Re: [time-nuts] Affordable PoE 6-digit time displays?

[Bob kb8tq]

Hi

I think this is one of those really small market items. You can probably cobble 
one
together from bits and pieces for less than you can buy a good one.

Bob

> On Jun 14, 2018, at 9:15 PM, David Andersen  wrote:
> 
> I'd hoped that ebay or aliexpress would yield a bounty given how seemingly
> simple these are, but I'm drawing a blank (and finding a lot of $300+ new
> options).  Anyone have a favorite source for either flat wall-mount or
> rackmount displays that will pull from an NTP/SNTP/whatever server?
> 
> (if wall-mount, PoE is optimal).  Used good.  Cheap good.  Looks good next
> to my random collection of antiquated time measurement gear provides
> amusement value but isn't really critical. :-)
> 
> Thanks!
> 
>  -Dave
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Re: [time-nuts] Spectracom 8140T Line Tap Schematic

[Bob kb8tq]

Hi

> On Jun 14, 2018, at 9:31 AM, gandalfg8--- via time-nuts  
> wrote:
> 
> 
> Hi Julien, 
> 
> 
> 
> Earlier replies that discussed removing the DC supply from the 8140 outputs 
> gave me the impression your requirement was to connect directly the outputs 
> of the 8140 without line tap modules, which is what I was addressing with my 
> recent suggestion of a series capacitor, but can see now that's not the case.
> 
> 
> 
> If you were to build your own termination the same principle would still 
> apply of course but perhaps another option for a reasonably compact solution, 
> aside from a coaxial DC block followed by a 50 ohm termination, might be a DC 
> blocking attenuator followed by a BNC shorting dust cap, as the latter are 
> generally quite small.
> 
> 
> For example, current Ebay item 332461304064 is a DC blocked 20dB attenuator, 
> they are also available in pairs at a slight discount, and that fitted with a 
> shorting cap would give you a return loss of 40dB, which is probably as good 
> as you'd get from most 50 ohm terminations anyway and would save having to 
> build your own.


I would be very surprised if the original terminations did any better than 20 
to 30 db return loss. They are not fancy devices.
I’ve also seen a lot of attenuators that only make it to about 20 db of return 
loss …..

Bob


> 
> 
> The VersaTaps phase lock an internal crystal, any frequency between 4 and 
> 20MHz, to the 10MHz input and then provide an output at the crystal frequency 
> or the crystal frequency divided by a fixed integer between 1 and 8,192, so 
> in that sense yes they're a synthesiser but the few I've seen were still 
> supplied preset for a specific frequency.
> 
> 
> However, "versatile" does not necessarilly mean quick or convenient to 
> reprogram.
> Aside from perhaps needing  to change the crystal the division ratio needs to 
> be set by adding or removing links across pairs of holes in the circuit 
> board. Those holes are on a standard 0.1inch pitch so fitting headers that 
> would take shorting links should be straightfoward enough, and I suspect what 
> was originally intended, but the units I have were supplied preprogrammed 
> using resistor style wire ended zero ohm links mounted above the circuit 
> board and soldered from below. Reprogramming one of these would involve 
> unsoldering and perhaps removing all the connectors etc in order to remove 
> the circuit board, so I'd certainly make darn sure they had headers fitted 
> before being returned to the box!
> 
> 
> 
> Nigel, GM8PZR
> 
> 
> 
> 
> 
> 
> -Original Message-
> From: Julien Goodwin 
> To: gandalfg8 ; Discussion of precise time and frequency 
> measurement 
> Sent: Thu, 14 Jun 2018 11:36
> Subject: Re: [time-nuts] Spectracom 8140T Line Tap Schematic
> 
> I'm somewhat tempted to take the schematic and see if I can fit it in
> the comparatively tiny Pomona boxes, although I have far too many side
> projects already, enough 10MHz taps, and I still need to do the terminators.
> 
> The VersaTaps are supposed to be an actual synthesizer IIRC.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
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Re: [time-nuts] Raw phase data of super-5065

[Bob kb8tq]

Hi

I’d say both have a “something” with a period of roughly 18 to 20 hours in their
data runs. 

Bob

> On Jun 14, 2018, at 4:54 AM, Attila Kinali  wrote:
> 
> On Wed, 13 Jun 2018 08:19:58 -0700
>  wrote:
> 
>> Would be interesting to see a long plot of the two 5065 against each
>> other!
> 
> I had a look at Luciano's data and it's probably safe to say, that
> the instability of the super-5065 would be the limit. The unmodified
> 5065 is incredibly stable (once you remove drift).
> 
> Attached are the two phase plots, both with quadratic drift removed.
> The unmodified 5065A has a kind of weird ~18day undulation. I would
> say it's an environmental effect, but the two cycles are too similar,
> so I do not know what to think of it.
> 
> The super-5065 (5065B) has quite a few bigger frequency jumps, with
> pretty stable phases in-between. My guess here would be that there
> are no environmental effects and it is limited by instabilities in
> the frequency discriminator electronics, ie offsets that show (close to)
> discrete jumps. or that the lamp brightness changes.
> 
>   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, Neil Stephenson
>  30days.png>___
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Re: [time-nuts] Spectracom 8140T Line Tap Schematic

[Bob kb8tq]

Hi

I think you would find a *lot* of smaller outfits “back in the day” running 
hand soldering lines. Small scale wave solder for through hole did not 
catch on the way reflow has for SMT. Dip solder was a rare item ….

Bob

> On Jun 13, 2018, at 11:28 PM, Charles Steinmetz  wrote:
> 
> Nigel wrote:
> 
>> with far too many assorted internal photos plus details of said interesting 
>> discovery, with extra brownie points to anyone who might already be thinking 
>> foam and cardboard sandwiches:-)
> 
> Oh, my, that brings back memories!  That method of "encapsulation" was used 
> by a number of Rochester electronics firms of the era.  It was developed by a 
> good friend of mine with whom I worked at another firm about a decade before 
> Spectracom was founded, and was introduced at Spectracom when he moved there.
> 
> It's hilarious now, looking at the crude PC layouts, the PC cards that look 
> like they were separated with hatchets (in reality, they used heavy-duty, 
> office-type guillotine paper cutters), and the "definitely not near mil-spec" 
> hand soldering job using at least 5x the optimum amount of solder.  
> Spectracom didn't even have a dip-soldering operation, much less a 
> wave-soldering system.
> 
> It was a much, much simpler time, one rung up the ladder from hippies in a 
> basement
> 
> Charles
> 
> 
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Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Bob kb8tq]

Hi

For several decades the Efratom FRK was the only “compact” Rb on the market. By 
today’s standards it’s a bit 
large, but in that era it was quite small. They went through a couple of 
re-designs over the years, but kept the 
basic form factor and nomenclature. The M-100 is the military version. EG ( 
and possibly others) cloned the 
package in an attempt to compete with Efratom. You see very few EG’s and a 
*lot* of Efratom’s ….

Bob

> On Jun 9, 2018, at 9:34 AM, Dana Whitlow  wrote:
> 
> What is an 'FRK'?
> 
> Thanks,
> 
> Dana
> 
> 
> On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts  wrote:
> 
>> Having followed the conversation and having looked at the p[possibility
>> using a FRK with laser diode, it is low on our list because of all the
>> ongoing projects but please if you want to spend time and money use any
>> thing but a FE5680. I was one of the first using it and noticed and posted
>> a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
>> attached. Do not have info as to who posted it.
>> Using a FRK is the easiest way to do so if interested contact me off list,
>> based on our tests is a close second to the HP 5065A.
>> Bert Kehren
>> 
>> In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
>> bruce.griffi...@xtra.co.nz writes:
>> 
>> 
>> Theres also
>> 
>> http://www.photonics.philips.com/application-areas/sensing/components
>> 
>> and
>> 
>> https://www.sacher-laser.com/home/industriallasers/point_
>> and_line_laser_module/industrial_laser_modules/micron_laser.html
>> Bruce
>>> On 09 June 2018 at 20:54 mimitech mimitech  wrote:
>>> 
>>> 
>>> Thanks Attila for your suggestion.
>>> 
>>> I prefer the 780/795nm VCSEL scheme for its simplicity. After some
>>> searching, looks like the 780nm VCSELs are also not easy to source,
>>> although other types of 780nm LD are common.
>>> 
>>> I have purchased small amount of Vixar P/N “795S--BC01” 795nm single
>>> mode VCSEL from a local distributor, price is about $500/pcs. I'm not
>> sure
>>> whether this model could work in CPT rubidium clock.
>>> 
>>> A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
>>> VCSEL, with unit price $800, which was proved to work as this paper
>>> "A compact atomic magnetometer for cubesats",
>>> https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
>> 0017N_11402.pdf
>>> ,
>>> 
>>> this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
>>> Trapping (CPT) in Rubidium"
>>> http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
>> Thesis_with_papers_V7.pdf
>>> 
>>> and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
>>> series. The cheapest model is SA.31m priced about $1100 at Digikey /
>>> Mouser.
>>> 
>>> Another paper "VCSEL Laser System for Atomic Clocks"
>>> http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
>>> several VCSEL from different vendors and found the ULM 794.7 nm single
>> mode
>>> VCSEL can work.
>>> 
>>> Thanks.
>>> 
>>> mimitech.
>>> 
>>> 
>>> On Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali 
>> wrote:
 
 On Mon, 4 Jun 2018 21:31:56 +0800
 mimitech mimitech  wrote:
 
> I'm planning to build a CPT (coherent-population-trapping) rubidium
>>> clock
> as my next hobby project. The main purpose is to learn the principles
> behind CPT rubidium clock, and hopefully got similar or better
>>> performance
> than commercial miniature rubidium clock such as FE-5680A.
 
 Building a CPT clock is slightly more involved than you might think
 at first. The laser diode is only one part of it. You will most likely
 be able to improve on the short-term stability of the FE-5680 (which
 is rather poor). But I doubt you will be able to improve much on
 the long term stability, which is where things actually become
>>> interesting,
 if you use a naive approach.
 
 Nevertheless, I have not seen many 794/795nm diodes around. The only
 one that I have the datasheet of is the one from Vixar.
 You might want want to consider going for the D2 line instead of the
 D1 line, as 780nm diodes are more commonly available than 795nm. You
>> will
 also need to buy several of those and select the ones that come closest
 to the wavelength at the desired opearating conditions (usuall spread
 is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
 temperature and current (rule of thumb is that you get about 10GHz
 per °C and mA). If you need more tuning range, you will need to add an
 external cavity (can give you up to 5nm range), which then needs to be
 tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
 
 Alternatively, you can get two S1-0780-XXX from Sacher Laser
 (cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
>> PLL).
 If you have enough money to spend, I'd go for two Cateye diode laser
>> CEL's
 from Moglabs (cost AFAIK 5000€ 

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

[Bob kb8tq]

Hi

With ADEV, you really need something closer to 100X your tau to get accurate 
data. The utter impossibility of doing this 
for long Tau is what has driven the development of other evaluation methods. 

Bob

> On Jun 8, 2018, at 10:36 AM, tim...@timeok.it wrote:
> 
> 
>   Hi Adrian,
>   as you know, to get real data up to 100K sec range, you should acquire at 
> least 500K 1M sec.
>   I say this from my personal experience. Soon I will have my 30 days run for 
> both the A and B version of the HP5065.
>   Very interesting the response of the GPSDO in the range 1 to 100 sec that I 
> had never had the chance to see for lack of an instrument as your A7.
>   ciao,
>   Luciano
> 
> 
>   Da "time-nuts" time-nuts-boun...@febo.com
>   A time-nuts@febo.com
>   Cc
>   Data Fri, 8 Jun 2018 15:46:50 +0200
>   Oggetto Re: [time-nuts] Raw phase data of super-5065
>   This is a 6 days run of a modified 5065'B' against GPS.
> 
>   Adrian
> 
>   Am 08.06.2018 um 14:05 schrieb tim...@timeok.it:
>> Here a ten days simultaneously run of the A and B version compared with my 
>> HP Z3816A GPSDO.
>> Luciano
>> 
>> 
>> Da "time-nuts" time-nuts-boun...@febo.com
>> A kb...@n1k.org
>> Cc "time-nuts" time-nuts@febo.com
>> Data Wed, 6 Jun 2018 08:18:27 +0200
>> Oggetto Re: [time-nuts] Raw phase data of super-5065
>> 
>> Hi,
>> 
>> certainly the environmental effects are significant and it is precisely for 
>> this reason that
>> acquisitions have been made simultaneously on two 5065, one modified and the 
>> other not.
>> To verify the results the same measures were taken with another pair of 
>> 5065, one modified and the other not.
>> This second test was carried out at another site 300Km from the first one.
>> Both tests showed a better and more consistent medium/long term ADEV than 
>> the unmodified HP5065A.
>> I want to clarify that these measures have the objective of verifying the 
>> medium / long term stability and not the short term stability of the Super 
>> version I agree it is improved..
>> Luciano
>> 
>> 
>> Da "Bob kb8tq" kb...@n1k.org
>> A "Luciano Paramithiotti" tim...@timeok.it,"Discussion of precise time and 
>> frequency measurement" time-nuts@febo.com
>> Cc
>> Data Tue, 5 Jun 2018 10:05:34 -0400
>> Oggetto Re: [time-nuts] Raw phase data of super-5065
>> Hi
>> 
>> It is pretty well known that without “help” ( beyond the filter stuff on the 
>> super) the 5065 has fairly poor temperature
>> stability and somewhat variable response to pressure and humidity. Taking 
>> two samples right off the production line
>> likely would have given you different long term data as a result.
>> 
>> If you are going to the trouble of watching these devices for a long time, 
>> monitor temperature, pressure and humidity.
>> I suspect you will find correlations ….
>> 
>> Bob
>> 
>>> On Jun 5, 2018, at 5:44 AM, tim...@timeok.it wrote:
>>> 
>>> 
>>> Hi Attila,
>>> I am doing the long therm stability test on a couple of HP5065, one 
>>> original A type, the second B or "super" compared with my best long therm 
>>> stability, a GPSDO HPz3816A.
>>> This test will be 30 days long. It is a second test, with a second couple 
>>> of HP5065A/B, to verify the long therm stability of both the version.
>>> 
>>> Up to now the data available for version B or "super" only concerned the 
>>> improvement of phase noise.
>>> 
>>> From the first results it seems that the HP5065A is more stable within 
>>> 30days than the modified version with the filter.
>>> It must be considered that the short-term stability of 5065 is better than 
>>> the GPSDO / TICC up to 10-80k sec then, in this test configuration the 
>>> valid data will be beyond these values.
>>> The results will be ready within 28 days and I will be happy to share them 
>>> in order to have everyone's opinion.
>>> Regards,
>>> Luciano
>>> 
>>> 
>>> Da "time-nuts" time-nuts-boun...@febo.com
>>> A "Discussion of precise time and frequency measurement" time-nuts@febo.com
>>> Cc
>>> Data Mon, 4 Jun 2018 10:11:50 +0200
>>> Oggetto [time-nuts] Raw phase data of super-5065
>>> Hoi zäme!
>>> 
>>> Would one (preferably multiple) of the owners of a super-5065 be so kind
>>> and share the raw phase data of an super-5065 against a stable reference
>>

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

[Bob kb8tq]

Hi

Having run tens of thousands of standards on these sorts of tests … the one 
that is more temperature / pressure sensitive *will*
show up as having worse long term stability.  

1) If your environment swings +/- 1C over 48 hours.

2) If unit A is 1 ppb 0 to 50 ( = 20 ppt / C)

3) If unit B is -0.2 ppb 0 to 50C ( = -4 ppt / C)

4) Both will have degraded stability on a plot that shows 2 days of data

5) Unit A is “at spec” for the 5065, unit B is better than the rated 
performance. After many decades .. who knows what the spec is ….

Unit B will show up as 5X better on a long term test than unit A with both in 
*exactly* the same environment.  Holding 1 C over 2 days
is doing well even for some ( but not all ) environmental chambers. 

I’m by no means claiming that this *is* the only source of the difference. The 
point is that the temperature stability rating on these 
devices is not very good. They are quite temperature sensitive. There are a lot 
of OCXO’s out there that do much better on stability
than a 5065 temperature wise. 

Bob

> On Jun 8, 2018, at 10:07 AM, tim...@timeok.it wrote:
> 
> Hi,
> 
> This test requires that the two Rubidiun be installed in the same cabinet so 
> they are subject to the same temperature and atmospheric pressure.
> Acquisitions were made simultaneously.To confirm the data collected, the same 
> test was repeated in another site with two different HP5065, one modified in 
> B or "supe" and the other unmodified.
>  
> The results were very similar, that is, both the Super version has a worse 
> lmedium term Adev than the unmodified version.
> All this suggests that the modification with the addition of the 780nm filter 
> worsens the medium term stability of the HP5065.
> 
> Therefore I would tend to exclude that the results obtained depend on the 
> different sensitiveness towards atmospheric pressure or to the variations of 
> the environmental temperature.
> 
> It would be interesting that for further confirmation of what I have deduced 
> other people could carry out the same tests in the medium and long term Adev 
> stability.
> 
> Luciano
> www.timeok.it
> 
> 
> 
> 
>   
> Da "Bob kb8tq" kb...@n1k.org
> A "Luciano Paramithiotti" tim...@timeok.it,"Discussion of precise time and 
> frequency measurement" time-nuts@febo.com
> Cc
> Data Fri, 8 Jun 2018 09:02:34 -0400
> Oggetto Re: [time-nuts] Raw phase data of super-5065
> 
> Hi
>  
> Ok, so this question should not come as a great surprise: Does one of the 
> 5065’s have about 3X the temperature
> sensitivity of the other? ( or pressure or humidity ).
>  
> Bob
>  
>  
>  
> > On Jun 8, 2018, at 8:05 AM, tim...@timeok.it wrote:
> >
> >
> > Here a ten days simultaneously run of the A and B version compared with my 
> > HP Z3816A GPSDO.
> > Luciano
> >
> >
> > Da "time-nuts" time-nuts-boun...@febo.com
> > A kb...@n1k.org
> > Cc "time-nuts" time-nuts@febo.com
> > Data Wed, 6 Jun 2018 08:18:27 +0200
> > Oggetto Re: [time-nuts] Raw phase data of super-5065
> >
> > Hi,
> >
> > certainly the environmental effects are significant and it is precisely for 
> > this reason that
> > acquisitions have been made simultaneously on two 5065, one modified and 
> > the other not.
> > To verify the results the same measures were taken with another pair of 
> > 5065, one modified and the other not.
> > This second test was carried out at another site 300Km from the first one.
> > Both tests showed a better and more consistent medium/long term ADEV than 
> > the unmodified HP5065A.
> > I want to clarify that these measures have the objective of verifying the 
> > medium / long term stability and not the short term stability of the Super 
> > version I agree it is improved..
> > Luciano
> >
> >
> > Da "Bob kb8tq" kb...@n1k.org
> > A "Luciano Paramithiotti" tim...@timeok.it,"Discussion of precise time and 
> > frequency measurement" time-nuts@febo.com
> > Cc
> > Data Tue, 5 Jun 2018 10:05:34 -0400
> > Oggetto Re: [time-nuts] Raw phase data of super-5065
> > Hi
> >
> > It is pretty well known that without “help” ( beyond the filter stuff on 
> > the super) the 5065 has fairly poor temperature
> > stability and somewhat variable response to pressure and humidity. Taking 
> > two samples right off the production line
> > likely would have given you different long term data as a result.
> >
> > If you are going to the trouble of watching these devices for a long time, 
> > monitor temperature, pressure and humidity.
> > I

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

[Bob kb8tq]

Hi

Ok, so this question should not come as a great surprise: Does one of the 
5065’s have about 3X the temperature 
sensitivity of the other? ( or pressure or humidity ). 

Bob



> On Jun 8, 2018, at 8:05 AM, tim...@timeok.it wrote:
> 
> 
>   Here a ten days simultaneously run of the A and B version compared with my 
> HP Z3816A GPSDO.
>   Luciano
> 
> 
>   Da "time-nuts" time-nuts-boun...@febo.com
>   A kb...@n1k.org
>   Cc "time-nuts" time-nuts@febo.com
>   Data Wed, 6 Jun 2018 08:18:27 +0200
>   Oggetto Re: [time-nuts] Raw phase data of super-5065
> 
>   Hi,
> 
>   certainly the environmental effects are significant and it is precisely for 
> this reason that
>   acquisitions have been made simultaneously on two 5065, one modified and 
> the other not.
>   To verify the results the same measures were taken with another pair of 
> 5065, one modified and the other not.
>   This second test was carried out at another site 300Km from the first one.
>   Both tests showed a better and more consistent medium/long term ADEV than 
> the unmodified HP5065A.
>   I want to clarify that these measures have the objective of verifying the 
> medium / long term stability and not the short term stability of the Super 
> version I agree it is improved..
>   Luciano
> 
> 
>   Da "Bob kb8tq" kb...@n1k.org
>   A "Luciano Paramithiotti" tim...@timeok.it,"Discussion of precise time and 
> frequency measurement" time-nuts@febo.com
>   Cc
>   Data Tue, 5 Jun 2018 10:05:34 -0400
>   Oggetto Re: [time-nuts] Raw phase data of super-5065
>   Hi
> 
>   It is pretty well known that without “help” ( beyond the filter stuff on 
> the super) the 5065 has fairly poor temperature
>   stability and somewhat variable response to pressure and humidity. Taking 
> two samples right off the production line
>   likely would have given you different long term data as a result.
> 
>   If you are going to the trouble of watching these devices for a long time, 
> monitor temperature, pressure and humidity.
>   I suspect you will find correlations ….
> 
>   Bob
> 
>> On Jun 5, 2018, at 5:44 AM, tim...@timeok.it wrote:
>> 
>> 
>> Hi Attila,
>> I am doing the long therm stability test on a couple of HP5065, one original 
>> A type, the second B or "super" compared with my best long therm stability, 
>> a GPSDO HPz3816A.
>> This test will be 30 days long. It is a second test, with a second couple of 
>> HP5065A/B, to verify the long therm stability of both the version.
>> 
>> Up to now the data available for version B or "super" only concerned the 
>> improvement of phase noise.
>> 
>> From the first results it seems that the HP5065A is more stable within 
>> 30days than the modified version with the filter.
>> It must be considered that the short-term stability of 5065 is better than 
>> the GPSDO / TICC up to 10-80k sec then, in this test configuration the valid 
>> data will be beyond these values.
>> The results will be ready within 28 days and I will be happy to share them 
>> in order to have everyone's opinion.
>> Regards,
>> Luciano
>> 
>> 
>> Da "time-nuts" time-nuts-boun...@febo.com
>> A "Discussion of precise time and frequency measurement" time-nuts@febo.com
>> Cc
>> Data Mon, 4 Jun 2018 10:11:50 +0200
>> Oggetto [time-nuts] Raw phase data of super-5065
>> Hoi zäme!
>> 
>> Would one (preferably multiple) of the owners of a super-5065 be so kind
>> and share the raw phase data of an super-5065 against a stable reference
>> with me? The longer the data trace, the better.
>> 
>> Thanks in advance!
>> 
>> 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, Neil Stephenson
>> ___
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Re: [time-nuts] Mark-- LH Milliseconds Display

[Bob kb8tq]

Hi

Even a “tenth of second” running display is not of much use to the human eye. 
Most 
OS’s will struggle with a “hundredth’s of second” display in terms of getting 
it through 
the display formatting code. Finding a monitor and display card that will do 
1KHz refresh 
rates / frame rate will be tough for your 1 ms digit. 

Now, doing all that with an LED display …. not all that hard. Your eyes still 
limit out at
the same point so the 0.0x and 0.00x digits are just a smear…. ummm …. errr …. 
been 
there / done that …. 

Bob

> On Jun 7, 2018, at 4:11 PM, Michael Baker  wrote:
> 
> Hello, Mark--
> 
> OOPS!!My bad!!  --I misunderstood what the "milliseconds"
> display was indicating.
> 
> It says:/TSZ  = *"- toggle show digital clock with milliseconds"
> 
> I took this literally to mean that the digital clock would display hours,
> minutes, seconds and milliseconds but that the "milliseconds" meant
> a running, incrementing, millisecond-by-millisecond display of the
> time and not the difference in the time of arrival of the RX time message.
> 
> *Thanks for the correction info!
> 
> Mike Baker
> Micanopy, FL
> *
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Re: [time-nuts] Raw phase data of super-5065

[Bob kb8tq]

HI

> On Jun 6, 2018, at 2:18 AM, tim...@timeok.it wrote:
> 
> Hi,
>  
> certainly the environmental effects are significant and it is precisely for 
> this reason that
> acquisitions have been made simultaneously on two 5065, one modified and the 
> other not.
> 
> To verify the results the same measures were taken with another pair of 5065, 
> one modified and the other not. 
> This second test was carried out at another site 300Km from the first one. 
> 
> Both tests showed a better and more consistent medium/long term ADEV than the 
> unmodified HP5065A.
> 
> I want to clarify that these measures have the objective of verifying the 
> medium / long term stability and not the short term stability of the Super 
> version I agree it is improved..
> 
> Luciano


Since my basement does one set of things ( temperature / humidity / pressure ) 
and somebody else runs in the garage ( different temperature / humidity / 
pressure) 
the data will be very specific to a single set of environmental conditions. 
Temperature is relatively easy to monitor, humidity and pressure are a bit more 
complex.
At least logging them so people can compare your setting to there’s does need 
to be part of the process.

Bob

> 
> 
>   
> Da "Bob kb8tq" kb...@n1k.org
> A "Luciano Paramithiotti" tim...@timeok.it,"Discussion of precise time and 
> frequency measurement" time-nuts@febo.com
> Cc
> Data Tue, 5 Jun 2018 10:05:34 -0400
> Oggetto Re: [time-nuts] Raw phase data of super-5065
> 
> Hi
>  
> It is pretty well known that without “help” ( beyond the filter stuff on the 
> super) the 5065 has fairly poor temperature
> stability and somewhat variable response to pressure and humidity. Taking two 
> samples right off the production line
> likely would have given you different long term data as a result.
>  
> If you are going to the trouble of watching these devices for a long time, 
> monitor temperature, pressure and humidity.
> I suspect you will find correlations ….
>  
> Bob
>  
> > On Jun 5, 2018, at 5:44 AM, tim...@timeok.it wrote:
> >
> >
> > Hi Attila,
> > I am doing the long therm stability test on a couple of HP5065, one 
> > original A type, the second B or "super" compared with my best long therm 
> > stability, a GPSDO HPz3816A.
> > This test will be 30 days long. It is a second test, with a second couple 
> > of HP5065A/B, to verify the long therm stability of both the version.
> >
> > Up to now the data available for version B or "super" only concerned the 
> > improvement of phase noise.
> >
> > From the first results it seems that the HP5065A is more stable within 
> > 30days than the modified version with the filter.
> > It must be considered that the short-term stability of 5065 is better than 
> > the GPSDO / TICC up to 10-80k sec then, in this test configuration the 
> > valid data will be beyond these values.
> > The results will be ready within 28 days and I will be happy to share them 
> > in order to have everyone's opinion.
> > Regards,
> > Luciano
> >
> >
> > Da "time-nuts" time-nuts-boun...@febo.com
> > A "Discussion of precise time and frequency measurement" time-nuts@febo.com
> > Cc
> > Data Mon, 4 Jun 2018 10:11:50 +0200
> > Oggetto [time-nuts] Raw phase data of super-5065
> > Hoi zäme!
> >
> > Would one (preferably multiple) of the owners of a super-5065 be so kind
> > and share the raw phase data of an super-5065 against a stable reference
> > with me? The longer the data trace, the better.
> >
> > Thanks in advance!
> >
> > 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, Neil Stephenson
> > ___
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> > and follow the instructions there.
>  

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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

Hmmm …… that’s a very big difference between the RINEX and the “precision 
survey”. 

How do each compare to other receivers on the same antenna ( and super duper 
stable mount) ?
Even with a tripod on the grass, meter level variations likely are not the 
tripod’s fault. :)

Bob

> On Jun 5, 2018, at 1:39 PM, Mark Sims  wrote:
> 
> I did Lady Heather's 48-hour precision survey on an NVS-08 receiver and 
> collected RINEX data at the same time.  The NVS was tracking GPS and SBAS 
> satellites.
> 
> The RINEX result had lat/lon/alt error estimates of .175/.153/.396 meters.
> 
> The difference between Heather's precision survey results and the RINEX 
> position were:
> lat/lon/alt:  -.638m/1.190m/1.526m
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Re: [time-nuts] Raw phase data of super-5065

[Bob kb8tq]

Hi

It is pretty well known that without “help” ( beyond the filter stuff on the 
super) the 5065 has fairly poor temperature 
stability and somewhat variable response to pressure and humidity. Taking two 
samples right off the production line
likely would have given you different long term data as a result. 

If you are going to the trouble of watching these devices for a long time, 
monitor temperature, pressure and humidity.
I suspect you will find correlations ….

Bob

> On Jun 5, 2018, at 5:44 AM, tim...@timeok.it wrote:
> 
> 
>   Hi Attila,
>   I am doing the long therm stability test on a couple of HP5065, one 
> original A type, the second B or "super" compared with my best long therm 
> stability, a GPSDO HPz3816A.
>   This test will be 30 days long. It is a second test, with a second couple 
> of HP5065A/B, to verify the long therm stability of both the version.
> 
>   Up to now the data available for version B or "super" only concerned the 
> improvement of phase noise.
> 
>   From the first results it seems that the HP5065A is more stable within 
> 30days than the modified version with the filter.
>   It must be considered that the short-term stability of 5065 is better than 
> the GPSDO / TICC up to 10-80k sec then, in this test configuration the valid 
> data will be beyond these values.
>   The results will be ready within 28 days and I will be happy to share them 
> in order to have everyone's opinion.
>   Regards,
>   Luciano
> 
> 
>   Da "time-nuts" time-nuts-boun...@febo.com
>   A "Discussion of precise time and frequency measurement" time-nuts@febo.com
>   Cc
>   Data Mon, 4 Jun 2018 10:11:50 +0200
>   Oggetto [time-nuts] Raw phase data of super-5065
>   Hoi zäme!
> 
>   Would one (preferably multiple) of the owners of a super-5065 be so kind
>   and share the raw phase data of an super-5065 against a stable reference
>   with me? The longer the data trace, the better.
> 
>   Thanks in advance!
> 
>   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, Neil Stephenson
>   ___
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Re: [time-nuts] Source for DC-blocking 50-ohm terminators? (Spectracom 8140)

[Bob kb8tq]

Hi

Without the taps, the Spectracom system really does not do much for you at all. 
There is no 
isolation / no buffering / no nice multiple output frequency stuff. Much 
cheaper and easier to 
just use a simple 10 MHz amp if that is all you want to do. 

Since you have significant voltage on the line, just dropping a 50 ohm load on 
there is a bad idea ….

Bob

> On Jun 4, 2018, at 11:24 AM, Arthur Dent  wrote:
> 
> If you're not going to use the Spectracom  taps that are the
> reason for the D.C. being on the coax, you can easily remove
> the inductors used to superimpose the D.C. on the coax lines.
> Without the 12V.D.C. on the outputs you can use standard 50
> ohm terminations. The open toroids are reachable if you take
> out a few screws to tip the back panel out and clip the leads
> to remove the parts.Using the 8140 as a DA without disabling
> the 12V.D.C. is a good way to fry some piece of test gear.
> Here is a photo of the schematic.
> 
> -Arthur
> <8140 output.jpg>___
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Re: [time-nuts] Source for DC-blocking 50-ohm terminators? (Spectracom 8140)

[Bob kb8tq]

Hi

DC blocked 50 ohm terminations are indeed a bit odd. One answer is to simply 
use the 
75 ohm version and move on. The gotcha there is that they may / may not have a 
block
that works well at 10 MHz ( = the cap is to small ). The one thing *not* to do 
is to run the
device with no termination on the cable. The gizmo will be perfectly happy. 
Your lab will
be a mess. The coax will normally be long enough to make a great antenna at 10 
MHz. 
Leaving the end un-terminated puts it in “antenna mode”. You will have RF all 
over everything.
I have a lot of experience with this specific problem …..

Bob

> On Jun 4, 2018, at 12:09 AM, Julien Goodwin  
> wrote:
> 
> I'm looking at using a Spectracom 8140 for 10Mhz distribution, and they
> specify using a DC-blocking 50-ohm terminator on each run.
> 
> These seem to be odd enough that none of my usual sources have them
> (75-ohm DC-blocking terminators yes, 50-ohm, no).
> 
> While it's easy enough to chain a DC block and a terminator, I'd prefer
> a single module I can more obviously label as the line termination.
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi


> On Jun 3, 2018, at 7:35 PM, Mark Sims  wrote:
> 
> As far as I'm concerned anything that you can do to improve the position 
> accuracy,  environmental changes,  noise environment, etc is a good thing.   
> Minimizing errors and disturbances can't hurt and may even improve things.  
> How much any improvement  provides ... ???   But  time nuts tend to be a bit 
> nutty about minimizing our therbligs  ;-)
> 
> Most receiver self-surveys seem to get your lat/lon to the 2-3 meter range.   
> Heather's median survey is in the 1-2 meter range.  PPP data is in the < 0.25 
> meter range... seems like something worthwhile.  (altitude errors are usually 
> around twice the lat/lon error).
> 
> There is always the possibility that some receiver model's computation of 
> lat/lon/alt could have some intrinsic bias in it.   If so,  a position 
> calculated by an external source could possibly degrade performance... 

If you go back to the NIST papers where they were testing timing modules, they 
indeed did find “gotcha’s” with putting in survey based coordinates. 
I don’t think they ever did PPP on the modules they published data on.

Bob

> 
> 
> 
>> Is this applicable to a Thunderbolt, and would this improved position
> accuracy be expected to improve the time accuracy from a Thunderbolt
> compared to using the older Lady Heather 24 hour self survey method?
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

Location will always impact things a bit. At some point it does become a minor 
contributor. What point that is varies with a lot of things. One of them is 
indeed
the propagation path to the satellites. 

How much the ionosphere and troposphere mess things up is very much a “that 
depends”
sort of thing. There are corrections applied to the data as part of normal GPS 
L! operation.
The degree to which these corrections work depends on how close things are to 
the “normal
model”. That in turn depends to some degree on how active the sunspot cycle is 
at the time.
Right now we are in a period of relatively low activity. That equates to the 
models mostly fitting
better most of the time.

If solar activity was somewhat higher, then things get more dynamic. The magic 
models and 
the broadcast data can’t keep up as well. That translates to more noise on the 
estimates and
worse timing ( as well as an impact on location). 

Bob

> On Jun 3, 2018, at 4:07 PM, Chris Caudle  wrote:
> 
> On Sun, June 3, 2018 12:57 am, Mark Sims wrote:
>> Well,  with a little prodding and help from Magnus,  I now have the
>> Trimble devices outputting RINEX files.
> 
> Is this applicable to a Thunderbolt, and would this improved position
> accuracy be expected to improve the time accuracy from a Thunderbolt
> compared to using the older Lady Heather 24 hour self survey method?  Or
> is ionospheric noise the limiting factor so determining more accurate
> position doesn't really help?
> 
> -- 
> Chris Caudle
> 
> 
> 
> 
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

If you are doing a longer run into one of the data analysis services - it does 
not seem to matter much what the 
spacing on the readings is. One second data does not seem to produce any better 
result than 30 second data. 
I don’t think that the 3 second rate on the Trimble will have much impact on a 
24 hour data set.

Bob

> On Jun 3, 2018, at 1:57 AM, Mark Sims  wrote:
> 
> Well,  with a little prodding and help from Magnus,  I now have the Trimble 
> devices outputting RINEX files.  They have pseudorange, doppler, and signal 
> strength observations.  A 5 hour 1Hz run was sent to CSRS-PPP and the 
> lat/lon/alt error ellipses were in the 250/250/700 mm range... that should 
> improve with a longer run.
> 
> Firmware issues in the original Resolution-T limit those to a 3 second 
> observation rate.
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

Indeed, if you look at a 30 minute data file from any of these receivers, it 
will not be giving you
quite the same performance. 

Bob

> On Jun 1, 2018, at 1:00 PM, Magnus Danielson  
> wrote:
> 
> Hi,
> 
> Well, when the resolution and stability is sufficient, other aspects
> weigh in, as being quick to have reduce biases in position and time.
> You can resolve much by averaging etc. but that takes time.
> 
> Cheers,
> Magnus
> 
> On 06/01/2018 02:10 PM, Bob kb8tq wrote:
>> Hi
>> 
>> I can’t say that’s a big surprise. The silicon on these gizmos made it past 
>> the “overkill” point at least 
>> a decade ago. There’s only so much you can do with a noisy signal ….. Yes, 
>> there are indeed feature
>> differences, ( like the Furuno pps ). The core of the device seems to have 
>> hit a limit a while ago. 
>> 
>> Bob
>> 
>>> On May 31, 2018, at 11:15 PM, Mark Sims  wrote:
>>> 
>>> I did another test to see if the M8T offered any positioning advantage over 
>>> the old (and cheap) LEA-4T and LEA-5T devices.   I drove the M8T and LEA-4T 
>>> with the same antenna,  collected data for 12 hours,  beamed the RINEX 
>>> files to Canada.
>>> 
>>> The results matched to within 3mm...  so, again, the M8T doesn't offer much 
>>> benefit for getting precise positions.
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

I can’t say that’s a big surprise. The silicon on these gizmos made it past the 
“overkill” point at least 
a decade ago. There’s only so much you can do with a noisy signal ….. Yes, 
there are indeed feature
differences, ( like the Furuno pps ). The core of the device seems to have hit 
a limit a while ago. 

Bob

> On May 31, 2018, at 11:15 PM, Mark Sims  wrote:
> 
> I did another test to see if the M8T offered any positioning advantage over 
> the old (and cheap) LEA-4T and LEA-5T devices.   I drove the M8T and LEA-4T 
> with the same antenna,  collected data for 12 hours,  beamed the RINEX files 
> to Canada.
> 
> The results matched to within 3mm...  so, again, the M8T doesn't offer much 
> benefit for getting precise positions.
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Re: [time-nuts] HP 5370B using manual start-stop

[Bob kb8tq]

Hi

We ran 5335’s in “long gate” mode via the gate open / gate close commands. It 
worked, but you had to 
compensate for rollovers. My guess is that you would run into similar stuff on 
the 5370A. Simple answer
is to try it and see … That’s what we did on the 5335 and then worked through 
all the issues we found. 

Bob

> On May 30, 2018, at 11:19 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> List,  
> I'd like to do 1000 second TIC measurements with my 5370B but I don't want to 
> have to perchase A HP 1B prologic or similar controller for the timeing.
> 
> As long as I'm interested in the TIC difference but not an absolute value is 
> it reasonable to use the manual start/stop switches and a stop watch or 
> similar timer?
> Regards,
> Perrier
> 
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

It’s not real clear what the magic L1 / L2 / L5 gizmo does for you right now 
today. As far as I can tell, 
the free processing services all only do two at a time. You can do L1 / L2 or 
L1 /L5. Possibly at some
point in the future that will change. 

Even with “only two” a fancy device will get you down to numbers that simply 
are not believable. Any
device that thinks it’s getting into 0.000x meter precision needs to back up 
and look at some of the 
reference points being used.  

Getting back to timing, if you guess that 0.3 m is about a nanosecond, the M8T 
is off by about a nanosecond
in lat and lon. It’s off by about 2 ns in elevation.  The time solution will be 
some sort of RMS of this. Unless
the one and only sat you can see passes directly over you, the full 2 ns isn’t 
going to come in. 

Location will always be one of a list of errors in getting time data. The 
bigger question will be how well the 
other stuff on the list is controlled / known. Coming up with an RF delay 
number that is good to < 1 ns on
any of these gizmos may be a bit tough…..

If frequency rather than time is the goal, the position error will indeed add 
to the “swing” over a day. Your 
antenna location / sky view will be a big part of the “how much” part of the 
question. You might see a 
nanosecond of swing on an hour to hour basis …. you probably would see less. 
Simply put, it’s in the
3x10^-12 or less range frequency wise. Most GPSDO’s struggle below a few parts 
in 10^-11 for a variety
of reasons ….

Bob

> On May 30, 2018, at 3:46 PM, Mark Sims  wrote:
> 
> Ok, I did the experiment.  I took an 8 hour M8T RINEX file with 
> GPS,SBAS,GLONASS,GALILEO data in it.  I then used to TEQC to extract GPS only 
> and GLONASS only data (CSRS-PPP ignores SBAS and GALILEO data).   The 95% 
> confidence error ellipse estimates ("rapid" orbits) were:
> 
> GPS+GLONASS:lat 0.245mlon 0.219malt 0.582m
> GPS ONLY: lat 0.269mlon 0.239malt 0.616m
> GLONASS ONLY:   lat 0.610mlon 0.755malt 1.835m
> 
> Conclusion... if you are just interested in an accurate antenna position,  a 
> $25 LEA-5T should do just fine.  GLONASS brings very little benefit (call it 
> an inch) to the party.  24 hours of observations can reduce those numbers by 
> around 50%   I used one of those $70 Chinese L1/L2/GLONASS/BEIDOU antennas 
> from Ebay.   Note that my antenna location/environment is HORRIBLE... 
> 
> Things might change if you get into expensive L1+L2(or L5) receivers.
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Re: [time-nuts] Tektronix FCA3103 ADEV measurement tau setting problem

[Bob kb8tq]

Hi

Any time I have tied a 53132 into TimeLab, I’ve used the serial port. That does 
a fine 
job of “talk only” data dump.

Bob

> On May 30, 2018, at 12:18 PM, Richard (Rick) Karlquist 
>  wrote:
> 
> 
> 
> On 5/28/2018 1:44 PM, Bob kb8tq wrote:
>> Hi
>> TimeLab will work with some counters and it will do most of the common 
>> plots. It is indeed free …..
>> Bob
> 
> The TimeLab manual says it will support any counter that can
> dump data in Talk Only mode.  The Tek manual doesn't mention
> Talk Only mode.  The TimeLab manual also (vaguely) says it
> will support the HP53132, but doesn't specify if this is
> simply referring to Talk Only mode, or a more complete interface.
> The Tek manual says that it has a 53132 compatibility mode
> available over GPIB using SCPI commands.  If the TimeLab
> interface uses SCPI as well, I might be in business.  Does
> anyone know about that?
> 
> Rick N6RK

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Re: [time-nuts] Tektronix FCA3103 ADEV measurement tau setting problem

[Bob kb8tq]

Hi

TimeLab will work with some counters and it will do most of the common plots. 
It is indeed free …..

Bob

> On May 28, 2018, at 3:17 PM, Richard (Rick) Karlquist  
> wrote:
> 
> I have a Tek FCA3103 300 MHz counter that measures ADEV
> as a built in function.  When I bring up the settings
> menu for the measurement, it has an entry window for
> "tau" (the averaging time, IE "sigma sub y of tau").
> It defaults to 200 ms.  I can enter larger values and
> ADEV gives reasonably results.  However, if I enter
> smaller values, even 199 ms, I don't get any error
> on the display, but I get clearly erroneous
> results for ADEV. I read the manual and cannot find
> anything to the effect that the instrument doesn't work
> for less than 200 ms.
> 
> BTW, I asked Tek "customer no support" about it and
> they were clueless.
> 
> 1.  Is this pilot error?  Can anyone tell me the trick?
> 
> 2.  Can anyone recommend a 300 MHz counter that measures
> ADEV, correctly :-)?  Bonus question:  a counter that
> measures Hadamard variance?
> 
> 3.  Can anyone recommend a 300 MHz counter that can
> measure ADEV and Hadamard using off the shelf software
> that runs on a PC?  I don't write software :-)
> Bonus question:  software to make these measurements
> that works with the FCA3103 that I already have?
> 
> I have an NI GPIB-USB-HS to interface the counter
> to the PC running the software if that helps.
> 
> 
> 
> Thanks
> 
> Rick N6RK
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Re: [time-nuts] 58503A VS SR625

[Bob kb8tq]

Hi

The key question on sat’s is - do you always have 4 locked? If so the device 
should  never go into holdover. 
Some GPSDO’s will stay out of holdover with as few as one sat locked. It’s best 
not to count on that. 

Simple setup for 10 MHz to 10 MHz is to hook one to the external reference 
input and the other to input A on the
counter. This works for most counters, not just the SR620. You often do need to 
dig out the manual to make sure
the external reference is being recognized and locked to. In some cases you 
discover that your counter needs a 
bit of service ( like re-adjusting the internal reference) for this to work. 
Set the gate time to something like 10 seconds
and look at the frequency. For fun change the gate time and watch the measured 
“error” get worse at the shorter
gate times. 

For 1 pps measurement on GPSDO’s things are a bit more complicated. The PPS 
signals both arrive at the same
time. Counters do not like to deal with this sort of thing. What I do is to dig 
out the manual on the GPSDO and find 
how to use the cable delay setting on one of the GPSDO’s. You set the cable 
delay to 500 ns or 1 us. That moves
the pps output of the GPSDO by 500 or 1000 ns. The two pps signals never 
collide when things are set this way. 
You are measuring a very short time period, so the time base on the counter 
does not matter much.

Getting the counter to properly start on channel A and stop on channel B is 
also a “back to the manual” thing for 
each counter you own. None of them are quite the same. Once you get it going, 
it should be quite clear what is
going on. That is another nice thing about the “round number” offset between 
the GPSDO’s. You know approximately
what the data is going to look like. 

Again - this process works for any dual channel counter and any GPSDO’s. It’s 
not restricted to one particular
brand or model. I keep one GPSDO around with the PPS offset simply to do this 
sort of work. It is much easier 
to just grab that signal than to go set things up every time. If you have 
several GPSDO’s you can measure them
all against the same offset PPS signal. You can then compare data between them 
all. 

Lots of fun !!!

Bob

> On May 28, 2018, at 11:52 AM, Anton Moehammad <moehan...@yahoo.com> wrote:
> 
> Hi All,
> Thank You for respond.
> Yes I will make 58503A to 58503A comparison but my problem are I got 
> difficulties found the suitable setting for my SR620 to do it if any one can 
> give a hint about proper setting for SR620 time interval setup I will happy 
> to follow it. I like to have 10MHz out comparison and 1PPS comparison too.
> my Antena is 30m above ground and according to Lady Heather I my worst S/N is 
> 35dB all time 
> 
> Pada Senin, 28 Mei 2018 21.17.25 GMT+7, Bob kb8tq <kb...@n1k.org> menulis:
> 
> 
> Hi
> 
> If you are seeing 0.3 ppb delta between various HP GPSDO’s the first question 
> would be “on for how long? / under what conditions?".  The HP devices take a 
> *long* time 
> to settle in ( like weeks ) to their final best performance loop settings. To 
> fully settle, they need to be locked the whole time. Staying locked means an 
> antenna that has a 
> good satellite view and the unit having a solid survey location. If they are 
> dropping out of lock from time to time, they will never really settle. 
> 
> Once settled, you still have a noise process. ADEV is one way to plot this 
> sort of noise. Your results will still depend on the gate time on your 
> counter(s) since that impacts 
> how you “see” the noise.  A very short gate will give you more variation than 
> a longer gate. Put another way, “tau” is part of any frequency measurement, 
> even if ADEV is 
> not being calculated. 
> 
> Bob
> 
> > On May 28, 2018, at 8:25 AM, Anton Moehammad via time-nuts 
> > <time-nuts@febo.com <mailto:time-nuts@febo.com>> wrote:
> > 
> > Hi All, I have 5 pcs 58503A with various firmware and 3 of them have 8 
> > channel recv and 2 have 6 channel receiver all is working but I found none 
> > of 5 has same result I mean when I compare it with my SR625 use SR620 or my 
> > CNT-90 use timelab there is a variation in the output.the variation about 3 
> > E-9 Hz. yes use same cable and same antenna, I also monitor the temp and I 
> > sure the temp variation is very minimal.any one has explanation about this 
> > ?Thank YouAnton
> > 
> > |  | Virus-free. www.avg.com  |
> 
> > 
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Re: [time-nuts] 58503A VS SR625

[Bob kb8tq]

Hi

If you are seeing 0.3 ppb delta between various HP GPSDO’s the first question 
would be “on for how long? / under what conditions?".  The HP devices take a 
*long* time 
to settle in ( like weeks ) to their final best performance loop settings. To 
fully settle, they need to be locked the whole time. Staying locked means an 
antenna that has a 
good satellite view and the unit having a solid survey location. If they are 
dropping out of lock from time to time, they will never really settle. 

Once settled, you still have a noise process. ADEV is one way to plot this sort 
of noise. Your results will still depend on the gate time on your counter(s) 
since that impacts 
how you “see” the noise.  A very short gate will give you more variation than a 
longer gate. Put another way, “tau” is part of any frequency measurement, even 
if ADEV is 
not being calculated. 

Bob

> On May 28, 2018, at 8:25 AM, Anton Moehammad via time-nuts 
>  wrote:
> 
> Hi All, I have 5 pcs 58503A with various firmware and 3 of them have 8 
> channel recv and 2 have 6 channel receiver all is working but I found none of 
> 5 has same result I mean when I compare it with my SR625 use SR620 or my 
> CNT-90 use timelab there is a variation in the output.the variation about 3 
> E-9 Hz. yes use same cable and same antenna, I also monitor the temp and I 
> sure the temp variation is very minimal.any one has explanation about this 
> ?Thank YouAnton
> 
> |  | Virus-free. www.avg.com  |
> 
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Re: [time-nuts] GNS-500A Rubidium

[Bob kb8tq]

HI

Unless I’m missing something, that’s an *old* Efratom. I would not count on
it working without some significant effort. The price is right though. 

Bob

> On May 25, 2018, at 10:21 AM, Clint Jay  wrote:
> 
> Just spotted on eBay, a rather sorry looking GNS-500A Rubidium standard,
> it's not expensive and is up for best offer, May or may not be of use to
> someone?
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Re: [time-nuts] 5950 Crystal impedance meter manual

[Bob kb8tq]

Hi

Basically when the modern era of network analyzer / standards calibrated 
devices came along, it was the
end of most of these magic test sets with knobs and dials. The Saunders stuff 
lived on well into that era, 
mainly because it was relatively inexpensive and most of the calibration was 
simple to do. The conversion
to what we would now call network analyzer techniques was well underway in the 
1970’s. It took us quite
a bit of work to get from there to where we are today. 

The operating principle of the older magic boxes is fairly simple. Build up an 
oscillator circuit that can be 
switched around to run over a wide range of frequencies and impedances. It 
generally is a very poor 
oscillator, but that’s not the point. Come up with a way to “zero” it to a 
given impedance and frequency. 
Plug in crystals and see how they deviate in impedance and nominal frequency. 
Shove in a load capacitance  
change and note the frequency change. From that data, you can calculate the 
crystal parameters.  To
the degree all the stray this and that is nulled out, your data will be more or 
less accurate.

Bob

> On May 24, 2018, at 1:40 AM, Bernd Neubig  wrote:
> 
> Hello,
> on the website of my company you can find a list of papers on the subject of 
> crystal measurement techniques.
> http://www.axtal.com/English/TechnicalNotes/TechnicalArticlesPublications/LiteratureaboutQuartzCrystals/
> 
> The actual standard procedure for crystal  measurement is by using modern 
> network analyzers with error correction, as given in the IEC publication 
> 60444-5. 
> A description of the method and its variants can be found in my 2012 paper 
> listed on the mentioned website.
> Enjoy
> 
> Bernd DK1AG
> 
> 
> -Ursprüngliche Nachricht-
> Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Brooke 
> Clarke
> Gesendet: Mittwoch, 23. Mai 2018 20:13
> An: tim...@timeok.it; Discussion of precise time and frequency measurement 
> 
> Betreff: Re: [time-nuts] 5950 Crystal impedance meter manual
> 
> Hi Luciano:
> 
> I have some web pages about crystals and testing them:
> http://www.prc68.com/I/CrystalImpedanceMeters.html - Crystal Impedance Meters 
> (Saunders 150) http://www.prc68.com/I/Xtal.shtml#TE - Crystals in general & 
> Test Equipment (see Trivia below) http://www.prc68.com/I/Xam.html - Crystal 
> Activity Meters http://www.prc68.com/I/Xec.shtml - Equivalent Circuit 
> http://www.prc68.com/I/4395A.shtml#ZT - The Z transform method is also used 
> in commercial crystal test sets like the HP E4915, E4916, E5100.
> 
> Trivia: The HP 4194 may be the only instrument that can really characterize 
> watch crystals ( 32768 Hz) for impedance which is in the meg Ohms range.  
> Some of the HP network analyzers can fit swept frequency data into an 
> equivalent crystal equivalent circuit.
> 
> --
> Have Fun,
> 
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> 
>  Original Message 
>>Hi all,
>>I found this Crystal Impedande Meter produced by RFL Industries inc, 
>> Boonton.
>>I would like to understand how to use it and I do not have any 
>> documentation.
>>I'm not even able to figure out if it works properly.
>>I would like to ask you if someone owns the service/operating manual and 
>> can share it with me.
>>Look at the picture thanks
>>Luciano
>> 
>> 
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Re: [time-nuts] TrueTime XL-AK Issues

[Bob kb8tq]

Hi

My guess would be that they are not in a mode that allows them to lock. Some
GPSDO’s require a “start” command. Others hold off locking until a site survey
is complete ( or they have verified the last survey is correct ).

Bob

> On May 23, 2018, at 1:31 PM, Richard Solomon  wrote:
> 
> I have had two of these sitting on the shelf for years. Today I decided to 
> see if they work.
> 
> It's a slow week !!
> 
> 
> I hooked them up to my external GPS Antenna through my Symmetricon Splitter 
> and
> 
> looked at the 10 MHz output on my HP 5334B (reference input derived from a 
> Trimble
> 
> T-Bolt).
> 
> 
> They both show a number of Satellites, but one reads 4.7 Hz low while the 
> other reads
> 
> 1.3 Hz low. I expected better.
> 
> 
> Any thoughts on what would cause such a large deviation from 10 Mhz ?
> 
> 
> Thanks for any replies,
> 
> 
> 73, Dick, W1KSZ
> 
> 
> Sent from Outlook
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Re: [time-nuts] 5950 Crystal impedance meter manual

[Bob kb8tq]

Hi

Gizmo’s like that were very common in the days before network analyzers became 
good enough to measure a crystal. They always were a troublesome item to keep 
running accurately. Without accuracy, their value was a bit limited. Every 
place I 
know of had a big drawer ( or cabinet ) of “magic crystals”. You plugged them in
and adjusted the instrument until they all read as they should. One could easily
challenge this in terms of accuracy. It did ensure that all the meters in the 
plant 
had some chance of reading the outgoing product the same way. 

So - you don’t just need the manual, you also need the batch of calibration 
crystals
(and their data) that went with it. Then you can duplicate the readings from 
whatever 
factory used it ….

Lots of fun !!!

Bob

> On May 23, 2018, at 4:44 AM, tim...@timeok.it wrote:
> 
> 
>   Hi all,
>   I found this Crystal Impedande Meter produced by RFL Industries inc, 
> Boonton.
>   I would like to understand how to use it and I do not have any 
> documentation.
>   I'm not even able to figure out if it works properly.
>   I would like to ask you if someone owns the service/operating manual and 
> can share it with me.
>   Look at the picture thanks
>   Luciano
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Re: [time-nuts] Sawtooth correction: next or previous PPS

[Bob kb8tq]

Hi

> On May 21, 2018, at 9:13 PM, Hal Murray  wrote:
> 
> 
> hol...@hotmail.com said:
>> One thing to look out for when messing with sawtooth messages is the
>> question of does the message come out before or after the PPS pulse...  good
>> look finding the answer in the receiver documentation... 
> 
> Has anybody asked the manufacturers?

At least in the framework of Furuno and myself … yes. Not via email but face to 
face
with their head of design engineering. 

> 
> This should be easy to see if you record the PPS offset referenced to a good 
> clock and compare that to the reported offset.  

The real simple answer is that you have four cases. Pulse before vs pulse after 
plus
adds or subtracts. That’s not so may that you can’t just try it and see. It 
turns out to 
be very obvious when you get the right one. 

Bob


> If the frequency is stable 
> and you are getting a sawtooth (rather than a bridge) then a point on a 
> corrected graph next to the jump in the sawtooth will look good if you have 
> it right or be off by a clock cycle if you have it wrong.
> 
> 
> hol...@hotmail.com said:
>> "After" seems to be the most common answer.  That makes hardware/delay line
>> compensation rather tricky.  ...
> 
> The slides from Tom Clark and Rick Hambly's VLBI talk (page 29) show a before 
> setup.
>  http://www.gpstime.com/files/TOW/tow-time2015.pdf
> 
> You said "most common".  That implies there are both types.  (or 
> documentation errors)  We should make a list of which GPS modules do it which 
> way.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Simple answer on any GPSDO is always “that depends”. The sawtooth correction
improves the PPS into the device by at least an order of magnitude on most GPS
modules. Less noise in pretty much always equates to less noise out. It also 
takes 
care of hanging bridges ( sawtooth stuck to one side) that will pass through 
just about
any control loop. The Furuno GT-87 parts are a bit of an exception to the rule. 
They 
only improve by about 3 to 5X when sawtooth correction is applied. Yes that’s 
looking 
at a 1 second measure. As you get out to 100,000 seconds things get a bit 
muddier. 
You also are down in the parts in 10^-13 ( or lower) range so it may or may not 
be that 
big a deal. With most designs, the emphasis is on “how fast can I cross over to 
GPS?”.
Once you get crossed over, the oscillator (or other flywheel) in your GPSDO 
really
does not matter. Getting that done at 100 seconds vs 1,000 *is* a big deal.

Bob

> On May 21, 2018, at 5:11 PM, Chris Caudle  wrote:
> 
> On Mon, May 21, 2018 2:23 pm, Gary E. Miller wrote:
>> I look forward to your patch!
> 
> My GPSDO doesn't have sawtooth error, so limited interest for me.
> 
> How much does one of those u-blox modules cost?
> 
> How would  you tell if it made the gpsd performance better?  I think that
> question came up a couple of weeks ago,  most of the ways to check time
> stability involve hardware test equipment logging electrical signals, and
> there isn't a good way to get an electrical signal generated cleanly from
> the gpsd software clock.
> 
> Is there a way to have a timestamp log from another instance of a PPS
> driver (another meaning the first instance is the one in use by ntpd)?  So
> you could have a PPS driver log timestamps from a really high quality
> input signal, such that any variation in the timestamps was due to the
> clock variation and not from the input signal, and then see if the
> variation in timestamps was less after adding sawtooth correction to gpsd.
> That's the only idea I can up up with off the top of my head to check
> whether such a patch would actually improve the clock estimate noticeably.
> In essence this is like trying to build a GPSDO without being able to see
> the output of the oscillator directly, so the normal approach to measuring
> stability with TICC, counters, phase noise analyzers, etc. doesn't really
> work.
> 
> -- 
> Chris Caudle
> 
> 
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Backing up a bit ….

If this is all about a system that can quantize to 52 ns at best … your ADEV
plot shows everything *well* below that at all offsets you display. If you 
assume
a +/- 1 LSB sort of quantization, you are out to 104 ns. That’s 10X anything on
the plot. You would very much need to dig into just how the i/o structure on the
device actually handles asynchronous inputs to be sure of what it really is 
doing. 
There are a lot of “debounce / re-synch” sort of structures that get pasted 
into 
devices these days.

Bob

> On May 21, 2018, at 3:21 PM, Gary E. Miller  wrote:
> 
> Gregory!
> 
> On Mon, 21 May 2018 19:06:17 +
> Gregory Maxwell  wrote:
> 
>> My best guess is that the magnitude of sawtooth error is just not
>> large enough to matter for typical applications of linux PPS.
> 
> No need to guess.  I recently posted that the RasPi 3B granularity is
> 52 nano Seconds and the PPS offset reported by UBX-TP is double that!
> 
> So, clearly it matters.
> 
> I'll do more data logging to get harder numbers.
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] Motorola GPS Antenna?

[Bob kb8tq]

Hi

Since timing is everything to TimeNuts ….. :)

The Motorola TV plant ( known as the Franklin Park North plant, not to be 
confused with Franklin Park South where they made
…. errr ….. oscillators ) to Panasonic in 1974. The whole transaction came as 
quite a shock to the people involved. The guy running
the division was very much caught off guard….. He happened to be presenting to 
a group of us the day after the announcement ….

The Panasonic cell tower timing antenna shows up under a *lot* of different 
labels. They do indeed sell it under the Panasonic brand
name as well. It is regarded as reasonably bullet proof in terms of blocking 
cell tower RFI.

Bob

> On May 21, 2018, at 2:56 PM, Gregory Beat  wrote:
> 
> Motorola has worked with Matsushita Electric Industrial Co., Ltd (now known 
> as Panasonic Corporation) since 1960s.  Motorola sold their television 
> division to Matsushita in 1970.
> —
> I believe that Motorola and Panasonic jointly developed this GPS antenna. 
> While Motorola exited the GPS receiver business over a decade ago, Panasonic 
> continued to OEM the VIC-100 antenna.
> 
> Synergy has a product page and data sheet for the Panasonic VIC-100 antenna.
> http://www.synergy-gps.com/index.php?option=com_content=view=139=114
> 
> greg, w9gb
> 
> Sent from iPhone 6s
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

> On May 21, 2018, at 2:08 PM, Gary E. Miller <g...@rellim.com> wrote:
> 
> Yo Bob!
> 
> On Mon, 21 May 2018 14:00:41 -0400
> Bob kb8tq <kb...@n1k.org> wrote:
> 
>>>> Ok, are you trying to hold close to UTC or simply have a second
>>>> that is as close to 1 second as possible?  
>>> 
>>> Yes.  One follows the other.  
>> 
>> Not really, you can have a source of seconds that are all within 0.1
>> ns of the right length but are offset from UTC by 200 ns. ( stable
>> but not accurate)
>> 
>> You can have a series of seconds that are all within 10 ns of UTC,
>> but one may be 20 ns to short and the next is 20 ns to long.
>> ( accurate but not stable )
>> 
>> So, which of the two is more important?
> 
> UTC is most important (to me), but if one has perfect UTC, then one also
> has perfect seconds.


Except that you are doing a design. That involves tradeoffs. Pre-processing a 
thing message
that comes in 800 ms before a pulse does not sound like a big deal to me. In 
your design it
apparently *is* a big deal. If you indeed want very tight UTC, that involves 
very similar
sorts of things. There are a *lot* of delays to be worked out. The offsets 
between GPS time
and UTC need to be downloaded and summed into the servo as well. 

A GPSDO ( or anything that works like one) will have accurate second to second 
timing. In a 
very general sense, it does not care about a time offset. A fixed delay of 100 
ns is no different 
than a fixed delay of 200 ns as far as it’s output or it’s function. 

So, no, it’s not a drop dead simple choice.

Bob 

> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi



> On May 21, 2018, at 1:44 PM, Gary E. Miller <g...@rellim.com> wrote:
> 
> Yo Bob!
> 
> On Mon, 21 May 2018 13:41:08 -0400
> Bob kb8tq <kb...@n1k.org> wrote:
> 
>> Ok, are you trying to hold close to UTC or simply have a second that 
>> is as close to 1 second as possible?
> 
> Yes.  One follows the other.

Not really, you can have a source of seconds that are all within 0.1 ns of the 
right length but are 
offset from UTC by 200 ns. ( stable but not accurate)

You can have a series of seconds that are all within 10 ns of UTC, but one may 
be 20 ns to short
and the next is 20 ns to long. ( accurate but not stable )

So, which of the two is more important?

Bob

> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Ok, are you trying to hold close to UTC or simply have a second that 
is as close to 1 second as possible?

Bob

> On May 21, 2018, at 1:33 PM, Gary E. Miller <g...@rellim.com> wrote:
> 
> Yo Bob!
> 
> On Mon, 21 May 2018 10:39:33 -0400
> Bob kb8tq <kb...@n1k.org> wrote:
> 
>>> Yeah, which does me zero good real time.  I'm putting the PPS into a
>>> TICC.  My TICC has not way to accept real time corrections.  So that
>>> does me no good, except as a post processing step.
>>> 
>> 
>> You have a *something* to read the TICC output it does not just do it
>> all on it’s own.
> 
> Yes, but by then it is not real time.  My real goal is to improve
> Linux time.  I'm not holding my breath for a kernel module that
> takes the corrections.  Someday.
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Ok so they changed that from the earlier parts. Time marches on. 

Bob

> On May 21, 2018, at 1:08 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> You have always been able to poll the time offset message on any of the uBlox
>> modules. Getting that message to auto repeat was the traditional issue on 
>> there
>> earlier products. A serial dump would tell you if u-center is getting the 
>> information
>> by polling or not.
> 
> Thanks for the information. I have checked the console dump (of the NEO-6M 
> module), it does not poll for TIM-TP, the message is sent automatically 
> (after enabling in u-center).
> 
> Oleg 
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Re: [time-nuts] Improving ocxo temp control

[Bob kb8tq]

Hi

There are a lot of reasons an OCXO drifts. Temperature control is rarely the 
issue. 
More likely you are looking at the drift / wander characteristics of the 
crystal ( and 
components) in the OCXO. The simple answer is to leave it on for a while ( like 
weeks)
to allow things to settle out a bit. 

The paper that Rick tossed up last week is a pretty good one in terms of 
temperature
control issues in an OCXO and what the issues are. 

This all assumes you are in a fairly benign environment. If you have lots of 
drafts, put a 
cardboard box over the unit to shield it. If you room temperature is all over 
the place, then
there are a lot of ways to get to ~ 1 or 2C sort of stability in a lab. What 
you do depends
a *lot* on what your situation is.

=

So, assuming you *do* want to improve the temperature control:

First you need to take out what’s in there now. If it’s wandering around get 
rid of it. This
involves tearing apart the OCXO.

Now take a look at Rick’s paper and redesign the thermal enclosure. Get the 
heater placement
and sensor placement right and feed that into a simple controller. 

Run some tests over temperature and check out the data. It’s likely your first 
guess at things 
is not going to be correct.

Try to optimize the heat sources and sensors and re-test the result. Everything 
interacts so
this is not a quick process.

Once you are reasonably happy with where things are, start looking at a more 
fancy controller.
A simple approach would be feeding thermistor voltage into some 24 bit ADC’s 
and then
processing the result with an MCU. 

Ok so that’s all a bit much.

=

What happens if you mess with the OCXO from the outside of the package? 

You change the heat loss out of the package. This increases the thermal gain. ( 
less power
to increase the oven temperature by 1 C ). Assuming the original circuit was 
balanced 
out, you have made things worse rather than better. 

Ok so you do an enclosure with a fan it it so the heat loss doesn’t get less. 

You now have more heat loss and the same issue applies. In addition the fan and 
it’s
nonsense probably haven’t done the poor little OCXO any good.

When one designs a double oven, the inner oven is optimized for performance 
*with* 
the outer oven present. Equally, the outer oven is optimized for performance 
with the
heat load (and dynamics) of the inner oven. 

=

Assuming you still want to head down this road, temperature controllers are no 
different 
than any control loop. The first place to start is a textbook on control loops 
and control 
theory. The basics of what a loop does and the terminology are what you are 
after. Anything
advanced will assume you understand this part first. 

Next up are temperature sensors. Simple answer here is that a glass bead 
thermistor is
the way to go. For heat, transistors are the normal go-to device. The controls 
loop takes
in the thermistor output and spits out a voltage to change the current through 
the transistor.

If you have the money for software licenses, the next stop is some good 
mechanical CAD
that will feed into thermal modeling. From that you can work out a proper heat 
flow and
gradient design. Assuming that is a bit to expensive, you are back to trial and 
error. There 
are no “just duplicate this” designs that I know of. 

Once you have the structure, sensors, heaters, and control you toss it into a 
temperature 
test chamber. That may be something fancy or something you put together. You 
run the
gizmo over temperature and observe what it does. You then optimize the P,I,D 
coefficients
in your control loop. Indeed you may not have all of them or you may have an 
extra one. 

===

Of course one could simply shop for a $20 OCXO on eBay. Even if you have to buy 
a
dozen before you find a good one, it’s still cheaper / faster / easier / more 
likely to succeed 
than all the nonsense above. If this is a commercial design for a product you 
are going 
to sell, that does not work very well. The same fundamental answer applies. If 
you need
better performance, shop for a better oscillator. 


Lots of fun 



> On May 21, 2018, at 12:23 PM, Club-Internet Clemgill 
> <clemg...@club-internet.fr> wrote:
> 
> Thanks for your interesting replies.
> What I am actually trying to do is the following: 
> I bough a small ocxo (size of half a ping-pong ball) that performs well 
> (Abracon / AOCJY3_B 10Mhz)
> Reaching about 5*10E-11 kind of MDEV at low point ("kind of"… because a I use 
> an HP52132a as input to Timelab)
> But it’s frequency is slowly drifting with time, with a quasi linear slope. 
> I wondered if placing it in a third ovenized enclosure could improve things. 
> I tried a few experiments but seems that the temp needs to be very accurately 
> controlled. 
> Any similar experience ? 
> Could you suggest papers describing high performance analog or digital 
> controllers ? 
> Thx, 
>

Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

You have always been able to poll the time offset message on any of the uBlox 
modules. Getting that message to auto repeat was the traditional issue on there
earlier products. A serial dump would tell you if u-center is getting the 
information 
by polling or not. 

Bob

> On May 21, 2018, at 11:05 AM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> Not by default You go through the 390 pages of their manual and eventually
>> find the bits to turn this and that on. When you do, those magic bits will 
>> enable
>> the data on a T version and will not enable it on a non-T version. At least 
>> that’s
>> the way it’s worked since the LEA-4T …
> 
> You can use uBlox u-center software to enable and disable messages you need, 
> the configuration can be saved.
> 
> It looks like the NEO-M8N (non timing one) module should provide sawtooth 
> correction data (at least the manual does not say that TIM-TP message is 
> available on timing modules only). I was able to enable TIM-TP message on the 
> older NEO-6M. You can test if it works with the help of u-center.
> 
> Best!
> Oleg 
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi


> On May 20, 2018, at 11:49 PM, Mark Sims  wrote:
> 
> I think what Gary really wants is a GPS receiver with the most stable PPS 
> output available.


Unfortunately that’s not how any of these devices are designed to be used. They 
all ( including the
Furuno ) have a sawtooth issue. It’s just how the fundamental process inside 
them works.

>  That is probably the Furuno GT-8736... 1.7 nsec sawtooth error.  Typical PPS 
> span is +/- 4 nsec.   Also, the Trimble Thunderbolt has 0 sawtooth error.

The TBolt is a GPSDO, which is a very different beast. It takes the “sawtooth" 
error it measures and shoves
it into the control loop for the OCXO. The net result is a zero average error 
vs GPS. That’s how all phase
lock based GPSDO’s  do things. 

The tradeoff is the magic word “average” that snuck in there. Depending on the 
control loop parameters 
( and a few other things ) the time out of the GPSDO may be off from GPS time 
by quite a bit. If “time 
right now” is what you are after ( this is TimeNuts after all ), a GPSDO may 
not be the ideal answer ….
If “time right now” is the goal, the real time clock corrections you can grab 
on the internet may well be
part of the total solution. 

Bob

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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi


> On May 20, 2018, at 10:58 PM, Gary E. Miller <g...@rellim.com> wrote:
> 
> Yo Bob!
> 
> On Sun, 20 May 2018 22:53:37 -0400
> Bob kb8tq <kb...@n1k.org> wrote:
> 
>> If you look at the section under “timing (page 79)” in the uBlox
>> manual you will find all the fun stuff that makes the T different.
>> One of the timing messages includes the time offset between the pps
>> output and the real GPS time solution. Page 351 and after are the
>> time related commands. The stuff back around page 358 looks like it’s
>> got the sawtooth data in it.
> 
> Yeah, which does me zero good real time.  I'm putting the PPS into a
> TICC.  My TICC has not way to accept real time corrections.  So that
> does me no good, except as a post processing step.
> 

You have a *something* to read the TICC output it does not just do it all 
on it’s own.

The same something at the same time gets the same data on the same
pulse to correct it. That’s real time. That device does the math for the 
correction and presents it instantaneously. That is very much real time.

>> Bottom line is that with the sawtooth correction applied, you can get
>> down to below 1x10^-9 at one second on your plot.
> 
> Yeah, which does me no good real time.
> 
>> The T version will
>> automatically output the magic message with the data in it. 
> 
> Not seeing it by default.

Not by default You go through the 390 pages of their manual and eventually
find the bits to turn this and that on. When you do, those magic bits will 
enable
the data on a T version and will not enable it on a non-T version. At least 
that’s
the way it’s worked since the LEA-4T …

Bob


> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Ok, let’s back up a bit. The market for “timing” GPS modules is in GPSDO’s and
similar devices. Your local network hub or cell tower is very much in a fixed 
location. 
They don’t put them in backpacks. Survey in and position lock is how it’s done,

The sawtooth is the error between the arbitrary ( locked to the TCXO) PPS edge 
and
the “real time” of the PPS edge. The reason it is commonly called sawtooth is 
the shape
of the data that comes out went plotted vs time. The sawtooth can get into a 
problem known
as a hanging bridge when the “tooth” reverses in mid transition.

If you look at the section under “timing (page 79)” in the uBlox manual you 
will find all the fun stuff
that makes the T different. One of the timing messages includes the time offset 
between
the pps output and the real GPS time solution. Page 351 and after are the time 
related commands.
The stuff back around page 358 looks like it’s got the sawtooth data in it.

Using the sawtooth information involves running it into either a control loop ( 
the normal
case in a GPSDO ) or into some sort of controlled delay line ( far less common 
). You need
the information every second to feed into the loop along with your measured 
phase information. 

There are tons of information about all of this in the archives. There are also 
a lot of posts
that probably will do a more in depth job of bringing you up to speed on all 
the various
terms and issues.

Bottom line is that with the sawtooth correction applied, you can get down to 
below
1x10^-9 at one second on your plot. The T version will automatically output the 
magic
message with the data in it. 

Bob

> On May 20, 2018, at 10:06 PM, Gary E. Miller <g...@rellim.com> wrote:
> 
> Yo Bob!
> 
> On Sun, 20 May 2018 19:26:33 -0400
> Bob kb8tq <kb...@n1k.org> wrote:
> 
>> The “big deal” features on the T series are the ability to do single
>> satellite timing
> 
> Which I always thought was pointless, that only works for a fixed
> antenna.  Any GPS in a fixed position lab will have a good rooftop
> antenna with clear skyview.
> 
>> and the auto output of the sawtooth correction
>> information. Cranking sawtooth correction into your data will move
>> the line down most of the way to the “JL” line.
> 
> Except that requires a post process step, so not useful for real time.
> 
> I just looked at the 'U-blox 8 Receiver Description' and it makes no
> mention of sawtooh anything.  Is that in a different doc?
> 
> I'll also test Surevey-In mode to see how much that helps.
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

Just as a reference point, one can get 0.006/0.006/0.012 sort of errors with a 
fairly rotten antenna
and 24 hours of data from a 2004 era L1 / L2 receiver. One key consideration is 
that the error bars on the 
“estimated locations” of the reference stations are close to those numbers. 

Bob

> On May 20, 2018, at 8:22 PM, Mark Sims  wrote:
> 
> The main significant difference between the M8N and M8T is the fact that the 
> M8T can output raw data (and sawtooth).   The hardware is the same so there 
> should not be much difference PPS wise between the two.
> 
> I have Lady Heather's RINEX writer working pretty well.  Tested with the 
> LEA-4T/5T/6T, the Furuno GT87, the NVS-08, and the Ashtech Z12 (with L1 and 
> L2 data).   It supports GPS/SBAS/GLONASS/GALILEO (with hooks for future 
> BEIDOU) observations).  GLONASS and GALILEO have not yet been tested with the 
> M8T...  I'm still waiting for the M8T to arrive.  It currently outputs RINEX 
> 2.11 format with some hooks for future v3.03 support.
> 
> L1 only results with 24 hours of observations and "ultra rapid" orbits yield 
> error estimates in lat/lon/alt of around 0.15/0.15/0.3 meters pk-pk.  With 2 
> hours of data the errors are around twice that.  L1/L2 with the Z12 were 
> 31/40/88 mm (antenna is in a TERRIBLE  location).
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Re: [time-nuts] ✘NEO-M8N vs. NEO-M8T

[Bob kb8tq]

Hi

The “big deal” features on the T series are the ability to do single satellite 
timing and the auto output of the sawtooth correction information. Cranking 
sawtooth correction into your data will move the line down most of the way 
to the “JL” line.

Bob

> On May 20, 2018, at 7:03 PM, Gary E. Miller  wrote:
> 
> Time-nuts!
> 
> I have heard for a long time to use the u-blox Time Sync products, instead
> of the basic GPS products, for precisin time.
> 
> So I ordered a NEO-M8T and compared it against a plain NEO-M8N.  Tests
> done using a TAPR-TICC and a JL GPSDO for reference.  All tests using the
> same antenna and 12 hours of data.
> 
> The results were disappointing.  See attached.  For 8x the price all I
> see is a slightly flatter ADEV curve.
> 
> The M8T also support raw data, so I can try to use it for RINEX files.
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] Cesium Clock Avialable

[Bob kb8tq]

Hi

At least these days, a 5071 comes back from the factory with the same Hazmat 
labels 
on it as it ships into their factory with. 

Bob

> On May 19, 2018, at 4:43 PM, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:
> 
> 
> In message <b17ed93d-0178-456f-b448-a93697e44...@n1k.org>, Bob kb8tq writes:
> 
>> Cs is classified rightly as a hazardous substance. Transporting and shipping 
>> hazardous stuff is indeed regulated (as it should be). For various silly 
>> reasons
>> the minute amount of Cs inside a virtually indestructible container in a Cs 
>> standard  falls into the hazardous category. 
> 
> The reason for this is actually not very silly.
> 
> Very potent Cs137 sources are used in borehole characterization in
> disturbingly high numbers, and they are licensed and tracked by the
> relevant national regulatory agency, NRC.gov in the USA.
> 
> The HAZMAT regulations used to be different for Cs137 (nuclear
> concerns) and Cs133 (chemical concerns) but smartasses in the oil
> industry discovered lower costs if they "couldn't remember the
> number".
> 
> I belive HP used to have an exemption for shipping factory new
> CS-tubes *from* their factory, but not for shipping new or used
> tubes *to* their factory, because customers could not be trusted
> to pack according to spec.
> 
> -- 
> 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] Cesium Clock Avialable

[Bob kb8tq]

Hi

Well I *can* say that when you ship a 5071 back to be re-tubed, you *do* 
run into the Cs shipping rule. HP did a bunch of stuff to demonstrate that
there was near zero chance of a problem. Ultimately it had zero impact on
how the rules were written. 

I’m by no means trying to tell people not to ship Cs standards. I just want 
them to be aware of what the might run into. It’s not the risk from the Cs
that is the issue to me …..

Bob

> On May 19, 2018, at 3:49 PM, paul swed <paulsw...@gmail.com> wrote:
> 
> Bob
> I believe that the Cesium 133 as I recall actually isn't.
> There was a document from HP. But its been a long time.
> I will bet folks ship the 5061s all the time without a thought either way.
> Just saying. Neither right or wrong.
> 
> Regards
> Paul
> 
> On Sat, May 19, 2018 at 2:18 PM, Bob kb8tq <kb...@n1k.org> wrote:
> 
>> Hi
>> 
>> Ok …. errr …. shipping …. about that.
>> 
>> Cs is classified rightly as a hazardous substance. Transporting and
>> shipping
>> hazardous stuff is indeed regulated (as it should be). For various silly
>> reasons
>> the minute amount of Cs inside a virtually indestructible container in a
>> Cs
>> standard  falls into the hazardous category.
>> 
>> So, to properly ship a Cs standard, you need to be properly trained and
>> certified
>> as a Hazmat shipper. You then need to register that training certificate
>> with your
>> favorite shipper and verify that they accept the certificate. They then
>> come out
>> and check your paperwork system to be sure it’s up to the proper
>> standards.
>> Once all that is accomplished you can originate a shipment of a Cs
>> standard.
>> Yes, there are a couple of fees involved in all that.
>> 
>> If all that sounds trivial or easy …. it’s not. Figure on a coupe of
>> months to get
>> it all done. Once you do get it all done you can put a nice big Hazmat
>> label on
>> the package and ship it out ( with of course an added charge for handling
>> the rest of the process ). If you do it once you at least will know what
>> is needed
>> for the annual renewal of certification and re-inspection process. ( and
>> the fees
>> involved ….)
>> 
>> So ….e …. yes. The bottom line is that even if a railroad locomotive
>> hits
>> the UPS truck, you aren’t going to get Cs all over the place. The risk of
>> actually
>> hurting anybody with Cs is essentially zero. This whole shipping process
>> is
>> probably not as risky as crossing the street when the “don’t walk” sign is
>> flashing.
>> 
>> Be aware though that if you are shipping one and label it as a Cs
>> standard, ( without
>> all the proper Hazmat shipping certifications )  you may get into all
>> sorts of nonsense.
>> If somebody spots it ( and that has happened ) your package is not going
>> to get delivered.
>> If it is in transit when noticed ( = they already accepted it) It probably
>> is not going to get
>> returned to you. I’d bet you at least get a bill for disposing of it ….
>> 
>> Equally if you ship one and don’t do it properly there is a slight chance
>> of it getting
>> noticed ( think in terms of a damaged box that gets attended to ) …. at
>> that point
>> all sorts of nasty legal sorts of things could happen.
>> 
>> Just another of life’s little pieces of excitement ….
>> 
>> Bob
>> 
>>> On May 19, 2018, at 1:36 PM, paul swed <paulsw...@gmail.com> wrote:
>>> 
>>> Bobs
>>> Comments are on target.
>>> The Cesium can last a long time on the shelf. But (Always a but) other
>>> stuff in the tube tends to pollute the tube.
>>> This causes the high current when you start the system that may or may
>> not
>>> clear up.Some great time-nuts threads on the subject and how to attempt
>> to
>>> recover the tube.
>>> 
>>> In my experience after the tubes up and running and in a locked state.
>> The
>>> beam current is relative. About 20-40 is good.
>>> The issue is there are some settings that can totally fake this reading
>> out
>>> like the meter sensitivity. As the current goes down you see more of the
>>> noise floor of the system that deteriorates the quality. Funny fact
>>> Frankenstein 5060/61 mix has barely originally showed .5 on the beam
>>> current. Yet still locks. Today beam current is 0 and its still locks.
>> The
>>> tube was deemed dead when it was given to me. In comparing it to another
>>> much later 5061 it is indeed locked nicely.
>

Re: [time-nuts] Cesium Clock Avialable

[Bob kb8tq]

Hi

Ok …. errr …. shipping …. about that. 

Cs is classified rightly as a hazardous substance. Transporting and shipping 
hazardous stuff is indeed regulated (as it should be). For various silly reasons
the minute amount of Cs inside a virtually indestructible container in a Cs 
standard  falls into the hazardous category. 

So, to properly ship a Cs standard, you need to be properly trained and 
certified
as a Hazmat shipper. You then need to register that training certificate with 
your 
favorite shipper and verify that they accept the certificate. They then come 
out 
and check your paperwork system to be sure it’s up to the proper standards. 
Once all that is accomplished you can originate a shipment of a Cs standard. 
Yes, there are a couple of fees involved in all that. 

If all that sounds trivial or easy …. it’s not. Figure on a coupe of months to 
get
it all done. Once you do get it all done you can put a nice big Hazmat label on
the package and ship it out ( with of course an added charge for handling
the rest of the process ). If you do it once you at least will know what is 
needed 
for the annual renewal of certification and re-inspection process. ( and the 
fees
involved ….)

So ….e …. yes. The bottom line is that even if a railroad locomotive hits
the UPS truck, you aren’t going to get Cs all over the place. The risk of 
actually
hurting anybody with Cs is essentially zero. This whole shipping process is 
probably not as risky as crossing the street when the “don’t walk” sign is 
flashing. 

Be aware though that if you are shipping one and label it as a Cs standard, ( 
without
all the proper Hazmat shipping certifications )  you may get into all sorts of 
nonsense. 
If somebody spots it ( and that has happened ) your package is not going to get 
delivered. 
If it is in transit when noticed ( = they already accepted it) It probably is 
not going to get 
returned to you. I’d bet you at least get a bill for disposing of it ….

Equally if you ship one and don’t do it properly there is a slight chance of it 
getting 
noticed ( think in terms of a damaged box that gets attended to ) …. at that 
point 
all sorts of nasty legal sorts of things could happen.

Just another of life’s little pieces of excitement ….

Bob

> On May 19, 2018, at 1:36 PM, paul swed <paulsw...@gmail.com> wrote:
> 
> Bobs
> Comments are on target.
> The Cesium can last a long time on the shelf. But (Always a but) other
> stuff in the tube tends to pollute the tube.
> This causes the high current when you start the system that may or may not
> clear up.Some great time-nuts threads on the subject and how to attempt to
> recover the tube.
> 
> In my experience after the tubes up and running and in a locked state. The
> beam current is relative. About 20-40 is good.
> The issue is there are some settings that can totally fake this reading out
> like the meter sensitivity. As the current goes down you see more of the
> noise floor of the system that deteriorates the quality. Funny fact
> Frankenstein 5060/61 mix has barely originally showed .5 on the beam
> current. Yet still locks. Today beam current is 0 and its still locks. The
> tube was deemed dead when it was given to me. In comparing it to another
> much later 5061 it is indeed locked nicely.
> 
> The option 004 tubes run hot and consume Cs more rapidly. Dead 004 tubes
> are pretty much dead.
> 
> As I recall in the manual there is a way to directly read the true beam
> current (If you actually have any) right off the tube.
> So some lucky sole in this tread will finally have a real ticking clock.
> Congrats and have fun. I think the darn clocks go for as much as Doug is
> asking. Shipping was about $130 or so from Az to Ma about a year ago when I
> picked up my 2nd 5061.
> I think this is a bit cheap as it came from a company that most likely gets
> a discount we don't.
> 
> Regards
> Paul
> WB8TSL
> 
> 
> On Sat, May 19, 2018 at 1:02 PM, Bob kb8tq <kb...@n1k.org> wrote:
> 
>> Hi
>> 
>> 
>> 
>>> On May 19, 2018, at 11:22 AM, Dana Whitlow <k8yumdoo...@gmail.com>
>> wrote:
>>> 
>>> Don't Cesium clocks have a beam current integrator of sorts so that it's
>>> possible
>>> to pretty accurately assess the remaining life of the tube?  If not, I'm
>>> terribly
>> 
>> Simple answer - no. The ones we are playing with came out *long* before
>> you could do
>> anything like that in a practical way. Even today I know of no atomic
>> standard made by
>> anybody that does something like that.
>> 
>> 
>>> surprised and disappointed.
>>> 
>>> Also, beginning with a new tube, roughly how long can one be run until it
>>> reaches exhaustion?  Are we speaking months, years, decades, or wh

Re: [time-nuts] Cesium Clock Avialable

[Bob kb8tq]

Hi



> On May 19, 2018, at 11:22 AM, Dana Whitlow <k8yumdoo...@gmail.com> wrote:
> 
> Don't Cesium clocks have a beam current integrator of sorts so that it's
> possible
> to pretty accurately assess the remaining life of the tube?  If not, I'm
> terribly

Simple answer - no. The ones we are playing with came out *long* before you 
could do
anything like that in a practical way. Even today I know of no atomic standard 
made by
anybody that does something like that. 


> surprised and disappointed.
> 
> Also, beginning with a new tube, roughly how long can one be run until it
> reaches exhaustion?  Are we speaking months, years, decades, or what?


Rated life on a high performance tube is in the 5 to 7 year range. I have 
indeed proven that
to be correct with a couple of tubes run on a 24/7/365 basis. A “standard 
grade” tube should
run for 2 or 3 times that long. A lot depends on exactly which model tube from 
what era and 
who made the specific tube. 

Tubes are not the only thing that dies in a Cs standard. The older ones ( = 
what we play with)
are mostly full of leaded parts described in manuals and schematics. They may 
not all be made
anymore, but various substitutes are out there. Also, chassis for Cs standards 
with dead 
tubes are pretty common. It’s the tubes we are most likely to run out of ….

Of course you *can* get a nice new tube from the factory. Last time I did that 
the bill was
about $38,000. That included them putting it in.

Bob

> 
> Dana
> 
> 
> On Sat, May 19, 2018 at 10:01 AM, Bob kb8tq <kb...@n1k.org> wrote:
> 
>> Hi
>> 
>> Unfortunately there really is no way to tell how much Cs is left in the
>> tube. You can
>> look at beam current and make a guess. All that really will tell you is
>> that the fuel
>> gauge is on empty or at least just off of empty.
>> 
>> Bob
>> 
>>> On May 19, 2018, at 2:30 AM, Paul Bicknell <p...@bicknells.f2s.com>
>> wrote:
>>> 
>>> Hi Doug
>>> 
>>> Is it possible to test its operation and
>>> can the time left on the cesium be calculated   Regards Paul
>>> 
>>> -Original Message-
>>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Doug
>> Millar
>>> via time-nuts
>>> Sent: 19 May 2018 05:04
>>> To: time-nuts@febo.com
>>> Subject: [time-nuts] Cesium Clock Avialable
>>> 
>>> Hi, I am willing to part with my HP 5061A cesium standard and manual. The
>>> unit was rebuilt and functioning some years ago and not used since then.
>>> There is usable cesium in the tube and the unit worked. I have not
>> tested it
>>> recently. It has a Patek-Philippe analogue clock in the front. The unit
>> is
>>> in great physical condition.  Asking $600 plus shipping from Long Beach,
>> CA.
>>> 90806
>>> I also have an ESI 242D resistance calibrator and a Julie primary
>> resistance
>>> standard in an oven. Let me know if you are interested. Very reasonable.
>>> Thanks, Doug K6JEY
>>> ___
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>>> 
>>> -
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2016.0.8048 / Virus Database: 4793/15670 - Release Date:
>> 05/19/18
>>> 
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>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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Re: [time-nuts] Cesium Clock Avialable

[Bob kb8tq]

Hi

Unfortunately there really is no way to tell how much Cs is left in the tube. 
You can 
look at beam current and make a guess. All that really will tell you is that 
the fuel 
gauge is on empty or at least just off of empty. 

Bob

> On May 19, 2018, at 2:30 AM, Paul Bicknell  wrote:
> 
> Hi Doug 
> 
> Is it possible to test its operation and 
> can the time left on the cesium be calculated   Regards Paul 
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Doug Millar
> via time-nuts
> Sent: 19 May 2018 05:04
> To: time-nuts@febo.com
> Subject: [time-nuts] Cesium Clock Avialable
> 
> Hi, I am willing to part with my HP 5061A cesium standard and manual. The
> unit was rebuilt and functioning some years ago and not used since then.
> There is usable cesium in the tube and the unit worked. I have not tested it
> recently. It has a Patek-Philippe analogue clock in the front. The unit is
> in great physical condition.  Asking $600 plus shipping from Long Beach, CA.
> 90806
> I also have an ESI 242D resistance calibrator and a Julie primary resistance
> standard in an oven. Let me know if you are interested. Very reasonable. 
>  Thanks, Doug K6JEY
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 
> 
> -
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2016.0.8048 / Virus Database: 4793/15670 - Release Date: 05/19/18
> 
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Re: [time-nuts] Improving ocxo temp control

[Bob kb8tq]

Hi

One key point about the need for “zero gradient”: 

Crystals and many other components are quite sensitive to thermal gradients. 
Very small 
fractions of a degree (as a gradient ) can have significant impact on the 
frequency of an 
oscillator. 

One of many “interesting things” about fiddling about OCXO’s. 

The equally frustrating thing about this is that unless you can tease kind 
paper authors
into posting things ( thanks Rick !!) the papers are behind pay walls. I pretty 
much despise
that practice. Referencing papers that send people off to spend money ….not so 
much.

Bob

> On May 19, 2018, at 12:03 AM, Richard (Rick) Karlquist 
>  wrote:
> 
> In my experience, the oven temperature controller is rarely
> the determining factor for static oven performance.  This article
> explains what the real determining factors are:
> 
> http://www.karlquist.com/oven.pdf
> 
> An analog oven temperature controller will be limited in
> its dynamics by how much capacitance you are able to
> design with.  Digital controllers get around this as well
> as having the capability of double integration for much
> better transient response.
> 
> Rick
> 
> On 5/18/2018 11:03 AM, Gilles Clement wrote:
>> Hi,
>> I am trying to improve performance of an OCXO.
>> Could you point me at a good design of a high resolution oven temperature 
>> controler please ? Preferably analog.
>> Thx much,
>> Gilles.
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Re: [time-nuts] Improving ocxo temp control

[Bob kb8tq]

Hi

There are a number of papers out and about about the limits on OCXO performance.
The bottom line is that coming up with a high resolution control circuit is the 
easy part
of the task.

Simple answer to the question: 

Set up a thermistor bridge and feed the difference into an op amp. Crank up the 
gain on
the op amp to whatever you feel comfortable running. 

Some simple numbers: 

Thermistor changes 3% / C 
Single thermistor bridge changes 1.5% / C
Output of the circuit will change the oven by 150C from power off to full on
Neglecting the scale factors for simplicity 
Put in a gain of 100 on the op amp

So, the bridge moves 1% and the controller goes from full off to full on. 
Crank in more gain “as required”. The op amp isn’t bothered until you get
into the millions.  

With the simplified numbers above, the circuit has a thermal gain of 150. 
Getting 
much past 300 with a single oven is unusual. 

Bob

> On May 18, 2018, at 2:03 PM, Gilles Clement  wrote:
> 
> Hi,
> I am trying to improve performance of an OCXO.
> Could you point me at a good design of a high resolution oven temperature 
> controler please ? Preferably analog.
> Thx much,
> Gilles.
> 
> 
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Re: [time-nuts] WTB: HP/Agilent/Symmetricom 58517A Distribution Amplifier

[Bob kb8tq]

Hi

What you really want is an LNA plus some filtering. MiniCircuits will sell you 
all sorts of 
“adequate” amplifiers. They show up surplus for reasonable prices. The key 
point is that 
ultra low noise figure it not needed. A 3db NF is just as good as 0.3 db in 
this case. The
antenna sets the noise for the system. ( unless you *really* run out of gain).

Bob

> On May 18, 2018, at 2:48 PM, Gary E. Miller  wrote:
> 
> Ole!
> 
> On Fri, 18 May 2018 20:31:22 +0200
> Ole Petter Rønningen  wrote:
> 
>> Just a heads up, in case you’re not concious of the fact; at least my
>> HP splitter (can’t recall model# off hand) is strictly L1 - many
>> others are wide band and will allow L2 and whatever else you might
>> later want.
> 
> I have had good luck with cheap chinese wide-band splitters.  No problems
> with L1, L2, GLONASS and more.
> 
> Like this one for $23:
> 
> https://www.ebay.com/itm/RF-coaxial-Power-Splitter-Divider-Combiner-SMA-2-way-800-2500MHz-signal-booster/282970977753
> 
> Also, mostly good luck with cheap Chinese DC injectors.  Some have had
> bad solder joints, easily fixed.
> 
> These have been good, for $9:
> 
> https://www.aliexpress.com/item/RF-Isolator-Bias-Feeder-Bias-Tee-10MHz-3GHz/32848444588.html
> 
> What I have not had luck with yet is finding a cheap LNA so I can recover
> the gain lost in the splitters.  The ones I have tested so far have all
> seriously degraded my SNRs.
> 
> Anyone know of a cheap and good L1/L2/etc. LNA?
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] WTB: HP/Agilent/Symmetricom 58517A Distribution Amplifier

[Bob kb8tq]

Hi

Well, a 4 port with 16 way splitters on each port is a *lot* of GPS devices……. 
Doing the
same with an 8 port is a lot of lot of devices :)

For a “over a hundred port” sort of solution, I think I would go with one of 
the custom GPS
amplifiers and then run passive splitters after that. It’s going to be very 
bulletproof and less
money than the prices you typically see on the 8 way HP devices. 

Given the way the HP amps do their thing, a passive splitter after a single amp 
is going to be
a lot closer to “equal access” than the HP device. 

Bob

> On May 18, 2018, at 10:35 AM, Clay Autery <caut...@montac.com> wrote:
> 
> Gotcha  and agree
> 
> The 58516a/58517a as the main distro amp allows me to power the antenna with 
> a separate supply (for many reasons).
> Essentially, I want to replace the 4-way with an 8-way amp with same power 
> setup.
> 
> Then if I want to cascade unpowered splitters from one or more unity gain 
> ports on the distro amp, I can do that.  
> 
> For much of what I am/will be doing, I want to be able to provide "equal 
> access" to antenna signal to designated devices to control variables somewhat.
> 
> *Clay Autery
> (318) 518-1389
> *
> On 05/18/18 08:50, Bob kb8tq wrote:
>> Hi
>> 
>> From what I have seen, it is a rare setup that requires all amplified 
>> distribution. Yes,
>> it is possible. Unless you are in that rare case, the MiniCircuits eight and 
>> sixteen port
>> splitters do a great job for *way* less money.
>> 
>> Bob
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Re: [time-nuts] WTB: HP/Agilent/Symmetricom 58517A Distribution Amplifier

[Bob kb8tq]

Hi

>From what I have seen, it is a rare setup that requires all amplified 
>distribution. Yes, 
it is possible. Unless you are in that rare case, the MiniCircuits eight and 
sixteen port
splitters do a great job for *way* less money.

Bob

> On May 17, 2018, at 10:33 PM, Clay Autery  wrote:
> 
> Need one of these:
> 
> *HP/Agilent/Symmetricom 58517A Distribution Amplifier (8 port)*
> 
> Ideally... actually definitely need the one with the external DC power input 
> with DC blocks on all 8 ports.
> 
> I have a 4-port, but it's going to be full by the end of the week.
> 
> 73,
> Clay, KY5G
> 
> -- 
> *Clay Autery
> (318) 518-1389
> MONTAC Enterprises*
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Re: [time-nuts] TruePosition GPSDO Holdover Issues

[Bob kb8tq]

Hi



> On May 15, 2018, at 3:52 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> One thing to consider - if you get far enough north, the “hole” closes and
>> you can get sat tracks from the other side of the north pole. Yes they are a
>> *long* ways away. It’s no worse than a lot of tracks that GPS thinks are
>> perfectly fine to use. For timing they aren’t going to do much good. They
>> will improve a navigation
> 
> Neat.  Thanks.  That raises several questions.
>  How high do satellites get if you are at a pole?
>  What is the best or worst latitude for timing?
>  What is the best/worst latitude for doing a survey?


The answer for both timing and survey is that you want to be on the equator as 
far
as sat elevation / tracks go. As long as you are “in the tropics” it is just 
about as good.

Bob


> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] TruePosition GPSDO Holdover Issues

[Bob kb8tq]

Hi

Most GPS antennas will do fine as close to the horizon as you would ever want 
to get. Tilting will 
simply make multi path worse. 

One thing to consider - if you get far enough north, the “hole” closes and you 
can get sat tracks from the
other side of the north pole. Yes they are a *long* ways away. It’s no worse 
than a lot of tracks that GPS
thinks are perfectly fine to use. For timing they aren’t going to do much good. 
They will improve a navigation
fix.

Bob

> On May 15, 2018, at 2:24 PM, gandalfg8--- via time-nuts <time-nuts@febo.com> 
> wrote:
> 
> 
> Yes, and we're quite a bit north of Hadrian's wall:-)
> 
> I've always been aware of the hole, it's just that I've always pointed GPS 
> antennas straight up without stopping before to consider whether or not 
> that's necessarilly the best option, but now it occurs to me that it might 
> not be for this location.
> 
> Whatever the optimum might be there's obviously going to be a limit but I do 
> think it might worth pursuing.
> 
> Web sites such as "In The Sky.org" can generate useful plots for any 
> specified location and time but I don't know if there's anything that will 
> allow building a projected map over a period, and I don't suppose there's 
> going to be anything anyway that allows experimatation with antenna angle 
> etc, so that really leaves using lady H to generate the plots in real time, 
> which she does do really well but for something like this might be akin to 
> watching grass grow:-)
> 
> Nigel, GM8PZR
> 
> 
> 
> 
> 
> 
> 
> 
> 
> -Original Message-
> From: Bob kb8tq <kb...@n1k.org>
> To: gandalfg8 <gandal...@aol.com>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com>
> Sent: Tue, 15 May 2018 17:44
> Subject: Re: [time-nuts] TruePosition GPSDO Holdover Issues
> 
> Hi
> 
> If you are in the northern hemisphere and looking at GPS satellite tracks, 
> there will always be a “hole”
> in the track plots to the north. The orbits do not cross either of the poles. 
> More or less they make it about
> to Hadrian’s Wall and that’s it.
> 
> Bob
> 
>> On May 15, 2018, at 12:38 PM, gandalfg8--- via time-nuts 
>> <time-nuts@febo.com> wrote:
>> 
>> 
>> Thanks Bob, and others, for comments on this.
>> 
>> From my observations with this running in position hold mode following a 
>> self survey, and based on previous experience in this location, my general 
>> impression is still that the TruePosition GPSDO does seem more prone to 
>> dropping into holdover than others I've used here under similar 
>> circumstances.
>> 
>> Having said that though, now running on a better sited antenna giving 
>> consistently higher signal strengths and with always at least 5 sats 
>> indicated, not counting PRN120:-), it hasn't dropped into holdover in the 
>> past 40 hours or so, so it is only under more marginal conditions that it 
>> would be evident.
>> 
>> As a bonus, the slightly tilted antenna is so far looking to be a reasonable 
>> success, with the hole to the north noticeably reduced and tending more to a 
>> closed circle and signal levels generally higher all round too, partially at 
>> least perhaps due to a change in antenna gain but either way another can of 
>> worms opened and begging further investigation:-)
>> 
>> Nigel, GM8PZR
>> 
>> 
>> 
>> 
>> From: Bob kb8tq <kb...@n1k.org>
>> Discussion of precise time and frequency measurement <time-nuts@febo.com>
>> Sent: Sun, 13 May 2018 19:05
>> Subject: Re: [time-nuts] TruePosition GPSDO Holdover Issues
>> 
>> Hi
>> 
>> When you are looking at timing, the SBAS / WAAS sat’s really don’t count as 
>> part of the total 
>> of 4 that you need for a basic fix. There also iis the subtle distinction of 
>> “tracking” vs “locked to”
>> on some devices. Tracking means we might get adequate data soon and locked 
>> means it is 
>> good enough to use on those devices.In that case, only the “locked” sats 
>> count towards the 
>> minimum of 4 that you must have. 
>> 
>> Past the minimum of 4 rule, most GPSDO’s also want to see that set of 
>> devices for some period
>> of time before they come out of holdover. You will drop in very quickly ( a 
>> second or two), but come
>> out slowly ( many minutes). Local noise can in some cases be enough to put 
>> you in holdover.
>> 
>> Bob
>> 
>>> On May 13, 2018, at 1:13 PM, gandalfg8--- via time-nuts 
>>> <time-nuts@febo.com> wrote:
>>> 
>>> The location at 

Re: [time-nuts] TruePosition GPSDO Holdover Issues

[Bob kb8tq]

Hi

If you are in the northern hemisphere and looking at GPS satellite tracks, 
there will always be a “hole”
in the track plots to the north. The orbits do not cross either of the poles. 
More or less they make it about
to Hadrian’s Wall and that’s it.

Bob

> On May 15, 2018, at 12:38 PM, gandalfg8--- via time-nuts <time-nuts@febo.com> 
> wrote:
> 
> 
> Thanks Bob, and others, for comments on this.
> 
> From my observations with this running in position hold mode following a self 
> survey, and based on previous experience in this location, my general 
> impression is still that the TruePosition GPSDO does seem more prone to 
> dropping into holdover than others I've used here under similar circumstances.
> 
> Having said that though, now running on a better sited antenna giving 
> consistently higher signal strengths and with always at least 5 sats 
> indicated, not counting PRN120:-), it hasn't dropped into holdover in the 
> past 40 hours or so, so it is only under more marginal conditions that it 
> would be evident.
> 
> As a bonus, the slightly tilted antenna is so far looking to be a reasonable 
> success, with the hole to the north noticeably reduced and tending more to a 
> closed circle and signal levels generally higher all round too, partially at 
> least perhaps due to a change in antenna gain but either way another can of 
> worms opened and begging further investigation:-)
> 
> Nigel, GM8PZR
> 
> 
> 
> 
> From: Bob kb8tq <kb...@n1k.org>
> Discussion of precise time and frequency measurement <time-nuts@febo.com>
> Sent: Sun, 13 May 2018 19:05
> Subject: Re: [time-nuts] TruePosition GPSDO Holdover Issues
> 
> Hi
> 
> When you are looking at timing, the SBAS / WAAS sat’s really don’t count as 
> part of the total 
> of 4 that you need for a basic fix. There also iis the subtle distinction of 
> “tracking” vs “locked to”
> on some devices. Tracking means we might get adequate data soon and locked 
> means it is 
> good enough to use on those devices.In that case, only the “locked” sats 
> count towards the 
> minimum of 4 that you must have. 
> 
> Past the minimum of 4 rule, most GPSDO’s also want to see that set of devices 
> for some period
> of time before they come out of holdover. You will drop in very quickly ( a 
> second or two), but come
> out slowly ( many minutes). Local noise can in some cases be enough to put 
> you in holdover.
> 
> Bob
> 
>> On May 13, 2018, at 1:13 PM, gandalfg8--- via time-nuts <time-nuts@febo.com> 
>> wrote:
>> 
>> The location at 55N, 5W, isn't ideal, there's quite a large hole to the 
>> north but this isn't something I've seen here before with any other GPS 
>> module or GPSDO.
>> 
>> When first noticed I'm sure it was whilst tracking six or seven sats, it was 
>> certainly five or more, which is why I commented in the first place, it was 
>> only later I thought there might be some correlation with it tracking low 
>> numbers.
>> 
>> There doesn't seem to be any adjustment for elevation mask on these, at 
>> least not via Lady H, but I've switched now from a flat survey antenna to a 
>> Symmetricom pod on a stub mast, so I can cheat a bit and angle it south 
>> slightly:-)
>> 
>> It'll take some time to build up a picture of the effect of that but it's 
>> tracking 8 sats at the moment.
>> Inmarsat-3, PRN120, seems to have joined in the mix now and keeps popping on 
>> and off the bottom of the list but I'm not sure whether or not that could 
>> contribute anything useful anyway.
>> 
>> Nigel, GM8PZR
>> 
>> 
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Re: [time-nuts] China, GCJ-02 & cartography

[Bob kb8tq]

Hi

Running with a very normal WGS-84 GPS “by the sea shore” can easily show you 
underwater. That
is very much a normal result of the model. It does not tell you what high (or 
low) tide level is going to 
be at your location. That stuff is simply to complex. 

The rest of it …… a lot of countries ( and states in the US ) run their own 
coordinate systems. It is 
not very unusual. Was *is* unusual is that the data providers for this or that 
have not re-normalized
the data. They have had to do that pretty much everywhere else ….

Bob

> On May 15, 2018, at 9:38 AM, Eric Scace  wrote:
> 
> The following was published on an email list to which I subscribe. Can others 
> on this list can shed more light on CGJ-02 vs WGS-84, and some of the 
> representations made in this article?
> 
> — Eric
> 
> The Problem with Chinese GPS
> If you’re in a foreign country and try to read a map, you may find it 
> difficult -- unless your host nation’s language is the same as your home 
> nation’s, the words are going to be different and, assuming you’re not 
> bilingual, will require some translation. But the locations of the roads, 
> rivers, buildings, and the like should be the same, regardless of whether the 
> map is in English, Spanish, or Chinese, right? Language aside, Google Maps 
> should work the same everywhere, right?
> 
> Well… no.
> 
> Pictured above is a map of the China/Hong Kong border via Google Maps; you 
> can see it yourself by clicking here 
> .
>  The map is your standard road map overlaid upon a satellite image. As you 
> can see, the roads -- the light grey lines -- don’t match up with reality. 
> There are roundabouts which purport to be in public parks, bridges which 
> don’t exist, and multi-lane highways which seem to be underwater. The whole 
> thing is a big navigational mess. Go far enough into Hong Kong, though, and 
> the problem abates.
> 
> What’s going on? The map data, basically, is being lost in translation.
> 
> The world -- China aside -- uses something called the World Geodetic System 
> 1984 
> 
>  (“WGS-84”) as the basis for the digital maps. Virtually all the navigation 
> tools we use online today -- the maps apps on our phones, the GPS systems in 
> our cars, the missile guidance systems in use by the military, and yes, 
> Google Maps -- all use WGS-84. China, though, goes its own way.
> 
> The Chinese use something called GCJ-02, an alternative system which the 
> cartography world colloquially refers to it as the “Mars Coordinates” as it 
> may as well be made for another planet. The Google Maps screenshot and link, 
> above, shows the problem: the road map data comes from the Chinese 
> government, which uses GCJ-02, but the satellite data is from a non-Chinese 
> source and uses WGS-84. (As China exerts control over, and takes 
> responsibility for mapping out the border between itself and Hong Kong, the 
> problem bleeds into the neighboring pseudo-sovereign state.) The two data 
> sets, effectively, are speaking different languages.
> 
> China isn’t just trying to be different, though; they’re trying to be 
> difficult. The government has long seen map data as a matter of national 
> security. There’s a “Surveying and Mapping Law of the People's Republic of 
> China 
> ”
>  which greatly restricts who can make maps. One needs a cartography license, 
> one which comes with many strings; if you’re creating digital map data, for 
> example, it needs to use GCJ-02 and has to be hosted on servers within China. 
> And this isn’t one of those anachronistic laws which go ignored and 
> unenforced. In 2015, for example, the country announced that those who 
> violate the law could face fines of 200,000 yuan (about $30,000 at the time) 
> and, according to CityLab 
> ,
>  “if the violation is deemed serious enough, [those who run afoul of th
 e law] can even find themselves booked on criminal charges.”
> 
> So why not just make a tool which translates GCJ-02 to WGS-84? Well, there 
> are a few, but they’re typically hard to come by and not all that reliable. 
> Multinational corporations like Google don’t want to deploy them as it could 
> hurt their standing with the Chinese government. And even if they did, the 
> results wouldn’t be great. GCJ-02 isn’t just an alternative coordinate 
> system; it’s an often unpredictable one. As Wikipedia explains 
> ,
>  “it uses an obfuscation algorithm which adds apparently random offsets to 
> both the latitude and longitude.” And 

Re: [time-nuts] Electronic Research Co. Precision Crystal Oscillator.

[Bob kb8tq]

Hi

Keep in mind that roughly 99.9% of all OCXO’s produced went into OEM specific 
applications
with spec sheets that reflected the OEM’s requirements. Both the OEM and the 
manufacturer 
had reasons to keep those documents private. In both cases it made it more 
difficult for 
competitors to “clone” the OCXO or end product. That protected the investment 
made in the
design (which was considerable). 

The first question on any surplus OCXO is - does the oven still work correctly? 
They can fail 
in several ways. When they do, repair involves tearing into the part. For 
maximum performance
one needs temperature test capability to “fine tune” the settings. (  = the 
circuitry has a residual 
temperature coefficient and the crystal is offset to null that out ). 

Next question generally is - can it be tuned on frequency? If so it has some 
use. 

Past that one would need to do ADEV and / or phase noise testing to work out 
what a specific 
example is still doing.

Yes this sounds like a lot of work. None of it is crazy hard in a basement 
setting. You do 
need to set up some gear to do it. Even that gear is not nutty to come up with 
….

Bob

> On May 14, 2018, at 5:48 PM, Dave B via time-nuts  wrote:
> 
> Hi.
> 
> A little while ago, I acquired an ERC EROS - 800-MIL-2  10MHz 24V
> powered OCXO, dated 95-23.
> 
> Well, it seems to work, and comparing with the trusty Thunderbolt, once
> warmed up and viewed on a dual channel 'scope, where one channel is
> triggered from one source, the drift relative to each other is some 16
> seconds for a full cycle of drift.
> 
> I've tried to lookup the spec of these things, and found surprisingly
> little, other than scan's of oriental data sheets, that of course
> neither I nor Google can translate.  But is that a reasonable sort of
> performance?
> 
> I have no idea what it came out of, but it's surprisingly lightweight,
> the outer casing get's "gently warm" after it's been powered on for an
> hour or so, but otherwise appears fine.
> 
> Is it worth keeping as a portable reference, or ???
> 
> Regards to All.
> 
> Dave B.  (G8KBV/G0WBX)
> 
> 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

> On May 14, 2018, at 1:50 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>>> If such conditions detected, I avoid problem by changing the counter clock. 
>>> But it does not solve the effects at "about OCXO" * N or "about OCXO" / M. 
>>> It is related to HW and I can probably control it only partially. I will 
>>> try to improve clock and reference isolation in the "normal" HW and of 
>>> cause I will thoroughly test such frequencies when that HW will be ready.
>> 
>> It’s a very common problem in this sort of counter. The “experts” have a lot 
>> of trouble with it
>> on their designs. One answer with simple enough hardware could be to run 
>> *two* clocks
>> all the time. Digitize them both and process the results from both.
> 
> I thought about such solution, unfortunately it can not be implemented 
> because of HW limitations. Switching 400MHz clock is also not ideal solution, 
> cause it will make trouble to GPS correction calculations, the latter can be 
> fixed in software, but it is not an elegant solution. It all still needs some 
> polishing...
> 
>> still have the issue of a frequency that is a multiple (or sub multiple) of 
>> both clocks.
> 
> The clocks (if we are talking about 400MHz) has very interesting values like 
> 397501220.703Hz or 395001831.055Hz , so it will really occur very rarely. 
> Also I am not limited by two or three values, so clock switching should solve 
> the problem, but not in elegant way, cause it breaks normal work of GPS 
> frequency correction algorithm, so additional steps to fix that will be 
> required :-\.
> 

What I’m suggesting is that if the hardware is very simple and very cheap, 
simply put two chips on the board.
One runs at Clock A and the other runs at Clock B. At some point in the process 
you move the decimated data
from B over to A and finish out all the math there ….


> BTW, after quick check of the GPS module specs and OCXO's one it looks like a 
> very simple algorithm can be used for frequency correction. OCXO frequency 
> can be measured against GPS for a long enough period (some thousands of 
> seconds, LR algorithm can be used here also) and we have got a correction 
> coefficient. It can be updated at a rate of one second (probably we do not 
> need to do it as fast). I do not believe it can be as simple. I feel I missed 
> something :)…

That is one way it is done. A lot depends on the accuracy of the GPS PPS on 
your module. It is unfortunately fairly easy to find
modules that are in the 10’s of ns error on a second to second basis. Sawtooth 
correction can help this a bit. OCXO’s have warmup
characteristics that also can move them a bit in the first hours of use. 

More or less, with a thousand second observation time you will likely get below 
parts in 10^-10, but maybe not to the 1x10^-11 level.

Bob

> 
> All the best!
> Oleg 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

> On May 14, 2018, at 5:25 AM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi Bob!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>>> I think it will be more than enough for my needs, at least now.
>>> 
>>>> From the 2.5 ns single shot resolution, I deduce a 400 MHz count clock.
>>> 
>>> Yes. It is approx. 400MHz.
>> 
>> I think I would spend more time working out what happens at “about 400  MHz” 
>> X N or
>> “about 400 MHz / M” …….
> 
> If such conditions detected, I avoid problem by changing the counter clock. 
> But it does not solve the effects at "about OCXO" * N or "about OCXO" / M. It 
> is related to HW and I can probably control it only partially. I will try to 
> improve clock and reference isolation in the "normal" HW and of cause I will 
> thoroughly test such frequencies when that HW will be ready.

It’s a very common problem in this sort of counter. The “experts” have a lot of 
trouble with it
on their designs. One answer with simple enough hardware could be to run *two* 
clocks
all the time. Digitize them both and process the results from both. …. just a 
thought …. You
still have the issue of a frequency that is a multiple (or sub multiple) of 
both clocks. With 
some care in clock selection you could make that a pretty rare occurrence ( 
thus making 
it easy to identify in firmware ….). 


Bob



> 
> All the best!
> Oleg 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi



> On May 13, 2018, at 5:13 PM, Oleg Skydan  wrote:
> 
> Hi Magnus,
> 
> From: "Magnus Danielson" 
>> I would be inclined to just continue the MDEV compliant processing
>> instead. If you want the matching ADEV, rescale it using the
>> bias-function, which can be derived out of p.51 of that presentation.
>> You just need to figure out the dominant noise-type of each range of
>> tau, something which is much simpler in MDEV since White PM and Flicker
>> PM separates more clearly than the weak separation of ADEV.
> 
> 
>> As you measure a DUT, the noise of the DUT, the noise of the counter and
>> the systematics of the counter adds up and we cannot distinguish them in
>> that measurement.
> 
> Probably I did not express what I meant clearly. I understand that we can not 
> separate them, but if the DUT noise has most of the power inside the filter 
> BW while instrument noise is wideband one, we can filter out part of 
> instrument noise with minimal influence to the DUT one.
> 
>> There is measurement setups, such as
>> cross-correlation, which makes multiple measurements in parallel which
>> can start combat the noise separation issue.
> 
> Yes, I am aware of that technique. I event did some experiments with cross 
> correlation phase noise measurements.
> 
>> Ehm no. The optimal averaging strategy for ADEV is to do no averaging.
>> This is the hard lesson to learn. You can't really cheat if you aim to
>> get proper ADEV.
>> 
>> You can use averaging, and it will cause biased values, so you might use
>> the part with less bias, but there is safer ways of doing that, by going
>> full MDEV or PDEV instead.
>> 
>> With biases, you have something similar to, but not being _the_ ADEV.
> 
> OK. It looks like the last sentence very precisely describes what I was going 
> to do, so we understood each other right. Summarizing the discussion, as far 
> as I understand, the best strategy regarding *DEV calculations is:
> 1. Make MDEV the primary variant. It is suitable for calculation inside 
> counter as well as for exporting data for the following post processing.
> 2. Study how PDEV calculation fits on the used HW. If it is possible to do in 
> real time PDEV option can be added.
> 3. ADEV can be safely calculated only from the Pi mode counter data. Probably 
> it will not be very useful because of low single shoot resolution, but Pi 
> mode and corresponding data export can be easily added.
> 
> I think it will be more than enough for my needs, at least now.
> 
>> From the 2.5 ns single shot resolution, I deduce a 400 MHz count clock.
> 
> Yes. It is approx. 400MHz.

I think I would spend more time working out what happens at “about 400 MHz” X N 
or 
“about 400 MHz / M” …….

Bob


> 
>>> I have no FPGA also :) All processing is in the FW, I will see how it
>>> fits the used HW architecture.
>>> 
>>> Doing it all in FPGA has many benefits, but the HW will be more
>>> complicated and pricier with minimal benefits for my main goals.
>> 
>> Exactly what you mean by FW now I don't get, for me that is FPGA code.
> 
> I meant MCU code, to make things clearer I can use the SW term for it.
> 
> Thank you for the answers and explanations, they are highly appreciated!
> 
> All the best!
> Oleg 
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Re: [time-nuts] GPS Timing Antenna Failure - Long

[Bob kb8tq]

Hi

The shape of the radome on your typical timing antenna is all because of birds. 
If the antenna is 60 feet up
a cell tower you do *not* want to have to pay a crew to go up there and knock 
the nest off of the  antenna. 

Even in the flatlands, you can get multipath. All it has to do is bounce off 
the ground and back to your antenna.
A wide open flat area actually is “ideal” for that particular type of problem ….

Bob

> On May 13, 2018, at 4:53 PM, Larry McDavid  wrote:
> 
> So there are 3D quadrifiliar GPS antennas; I am gratified to hear that as I 
> surely remember promotions for GPS antennas that showed a quadrifiliar design.
> 
> Regarding GPS multipath, I agree that is a problem. But, here on the 
> flatlands of Anaheim, I can stand on the roof of my 2-storey home (where the 
> GPS antennas are located) and be the tallest thing around for many miles. 
> Yes, there are surrounding LA area mountains, but those are miles and miles 
> away. Trees? This is Southern California! There are no tall trees anywhere 
> near me. There is little nearby to produce GPS multipath.
> 
> GPS receivers, at least in my GPSDO units, have an Elevation Mask option to 
> inhibit processing data from satellites near the horizon. I believe I set 
> those to 10 or 15 degrees.
> 
> The Symmetricom 58532A antenna does use a patch element and does not need the 
> cone-shaped radome to provide space for a quadrifiliar element. That cone 
> shape must be entirely for environmental reasons for it surely adds cost to 
> the antenna. Snow release? Beats me! There is snow atop Matterhorn Mountain 
> in nearby Disneyland but non falls here...
> 
> Larry
> 
> 
> 
> On 5/13/2018 5:20 AM, Azelio Boriani wrote:
>> Usually GPS antennas are patch antennas. The PROCOM GPS4 (I have 2 of
>> them) should be a real QFH (I haven't opened it to verify), the
>> Vaisala radiosonde RS92 has a real QFH. The Sarantel SL series seem is
>> a double helix not a classic QFH with the two different-size loops.
>> They name their series GeoHelix.
>> 
>> 
>> 
>> ...
> 
> -- 
> Best wishes,
> 
> Larry McDavid W6FUB
> Anaheim, California  (SE of Los Angeles, near Disneyland)
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

> On May 13, 2018, at 1:31 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi Bob!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> I guess it is time to ask:
>> 
>> Is this a commercial product you are designing?
> 
> No. I have no abilities to produce it commercially and I see no market for 
> such product. I will build one unit for myself, I may build several more 
> units for friends or if somebody will like it. I will show the HW details 
> when it will be ready.
> 
> What I gain doing it?
> 1. I will have a new counter that suits my current needs
> 2. I will study something new
> 
>> If so, that raises a whole added layer to this discussion in terms of “does 
>> it do
>> what it says it does?”.
> 
> This question is also important for amateur/hobby measurement equipment. I do 
> not need equipment that "does not do what it says it does" even if it is 
> build for hobby use.
> 
> The theme about *DEV calculations has many important details I want to 
> understand right, sorry if I asked too many questions (some of them probably 
> were naive) and thank you for the help, it is very appreciated! I hope our 
> discussion is useful not only for me.
> 

You are very much *not* the first person to run into these issues. They date 
back to the very early use of things like
ADEV. The debate has been active ever since. There are a few other sub debates 
that also come up. The proper 
definition of ADEV allows “drift correction” to be used. Just how you do drift 
correction is up to you. As with filtering, 
drift elimination impacts the results. It also needs to be defined ( if used)., 

Bob

> Thanks!
> Oleg 
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Re: [time-nuts] TruePosition GPSDO Holdover Issues

[Bob kb8tq]

Hi

When you are looking at timing, the SBAS / WAAS sat’s really don’t count as 
part of the total 
of 4 that you need for a basic fix. There also iis the subtle distinction of 
“tracking” vs “locked to”
on some devices. Tracking means we might get adequate data soon and locked 
means it is 
good enough to use on those devices.In that case, only the “locked” sats count 
towards the 
minimum of 4 that you must have. 

Past the minimum of 4 rule, most GPSDO’s also want to see that set of devices 
for some period
of time before they come out of holdover. You will drop in very quickly ( a 
second or two), but come
out slowly ( many minutes). Local noise can in some cases be enough to put you 
in holdover.

Bob

> On May 13, 2018, at 1:13 PM, gandalfg8--- via time-nuts  
> wrote:
> 
> The location at 55N, 5W, isn't ideal, there's quite a large hole to the north 
> but this isn't something I've seen here before with any other GPS module or 
> GPSDO.
> 
> When first noticed I'm sure it was whilst tracking six or seven sats, it was 
> certainly five or more, which is why I commented in the first place, it was 
> only later I thought there might be some correlation with it tracking low 
> numbers.
> 
> There doesn't seem to be any adjustment for elevation mask on these, at least 
> not via Lady H, but I've switched now from a flat survey antenna to a 
> Symmetricom pod on a stub mast, so I can cheat a bit and angle it south 
> slightly:-)
> 
> It'll take some time to build up a picture of the effect of that but it's 
> tracking 8 sats at the moment.
> Inmarsat-3, PRN120, seems to have joined in the mix now and keeps popping on 
> and off the bottom of the list but I'm not sure whether or not that could 
> contribute anything useful anyway.
> 
> Nigel, GM8PZR
> 
> 
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Re: [time-nuts] TruePosition GPSDO Holdover Issues

[Bob kb8tq]

Hi

Assuming the device has the “normal stuff” in it, it will look at the location 
in memory and
compare that to the current solution. If the solution is off by more than the 
limit, it will
reject it. If it rejects enough data ( = no good solution) it goes into 
holdover. Some devices
will operate down to a single satellite against a memorized position. That is 
not true of all
gizmos. Even with the “single sat” devices, there is a multi sat / bad location 
solution situation 
that will send you into holdover. 

Bottom line is that it usually is antenna location. Clear view of the sky and 
an appropriate 
elevation mask are what you are after.

Bob

> On May 13, 2018, at 10:27 AM, gandalfg8--- via time-nuts  
> wrote:
> 
> Ok, I give up
> 
> I've been logging this with Lady H and was watching again this afternoon as 
> the sat count dropped but this time there was no dropping into holdover as 
> the number of sats dropped from four to threedamn, it just carried on 
> doing its thing until the count went up again:-)
> 
> I'm still seeing the occasional reported random holdover event but am still 
> no nearer to knowing why.
> 
> Otherwise it's a nice unit and does handle the holdover well, even a longer 
> event yesterday whilst there was a supposed antenna fault didn't reflect into 
> the frequency plots, but time to call a halt for now.
> 
> Nigel, GM8PZR
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

I guess it is time to ask:

Is this a commercial product you are designing? 

If so, that raises a whole added layer to this discussion in terms of “does it 
do 
what it says it does?”.

Bob

> On May 13, 2018, at 3:07 AM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi Bob!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> It’s only useful if it is accurate. Since you can “do code” that gives you 
>> results that are better than reality,
>> simply coming up with a number is not the full answer. To be useful as ADEV, 
>> it needs to be correct.
> 
> I understand it, so I try to investigate the problem to understand what can 
> be done (if any :).
> 
>> I’m sure it will come out to be a very cool counter. My *only* concern here 
>> is creating inaccurate results
>> by stretching to far with what you are trying to do. Keep it to the stuff 
>> that is accurate.
> 
> I am interested in accurate results or at least with well defined limitations 
> for a few specific measurements/modes. So I will try to make results as 
> accurate as I can do/it can be done keeping simple hardware.
> 
> Thanks!
> Oleg 
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Re: [time-nuts] GPS Timing Antenna Failure - Long

[Bob kb8tq]

Hi

As mentioned a number of times, quadrafilar antennas were only popular for a 
very short
while back in the 1980’s. Once people started using GPS for “stuff” they 
rapidly lost out in
the antenna race. They were made popular by an early NIST paper. Later on NIST 
effectively 
said “oops !!” in reference to that paper. 

So yes, any modern GPS antenna is likely to be a patch antenna. Trimble and 
Novatel both 
have “exotic” antennas, but they still are fundamentally a patch. 

Why all of this? Multi-path.  You want to *reject* signals close to the horizon 
since they are
the ones most likely to be distorted by reflections.  Indeed choke rings and 
the various other
exotic approaches are all aimed at multiparty rejection by reducing gain at (or 
below) the horizon. 

Bob

> On May 12, 2018, at 4:07 PM, Larry McDavid  wrote:
> 
> I recently had an unexpected failure of a white-conical-dome HP/Symmetricom 
> 58532A GPS antenna that had been in-place about 5 feet above the roof of my 
> two-story home in Southern California for about ten years. I have two similar 
> GPS antennas located about ten feet apart on this roof, one fed with about 50 
> feet of Andrews Heliax and the other with LMR400; the other antenna continued 
> to work ok. The antennas feed 4x and 8x amplified GPS Source (brand name) 
> antenna splitters. I noticed the failure when several GPSDO units and a GPS 
> Clock failed to sync with the GNSS. I confirmed the failure was not the 
> antenna splitter and I replaced the failed GPS antenna one of the same type, 
> after which all returned to normal.
> 
> I removed the conical radome from the failed antenna and was surprised to 
> find the antenna element was actually a patch, not the quadrafilar I expected 
> under that conical dome. Subsequently I opened the radomes of three other 
> similar GPS timing antennas made by various manufacturers and found that all 
> use patch antennas. I had believed these timing antennas used a quadrafilar 
> design to benefit from higher low-angle gain.
> 
> So, it appears the conical radome shape is really only to prevent snow 
> accumulation. Well... from my experience here on the flatlands of Anaheim 
> near Disneyland, that seems to be completely effective as I've surely had no 
> snow buildup! :) But, I had surely expected the conical radome covered a 
> quadrafilar antenna. Am I alone in expecting a quadrafilar antenna?
> 
> Further troubleshooting of this failed antenna revealed many discrete 
> components on the underside of the round board holding the patch antenna. The 
> circuit uses a three-stage gain amplifier with three Toko bandpass filters, 
> numerous bypass capacitors and stripline inductors. Probing the circuit with 
> a sig gen and spectrum analyzer showed that all three gain stages were 
> working about as expected. Of course, even with 26-30 dB gain in the antenna, 
> the SA did not have enough gain nor low enough noise floor to see any GPS 
> signal from the antenna. But, each gain stage seemed to be working ok. So, 
> what was the failure?
> 
> Upon removing the radome, one unexpected thing was seen. The construction 
> uses a short coax cable up from the N connector, through a hole in the 
> circuit board, where it is bent over and finally soldered to circuit board 
> pads for the shield and center conductor. There was a great deal of very dark 
> flux residue around this coax solder connection. The appearance was so bad it 
> even looked like a cracked solder joint, though that proved not to be the 
> case when the flux residue was thoroughly removed. It did not occur to me to 
> functionally test the antenna at this point. Later, it was necessary to 
> unsolder this coax so the board could be removed to access the components on 
> the underside for detailed testing. But, stage-by-stage RF gain testing did 
> not reveal any problems, so the antenna was reassembled for actual field 
> testing.
> 
> The result? The antenna now works ok; locking sync to the GPS GNSS. I gotta 
> conclude the flux residue was attenuating the signal out of the antenna. 
> Careful inspection of that coax solder joint absolutely did not show any 
> problem after the flux was removed so I believe continuity was ok.
> 
> I next removed the radome from one of my (new) Symmetricom antennas to 
> inspect its coax solder joint and discovered this (perhaps newer) version has 
> a metal shield-can soldered over the coax solder pads; I am loathe to remove 
> that shield just to inspect the solder joint flux. However, there is no flux 
> evident on the solder tabs where the metal shield-can is soldered to the 
> circuit board so the whole thing must have been defluxed after soldering. 
> That would be a better process anyway.
> 
> To make this very long story into a short one, I learned that the 
> HP/Symmetricom 58532A GPS Reference (timing) antennas use a simple patch 
> antenna instead of a quadrafilar antenna and that old solder flux residue 

Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi


> On May 12, 2018, at 1:20 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> There is still the problem that the first post on the graph is different 
>> depending
>> on the technique.
> 
> The leftmost tau values are skipped and they "stay" inside the counter. If I 
> setup counter to generate lets say 1s stamps (ADEV starts at 1s) it will 
> generate internally 1/8sec averaged measurements, but export combined data 
> for 1s stamps. The result will be strictly speaking different, but the 
> difference should be insignificant.

Except here are a *lot* of papers where they demonstrate that the difference 
may be *very* significant. I would
suggest that the “is significant’ group is actually larger than the “is not” 
group. 


> 
>> The other side of all this is that ADEV is really not a very good way to 
>> test a counter.
> 
> Counter testing was not a main reason to dig into statistics details last 
> days. Initially I used ADEV when tried to test the idea of making the counter 
> with very simple HW and good resolution (BTW, it appeared later it was not 
> ADEV in reality :). Then I saw it worked, so I decided to make a "normal" 
> useful counter (I liked the HW/SW concept). The HW has enough power to 
> compute various statistics onboard in real time, and while it is not 
> requisite feature of the project now, I think it will be good if the counter 
> will be able to do it (or at least if it will export data suitable to do it 
> in post process). The rest of the story you know :)

Again, ADEV is tricky and sensitive to various odd things. This whole debate 
about it being sensitive goes 
back to the original papers in the late 1960’s and 1970’s. At every paper I 
attended the issue of averaging
and bandwidth came up in the questions after the paper. The conversation has 
been going on for a *long*
time. 

> 
>> If you are trying specifically just to measure ADEV, then there are a lot of 
>> ways to do that by it’s self.
> 
> Yes, but if it can be done with only some additional code - why not to have 
> such ability? Even if it has some known limitations it is still a useful 
> addition. Of cause it should be done as good as it can be with the HW 
> limitations. Also it was/is a good educational moment.

It’s only useful if it is accurate. Since you can “do code” that gives you 
results that are better than reality,
simply coming up with a number is not the full answer. To be useful as ADEV, it 
needs to be correct. 

> 
> Now it is period of tests/experiments to see the used technology 
> features/limitations(of cause if those experiments can be done with the 
> current "ugly style HW"). I have already got a lot of useful information, it 
> should help me in the following HW/FW development. The next steps are analog 
> front end and GPS frequency correction (I should get the GPS module next 
> week). I have already tested the 6GHz prescaler and now wait for some parts 
> to finish it. Hope this project will have the "happy end" :).

I’m sure it will come out to be a very cool counter. My *only* concern here is 
creating inaccurate results
by stretching to far with what you are trying to do. Keep it to the stuff that 
is accurate.

Bob


> 
> All the best!
> Oleg 
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Re: [time-nuts] Commercially available empty ovens for oscillator testing?

[Bob kb8tq]

Hi

There are places that sell them. Most are looking for a couple thousand dollars 
for 
one. If that is inside your budget you might get in touch with them. Far 
cheaper to
get an eBay scrap OCXO and use its parts. 

An OCXO depends on the combination of two things to make it stable:

1) The oven holds temperature well

2) The crystal in the oscillator is cut to be *very* flat temperature wise at 
the oven temperature. 

(yes there’s more to it than that, but we’re keeping things simple) 

Both are equally important if you are after the sort of thing you see in a 
normal OCXO. 
A typical oscillator may well have a crystal that is 100 to 1,000 times “less 
flat” than 
what is used in an OCXO. 

Bob

> On May 12, 2018, at 12:55 PM, Julien Goodwin  
> wrote:
> 
> Does anyone know if there's anyone who sells essentially just the oven &
> casing for an OCXO on its own?
> 
> I have a project for which I'm currently using a VCTCXO, but I'm
> wondering if enclosing a plain VCXO, plus the control DAC & voltage
> reference in a single small oven would end up more stable, and possibly
> not even much more expensive.
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Re: [time-nuts] Anybody have suggestions for time related science fair projects?

[Bob kb8tq]

Hi



> On May 12, 2018, at 7:01 AM, jimlux  wrote:
> 
> On 5/11/18 9:08 PM, Jeff Woolsey wrote:
>> David.vanhorn wrote:
>>> Measuring the speed of light (Fizeau or Michelson method? Other ways)
>>> 
>>> 
>>> I saw a great demo of this at the Exploratorium in SF.  They had a long 
>>> spool of fiber optic, a disc with holes, and a light source.  When static, 
>>> if the light shines through the hole in the disc into the fiber, then you 
>>> can see the light coming out the other end of the fiber through a different 
>>> hole.   When rotating, you increase speed and the fiber output gets dimmer 
>>> and dimmer till it's gone.   At that point, the light going into the fiber 
>>> arrives when the other end is blocked, and vice versa.  High tech, but 
>>> simple.
>>> 
>> My favorite exhibit that we never see anymore.   IIRC it was a quarter
>> mile of fiber and a green laser.  And ISTR that the disc had one hole on
>> one arm and two radially on the other, but I can't remember why.  I
>> thought that the light would pass through the same hole twice, once on
>> the way in and on the way out when that same hole rotated 180 degrees to
>> the other end of the fiber.  The disk spun somewhere around 50 rps (60
>> with an AC motor?).
> 
> 
> 1km in free space would be 6 microseconds round trip. I'm not sure a disk 
> spinning at 3600 rpm would work.  you'd need to have the "hole spacing" be on 
> the order of 6 microseconds - and at 100 rps (6000 RPM), 10 ms/rev, you'd 
> need the sending and receiving hole 6/1 of a rev apart (about 0.2 
> degrees).
> 
> if you had 10 km of fiber, it would be a bit easier.

I think the term “long fiber” in this case should really be “very very long”.  
Exactly how the typical student
funds the acquisition of something in the “many miles” range, I have no idea. 

You could use an optical grating of some sort as your “spinning disk”. The end 
of the fiber is going to be 
mighty small. The spacing on the grating could be quite tight. Where you get a 
circular part like that ….
again no idea. 

Bob


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Re: [time-nuts] Help Identifying this surplus Timing Module

[Bob kb8tq]

Hi

Ok, the gizmo on the front it an Altera CPLD. Not a lot of gates, so not a lot 
going 
on there. Whatever the real functions are, they are in the chip with no 
labeling. 

Even with the full information (let’s say): 

Takes in a 16 stream OC-blah blah and provides the following alarms on the 
status
channel. Hookup up the data stream and backup to pins X and Y. Status alarms 
also come
out on A, B, and C. Power is 12 V +/- 10% on pin M. Enable and control are on 
pins
E,F,G. 

Unless you happen to be building an OC-3 system in the basement and have all
the optical fiber stuff to do it …. not a lot of use. It is very similar to a 
lot of product
I designed over the years. It likely does a great job in it’s intended OEM 
application.
It’s pretty much useless for anything more general purpose as it is right now.

Without a schematic, the source code for the DSP and CPLD  and the proper tool 
sets, not much you can modify it to do. Even with all that stuff, probably the 
best you 
could do is a fairly basic 1 pps in. to  38.88 MHz) / M  out PLL. 

Indeed this *is* where timing has gone over the last few decades. TimeNuts 
normally may 
not look at telecom timing as an exciting thing. There is a vast amount of gear 
that 
has been built to distribute signals inside these networks. As far as Crazy Bob 
at
home is concerned, it’s all out of reach. It also is all designed for 
maintenance of 
data sync rather than time of day. It’s still very much time, just a different 
way of
looking at it. 

Bob

> On May 11, 2018, at 11:45 PM, CubeCentral  wrote:
> 
> Thank you bob and Gary for your investigations!  I appreciate it!  Here are a 
> couple more views:
> 
> https://imgur.com/a/auWdXvq
> 
> "This is the picture with sticker removed.   The large IC at the back has its 
> label scratched off.  ... that was intentional, but he has a note saying it 
> is a member of Motorola DSP56300 family. It was likely purchased in 2010 
> based on an eBay invoice which has no date on it, but the scanned date was 
> Feb 2011."
> 
> If anyone else has any more ideas, I would gladly hear them!  Thanks again!
> 
>   -Randal   (at CubeCentral)
> 
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Gary Chatters
> Sent: Friday, May 11, 2018 19:07
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Help Identifying this surplus Timing Module
> 
> A little Googling found a two page datasheet.  It doesn't tell you much more 
> than what you already found out, but does have specifications.
> 
> I can't figure out the correct link to include here, but a Google search with 
> the string "ATiMe-s 38.88" (don't include the quotes) should bring up the 
> link in the first couple of hits.  It is a PDF at the www.sbtron.co.kr 
> website.
> 
> gc
> 
> On 05/11/2018 07:16 PM, CubeCentral wrote:
>> Hello All!
>> 
>> 
>> 
>> I would like to enlist your help in identifying this "surplus Timing
>> Module":  https://imgur.com/a/Psw8gP7
>> 
>> 
>> 
>> All the hints I've been given are:
>> 
>> - Purchased about a decade ago
>> 
>> - Might use a Motorola DSP as the processor
>> 
>> 
>> 
>> A quick google search lead me to a possible description:
>> 
>> "High speed, hitless, ultra low jitter timing module for OC-N line
>> interfaces:  The TF Systems / ATiMe-LC is a timing reference source for OC-N
>> and STM-N interfaces. It complements TeraSync's central timing modules to
>> provide a complete and redundant timing solution at the system level."
>> 
>> 
>> 
>> ...but I'm unsure if that is 100% the same module.  If you would like to get
>> some different photos, please let me know and I will see what I can do.  Any
>> thoughts or ideas would be greatly appreciated!  Thanks!
>> 
>> 
>> 
>> -Randal   (at CubeCentral)
>> 
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Re: [time-nuts] Help Identifying this surplus Timing Module

[Bob kb8tq]

Hi

The big chip with the sticker on it is an Altera FPGA. A picture of the back
side might help a little (if there is anything on the back side …).

Simple answer - it’s a nice source of parts ….

Bob

> On May 11, 2018, at 7:16 PM, CubeCentral  wrote:
> 
> Hello All!
> 
> 
> 
> I would like to enlist your help in identifying this "surplus Timing
> Module":  https://imgur.com/a/Psw8gP7 
> 
> 
> 
> All the hints I've been given are:
> 
> - Purchased about a decade ago
> 
> - Might use a Motorola DSP as the processor
> 
> 
> 
> A quick google search lead me to a possible description:
> 
> "High speed, hitless, ultra low jitter timing module for OC-N line
> interfaces:  The TF Systems / ATiMe-LC is a timing reference source for OC-N
> and STM-N interfaces. It complements TeraSync's central timing modules to
> provide a complete and redundant timing solution at the system level."
> 
> 
> 
> ...but I'm unsure if that is 100% the same module.  If you would like to get
> some different photos, please let me know and I will see what I can do.  Any
> thoughts or ideas would be greatly appreciated!  Thanks!
> 
> 
> 
>-Randal   (at CubeCentral)
> 
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Re: [time-nuts] Help Identifying this surplus Timing Module

[Bob kb8tq]

Hi

Given the frequency of the oscillator, it’s some sort of sync module for a 
telecom system. What data rate and what sort of coding …. who knows …

Bob

> On May 11, 2018, at 7:16 PM, CubeCentral  wrote:
> 
> Hello All!
> 
> 
> 
> I would like to enlist your help in identifying this "surplus Timing
> Module":  https://imgur.com/a/Psw8gP7 
> 
> 
> 
> All the hints I've been given are:
> 
> - Purchased about a decade ago
> 
> - Might use a Motorola DSP as the processor
> 
> 
> 
> A quick google search lead me to a possible description:
> 
> "High speed, hitless, ultra low jitter timing module for OC-N line
> interfaces:  The TF Systems / ATiMe-LC is a timing reference source for OC-N
> and STM-N interfaces. It complements TeraSync's central timing modules to
> provide a complete and redundant timing solution at the system level."
> 
> 
> 
> ...but I'm unsure if that is 100% the same module.  If you would like to get
> some different photos, please let me know and I will see what I can do.  Any
> thoughts or ideas would be greatly appreciated!  Thanks!
> 
> 
> 
>-Randal   (at CubeCentral)
> 
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Re: [time-nuts] HP 5372A

[Bob kb8tq]

HI

> On May 11, 2018, at 3:12 PM, Magnus Danielson  
> wrote:
> 
> Hi Don,
> 
> On 05/10/2018 02:59 PM, Don Murray via time-nuts wrote:
>> Hi Magnus...
>>  
>>  
>> Appreciate any help!
>>  
>> I participate in the ARRL Frequency Measuring Test,
>> and I would like to automate the measuring process.
>>  
>> I have two frequencies, A and B...
>>  
>> A is a GPS locked HP 3336B set to 455,000.000 Hz
>>  
>> I use the 3336B instead of the 455,000Hz BFO
>> signal from my GPS locked Racal receiver so
>> that I can measure AM stations without the
>> annoying beat note.  ;-)
>>  
>> B is an IF signal which should appear between
>> 455,000.000Hz and 455,001.000 Hz
>> 
>> I would like the 5372A to calculate the B minus A
>> delta, over a manually started and automatically
>> stopped measurement period of 110 seconds.
>>  
>> I would like a delta resolution of 0.001Hz to be
>> developed by the box.
> 
> There is no point in using two channels and a generator.
> You can do that straight out of the box just by locking it to the GPS,
> which you should do anyway.
> 
> Just measure the signal. Using the Math you can subtract or add whatever
> frequency you want. You can get A-B or B-A measures in Frequency mode,
> it's just not necessary.
> 
> Now, you want to use the single-shot run mode.
> 
> It should be relative trivial to setup a large number of samples with a
> suitable distance inbetween them.
> 
> Getting 1 mHz resolution isn't too hard that way, considering you have
> 110 s of time to do it.
> 
>> Now, there will be doppler.  I want the box
>> to analyze and give me a best statistical guess
>> for the B minus A delta.
> 
> Now, doppler is tricky, as the HP5372A in all its glory does not have
> built-in compensation for it, and besides, you need to figure out where
> the true zero is.
> 
> What the box will give you is a frequency estimation assuming doppler
> free conditions. If you want to do smarter things, you need to pull the
> data off the counter in binary form and post-process it yourself. The
> programmers manual for the HP5372A is a great teaching tool for how
> these beasts process stuff.
> 
>> BTW the B minus A delta will be added to the
>> frequency of my Racal receiver to give me the
>> best "guess" as to the correct frequency of the
>> target signal.
> 
> For sure. This is BTW something you can do in the Math part of the
> HP5372A, so you can have it crunch out the right value straight out.
> 
>> The Racal reads out to the Hz, and I am able to
>> accurately determine if the Racal is tuned above
>> or below the "target" frequency.
>>  
>> I will be tuned below the "target" and within
>> 1 Hz of the "target."
>>  
>> I assume I will be in the one frequency mode.
>>  
>> Can the box give me the desired resolution?
> 
> Sure, assuming the doppler limitation.
> 
>> What sampling period would be the best to use?
> 
> Use one short enough to get as many sample points over the 110 s you want.


The 110 seconds is the big gotcha here. What you really want is a unified 
record 
of the entire time they are transmitting. If it’s less than 2 minutes, you are 
fine. If
it runs for 5, 10 or 15 minutes that’s not quite so good. Stitching data 
together 
gets you back to binary dumps and a lot of post processing.  Once you do that, 
there really is no advantage over a SDR running on the same signal. 

Bob


> 
>> What statistical result would I use as my delta?
> 
> Mean value on the Statistics display. It's a linear regression result,
> which has good processing gain for frequency.
> 
>> Appreciate your help.  My head is spinning whenever I
>> get into the operating manual!
> 
> It's a beast, for sure. It took some time to master, but it's a lovely
> tool when you understand it and accept it's up-front complexity.
> 
> I could maybe take mine for a test-spin somewhat later.
> 
> Cheers,
> Magnus
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Re: [time-nuts] HP 5372A

[Bob kb8tq]

Hi

Well, having actually run FMT virtually “in the back yard” of the transmitting 
station …. it’s surprising 
what 70 miles will do. In this case, back yard really does mean on the 
premises. There is a lot that 
gets into even fairly sort distance propagation. 

Bob

> On May 11, 2018, at 1:52 PM, Jerry Hancock  wrote:
> 
> If you were in Connie’s back yard or had a very stable ground wave, then yes, 
> you could automate the testing.
> 
> There are a number of challenges with this method as looking at the data with 
> a simple graph will tell.  You might have large fluctuations on the high 
> frequency side only, for instance, that any averaging or algorithm would 
> assume to be valid data.
> 
> The next issue is the length of the dataset as the key-down time is only a 
> few minutes so you end-up with not that many samples.  
> 
> Regards,
> 
> Jerry
> 
>> On May 10, 2018, at 5:59 AM, Don Murray via time-nuts  
>> wrote:
>> 
>> Hi Magnus...
>> 
>> 
>> Appreciate any help!
>> 
>> I participate in the ARRL Frequency Measuring Test,
>> and I would like to automate the measuring process.
>> 
>> I have two frequencies, A and B...
>> 
>> A is a GPS locked HP 3336B set to 455,000.000 Hz
>> 
>> I use the 3336B instead of the 455,000Hz BFO
>> signal from my GPS locked Racal receiver so
>> that I can measure AM stations without the
>> annoying beat note.  ;-)
>> 
>> B is an IF signal which should appear between
>> 455,000.000Hz and 455,001.000 Hz
>> 
>> I would like the 5372A to calculate the B minus A
>> delta, over a manually started and automatically
>> stopped measurement period of 110 seconds.
>> 
>> I would like a delta resolution of 0.001Hz to be
>> developed by the box.
>> 
>> Now, there will be doppler.  I want the box
>> to analyze and give me a best statistical guess
>> for the B minus A delta.
>> 
>> BTW the B minus A delta will be added to the
>> frequency of my Racal receiver to give me the
>> best "guess" as to the correct frequency of the
>> target signal.
>> 
>> The Racal reads out to the Hz, and I am able to
>> accurately determine if the Racal is tuned above
>> or below the "target" frequency.
>> 
>> I will be tuned below the "target" and within
>> 1 Hz of the "target."
>> 
>> I assume I will be in the one frequency mode.
>> 
>> Can the box give me the desired resolution?
>> 
>> What sampling period would be the best to use?
>> 
>> What statistical result would I use as my delta?
>> 
>> Appreciate your help.  My head is spinning whenever I
>> get into the operating manual!
>> 
>> TNX...
>> 
>> 
>> 73
>> Don
>> W4WJ
>> 
>> In a message dated 5/10/2018 2:19:49 AM Central Standard Time, 
>> mag...@rubidium.dyndns.org writes:
>> 
>> 
>> Hi,
>> 
>> What issues do you have?
>> 
>> Cheers,
>> Magnus
>> 
>> On 05/08/2018 02:32 AM, Don Murray via time-nuts wrote:
>>> Hello Time Nuts...
>>> 
>>> 
>>> 
>>> Who is the resident expert on the HP5372A?
>>> 
>>> I have some operational questions.  ;-)
>>> 
>>> email off list please.  w4wj at aol.com
>>> 
>>> TNX all...
>>> 
>>> 73
>>> Don
>>> W4WJ
>>> 
>>> 
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>>> 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

If you do the weighted average as indicated in the paper *and* compare it to a 
“single sample” computation, 
the results are different for that time interval. To me that’s a problem. To 
the authors, the fact that the rest of
the curve is the same is proof that it works. I certainly agree that once you 
get to longer tau, the process 
has no detrimental impact. There is still the problem that the first post on 
the graph is different depending 
on the technique. 

The other side of all this is that ADEV is really not a very good way to test a 
counter. It has it’s quirks and it’s
issues. They are impacted by what is in a counter,  but that’s a side effect. 
If one is after a general test of 
counter hardware, one probably should look at other approaches.

If you are trying specifically just to measure ADEV, then there are a lot of 
ways to do that by it’s self. It’s not
clear that re-invinting the hardware is required to do this. Going with an 
“average down” approach ultimately
*will* have problems for certain signals and noise profiles. 

Bob

> On May 11, 2018, at 10:42 AM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi
> 
> ----------
> From: "Bob kb8tq" <kb...@n1k.org>
>> The most accurate answer is always “that depends”. The simple answer is no.
> 
> I have spent the yesterday evening and quite a bit of the night :) reading 
> many interesting papers and several related discussions in the time-nuts 
> archive (the Magnus Danielson posts in "Modified Allan Deviation and counter 
> averaging" and "Omega counters and Parabolic Variance (PVAR)" topics were 
> very informative and helpful, thanks!).
> 
> It looks like the trick to combine averaging with the possibility of correct 
> ADEV calculation in the post processing exists. There is a nice presentation 
> made by prof. Rubiola [1]. There is a suitable solution on page 54 (at least 
> I understood it so, maybe I am wrong). I can switch to usual averaging 
> (Lambda/Delta counter) instead of LR calculation (Omega counter), the losses 
> should be very small I my case. With such averaging the MDEV can be correctly 
> computed. If ADEV is needed, the averaging interval can be reduced and 
> several measurements (more then eight) can be combined into one point 
> (creating the new weighting function which resembles the usual Pi one, as 
> shown in the [1] p.54), it should be possible to calculate usual ADEV using 
> such data. As far as I understand, the filter which is formed by the 
> resulting weighting function will have wider bandwidth, so the impact on ADEV 
> will be smaller and it can be computed correctly. Am I missing something?
> 
> I have made the necessary changes in code, now firmware computes the Delta 
> averaging, also it computes combined Delta averaged measurements (resulting 
> in trapezoidal weighting function), both numbers are computed with continuous 
> stamping and optimal overlapping. Everything is done in real time. I did some 
> tests. The results are very similar to the ones made with LR counting.
> 
> [1] http://www.rubiola.org/pdf-slides/2012T-IFCS-Counters.pdf
>   E. Rubiola, High resolution time and frequency counters, updated version.
> 
> All the best!
> Oleg UR3IQO 
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Re: [time-nuts] Anybody have suggestions for time related science fair projects?

[Bob kb8tq]

Hi

NTP time offsets through various phases of the distribution process …..

Bob

> On May 11, 2018, at 12:55 AM, Hal Murray  wrote:
> 
> 
> A few months ago, I was a judge for the county level middle school science 
> fair.  (I'm not very good at what they wanted, but that's a different 
> problem.)
> 
> What sort of interesting time related experiments can a middle school geek do?
> 
> Borrowing serious gear may not be off scale as long as a youngster can run it.
> 
> -
> 
> An alternat meaning to the "nut" part of time-nuts:  ")
>  https://www.snopes.com/fact-check/schools-removing-analog-clocks/
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

> On May 10, 2018, at 1:44 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Bob, thanks for clarification!
> 
> From: "Bob kb8tq" <kb...@n1k.org>
>> If you collect data over the entire second and average that down for a 
>> single point, then no, your ADEV will not be correct.
> 
> That probably explains why I got so nice (and suspicious) plots :)
> 
>> There are a number of papers on this. What ADEV wants to see is a single 
>> phase “sample” at one second spacing.
> 
> After I read your answer I remembered some nice papers from prof. Rubiola, me 
> bad - I was able to answer my question by myself. When we take a single phase 
> "sample" at start and at end time of the "each tau" it is equivalent to 
> summing all timestamps intervals I collect during that "tau", but by doing LR 
> processing I calculate *weighted* sum, so the results will differ. So, it 
> appears "ADEV" calculations is PDEV (parabolic) in reality, because of the 
> current firmware processing.
> 
> I made a test with two plots for illustration - one is the classical ADEV 
> (with 2.5ns time resolution), the second one with LR processed data (5e6 
> timestamps per second). Both plots are made from the same data. It is obvious 
> the classical ADEV is limited by the counter resolution in the left part of 
> the plot. It is interesting is it possible to use the 498 extra points 
> per each second to improve counter resolution in ADEV measurements without 
> affecting ADEV?

The most accurate answer is always “that depends”. The simple answer is no. If 
you take a look at some of the papers from 
the 90’s you can find suggestions on doing filtering on the first point in the 
series. The gotcha is that it does impact the first
point. The claim is that if you do it right, it does not impact the rest of the 
points in the series. 

Bob


> 
> Thanks!
> Oleg UR3IQO 
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

More or less: 

ADEV takes the *difference* between phase samples and then does a standard
deviation on them. RMS of the phase samples makes a lot of sense and it was
used back in the late 50’s / early 60’s. The gotcha turns out to be that it is 
an 
ill behaved measure. The more data you take, the bigger the number you get. 
( = it does not converge ). That problem is what lead NBS to dig into a better 
measure. The result was ADEV.

The point about averaging vs decimation relates to what you do to the data 
*before*
you ever compute the ADEV. If you have 0.1 second samples, you have to do 
something
to get to a tau of 1 second or 10 seconds or … The process you use to get the 
data
to the proper interval turns out to matter quite a bit. 

Bob

> On May 10, 2018, at 12:17 PM, Dana Whitlow <k8yumdoo...@gmail.com> wrote:
> 
> I'm a bit fuzzy, then, on the definition of ADEV.  I was under the
> impression that one measured a series of
> "phase samples" at the desired spacing, then took the RMS value of that
> series, not just a single sample,
> as the ADEV value.
> 
> Can anybody say which it is?   The RMS approach seems to make better sense
> as it provides some measure
> of defense against taking a sample that happens to be an outlier, yet
> avoids the flaw of tending to average
> the reported ADEV towards zero.
> 
> Dana   (K8YUM)
> 
> 
> On Thu, May 10, 2018 at 9:21 AM, Bob kb8tq <kb...@n1k.org> wrote:
> 
>> Hi
>> 
>> If you collect data over the entire second and average that down for a
>> single point, then no, your ADEV will not be correct.
>> There are a number of papers on this. What ADEV wants to see is a single
>> phase “sample” at one second spacing. This is
>> also at the root of how you get 10 second ADEV. You don’t average the ten
>> 1 second data points. You throw nine data points
>> away and use one of them ( = you decimate the data ).
>> 
>> What happens if you ignore this? Your curve looks “to good”. The resultant
>> curve is *below* the real curve when plotted.
>> 
>> A quick way to demonstrate this is to do ADEV with averaged vs decimated
>> data ….
>> 
>> Bob
>> 
>>> On May 10, 2018, at 4:46 AM, Oleg Skydan <olegsky...@gmail.com> wrote:
>>> 
>>> Hi
>>> 
>>> I have got a pair of not so bad OCXOs (Morion GK85). I did some
>> measurements, the results may be interested to others (sorry if not), so I
>> decided to post them.
>>> 
>>> I ran a set of 5minutes long counter runs (two OCXOs were measured
>> against each other), each point is 1sec gate frequency measurement with
>> different number of timestamps used in LR calculation (from 10 till 5e6).
>> The counter provides continuous counting. As you can see I reach the HW
>> limitations at 5..6e-12 ADEV (1s tau) with only 1e5 timestamps. The results
>> looks reasonable, the theory predicts 27ps equivalent resolution with 1e5
>> timestamps, also the sqrt(N) law is clearly seen on the plots. I do not
>> know what is the limiting factor, if it is OCXOs or some counter HW.
>>> 
>>> I know there are HW problems, some of them were identified during this
>> experiment. They were expectable, cause HW is still just an ugly
>> construction made from the boards left in the "radio junk box" from the
>> other projects/experiments. I am going to move to the well designed PCB
>> with some improvements in HW (and more or less "normal" analog frontend
>> with good comparator, ADCMP604 or something similar, for the "low
>> frequency" input). But I want to finish my initial tests, it should help
>> with the HW design.
>>> 
>>> Now I have some questions. As you know I am experimenting with the
>> counter that uses LR calculations to improve its resolution. The LR data
>> for each measurement is collected during the gate time only, also
>> measurements are continuous. Will the ADEV be calculated correctly from
>> such measurements? I understand that any averaging for the time window
>> larger then single measurement time will spoil the ADEV plot. Also I
>> understand that using LR can result in incorrect frequency estimate for the
>> signal with large drift (should not be a problem for the discussed
>> measurements, at least for the numbers we are talking about).
>>> 
>>> Does the ADEV plots I got looks reasonable for the used "mid range"
>> OCXOs (see the second plot for the long run test)?
>>> 
>>> BTW, I see I can interface GPS module to my counter without additional
>> HW (except the module itself, do not worry it will not be another

Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

If you collect data over the entire second and average that down for a single 
point, then no, your ADEV will not be correct. 
There are a number of papers on this. What ADEV wants to see is a single phase 
“sample” at one second spacing. This is
also at the root of how you get 10 second ADEV. You don’t average the ten 1 
second data points. You throw nine data points
away and use one of them ( = you decimate the data ). 

What happens if you ignore this? Your curve looks “to good”. The resultant 
curve is *below* the real curve when plotted. 

A quick way to demonstrate this is to do ADEV with averaged vs decimated data ….

Bob

> On May 10, 2018, at 4:46 AM, Oleg Skydan  wrote:
> 
> Hi
> 
> I have got a pair of not so bad OCXOs (Morion GK85). I did some measurements, 
> the results may be interested to others (sorry if not), so I decided to post 
> them.
> 
> I ran a set of 5minutes long counter runs (two OCXOs were measured against 
> each other), each point is 1sec gate frequency measurement with different 
> number of timestamps used in LR calculation (from 10 till 5e6). The counter 
> provides continuous counting. As you can see I reach the HW limitations at 
> 5..6e-12 ADEV (1s tau) with only 1e5 timestamps. The results looks 
> reasonable, the theory predicts 27ps equivalent resolution with 1e5 
> timestamps, also the sqrt(N) law is clearly seen on the plots. I do not know 
> what is the limiting factor, if it is OCXOs or some counter HW.
> 
> I know there are HW problems, some of them were identified during this 
> experiment. They were expectable, cause HW is still just an ugly construction 
> made from the boards left in the "radio junk box" from the other 
> projects/experiments. I am going to move to the well designed PCB with some 
> improvements in HW (and more or less "normal" analog frontend with good 
> comparator, ADCMP604 or something similar, for the "low frequency" input). 
> But I want to finish my initial tests, it should help with the HW design.
> 
> Now I have some questions. As you know I am experimenting with the counter 
> that uses LR calculations to improve its resolution. The LR data for each 
> measurement is collected during the gate time only, also measurements are 
> continuous. Will the ADEV be calculated correctly from such measurements? I 
> understand that any averaging for the time window larger then single 
> measurement time will spoil the ADEV plot. Also I understand that using LR 
> can result in incorrect frequency estimate for the signal with large drift 
> (should not be a problem for the discussed measurements, at least for the 
> numbers we are talking about).
> 
> Does the ADEV plots I got looks reasonable for the used "mid range" OCXOs 
> (see the second plot for the long run test)?
> 
> BTW, I see I can interface GPS module to my counter without additional HW 
> (except the module itself, do not worry it will not be another DIY GPSDO, 
> probably :-) ). I will try to do it. The initial idea is not try to lock the 
> reference OCXO to GPS, instead I will just measure GPS against REF and will 
> make corrections using pure math in SW. I see some advantages with such 
> design - no hi resolution DAC, reference for DAC, no loop, no additional 
> hardware at all - only the GPS module and software :) (it is in the spirit of 
> this project)... Of cause I will not have reference signal that can be used 
> outside the counter, I think I can live with it. It worth to do some 
> experiments.
> 
> Best!
> Oleg UR3IQO 
> <Снимок экрана (1148).png><Снимок экрана (1150).png><Снимок экрана 
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Re: [time-nuts] how long dues this rubidium standard last for

[Bob kb8tq]

Hi

Rubidium standards are a “who knows” sort of thing in terms of life. Best guess
for the telecom Rb’s is 10 to 20 years. For a normal Cs standard with a high
performance tube, the life may be in the 6 or 7 year range ( I have replaced a 
couple of those). 

The HP 5065 is a rare beast. One sold on the list a little while back for ~$4K.

Bob

> On May 9, 2018, at 5:45 PM, Paul Bicknell  wrote:
> 
> 
> Hi all 
> as I am new to time nuts could someone please help with e following 
> 
> questions 
> 
> I have a Racal 9475 and a comment was it is a good entry level rubidium
> That is not working yet 
> how long dues the rubidium standard last for and how much to replace  ? 
> 
> I assume rubidium & cesium's are left on 24/7
> ?
> 
> I think I would like a HP 5065 
> so how long dues this rubidium standard last for
> ?
> and how much to replace
> ?
> 
> 
> regarding the HP 5065 how much am I going to have to pay for one
> ?
> 
> I want to also do the Corby Dawson optical window modification 
> so How much is the new optical window
> ?
> 
> I realise the are a lot of questions but any answers would be welcome 
> 
> Regards Paul B
> 
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Re: [time-nuts] Ashtech Z12 question.

[Bob kb8tq]

Hi

What you describe sure sounds like a ram battery died sort of thing. I’ve never 
noticed one in the boards I’ve
torn apart. I’d also admit that was a few years back ….

Bob

> On May 6, 2018, at 6:12 PM, Mark Sims  wrote:
> 
> I just added support for the Z12 to Lady Heather and fired up my Z12 for the 
> first time in a few years.   It powers up in some kind of a weird loopback 
> mode and you have to reset the receiver memory to get it working.   
> 
> Does the Z12 have an internal memory backup battery?   Mine is currently 
> doing a long L1/L2 RINEX capture and I can't open it and check right now.
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Bob kb8tq]

Hi

First off, I don’t think there *is* an ideal antenna that “just works”. Maybe a 
proper set of EMAG 
probes that come with calibration sheets come close. For a home built this or 
that …. there are
a lot of variables. 

First up is very much part of receiving WWVB in the first place. Coax to an 
antenna can have currents
on the outer shield. If they meet up with everything else at the antenna, you 
are not just measuring 
the antenna output. Equally, if reception is the goal, you may have a ton of 
noise that you didn’t really
want to have. Of course, the coax might act as a really good antenna …. who 
knows. 

Something like a 6” diameter single turn  loop with a good choke at the antenna 
end of the coax would
be my first choice. Not super sensitive. It’s not the ideal reception antenna. 
For chasing down noise, smaller
is often better. As mentioned earlier we are after stuff that may be in the 
millivolts per meter range. 

Classic data:

ftp://ftp.ngdc.noaa.gov/ionosonde/documentation/CCIR%20-%20Characteristics%20and%20Applications%20of%20Atmospheric%20Radio%20Noise%20Data.PDF
 


puts the atmospheric noise at 120 db above KTB in the vicinity of 60 KHz. That 
would put it in the roughly
-54 dbm / Hz range. If your spectrum analyzer has a 1KHz bandwidth, that’s 30 
db relative to 1 Hz. Your
SA should read about -24 dbm ( with an efficient antenna).  Coming up with a 
1/4 wave vertical at 60 KHz
may make getting those numbers a bit difficult :). Bottom line is still — 
there’s a lot of noise at 60 KHz. Also
note that the report came out *long* before the modern era of 60 KHz switchers 
…..

Bob 

> On May 6, 2018, at 1:08 PM, Charles Steinmetz  wrote:
> 
> Hal wrote:
> 
>> I assume the problem is noise.  Is there any simple way to measure the noise
>> around 60 KHz?  How about not so simple?
>> 
>> Extra credit for a way that others nuts can reproduce so we can compare the
>> noise at my location with other locations.
> 
> For any location near a city, the noise level (QRM and QRN -- mostly the 
> former unless there is storm activity within a few hundred km) is shockingly 
> high.  High enough to be clearly seen and measured with a good spectrum 
> analyzer.  So the *simplest* way (but not necessarily the cheapest, depending 
> on what is in your lab already) is to use a good spec an with noise 
> integration over the band of interest (e.g., HP 3585A or B).  You get noise 
> density readings in volts per root Hz.  Divide by the antenna length and you 
> have volts per root Hz per meter.
> 
> Lacking a suitable spec an, any receiver with a reasonably narrow rx B/W and 
> a calibrated, input-referred detector can be used.  Wave analyzers 
> (frequency-selectable voltmeters, e.g., HP 3586) are good candidates, as are 
> some commercial receivers with calibrated "S" meters (e.g., Ten-Tec RX340).  
> It would also be pretty easy to design a simple "sniffer"-type receiver 
> (input op-amp, active filter, logarithmic detector feeding a standard 1mA 
> meter movement) that could be calibrated by design from first principles and 
> that everyone interested could build for, perhaps, $25-30.
> 
> In the suburbs of a fairly large US city with aerial electric service, I 
> generally see noise densities measured in tens to hundreds of uV per root Hz 
> per meter below 100kHz.  In other, similar locations I have seen as much as 
> hundreds of mV or more per root Hz per meter.  It depends on local factors 
> (whether the electric service is buried or aerial, how well the power utility 
> maintains its equipment, how far away the nearest industrial neighborhood is, 
> how far between dwellings, how much noisy technology the neighbors use, etc, 
> etc.).
> 
> In order to compare with others, everyone needs to use the same antenna.  
> There are lots of possibilities, but for the sake of universality I recommend 
> a 1m vertical whip.  Everyone can make one of those.
> 
> Note that this sort of antenna is NOT the best type to minimize received 
> noise and maximize received S/N ratio.  For that, you generally want a 
> balanced, shielded loop.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Bob kb8tq]

Hi

The sample rate on a sound card is not always a good indication of it’s 
performance. Some 192 KS/s cards have cutoff’s below 50 KHz. Others
have a noise spectrum that rises quite a bit past 30 or 40 KHz. 

Lots to dig into ….

Bob

> On May 5, 2018, at 5:42 PM, Alberto di Bene  wrote:
> 
> If you have a sound card capable of sampling at 192 kS/s, you don't need an 
> SDR
> to receive a signal at 60 kHz... just connect the output of an active 
> antenna, like
> e.g. the mini-whip, directly to the Line-In of the sound card, then use, for 
> example,
> HDSDR as software, setting the sampling frequency of the sound card to 192 
> kS/s,
> the LO to zero, and the TUNE to 60 kHz.
> 
> I used this method in the past to successfully receive the SAQ transmission 
> at 17.2 kHz
> Look here :
> 
> http://www.sdradio.eu/SAQ_2009_12_24.html
> 
> 73  Alberto  I2PHD
> 
> 
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Bob kb8tq]

Hi

If you want delay ( hardware delay and not propagation), calibrating a SDR 
should not
be to nutty. Some boards ( the Lime SDR comes to mind) will generate a signal 
as well
as receive one. That could be piped into a scope to make the measurement fairly
easy. Once you know what is going into the receiver and what is coming out, 
it’s just 
twiddling the knobs ….

Bob

> On May 5, 2018, at 5:50 AM, Dana Whitlow  wrote:
> 
> Hal,
> 
> Some SDRs can tune that low and should provide a means to determine
> if noise is really the problem as well as give some clues as to the
> character
> of said noise.  But they are much less likely to help with delay
> determination,
> unless you can figure out a practical way to ascertain the latency in both
> the
> SDR's HW and its SW.  The latter component will also vary considerable
> depending on what computer you are using with the SDR, as well as with
> random variations due to the vagrancy of typical operating systems.
> 
> I recently did a crude delay estimation for WWV (not WWVB) using my
> Sony ICF-2010 receiver, a 2-channel DSO, and an Adafruit "Ultimate GPS"
> module's PPS output.  The combined (receiver + propagation) delay was
> very close to 5 msec in Kerrville, TX.  The precision was mostly limited by
> my inability to decide precisely where each WWV tick started on the 'scope's
> display due to distortion arising from multipath and the receiver's
> filters.
> The actual received waveform varied considerably from second to second.
> 
> Dana
> 
> 
> On Sat, May 5, 2018 at 3:08 AM, Hal Murray  wrote:
> 
>> Review/background:  I have an UltraLink 333 WWVB receiver.  It didn't
>> work.
>> Several weeks ago. a discussion here mentioned that the phone cable
>> between
>> the main box and antenna needs to be straight through rather than the
>> typical
>> reversed.  That was my problem.  With the correct cable, the meter shows
>> signal and bounces around such that with practice, I could probably read
>> the
>> bit pattern.  But it didn't lock up.
>> 
>> That was several weeks ago.  I left it running.  When I looked last night,
>> it
>> had figured out that it is 2018.  I wasn't watching or monitoring, so I
>> don't
>> know how long it took.
>> 
>> I assume the problem is noise.  Is there any simple way to measure the
>> noise
>> around 60 KHz?  How about not so simple?
>> 
>> Extra credit for a way that others nuts can reproduce so we can compare
>> the
>> noise at my location with other locations.
>> 
>> Can any audio cards be pushed that high?  I see sample rates of 192K, but
>> I
>> don't know if that is useful.
>> 
>> I'd also like to measure the propagation delays on WWV so a setup for HF
>> that
>> also works down to 60 KHz would be interesting.
>> 
>> --
>> 
>> The UltraLink documentation says the display has a slot for a C or H.  The
>> C is for Colorado and the H is for Hawaii.  Did WWVH have a low frequency
>> transmitter many years ago?  The NIST history of WWVH doesn't mention it.
>> 
>> My guess is a cut+paste from a version that listened to WWV/WWVH.
>> 
>> 
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
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>> 
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Bob kb8tq]

Hi

Even if you get the 60 KHz process working, a $20 GPS module ( or maybe $50) 
will 
do a much better job. That’s not saying *don’t* do the WWVB stuff. Just realize 
it’s 
limitations. A second limitation is that the new phase modulation process makes 
comparison a bit more complex. 

60 KHz noise can be measured with any of a number of SDR’s that tune down 
there. 
An RTL-SDR probably isn’t ideal, but there are a lot of sub $200 devices that 
will do
very well. 

Once you have a tuner you need a “standard” antenna (if this is for noise). 
Some sort
of single turn loop is probably the best bet. Assuming the input to the SDR 
comes 
pre-calibrated you are ready to go. If it’s not calibrated you will need to 
squirt a test
tone of known level in at 60 KHz to calibrate it ( likely a one time thing). 

60 KHz reception is a bit iffy these days. The low cost world *loves* 60KHz as 
a 
switcher frequency. It only takes one of them near your reception site to mess 
things
up. The E-field probe vs loop debate has been going on for at least a century 
by now. 
I’d go with some sort of loop. With a proper location, either can work well.

Lots of fun ….

Bob

> On May 5, 2018, at 9:17 AM, Ulrich Rohde via time-nuts  
> wrote:
> 
>  
> I am trying to use the 60 KHz for synchronization of a Rb receiver. The local 
> NJ noise and the signal in dBuV are about the same with an active antenna, 
> electric field.  A better solution might be a ferrite selective antenna, H 
> field , if I find one.
>  
> 73 de N1UL 
>  
>  
> In a message dated 5/5/2018 4:09:25 AM Eastern Standard Time, 
> hmur...@megapathdsl.net writes:
> 
>  
> Review/background: I have an UltraLink 333 WWVB receiver. It didn't work. 
> Several weeks ago. a discussion here mentioned that the phone cable between 
> the main box and antenna needs to be straight through rather than the typical 
> reversed. That was my problem. With the correct cable, the meter shows 
> signal and bounces around such that with practice, I could probably read the 
> bit pattern. But it didn't lock up.
> 
> That was several weeks ago. I left it running. When I looked last night, it 
> had figured out that it is 2018. I wasn't watching or monitoring, so I don't 
> know how long it took.
> 
> I assume the problem is noise. Is there any simple way to measure the noise 
> around 60 KHz? How about not so simple?
> 
> Extra credit for a way that others nuts can reproduce so we can compare the 
> noise at my location with other locations.
> 
> Can any audio cards be pushed that high? I see sample rates of 192K, but I 
> don't know if that is useful.
> 
> I'd also like to measure the propagation delays on WWV so a setup for HF that 
> also works down to 60 KHz would be interesting.
> 
> --
> 
> The UltraLink documentation says the display has a slot for a C or H. The C 
> is for Colorado and the H is for Hawaii. Did WWVH have a low frequency 
> transmitter many years ago? The NIST history of WWVH doesn't mention it.
> 
> My guess is a cut+paste from a version that listened to WWV/WWVH.
> 
> 
> 
> -- 
> These are my opinions. I hate spam.
> 
> 
> 
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Re: [time-nuts] LEA-6T TCXO measurements

[Bob kb8tq]

Hi

Two different meanings of the term sawtooth.

The first plot shows a very normal phase rollover process. That (when 
incorrectly 
unwound) can create errors. In some cases those sorts of errors are inevitable 
and 
it is always wise to see if data “noise” occurs right at a wrap around point. 

The other meaning of sawtooth in the case of GPS is rooted in the same process. 
The GPS time solution and local time have a pattern very much like the first 
plot. 
As long as it is running as shown in the first plot, it averages out (provided 
there is 
averaging).  The problem comes in when the plot does *not* look like the first 
graph. 
If the TCXO comes to a flat spot on it’s compensation curve, it can “hang out” 
to one
side of the error band. Instead of a sawtooth you get a curve. That process of 
staying
to one side of the error band does not average out and you get a bump in the 
time
record. 

If you dig into the archives, there are lots of plots showing typical data.

Bob

> On May 4, 2018, at 5:18 AM, Gabs Ricalde <gsrica...@gmail.com> wrote:
> 
> On Thu, Apr 26, 2018 at 8:36 PM, Bob kb8tq <kb...@n1k.org> wrote:
>> Hi
>> 
>> What you are looking at appear to be sawtooth jumps. Simply put, the module 
>> is
>> looking at the closest edge on the TCXO to do it’s timing. When the device 
>> drifts,
>> it can “slip” to another cycle. If you watch the PPS out, there are also 
>> artifacts that
>> result from this process operating in a non-ideal fashion. Lots of details 
>> on that in
>> the archives.
>> 
> 
> Hi Bob,
> 
> The raw data has a sawtooth pattern due to millisecond clock jumps
> [1], but TimeLab unwraps it and they happen more frequently than the
> frequency jumps.
> I redid the the experiment using the same receiver (pink trace) and
> another LEA-6T (green trace), there were no frequency jumps. SBAS was
> enabled in the old measurements (blue trace). I'm not sure if that
> explains it, but the manual does not recommend SBAS for timing.
> 
> 
> [1] "GNSS Receiver Clocks" http://www.insidegnss.com/node/2512
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Re: [time-nuts] What is considered the best deal now days on ...

[Bob kb8tq]

Hi

Outputs a pps is not impossible to find on an L1 / L2 receiver. Outputs 10 MHz 
is 
very unusual on an L1 / L2 device.

Bob

> On May 3, 2018, at 7:42 PM, Pete Lancashire  wrote:
> 
> ... a L1 / L2 receiver that also outputs either one PPS or 10 megahertz
> 
> -pete
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Re: [time-nuts] nuts about position (cheap receiver)

[Bob kb8tq]

Hi

…… and the quoted errors are in the 10’s of cm range. Thus you need a few years,
even if you are moving an inch per year. 

Bob

> On May 3, 2018, at 2:19 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> If you have a very good survey grade receiver and take a long enough data
>> set, yes you can  watch your location drift in some parts of the world. In
>> most locations, fixes a few years apart would be a better bet. 
> 
> I'm in Silicon Valley.  The San Andreas fault is a few miles from here.  A 
> map of the bay area will show a dozen major faults.  A neighborhood map may 
> have several smaller lines.
>  https://earthquake.usgs.gov/earthquakes/events/1906calif/virtualtour/bayarea
> .php
> 
> The USGS has good GPS receivers sprinkled around the area.  You can see 
> occasional
> antenna domes on a post alongside the highway.
>  http://www.quake.geo.berkeley.edu/usgs-gps/
> (Time sink warning.)
> 
> The fault moves about as fast as your fingernails grow, an inch per year.  
> That's one side relative to the other.  I don't know how fast the pair is 
> moving.
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Racal 9475 Rubidium

[Bob kb8tq]

Hi

You *really* need to keep the baseplate of the FRK series devices down. Their 
reliability drops quite a bit
as you go from 40 to 50 to 60 C on the baseplate. I would avoid boosting the 
input voltage without a very
good heatsink ( or heatsink + fan ) setup. 

I’ve …. ummm ….. cooked … a number of FRK’s over the years. 

Bob

> On May 3, 2018, at 12:40 PM, Nick Sayer via time-nuts  
> wrote:
> 
> 
> 
>> On May 2, 2018, at 7:13 PM, Roger Tilsley  wrote:
>> 
>> 
>> 
>> In my experience, FRK modules produce their best performance when operated  
>> from a supply voltage between 27 V and 28 V, selected for individual units 
>> but 27.6 V is a good starting figure. 
> 
> Would there be any value to designing a 24 -> 27.5 volt boost converter that 
> one could use to power it from a more conventional supply? How much current 
> would it need?
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Re: [time-nuts] nuts about position (cheap receiver)

[Bob kb8tq]

Hi

If you have a very good survey grade receiver and take a long enough data set, 
yes you can 
watch your location drift in some parts of the world. In most locations, fixes 
a few years apart
would be a better bet.

Indeed this does get a bit far from the world of timing …… The distances 
involved are nasty
small. Even for the location of your telescope when doing astronomical timing 
observations, 
they are unlikely to matter on a yearly basis. At some point the error is “to 
small to matter” ….

Bob

> On May 3, 2018, at 11:12 AM, Artek Manuals  wrote:
> 
> To further Chris' question if I took data say on the same day every year can 
> I measure which way my tectonic plate is moving and how far?
> 
> -DC
> manu...@artekmanuals.com
> 
> On 5/3/2018 10:17 AM, Chris Caudle wrote:
>> On Wed, May 2, 2018 11:36 pm, Mark Sims wrote:
>>> have Heather do all the receiver configuring, data
>>> capture, and RINEX making...
>> I have been following along with the update messages, and this seems like
>> really cool improvements to the underlying infrastructure pieces that a
>> lot of us use (Lady Heather, support for more GPS  modules, etc.), but I
>> am having trouble putting all the pieces together.
>> 
>> Having submitted the files to some post-processing server, do you only get
>> back information showing your position to some small number of
>> centimeters, or does it send back a stream of values showing the
>> corrections to the full position + time equations at each reading?
>> Can you use this data to go back to, for example, a stream of timestamps
>> and add a correction factor to the timestamps to get improved time
>> accuracy on historical data?
>> 
> 
> -- 
> Dave
> manu...@artekmanuals.com
> www.ArtekManuals.com
> 
> 
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
> 
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Re: [time-nuts] nuts about position (cheap receiver)

[Bob kb8tq]

Hi

The sites are aimed at improving position information. To the degree that 
having an
accurate location for your antenna improves timing, simply doing that is a step 
forward
for your GPSDO. 

Most sites also will give you information that shows the timing solution at a 
given point
in time. To the degree that you can connect that to prior data it could be 
useful. There
are more than a few steps involved in getting this to work.

Bob

> On May 3, 2018, at 10:17 AM, Chris Caudle  wrote:
> 
> On Wed, May 2, 2018 11:36 pm, Mark Sims wrote:
>> have Heather do all the receiver configuring, data
>> capture, and RINEX making...
> 
> I have been following along with the update messages, and this seems like
> really cool improvements to the underlying infrastructure pieces that a
> lot of us use (Lady Heather, support for more GPS  modules, etc.), but I
> am having trouble putting all the pieces together.
> 
> Having submitted the files to some post-processing server, do you only get
> back information showing your position to some small number of
> centimeters, or does it send back a stream of values showing the
> corrections to the full position + time equations at each reading?
> Can you use this data to go back to, for example, a stream of timestamps
> and add a correction factor to the timestamps to get improved time
> accuracy on historical data?
> 
> -- 
> Chris Caudle
> 
> 
> 
> 
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Re: [time-nuts] nuts about position (cheap receiver)

[Bob kb8tq]

Hi

Thank goodness it now is almost all self contained. Typing three or for lines 
of a script is *so* last century :)

Sounds very cool !! 

LH continues to do amazing things. She is an impressive lady. Do you ever have 
time to sleep?

My guess is that some sort of write up for doing the submittal to each of the 
“likely victim” agencies will be 
needed. Then of course there is the data reduction and plotting on the returned 
file …… hmmm …… :) 

Bob

> On May 3, 2018, at 3:56 AM, Mark Sims  wrote:
> 
> Woohoo! Success!I sent a RINEX 2.10 formatted .obs file generated by 
> Heather from a Ublox 5 to Canada for post-processing.   The results matched 
> those from RTKLIB processing to within 1mm.  Oh, and on noth cases the 
> post-processing used the "emu" orbit info.
> 
> I haven't heard back from Australia, but I think the file that I sent down 
> under has some duplicate data block errors.
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Re: [time-nuts] Racal 9475 Rubidium

[Bob kb8tq]

Hi

Ok, quick intro to Rb standards:

On an Rb you have a light bulb. It’s a really weird bulb but a bulb none the 
less. 
On most (but not all ) designs the bulb has a finite life. Various improvements
over the years have stretched out the life. Just when which outfits did which 
improvements …. who knows ….

Rb’s need to run hot. They have a couple of heated zones inside the physics 
package. Heat and electronics are not a good combo. Various designs have
issues on the stuff inside the hot zones. 

In addition to all this, they have crystal oscillators that drift. Once the 
oscillator
drifts far enough, the device isn’t going to lock up. 

That’s a quick, very non-specific to your unit, list.

Bob

> On May 1, 2018, at 5:18 AM, Paul Bicknell  wrote:
> 
> Hi all new member hear could any of you help with the following information
> 
> 
> 
> As I have just bought a Racal 9475 Rubidium and it has problems
> 
> 
> 
> Is there any stock faults ?
> 
> What is the life of the rubidium standard?
> 
> 
> 
> Regards Paul 
> 
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

The “drops stuff” problem is exactly what I saw trying to run at lower baud 
rates. 
The port is *not* full of data, there’s plenty of time to get it all out at a 
lower baud
rate. For some reason (buffers maybe) these modules start dropping data *way*
earlier than you would think they should. 

Bob

> On Apr 30, 2018, at 10:48 PM, Mark Sims  wrote:
> 
> I once spent way too much time trying to get Heather to spit out a RINEX file 
> from a Thunderbolt.   I could never get any of the post-processors to accept 
> it.   The Thunderbolt's raw data needs to somehow be tweaked to be compatible 
> and I didn't really know what I was doing.
> 
> A LEA-6T seems to be able to cope with the data stream at it's default 9600 
> baud.  I just tried a NEO-8N and it drops packets, etc.   Even weirder, it 
> does not output any of the requested packets that might be flooding the port, 
> but still drops packets.  
> 
> 
> ---
> 
>> You mean that LH does not translate the data to the correct format *and* 
>> submit it for post processing ? 
> 
> There *is* a lot of data when you turn all this stuff on. If you can get 
> above 115K baud, it’s well worth it. 
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

You mean that LH does not translate the data to the correct format *and* submit 
it for post processing ? 

There *is* a lot of data when you turn all this stuff on. If you can get above 
115K baud, it’s well worth it. 

=

One important qualifier to re-state. L1 post processing is very dependent on 
the distance to an “open” source
of correction data. The spacing of those sites over the US is highly variable. 
If you get outside the US it is very 
much a “that depends” sort of thing. Some countries apparently don’t have the 
same sort of open site network 
that we have in the US. 

Bob

> On Apr 30, 2018, at 4:36 PM, Mark Sims  wrote:
> 
> Coincidentally, yesterday I tweaked up Lady Heather's Ublox code to enable 
> all of the necessary raw data messages.  Heather also enables the raw 
> messages from Trimble TSIP speaking receivers,  the NVS CSM24 receiver, and 
> the Furuno GT87 receiver (if baud rate is >=115200).
> 
> Heather can write a raw data capture file (/dr=filename on the command line 
> or WY from the keyboard).  You should be able to convert those raw capture 
> files to RINEX and then post-process those.
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Re: [time-nuts] nuts about position

[Bob kb8tq]

Hi

If you are looking at doing a self survey on a timing module, there is a lot
of information in the archives. It turns out that (like it or not) there is very
likely to be a ~24 hour periodicity in your self survey data.  Therefor 
something
like a two, three, or four day survey will enhance your position estimate. 

Again - for all get gory details dig into the archives.

Since the timing is done against the module’s “best estimate” of it’s position, 
there isn’t a lot of benefit in having a surveyed correct position instead. More
or less, the same errors that goofed the position also goof the timing in the
same direction. Again, info in the archives. 

Bob

> On Apr 30, 2018, at 2:41 PM, Achim Gratz  wrote:
> 
> Tim Lister writes:
>> It has taken me quite a bit longer that I had hoped but I have finally
>> published a writeup and howto of collecting raw ublox data, converting
>> it to RINEX and how to do (or get the NRC experts to do) the
>> post-processing. It's at a new website I have setup:
>> https://adventuresinprecision.space/howtos/precise-gps-positions/
>> Please let me know any comments or suggestions you have to improve it
>> or make it more comprehensible and comprehensive.
> 
> Thanks for taking the time to write that up.  Out of curiosity, how far
> away from the RINEX coordinates is an RMS or median of the original
> coordinates as recorded by the GPS and how does the convergence curve
> look like?  I'm trying to gauge how long I need to run my timing module
> in survey mode…
> 
> 
> Regards,
> Achim.
> -- 
> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
> 
> Wavetables for the Waldorf Blofeld:
> http://Synth.Stromeko.net/Downloads.html#BlofeldUserWavetables
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

As you have noticed already, it is amazingly easy to get data plots with more 
than the 
real number and less than the real number of digits. Only careful analysis of 
the underlying
hardware and firmware will lead to an accurate estimate of resolution.  

This is by no means unique to what you are doing. Commercial counters are 
very often falling into this trap. If you hook up a SR-620 to it’s internal 
standard, 
you will see a *lot* of very perfect looking digits …. they aren’t real. The HP 
5313x
counters have issues with integer related inputs / reference. This isn’t easy.

Bob

> On Apr 27, 2018, at 2:47 PM, Oleg Skydan <olegsky...@gmail.com> wrote:
> 
> Hi
> 
> From: "Bob kb8tq" <kb...@n1k.org>
> Sent: Friday, April 27, 2018 4:38 PM
>> Consider a case where the clocks and signals are all clean and stable:
>> 
>> Both are within 2.5 ppb of an integer relationship. ( let’s say one is 10
>> MHz and the other is 400 MHz ). The amount of information in your
>> data stream collapses. Over a 1 second period, you get a bit better than
>> 9 digits per second.  Put another way, the data set is the same regardless
>> of where you are in the 2.5 ppb “space”.
> 
> Thanks a lot for pointing me to this problem! It looks like that was the 
> reason I lost a digit. The frequency in my experiment appear to be close to 
> the exact subharmonic of the PLL multiplied reference. It was not less than 
> 2.5ppb off frequency (the difference was approx 0.3ppm), but it still was 
> close enough to degrade the resolution.
> 
> Fortunately it can be fixed in firmware using various methods and I have made 
> the necessary changes. Here are Allan deviation and frequency drift plots. 
> The first one with the old firmware, the second one with the updated firmware 
> that count for the lost of information you mention.
> 
> The frequency difference plot also shows the measurement "noise" now is much 
> lower. It looks like I have got 11 significant digits now and my old OCXOs 
> are better than manufacturer claims by almost 10 times.
> 
> Thanks!
> Oleg UR3IQO
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Re: [time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

So what’s going on here? 

With any of a number of modern (and not so modern) FPGA’s you can run a clock 
in the 400 MHz region. 
Clocking with a single edge gives you a 2.5 ns resolution. On some parts, you 
are not limited to a single 
edge. You can clock with both the rising and falling edge of the clock. That 
gets you to 1.25 ns. For the 
brave, there is the ability to phase shift the clock and do the trick yet one 
more time. That can get you
to 0.6125 ns. You may indeed need to drive more than one input to get that 
done. 

As you get more and more fancy, the chip timing gets further into your data. A 
very simple analogy is
the non-uniform step size you see on an ADC. Effectively you have a number that 
has a +/- ?.?? sort
of tolerance on it. As before that may not what you expect in a frequency 
counter. It still does not mean
the the data is trash. You just have a source of error to contend with. 

You could also feed the data down a “wave union” style delay chain. That would 
get you into the 100ps
range with further linearity issues to contend with. There are also calibration 
issues as well as temperature
and voltage dependencies. Even the timing in the multi phase clock approach 
will have some voltage
and temperature dependency. 

Since it’s an FPGA, coming up with a lot of resources is not all that crazy 
expensive. You aren’t buying 
gate chips and laying out a PCB. A few thousand logic blocks is tiny by modern 
standards. Your counter
or delay line ideal might fit in < 100 logic blocks.  There’s lots of room for 
pipelines and I/O this and that. 
The practical limit is how much you want to put into the “pipe” that gets the 
data out of the FPGA.

In the end, you still are still stuck with the fact that many of the various 
TDC chips have higher resolution / lower cost. 
You also have a pretty big gap between raw chip price and what a fully 
developed instrument will run. 
That’s true regardless of what you base it on and how you do the design. 

Bob



> On Apr 26, 2018, at 5:28 PM, Oleg Skydan  wrote:
> 
> From: "Hal Murray" 
> Sent: Thursday, April 26, 2018 10:28 PM
> 
>> Is there a term for what I think you are doing?
> 
> I saw different terms like "omega counter" or multiple time-stamp
> average counter, probably there are others too.
> 
>> If I understand (big if), you are doing the digital version of magic
>> down-conversion with an A/D.  I can't even think of the name for that.
> 
> No, it is much simpler. The hardware saves time-stamps to the memory at
> each (event) rise of the input signal (let's consider we have digital logic
> input signal for simplicity). So after some time we have many pairs of
> {event number, time-stamp}. We can plot those pairs with event number on
> X-axis and time on Y-axis, now if we fit the line on that dataset the
> inverse slope of the line will correspond to the estimated frequency.
> 
> The line is fitted using linear regression.
> 
> This technique improves frequency uncertainty as
> 
> 2*sqrt(3)*tresolution/(MeasurementTime * sqrt(NumberOfEvents-2))
> 
> So If I have 2.5ns HW time resolution, and collect 5e6 events,
> processing should result in 3.9ps resolution.
> 
> Of cause this is for the ideal case. The first real life problem is
> signal drift for example.
> 
> Hope I was able to tell of what I am doing.
> 
> BTW, I have fixed a little bug in firmware and now ADEV looks a bit better.
> Probably I should look for better OCXOs. Interesting thing - the counter
> processed 300GB of time-stamps data during that 8+hour run :).
> 
> All the best!
> Oleg 
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