1A fuse, after it is on about
> 1
> >> hour.
> >> The fuse appears to have just melted (not a black mark as the result of
> a
> >> flash, in the case of a high current short.)… just looks like the fuse
> wire
> >> (inside the glass capsule) melted into some little blobs, for about 1/4
> >> the fuse length, near the middle. It wasn't a fast-blo or slow-blo
> fuse...
> >> just the normal kind.
> >> I think the unit is drawing just a little too much current, as the
> result
> >> of the batteries needing charging (I had the fast charge option on when
> the
> >> fuse blew.) And so, the fuse heated up, and finally melted. Not sure why
> >> the batteries were not charging normally... but 20.1 volts is what I
> >> measured across the pack, initially, and 23.4 V after about 45 min of
> >> charging.
> >> I am charging the batters, from a power cube, at 510 ma, and dropping
> >> (cube gives 25V, 500mA max)… the batteries are 20 C size NiCads, wired
> in
> >> series... that of course is a retrofit.
> >> I don't want to put another fuse in, and blow that too, without some
> >> reasonable explanation of why the first one failed!
> >> Please, any comments, or hints/suggestions... much appreciated.
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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> >>
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> >> To 

Re: [time-nuts] What is the BEST crystal?

[Dana Whitlow]

Bruce, is there any text about the ring resonator which discusses the
features in the
interferogram?  Also I'd be interested in the configuration of the
electrodes.

My present interpretation is that the vibratory resonance stems from
contra-rotating
modes each propagating around the ring, and that the fringe pattern is
complicated
by the two surfaces being a little bit out of parallel and with a hint of
roughly spherical
curvature relative to each other (probably not deliberate).

I used to do a good bit of holographic interferometry, mostly related to
identifying
resonances and vibratory modes of blades on jet turbine rotors, and it's
hard to
break the habit of trying to interpret interference patters.

Dana


On Sat, Feb 29, 2020 at 7:34 PM Bruce Griffiths 
wrote:

> Interferogram showing vibration nodes etc for quartz ring resonator
> frequency standard attached.
>
> Bruce
> > On 01 March 2020 at 14:27 Bob kb8tq  wrote:
> >
> >
> > Hi
> >
> > It’s also the size of the 2.5 MHz 5th’s and similar parts made “way
> back”. They went into glass packages
> > the size of door knobs. Packaging / design / mounting / processing has
> changed a lot since then.
> >
> > Bob
> >
> > > On Feb 29, 2020, at 7:41 PM, John Moran, Scawby Design <
> j...@scawbydesign.co.uk> wrote:
> > >
> > > Wow, that provoked an interesting discussion!
> > >
> > > Thanks for all the information and references to further information -
> it should keep me quiet for a while.
> > >
> > > Interestingly 50mm diameter was about the diameter of the crystals
> used by the British Post Office in the early days for generating a master
> oscillator. It wasn't ground into a plano-convex lens but as a ring and was
> about 10mm thick. Like the old WW2 crystals the electrodes weren't plated
> but just contact rings. I have no idea what frequency they were ... by the
> time that I realised they were scrapping all this kit it was gone and I
> only managed to salvage two GPO Type 36 master 1S pendulums from a dumpster!
> > >
> > > Thanks again for all the feedback.
> > >
> > > John
> > > ___
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> > > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> >
> >
> > ___
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Re: [time-nuts] Synchronisation of crystal oscillators

[Dana Whitlow]

Yes, oscillators that are harmonically related can indeed injection lock.
I've done it in
a project about 40 years ago.

In your case, you need to avoid RF cross-coupling between the oscillators.
This includes
both electromagnetic coupling, "direct coupling" via use of a common power
supply, and
perhaps even "acoustic" coupling via physical vibrations coupled through
whatever you
have the crystals mounted on.

But I'd think that more than half the fun of your project could be in
finding out if there is
a problem and in attempting to isolate the cause(s).  Go for it! (and tell
us what you learn).

Dana




On Sun, Mar 1, 2020 at 4:28 PM John Moran, Scawby Design <
j...@scawbydesign.co.uk> wrote:

> My apologies if this is slightly off-topic, but it does concern crystal
> oscillators.
>
> I have a small collection of ancient crystals amassed over the past 50
> years or so. Half a dozen are low frequency (3,600Hz, 10kHz,  and 100kHz),
> long bar, crystals sealed into B7G vacuum tube bodies. I was considering
> mounting them all in a neat row in a nice aluminium housing with individual
> oscillator circuitry and LDO regulators to ensure that they were all
> independent. For fun I will divide each oscillator down to 1PPS and use
> that the flash individual LEDs in the face of the housing, and watch them
> all slowly move in and out of phase with each other.
>
> However, I then remembered Huygens's discovery that 1S pendulums mounted
> on the same wall, or beam, would synchronise and swing either in phase, or
> out of phase and sometimes one would be stopped, by the minute interactions.
>
> So, my question is - will my row of low frequency crystals 'talk' to each
> other and synchronise in their frequency groups as well? Remember that
> these crystals are long thin bars of quartz - one of the 3,600Hz crystals
> being 2mm square by 60mm long - so they will possibly vibrate quite
> vigorously compared with squat discs.
>
> I look forward to your comments.
>
> John
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Re: [time-nuts] Are there SC-crystals out there in the wild that are not Overtone?

[Dana Whitlow]

If you start off viewing the crystal in series (S21) I believe that you'll
be able to see
some response far enough away from the resonance to make it easier to find.

Dana


On Thu, Feb 27, 2020 at 9:39 AM Magnus Danielson  wrote:

> Hi,
>
> Even if my VNA steps in 1 Hz if I ask it kindly, it can be a bit
> teadious work to find it.
>
> Cheers,
> Magnus
>
> On 2020-02-27 14:35, Bob kb8tq wrote:
> > Hi
> >
> > Ok, so just to run the math:
> >
> > 5 MHz / 2.9 = 1.724 MHz
> >
> > If the Q at the fundamental is 500K (a wild guess) then 1.724 MHz /
> 500,000 = 3.4 Hz
> >
> > In a world where a synthesized sweeper *might* be stepping in 10Hz
> steps, that’s an
> > easy one to miss.
> >
> > Bob
> >
> >
> >> On Feb 26, 2020, at 11:40 PM, Bernd Neubig  wrote:
> >>
> >> Hi Gerhard,
> >> I am rather sure that it is a 5 MHz 3rd overtone crystal.
> >> the resistance should be in the 80 to 110 Ohm range and Q about 1.5
> million. You can see the resonance without ringing in a span of 100 Hz or
> smaller with a sweep time of 10 sec minimum.
> >> See attached the response of a 5 MHz SC3 crystal in HC-40/U package.
> >> Indeed the 5.45 MHz is the B-mode which has a temperature coefficient
> of -30 ppm/K
> >> Because the crystal blank  has  a plano-convex shape. The overtones are
> quite far away from 3 times or 5 times the fundamental mode. 3rd overtone
> is about (rough guess) 2.9 time of fundamental mode.
> >> To find them you must really carefully sweep around a few 10 to 100 kHz
> span with slow sweep time a narrow bandwidth
> >>
> >> Regards
> >> Bernd
> >> DK1AG
> >>
> >> -Ursprüngliche Nachricht-
> >> Von: time-nuts [mailto:time-nuts-boun...@lists.febo.com] Im Auftrag
> von Gerhard Hoffmann via time-nuts
> >> Gesendet: Mittwoch, 26. Februar 2020 01:42
> >>
> >> To get a first impression, I soldered the crystal to an SMA plug and
> put it on an
> >> R ZVB-8 network analyzer and measured S11. I could see the 5 MHz
> resonance
> >> as a 15 dB dip.  There was also a resonance at 5.45 and a smaller one
> another 90 KHz
> >> higher. the +10% suggest that it is an SC cut.
> >> But I could not see anything at 1 or 1. MHz, so it should be a
> fundamental crystal?
> >> Is that common?
> >> I made most measurements at room temperature. I can turn the hot air
> solder
> >> station down to 91°C which is not far away from the crystal's 87.7°C
> >> inflection point, and I could see some variation on the 5.45 MHz
> resonance vs. temp.
> >> I must build a fixture for the hot air because the sweep time at 1 Hz
> bandwidth
> >> is close to eternal.
> >> Is the un-harmonicity (???) between fundamental and overtones stronger
> with SC-cuts
> >> than normal AT? I also could not see anything at 15 MHz. Next I'll make
> a board
> >> for the PI fixture as described by Bernd Neubig in his crystal cookbook.
> >> BTW I could see some more dips with >= 10 Hz resolution. I hope that
> does not mean
> >> that the ZVB needs service.
> >>
> >>
> >>
> >>
> >> ___
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> to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >> <5MC5735H.jpg>___
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> >
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Re: [time-nuts] Time-Nutters-- Adding Rubidium to a Thunderbolt...?

[Dana Whitlow]

Matthias,

You said that the LPRO has a pulling range of 4 PPM.  Really?  I
would think that 4PPB would be much more likely for a Rb.

Dana


On Mon, Mar 2, 2020 at 3:21 PM Matthias Welwarsky 
wrote:

> On Montag, 2. März 2020 18:32:44 CET Skip Withrow wrote:
> [...]
> > The Thunderbolt DAC steps in 10uV steps IIRC.  And it steps its DAC
> > voltage every second.  With GPS signals jumping around you can still
> > (will) end up with poorer short term performance than if the Rb was
> > left to its own devices.  Hint, let the Thunderbolt do its thing with
> > the Rb, but use Lady Heather and disable disciplining when making
> > measurements/comparisons.
>
> The LPRO has a pulling range of just 4ppm at the external C-Field input
> (0-5V
> swing). 10µV steps over 6V should be, like 19 bits or so? That should give
> at
> least 7e-15 resolution for the DAC.
>
> With a reasonably stable PPS from a timing receiver, just looking at the
> DAC
> movements, it should not be a problem to have a MDEV of 1e-14'ish for
> tau=1s.
> The LPRO itself probably has a MDEV of somewhere between 1e-11 to 1e-10 at
> tau=1s, so the GPSDO is not going to cause a lot of disturbance. Some,
> yes.
> The undisturbed Rb will always be better short-term than the disciplined
> one.
> But not an awful lot.
>
> BR,
> Matthias
>
> >
> > Regards,
> > Skip Withrow
> >
> > ___
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> > the instructions there.
>
>
>
>
>
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Re: [time-nuts] Time-Nutters-- Adding Rubidium to a Thunderbolt...?

[Dana Whitlow]

Probably the easiest solution would be to feed 1 PPS from the T'bolt into a
full-featured
PRS-10 Rb, then fiddle with the loop parameters in the PRS-10 to best suit
your needs.
Unfortunately, I'm told that most of the surplus PRS-10s have been stripped
of this capability.
But a new PRS-10 *does* have this capability, at the price of approx
$1500.  Or, one could
do the locking system on one of the surplus units from scratch at the cost
of a huge investment
of one's time.

Dana


On Mon, Mar 2, 2020 at 12:21 AM mp...@clanbaker.org 
wrote:

> Hello, Time-Nutters--
>
> Is it possible to add/combine/mate a rubidium osc to a Trimble
> Thunderbolt GPSDO?
>
> Have there been any examples of this that I could use as a guide?
>
> Thanks for any info/feedback on this!!
>
> Mike Baker
> Gainesville/Micanopy
> Florida USA
> ***
>
>
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Re: [time-nuts] Digital Pots, wiper noise and fine tweaking oscillators

[Dana Whitlow]

Perrier,

I see that several others have beat me to the punch on the digipot issues.
 So I
think I'll sit this one out and just try to learn.

Dana


On Mon, Jan 27, 2020 at 7:50 AM Dana Whitlow  wrote:

> Perrier,
>
> In answer to your 2nd question, I am unaware of any oscillator technology
> for which
> tuning the actual oscillator frequency has either (much less both) of
> instant full
> response or absolutely zero effect on its frequency drift trend
> afterwards.
>
> Instantaneous full response is generally not expected nor even desirable,
> as long
> as it's fast enough as not to interfere with closed loop bandwidth &
> desired loop
> stability goals.  This is true even if the EFC input is being adjusted
> manually- it is
> frustrating to tune a slowly-responding oscillator by hand, for the
> operator then has
> to wait around for some time before it is possible to meaningfully assess
> the effect
> or each trial frequency adjustment.
>
> On the other hand, a truly instantaneous full response to EFC input is
> possibly
> incompatible with use of a high-Q resonator in the oscillator.  Further,
> it would
> imply infinite tuning bandwidth, which would require extra care, possibly
> *considerable*
> extra care, to assure that high frequency noise in the tuning circuitry is
> not passed
> along to the VCO.  If proper attention is not paid to this detail, one is
> likely to find that
> the phase noise sidebands of the oscillator's output are intolerably
> strong.
>
> As to trend effects there are numerous mechanisms by which resetting the
> frequency
> of an oscillator will also alter its drift trend.  The severity of this
> effect varies widely with
> circumstances, but in many cases leads to intolerable problems.  Hence in
> critical
> applications is it often preferred to leave the primary oscillator alone
> and deal with
> drift in some other way.  Celestial navigators of yore were well aware of
> this issue and
> adjusting the rate of a watch used for this application was a cardinal sin
> (especially if
> attempted at sea).  Instead, they started a voyage armed with a record of
> past drift rate,
> updated this as circumstances permitted, and probably kept a healthy
> degree of
> skepticism regarding each new update.
>
> In the more modern context, the primary oscillator is left alone and the
> desired final
> output frequency is achieved by use of a "microstepper", which is a
> effectively a special
> purpose synthesizer.  A good example of this is the well-regarded MHM-2010
> active
> hydrogen maser, which comes equipped with a good integrated microstepper.
>
> Obviously an exception can (and must) be made in the case of a secondary
> VCO which
> is being phase locked to the primary oscillator, as a part of such a
> microstepper or other
> synthesizer, for example.  Here, long term drift of the VCO is of less
> immediate concern
> until it grows so large that the phase locking loop is no longer able to
> maintain lock.
>
> Regarding "digital pots", I'll write separately, probably as a private
> note.
>
> Dana
>
>
>
> On Mon, Jan 27, 2020 at 12:54 AM Perry Sandeen via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>> Yo Bubba Dudes!,
>> Previous posts mentioned wiper noise and stability of a mechanical pots
>> after tweaking.
>> My questions are:
>> Do digital pots after setting have wiper noise?
>> When making fine tuning tweaks to the EFC of an OCXO, can one move it to
>> its *dead on* setting right away or is there some lag that must be
>> considered requiring to do it in steps?
>> Regards,
>> Perrier
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