Re: [time-nuts] PPP GPSDO v2 - ADEV ~3e-13, e-14 at ~2000 seconds

[Ole Petter Ronningen]

Sorry, typo in the link to the data:
http://www.efos3.com/downloads/GPSDO_brux_28.05.18.zip


On Mon, May 28, 2018 at 10:46 AM Ole Petter Ronningen <opronnin...@gmail.com>
wrote:

> Hi, All
>
> Another somewhat long winded post, my apologies. First off, thank you Bob
> for encouragement and good advice!
>
> A couple of weeks ago I posted some results from a GPSDO based on a
> geodetic GPS dual frequency receiver and real time PPP, hitting e-14 at
> around 6-7.000 seconds with an adev *ceiling* of 5e-13.
>
> This scheme discplines the local oscillator to what amounts to "IGST as
> realized by GPS observations and real time corrections, filtered through
> the PPP process", for lack of a shorter description. I also posted some
> results from measuring, in a somewhat haphazard way, the stability of this
> "IGST virtual clock" - and it was not awesome, at least compared to IGST as
> realized with IGS Rapid products.
>
> The logical next step is to treat this "IGST-like timescale" as a transfer
> clock: (clock A - clock C) - (clock B - clock C) = clock A - clock B, as I
> am led to believe.
>
> The scheme is as follows:
> At the "master" site there is a dual frequency GPS receiver clocked by a
> maser, which makes available a stream of observations to the slave site
> over tcp/ip.
>
> At the "slave" site there is a dual frequency GPS receiver clocked by the
> oscillator we want to discipline, feeding observations to RTKLib which does
> real time PPP using some real time product stream. Also at the slave site
> is another instance of RTKLib, processing the real time stream of
> observations from the master site, using the same corrections. The
> resulting two phase records are then differenced, and the result used to
> feed the PLL which disciplines the local oscillator at the slave site.
>
> Given that TAI is (partially) calculated using pretty much this method[1]
> - apart from the whole real time and disciplining aspect - I had pretty
> high hopes. The instabilities of the "quasi IGST" should simply fall away
> in the differencing, and with some caveats and if's and but's we should
> have access to "maser-like" stability to discipline towards - ofcourse with
> some added noise and some delay - simply through a single TCP port from
> halfway across the world. I thought that would be rather neat.
>
> I've found a paper[2] thats pretty close to what I try to do (except the
> whole "disciplining" thing), and from a cursory reading it seems the basic
> idea is sane.
>
> I ran a zero-baseline experiment doing precisely what I outlined above:
> Two separate GPS receivers in my lab, with separate local oscillators (the
> maser being one of them), each feeding an instance of RTKLib using the same
> settings and the same stream of corrections. The resulting clock solutions
> was matched by timestamps, and the differenced output - simply "phase A -
> phase B", was used as input to a PI-controller that disciplines the local
> oscillator of one receiver.
>
> The results was encouraging - e-14 in 3000 seconds or so, but I am too
> impatient to wait for long enough. I then decided I should try to
> discipline the BVA to a different maser - and as luck would have it, the
> IGS Network has dozens of sites clocked by masers and the observations can
> be had real time. Ideal for what I am trying to achieve. I selected a
> receiver/maser in Bruxelles and left it alone over night. This morning,
> Timelab had some nice traces, attached.
>
> The screenshot shows two traces: Purple, all data. Teal, 1 hour starting
> at approx 00:00 UTC deleted.
>
> Two things are evident in the plot: the basic approach works - but it does
> not work "perfectly". Even when differencing the phase records, there is
> plently of crud left. I need to run a zero baseline common clock
> comparison. In particular there is an unsightly bump starting at precisely
> 00:00 UTC - I have not chased down the cause of this, but I suspect it can
> be managed/compensated for.
>
> It was precisely this kind of crud I was hoping the differencing would get
> rid of. As it stands, the approach works pretty well, but I am not
> confident it works very much better than simply disciplining to IGST
> directly. In [2] they do some pretty hefty cleanup of the data, that I dont
> think will make it into RTKLib (at least I am not competent to put it
> there..)
>
> Anyway, I thought it was a neat experiment. And theres *much* that still
> needs testing (which correction streams[3], should GLONASS be included, L2C
> or not, various PPP knobs and dials, PI-tuning, optimal sampleinterval, etc
> etc), and of course much more data to col

[time-nuts] PPP GPSDO v2 - ADEV ~3e-13, e-14 at ~2000 seconds

[Ole Petter Ronningen]

Hi, All

Another somewhat long winded post, my apologies. First off, thank you Bob
for encouragement and good advice!

A couple of weeks ago I posted some results from a GPSDO based on a
geodetic GPS dual frequency receiver and real time PPP, hitting e-14 at
around 6-7.000 seconds with an adev *ceiling* of 5e-13.

This scheme discplines the local oscillator to what amounts to "IGST as
realized by GPS observations and real time corrections, filtered through
the PPP process", for lack of a shorter description. I also posted some
results from measuring, in a somewhat haphazard way, the stability of this
"IGST virtual clock" - and it was not awesome, at least compared to IGST as
realized with IGS Rapid products.

The logical next step is to treat this "IGST-like timescale" as a transfer
clock: (clock A - clock C) - (clock B - clock C) = clock A - clock B, as I
am led to believe.

The scheme is as follows:
At the "master" site there is a dual frequency GPS receiver clocked by a
maser, which makes available a stream of observations to the slave site
over tcp/ip.

At the "slave" site there is a dual frequency GPS receiver clocked by the
oscillator we want to discipline, feeding observations to RTKLib which does
real time PPP using some real time product stream. Also at the slave site
is another instance of RTKLib, processing the real time stream of
observations from the master site, using the same corrections. The
resulting two phase records are then differenced, and the result used to
feed the PLL which disciplines the local oscillator at the slave site.

Given that TAI is (partially) calculated using pretty much this method[1] -
apart from the whole real time and disciplining aspect - I had pretty high
hopes. The instabilities of the "quasi IGST" should simply fall away in the
differencing, and with some caveats and if's and but's we should have
access to "maser-like" stability to discipline towards - ofcourse with some
added noise and some delay - simply through a single TCP port from halfway
across the world. I thought that would be rather neat.

I've found a paper[2] thats pretty close to what I try to do (except the
whole "disciplining" thing), and from a cursory reading it seems the basic
idea is sane.

I ran a zero-baseline experiment doing precisely what I outlined above: Two
separate GPS receivers in my lab, with separate local oscillators (the
maser being one of them), each feeding an instance of RTKLib using the same
settings and the same stream of corrections. The resulting clock solutions
was matched by timestamps, and the differenced output - simply "phase A -
phase B", was used as input to a PI-controller that disciplines the local
oscillator of one receiver.

The results was encouraging - e-14 in 3000 seconds or so, but I am too
impatient to wait for long enough. I then decided I should try to
discipline the BVA to a different maser - and as luck would have it, the
IGS Network has dozens of sites clocked by masers and the observations can
be had real time. Ideal for what I am trying to achieve. I selected a
receiver/maser in Bruxelles and left it alone over night. This morning,
Timelab had some nice traces, attached.

The screenshot shows two traces: Purple, all data. Teal, 1 hour starting at
approx 00:00 UTC deleted.

Two things are evident in the plot: the basic approach works - but it does
not work "perfectly". Even when differencing the phase records, there is
plently of crud left. I need to run a zero baseline common clock
comparison. In particular there is an unsightly bump starting at precisely
00:00 UTC - I have not chased down the cause of this, but I suspect it can
be managed/compensated for.

It was precisely this kind of crud I was hoping the differencing would get
rid of. As it stands, the approach works pretty well, but I am not
confident it works very much better than simply disciplining to IGST
directly. In [2] they do some pretty hefty cleanup of the data, that I dont
think will make it into RTKLib (at least I am not competent to put it
there..)

Anyway, I thought it was a neat experiment. And theres *much* that still
needs testing (which correction streams[3], should GLONASS be included, L2C
or not, various PPP knobs and dials, PI-tuning, optimal sampleinterval, etc
etc), and of course much more data to collect.

Ole

.tim-file (with all data) here: http://www.efos3
,com/downloads/GPSDO_brux_28.05.18.zip

[1]: The TAIPPP pilot experiment (
https://www.researchgate.net/publication/224564551_The_TAIPPP_pilot_experiment
)
[2]: Monitoring of UTC(k)’s using PPP and IGS real-time products (
http://sci-hub.tw/10.1007/s10291-014-0377-5)
[3]: Assessment of Multiple GNSS Real-Time SSR Products from Different
Analysis Centers (http://www.mdpi.com/2220-9964/7/3/85/pdf)
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Re: [time-nuts] Sub 5e-13 ADEV GPSDO

[Ole Petter Ronningen]

Hi, Bert

Yes, the ionosphere is most definately taken out of the equation using this
method, as is a few other effects such as solid earth tides. I am working
on a writeup here http://www.efos3.com/GPSDO/GPSDO.html

Still work in progress, but it has come along some way - you're welcome to
a "preview".

The actual receiver does not matter very much, the method is not specific
to the Novatel. I am also running a Trimble NetRS which works just fine for
monitoring my maser, and I am sure many other would work, I know some
timing labs used a variant of the Ashtec Z-12; the only think that matters
is that 1) it will take an external reference frequency, and 2) you can get
the raw GPS observations out of it. If RTKLib can parse the obervation
messages directly, you will save yourself some hassle. (It can parse many
different formats, although I have only tested Novatel and Trimble RT17,
both work fine.) The PPP processing takes care of the rest. I also have a
writeup on how to use PPP for frequency monitoring here if you are
interested: http://www.efos3.com/ppp.html

I could be interested in borrowing a Furuno if you are willing, it could be
interesting to compare it to my maser - would give some pretty good
measurements of the PPS accuracy
Ole

On Tue, May 15, 2018 at 12:07 PM ew via time-nuts 
wrote:

> Thank you Ole
> Juerg and I spend most our time on frequency,control and measuring. We
> also see 2 E-12 frequency using GPS and blame the Ionosphere. Which brings
> up the Question does the way you use the OEMV-3 in your experiment use L1
> L2 compensation and where can I buy one? Looked for hours last night.
> Second have you looked at the Furuno GT-87 we bought the latest version
> which claims 1.7 nsec saw tooth . Buerklin in Germany sells them, we bought
> some and I expect boards tomorrow. If you want some boards I mail them to
> you.
> Bert
>
> In a message dated 5/14/2018 4:16:03 PM Eastern Standard Time,
> opronnin...@gmail.com writes:
>
>
>  Hi
>
> Perhaps this is of interest to some. I finally got around to doing an
> experiment I've been mulling over for some time.
>
> In short, I use a Novatel OEMV-3 GPS receiver, clocked by an Oscilloquartz
> 8600 BVA, process the observations with RTKLib and real time corrections
> from igs - and use the resulting clock solutions as inputs to a software
> PLL that sets the EFC on the BVA via a Keysight 33510B function generator
> set to DC. A bit of a contraption, but it works surprisingly well (or
> perhaps I should say it surprisingly works!)
>
> I measured the GPSDO using a TimePod and my maser.
>
> There is *much* room for improvement, and probably too little data, but I
> thought the preliminary results worthy of a post: The ADEV is <5e-13 on the
> "hump". It passes through to e-14 territory around 6-7000 seconds, at least
> in this dataset. The TDEV flattens out around 2e-10 at 2000 seconds or so
> (a little wiggle on the end, but I choose to ignore that and blame it on
> not enough data).
>
> If the masks in TimeLab are to be trusted, it is very close to a 5071A high
> performance option in this region (400 to 1 seconds), and of course
> much better at lower taus.
>
> The frequency accuracy stays within 2-3e-12, and the phase rarely wanders
> off more than 1 ns.
>
> I have pretty much everything to learn about tuning GPSDO's, but I think it
> shows that the approach is viable. I ofcourse also need to collect a *lot*
> more data, get a proper DAC in place and so forth, but still.
>
> To get some sort of baseline, I also processed in real time using the same
> correction stream observations from a Trimble NetRS clocked by the hydrogen
> maser (sadly not at the same time) - the resulting curves should pretty
> accurately show the limits of the approach - at least using the corrections
> I was using (CLK93; there are many to chose from, and frankly I don't know
> which would be best for something like this. )
>
> The .tim-files are here: http://www.efos3.com/downloads/GPSDO_14.05.18.zip
>
> As a final thought - this setup can be made "self documenting": log the
> observations to RINEX-files, and solve with PPP and IGS Rapid or other
> corrections. The resulting phase record should be good to at least low e-15
> from what I understand (and observe).
>
> Ole
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[time-nuts] Sub 5e-13 ADEV GPSDO

[Ole Petter Ronningen]

Hi

Perhaps this is of interest to some. I finally got around to doing an
experiment I've been mulling over for some time.

In short, I use a Novatel OEMV-3 GPS receiver, clocked by an Oscilloquartz
8600 BVA, process the observations with RTKLib and real time corrections
from igs - and use the resulting clock solutions as inputs to a software
PLL that sets the EFC on the BVA via a Keysight 33510B function generator
set to DC. A bit of a contraption, but it works surprisingly well (or
perhaps I should say it surprisingly works!)

I measured the GPSDO using a TimePod and my maser.

There is *much* room for improvement, and probably too little data, but I
thought the preliminary results worthy of a post: The ADEV is <5e-13 on the
"hump". It passes through to e-14 territory around 6-7000 seconds, at least
in this dataset. The TDEV flattens out around 2e-10 at 2000 seconds or so
(a little wiggle on the end, but I choose to ignore that and blame it on
not enough data).

If the masks in TimeLab are to be trusted, it is very close to a 5071A high
performance option in this region (400 to 1 seconds), and of course
much better at lower taus.

The frequency accuracy stays within 2-3e-12, and the phase rarely wanders
off more than 1 ns.

I have pretty much everything to learn about tuning GPSDO's, but I think it
shows that the approach is viable. I ofcourse also need to collect a *lot*
more data, get a proper DAC in place and so forth, but still.

To get some sort of baseline, I also processed in real time using the same
correction stream observations from a Trimble NetRS clocked by the hydrogen
maser (sadly not at the same time) - the resulting curves should pretty
accurately show the limits of the approach - at least using the corrections
I was using (CLK93; there are many to chose from, and frankly I don't know
which would be best for something like this. )

The .tim-files are here: http://www.efos3.com/downloads/GPSDO_14.05.18.zip

As a final thought - this setup can be made "self documenting": log the
observations to RINEX-files, and solve with PPP and IGS Rapid or other
corrections. The resulting phase record should be good to at least low e-15
from what I understand (and observe).

Ole
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Re: [time-nuts] nuts about position (cheap receiver)

[Ole Petter Ronningen]

In my experience, there is little difference between the Final and Rapid,
which will be out just about now (for yesterdays observations)

Ole

On Thu, May 3, 2018 at 6:26 PM Mark Sims  wrote:

> To give an idea about the possible improvement in antenna location
> available by post-processing the data,  I first did a 2 hour self-survey
> and that put the receiver into position hold mode.  Then I collected RINEX
> data for 16 hours.   The post-processed lat/lon/alt values differed around
> 1/1/3 meters better than the self-survey values (with estimated error
> ellipses of 0.17/0.15/0.4 meters).   Those results were with the "ultra
> rapid" orbits.  It will be interesting to see what they look like when the
> final precise orbits are available in a couple of weeks.
>
> I also need to see how those values compare to Lady Heather's precision
> survey results.
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Re: [time-nuts] nuts about position

[Ole Petter Ronningen]

Hi

I just ran a quick test - a Ublox 6T was configured to output the RXM-RAW
messages every second and logging for some 14 hours using U-Center. The
.ubx-file was converted to RINEX using teqc.exe, and uplaoded to NrCAN PPP.
NrCAN PPP will process single frequency observations and correct using
ionospheric maps I *believe*. (If I am wrong, ignore this post!)

I also continously log observations from a Trimble NetRS dual frequency GPS
receiver, hooked up to the same antenna. I trust the PPP-calculated
position accuracy of this receiver to within low double digits to high
single digit millimeters.

(For comparison, the report from NrCAN gives a 95% error ellipse on the
UBlox as semi-major: 2.494dm, semi-minor: 1.760dm. The corresponding
numbers for the NetRS is semi-major: 1.245cm, semi-minor: 0.760cm - the
reports are usually below 10 mm in both axis. Note difference in units.)

Comparing the calculated ECEF coordinates from the ppp-results using
Pythagoras gives me a distance of 76 cm - 53 cm if we simply ignore height.

This is with a survey grade antenna in a good location. It might be
possible to shrink this to 30 cm and still have confidence in the results,
but I think it would not be easy. I would guess a lot more data would be
required, and it is also possible that delaying processing until more
accurate ionospheric maps are available could help.

I will reprocess in a couple of days and see if theres much of a difference.

Ole

On Wed, Apr 25, 2018 at 4:56 PM, Tom Van Baak  wrote:

> List -- I had a recent query by a researcher who would like to pinpoint
> the location of his telescope(s) within 0.3 meters. Also (he must be a true
> scientist) he wants to do this on-the-cheap. He may have timing
> requirements as well, but that's another posting.
>
> So I toss the GPS question to the group. Surely some of you have crossed
> the line from precise time to precise location?
>
> How easy, how cheap, how possible is it to obtain 0.3 m accuracy in 3D
> position?
>
> When we run our GPSDO in survey mode how accurate a position do we get
> after an hour, or even 24 or 48 hours? And here I mean accurate, not
> stable. Have any of you compared that self-reported, self-survey result
> against an independently measured professional result or known benchmark?
>
> Do you know if cheap ublox 5/6/7/8 series receivers are capable of 1 foot
> accuracy given enough time?
>
> If not, what improvement would -T models and RINEX-based web-service
> post-processing provide?
>
> It that's still not close enough to 0.3 m, is one then forced to use more
> expensive multi-frequency (L1/L2) or multi-band (GPS, GLONASS, Galileo) to
> achieve this level of precision? If so, how cheaply can one do this? Or is
> the learning curve more expensive than just hiring an survey specialist to
> make a one-time cm-level measurement for you?
>
> Something tells me 1 foot accuracy in position is possible and actually
> easier than 1 ns accuracy in time. I'm hoping some of you can help
> recommend solution(s) to the researcher's question or shed light on this
> interesting challenge.
>
> Thanks,
> /tvb
>
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Re: [time-nuts] ADEV slopes and measurement mode

[Ole Petter Ronningen]

Thanks!

I think it will require more than one reading.. :)

Ole

On Thu, Apr 19, 2018 at 12:08 AM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Hi Ole Petter,
>
> On 04/16/2018 12:12 PM, Ole Petter Ronningen wrote:
> > Hi, All
> >
> > This will be a bit long, and I apologize for it. Perhaps someone else
> also
> > struggle with the same.
> >
> > One of the properties of the familiar ADEV-plots are the slopes - and how
> > the slope identify the dominant noise type for the various portions of
> the
> > plots. My understanding is that the slopes stem from "how the noise
> behaves
> > under averaging" - White FM follows the usual white noise slope of
> > 1/sqrt(N), or to put it another way; the standard deviation of a set of
> > many averages of length N will fall as sqrt(N) when N increases. If the
> > standard deviation of the whole non-averaged list is 1, the standard
> > deviation of a set of 100-point averages will be 1/10. Other noise types
> > does not follow the same 1/sqrt(N) law, hence will give rise to other
> > slopes as the number of points averaged increases as we look further to
> the
> > right of the plot.
> >
> > If I have already droppped the ball, I'd appreciate a correction..
>
> Hrhrm!
>
> It's not directly averaging but kind of. Ehm. Let me see how to explain
> this...
>
> When you measure frequency, one way or another, two time-stamps is
> formed. The distance between those two time-stamps will be the
> observation time tau. As you count how many cycles, often called events,
> that occurred over that time, you can calculate the frequency as
> events/time. This is the basis of all traditional counters, which we
> these days call Pi-counters, for reasons I will explain separately.
>
> Now, we could be doing this measurement as N sequential back-to-back
> measurements, where the stop event becomes the start event of the next
> measurmeent. As we sum these up the phase of the stop and the start of
> the next cancels and the full sum will become that of the first
> start-event and last stop-event. Regardless how we divide it up or not,
> it will end up being the same measurement. The averaging thus kind of
> cancels out and interestingly does not do anything.
>
> Now, as we attempt to establish the statistical stability of this value
> using the normal standard variance and standard deviation methods, also
> known as Root Mean Square (RMS) algorithm, we have a bit of a problem,
> because the noises of an oscillator is non-convergent. So, an
> alternative method to handle that was presented in the 1966 Feb article
> by that David Allan. It still provide variance and deviation measures,
> but without being caught by the convergence problems.
>
> The ADEV for a certain observation interval is thus an equivalent to
> standard deviation measure, to explain how good stability there is for
> the measure at that observation interval, regardless of how we divided
> the measurement up to form the frequency estimations, as long as they
> form a continuous measurement, thus without dead-time.
>
> The slopes stems from how the 1/f^n power distributions of noises gets
> inverse Fourier transformed into time-domain, which is the basis for
> David Allans article, he uses that out of the M.J.Lighthill "An
> introduction to Fourier analysis and generalised functions" and adapts
> to the power distributions noises. Because different 1/f^n noises is
> dominant in different parts of the spectrum, their slopes in the time
> domain will also show the same dominant features and thus be the limit
> of precision in our measurement.
>
> Now, if there happens to be gaps in the data as gathered, the dead-time
> would cause a bias in the estimated stability, but that bias can be
> predicted and thus compensated for, and was passed to a separate bias
> function that was also modeled in the same article. That way, the bias
> of the counters they had at the time could be overcome to result in
> comparable measures.
>
> The obsticle of the averaging over N samples that prohibited the use of
> the normal RMS function could be separated out into another bias
> function that also was modeled in the article. This way a 5-point
> stability measure and a 3-point stability measure could be compared, by
> converting it into the 2-point stability measure. The 2-point variance
> later became coined Allan's variance and later Allan variance. That
> article forged the ring to control the variances.
>
> I can explain more about how the averaging does not give you more help,
> but the bias function is good enough. I've done simulations to prove
> this to myself and it is really amazing 

Re: [time-nuts] 53230A weirdness

[Ole Petter Ronningen]

Although, as I read the paper again, it is possible that the frequency bias
in the 10 second CONT-mode measurements could come from this effect.

That particular series (and only that) was collected using TimeLab. I
supplied them with a custom compiled driver that does not use repeated
calls to READ - and therefore does not exhibit this particular bias. I
always assumed that this driver was used to collect that series, but the
paper does not state this explicitly so I might be wrong.

The bias I am pointing to is gate time dependant, the bias getting smaller
with longer gate times. It is possible it will be at the E-15 level at 10
second gatetime, like in the paper.

Ole

On Fri, Nov 24, 2017 at 2:45 PM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Ole,
>
> Is this part of the behavior that the Norwegian NMI was presenting at a
> poster session at EFTF 2016 in York?
>
> I remember they borrowed your 53230A for that work.
>
> Cheers,
> Magnus
>
>
> On 11/23/2017 09:05 PM, Ole Petter Ronningen wrote:
>
>> Hi, all
>>
>> I've done some experiments on my 53230A, and I've come across an issue I
>> think could be worth knowing about.
>>
>> I have not tested this on other 53230A's - if anyone has a 53230A and some
>> spare time, I'd be grateful if someone could try to replicate.
>>
>> In a nutshell, the first frequency measurement following an INIT is
>> biased.
>> The magnitude of the bias is dependant on measurement mode (CONT/RCON),
>> and
>> gate time.
>>
>> It is worth noting that every READ implicitly calls INIT - so any software
>> collecting a time series using repeated calls to READ to fetch single
>> readings will give biased results. Not for the first sample in the series,
>> but all of them.
>>
>> As an example, the last time series I collected this way using RCON and
>> 0.1s gatetime gave an average frequency error of -5.2e-10.
>>
>> A writeup is here: http://www.efos3.com/HPAK53230A-1.html
>>
>> Best regards,
>> Ole
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Re: [time-nuts] 53230A weirdness

[Ole Petter Ronningen]

Hi Magnus

No, I believe this is a separate issue. The data for that paper was
collected gap free, and was not affected by this particular issue.

It may be related somehow - as presented in that paper, data collected in
CONT mode shows a slope of tau^-1/2 on ADEV.

Data collected gap free in RCON-mode (i.e. not by repeated calls to READ)
shows the expected slope of Tau^-1.

The issue I point out here is that if data is collected using repeated
calls to "READ", even data collected in RCON-mode shows a slope of
tau^-1/2, in addition to a frequency bias. The magnitude of the frequency
bias is gate time dependent.

Ole

On Fri, Nov 24, 2017 at 2:45 PM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Ole,
>
> Is this part of the behavior that the Norwegian NMI was presenting at a
> poster session at EFTF 2016 in York?
>
> I remember they borrowed your 53230A for that work.
>
> Cheers,
> Magnus
>
>
> On 11/23/2017 09:05 PM, Ole Petter Ronningen wrote:
>
>> Hi, all
>>
>> I've done some experiments on my 53230A, and I've come across an issue I
>> think could be worth knowing about.
>>
>> I have not tested this on other 53230A's - if anyone has a 53230A and some
>> spare time, I'd be grateful if someone could try to replicate.
>>
>> In a nutshell, the first frequency measurement following an INIT is
>> biased.
>> The magnitude of the bias is dependant on measurement mode (CONT/RCON),
>> and
>> gate time.
>>
>> It is worth noting that every READ implicitly calls INIT - so any software
>> collecting a time series using repeated calls to READ to fetch single
>> readings will give biased results. Not for the first sample in the series,
>> but all of them.
>>
>> As an example, the last time series I collected this way using RCON and
>> 0.1s gatetime gave an average frequency error of -5.2e-10.
>>
>> A writeup is here: http://www.efos3.com/HPAK53230A-1.html
>>
>> Best regards,
>> Ole
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[time-nuts] 53230A weirdness

[Ole Petter Ronningen]

Hi, all

I've done some experiments on my 53230A, and I've come across an issue I
think could be worth knowing about.

I have not tested this on other 53230A's - if anyone has a 53230A and some
spare time, I'd be grateful if someone could try to replicate.

In a nutshell, the first frequency measurement following an INIT is biased.
The magnitude of the bias is dependant on measurement mode (CONT/RCON), and
gate time.

It is worth noting that every READ implicitly calls INIT - so any software
collecting a time series using repeated calls to READ to fetch single
readings will give biased results. Not for the first sample in the series,
but all of them.

As an example, the last time series I collected this way using RCON and
0.1s gatetime gave an average frequency error of -5.2e-10.

A writeup is here: http://www.efos3.com/HPAK53230A-1.html

Best regards,
Ole
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Ole Petter Ronningen]

>
>
> > 4.5 liters in EFOS type masers - so not *that* small. I believe other
> > masers are the same order of magnitude.
>
> Hehe.. Yes. It's "small" compared to the cavity. Depending on the
> exact cavity construction, the storage space can be as small as
> a tenth of the total cavity volume.


Thats interesting, I would think a small volume would result in increased
spin exchange - do you have any papers detailing the tradeoffs with
big/small storage bulbs?
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Ole Petter Ronningen]

On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali  wrote:

> [...] The advantage of the platinum valve
> system is that it "generates" single atom Hydrogen, as required
> by the maser.


Picking nits here.. It was my understanding that the splitting of molecular
hydrogen into atomic hydrogen happens using RF in the dissociator - not in
the platinum leak valve. Is my understanding incorrect?


> Within the cavity there is a small glass bulb that keeps the atoms
> in the right position of the cavity field.


4.5 liters in EFOS type masers - so not *that* small. I believe other
masers are the same order of magnitude.


> Yes, IIRC normal numbers are several 10s to 100s of wall collisions
> before the atom loses its state due to wall colisions and without
> contributing to the signal.
>

Lifetime ~1 second I think


> > I've long wondered what causes the slow frequency drift, typically
> amounting
> > to about 3E-14 over a time span of several months.
>
> Mostly changes in the wall coating leading to a different wall collision
> shift and mechanical changes of the cavity dimension (think air pressure
> and creep) leading to a different cavity pulling. To a lesser extend
> it's the changes in the quality of the vacuum and number of Hydrogen atoms
> in the cavity.


Also aging of electronic components - coarse tuning of the cavity is done
by temperature, and any drift if the temperature-sensor/amplifiers etc will
result in drift. At least for EFOS type masers.

Ole
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Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

[Ole Petter Ronningen]

Hi, Jim!

On Wed, Nov 8, 2017 at 3:12 AM, jimlux  wrote:

>
> http://www.navipedia.net/index.php/Ionospheric_Delay
> has a nice discussion with simple equations to turn TEC into delay, etc.
>

I've already skimmed this, and it requires a bit more brainpower than I can
muster for what I want to accomplish.. :) BUT! Re-reading it I got to the
page on "Combination of GNSS Measurements" - and the geometry free
combination of L1 and L2 is exactly what I was looking for; some quantity
proportional to TEC that I can correlate with the daily excursions of the
Ublox PPS. So, yeah, thanks! That gave me just what I needed! :) Now to
cobble up a RINEX parser..


> You might also look into seeing if you can put your data in a form to be
> processed by GIPSY at JPL - they have a service where you can upload your
> raw observables and they post process it.
>

GIPSY solves using PPP, does it not? I already process the data with PPP
from each of the receivers using both the  NRCan online service and locally
using gLAB - using one to "sanity check" the results from the other, but
I'll have another look at GIPSY.

Thanks!
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Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

[Ole Petter Ronningen]

Yes, I thought so too - but on the same antenna I have a couple of L1/L2
continously logging survey receivers; the position accuracy should be
within 5-10 mm. Unless I've messed something up with coordinate systems,
the position the UBlox thinks it has should be pretty good.

Ole

On Tue, Nov 7, 2017 at 5:43 PM, Jean-Louis Oneto <jl.on...@free.fr> wrote:

> Hi Ole,
> I think that the long term undulation are caused by a (small) error in
> geodetic position of the antenna. The period should be a sidereal day
> (23:56...)
> Have a good day,
> Jean-Louis
>
>
>
> Envoyé depuis mon appareil mobile Samsung.
>
> -------- Message d'origine 
> De : Ole Petter Ronningen <opronnin...@gmail.com>
> Date :07/11/2017  15:15  (GMT+01:00)
> A : Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Objet : Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?
>
> Hi all
>
> Attached is a 24 hour plot of PPS out from a UBlox 6T against a hydrogen
> maser. From 00:00 the bare receiver board was inside a polystyrene box
> where it has soaked for many months, at 16:00 I removed the box exposing
> the board to the airflow in the room, including AC. The box was left off
> for the rest of the day.
>
> The green trace is temperature in the lab. The "long term undulation" in
> phase is normal, although I do not know the precise cause (multipath or
> something else. I am reasonably sure it is not related to temperature in
> the lab.
>
> [image: Inline image 1])
>
> Ole
>
> On Sat, Nov 4, 2017 at 6:06 PM, Denny Page <de...@cococafe.com> wrote:
>
> > [I hate finding unsent email in my folder :-]
> >
> > Others may disagree, but I doubt that the type of small temperature
> > variation you are referring to has any meaningful effect on tracking.
> While
> > the datasheet for the M8T says that there can be "significant impact" to
> > the specifications at “extreme operating temperatures,” it gives the
> > operating temperature as -40 to +85 C. Simply said, if you can stand to
> be
> > in the same room/space with it, I think you are fine.
> >
> > Of much greater interest would be the antenna and it’s placement. I’m
> > afraid I can’t specifically recommend a “good” antenna, but perhaps
> others
> > on the list can. For my EVK-M8T, I’m using the antenna that came with the
> > kit and it works very well. I haven’t tested other antennas with the M8T
> at
> > this time, but I do have a number of other devices with antennas that
> work
> > well. I also have a few antennas that work poorly with all the devices,
> > including the ones with which they came. Unfortunately pretty much all of
> > them lack sufficient identification markings to identify
> manufacture/model
> > info.
> >
> > Regarding placement, I’ve found that in a restricted area even a few
> > inches can have a significant impact on the average number of satellites
> > and signal level. In my case, it’s associated with the single building
> > structure, but it sounds your case is even more restrictive. Although it
> > can be a very lengthy process, performing antenna surveys may help
> improve
> > your situation. For each location, you need to monitor the number of
> > satellites and signal level for 24 hours or more before determining the
> > relative merit of that location. Repeat… and repeat.. and repeat.
> > Determining the very best location for the antenna will likely require as
> > many antenna surveys as you have patience for. :)
> >
> > Hope this helps.
> >
> > Denny
> >
> >
> > > On Nov 02, 2017, at 18:54, MLewis <mlewis...@rogers.com> wrote:
> > >
> > > Earlier this week, I put the breakout board with my NEO-M8T into an
> > aluminum can. The can is split into a lower half and an upper half. The
> > lower half was insulated on its sides internally, but open to the upper
> > half, which wasn't insulated. The lower area contains the NEO-M8T on its
> > breakout board and its matching com breakout board.
> > >
> > > In the unusual skyview/RF environment described below:
> > > - LH was typically showing two or three green sats, with a min of none
> > and a max of five for very brief periods.
> > > - The average dBc of the green sats was 22 dBc, with a max of 29 dBc.
> > > - Two screen shots of LH from this time period show an Accu of 12 ns
> and
> > 33 ns.
> > >
> > > This morning, I insulated the inside of the upper half of the can, and
> > added insulation to seal the top of the lower area into a chamber that
> &

Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

[Ole Petter Ronningen]

Hi all

Attached is a 24 hour plot of PPS out from a UBlox 6T against a hydrogen
maser. From 00:00 the bare receiver board was inside a polystyrene box
where it has soaked for many months, at 16:00 I removed the box exposing
the board to the airflow in the room, including AC. The box was left off
for the rest of the day.

The green trace is temperature in the lab. The "long term undulation" in
phase is normal, although I do not know the precise cause (multipath or
something else. I am reasonably sure it is not related to temperature in
the lab.

[image: Inline image 1])

Ole

On Sat, Nov 4, 2017 at 6:06 PM, Denny Page  wrote:

> [I hate finding unsent email in my folder :-]
>
> Others may disagree, but I doubt that the type of small temperature
> variation you are referring to has any meaningful effect on tracking. While
> the datasheet for the M8T says that there can be "significant impact" to
> the specifications at “extreme operating temperatures,” it gives the
> operating temperature as -40 to +85 C. Simply said, if you can stand to be
> in the same room/space with it, I think you are fine.
>
> Of much greater interest would be the antenna and it’s placement. I’m
> afraid I can’t specifically recommend a “good” antenna, but perhaps others
> on the list can. For my EVK-M8T, I’m using the antenna that came with the
> kit and it works very well. I haven’t tested other antennas with the M8T at
> this time, but I do have a number of other devices with antennas that work
> well. I also have a few antennas that work poorly with all the devices,
> including the ones with which they came. Unfortunately pretty much all of
> them lack sufficient identification markings to identify manufacture/model
> info.
>
> Regarding placement, I’ve found that in a restricted area even a few
> inches can have a significant impact on the average number of satellites
> and signal level. In my case, it’s associated with the single building
> structure, but it sounds your case is even more restrictive. Although it
> can be a very lengthy process, performing antenna surveys may help improve
> your situation. For each location, you need to monitor the number of
> satellites and signal level for 24 hours or more before determining the
> relative merit of that location. Repeat… and repeat.. and repeat.
> Determining the very best location for the antenna will likely require as
> many antenna surveys as you have patience for. :)
>
> Hope this helps.
>
> Denny
>
>
> > On Nov 02, 2017, at 18:54, MLewis  wrote:
> >
> > Earlier this week, I put the breakout board with my NEO-M8T into an
> aluminum can. The can is split into a lower half and an upper half. The
> lower half was insulated on its sides internally, but open to the upper
> half, which wasn't insulated. The lower area contains the NEO-M8T on its
> breakout board and its matching com breakout board.
> >
> > In the unusual skyview/RF environment described below:
> > - LH was typically showing two or three green sats, with a min of none
> and a max of five for very brief periods.
> > - The average dBc of the green sats was 22 dBc, with a max of 29 dBc.
> > - Two screen shots of LH from this time period show an Accu of 12 ns and
> 33 ns.
> >
> > This morning, I insulated the inside of the upper half of the can, and
> added insulation to seal the top of the lower area into a chamber that
> contained the GPS module board & its com board. Since then, its run for
> around ten hours, same weather as yesterday except more rain, ambient room
> temperature wasn't measured but is definitely warmer. Since after around an
> hour of running:
> > - LH has been showing between two and eight green sats, typically three
> to five:
> > - Their average dBc is 30 dBc, with a max of 37 dBc.
> > - LH Accu is showing as 6 ns.
> >
> > I have no idea what the temperature is inside the chamber.
> >
> > As I write this, LH is showing three green sats, at 33, 34 and 35 dBc.
> >
> > I expected a more stable internal TCXO in the GPS module, but I didn't
> expect stronger signals. Although perhaps I should have, as the block
> diagram for the NEO-M8T does show its TCXO pointing at a "Fractional N
> Synthesizer" inside the UBX-M8030's "RF Block". It also shows a RTC Crystal
> for a RTC inside the "Digital Block".
> >
> > Is this coincidence or can reception improve with:
> > - a higher temperature module?
> > - a more stable module temperature?
> >
> > I'm tempted to add some thermal mass (block of Al) to the top of the M8T
> and a chunk of insulation on top of that.
> >
> > Michael
> >
> > p.s.
> > As I finish this, LH is showing five sats, 23, 30, 31, 32 & 34 dBc, Accu
> 6 ns
> >
> > On 01/11/2017 9:55 AM, MLewis wrote:
> >> I had anticipated reception issues, which is why I went with the M8T
> for its sensitivity, multi-constellation and it's a timing module so a good
> PPS on a single sat - only to get surprised that my version didn't have GAL
> enabled. But I didn't 

Re: [time-nuts] I've been thinking about a GPS receiver experiment

[Ole Petter Ronningen]

I did log the #TIME message for several weeks on an OEMV-3 a while back.
The results were a bit suspicious, so I checked with Novatel support -
turns out the PPS on the OEMV (and I presume that also holds for OEM4) is
derived from L1 only - and the jitter is nothing to brag about. So for
disciplining with PPS, something like a UBlox would be better as far as I
can tell.

The other option is to log the #RANGE-message from the Novatel, convert to
RINEX and solve with PPP, and use the output of that to adjust the
rubidium. The added benefit is that you'll have an excellent log of what
your reference is doing if you get odd results in some measurements.

Ole

On Wed, Oct 25, 2017 at 12:56 AM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Skip,
>
> I would rather use the rich Novatel reports and read out the time error
> and use that as your phase detector, then the normal PI-loop stuff with an
> optional low-pass to add and then use that to steer the rubidium.
>
> It's one of those, when I get time, projects.
>
> Cheers,
> Magnus
>
>
> On 10/25/2017 12:17 AM, Skip Withrow wrote:
>
>> Hello time-nuts,
>>
>> I've been thinking about a GPS receiver experiment and just wondering
>> if there are any opinions or prior experience that might save me a lot
>> of time.
>>
>> What I have been thinking about doing is taking a GPS receiver
>> (Novatel OEM4-G2) that has provisions for an external clock (5 or 10
>> MHz) and driving it with a rubidium oscillator (that has 1pps
>> disciplining, (such as the X72 v5.05 or SRS PRS-10).  The GPS even has
>> settings for OCXO/rubidium/cesium dynamics.
>>
>> Then, (and here is the unknown part) what if the GPS receiver 1pps is
>> used to discipline the rubidium?  This basically forms a feedback
>> loop, so could either hurt or help - depending.  Supposedly the better
>> oscillator would give a better GPS solution.  And the better solution
>> (1pps) should provide a better oscillator frequency.
>>
>> We know that GPS receivers using asynchronous clocks have 1pps errors
>> and hanging bridges (OEM4 is spec'd at 20ns rms), If the oscillator is
>> on 10MHz and disciplined will the 1pps error be reduced such as the
>> Thunderbolt?
>>
>> Comments appreciated.
>>
>> Regards,
>> Skip Withrow
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[time-nuts] Outlier detection and removal

[Ole Petter Ronningen]

Hi, all

A reasonably well known method of outlier detection in phase data is to
convert to frequency and look for outliers more than k multiples of the
Median Absolute Deviation. I believe this is how outlier detection is done
in Stable32[1].

I have implemented an approximation to this method - I do not convert to
"frequency" as such, instead I simply take differences of subsequent phase
points. Then calculate the (absolute) median of the result, remove outliers
bigger than k multiples of the median, and integrate back to phase.

The results agree with Stable32 (bar a factor of 1.48-something on k) - the
same number of outliers are identified, so I have a reasonable confidence
in my approach. I have a gut feeling that my approach is equivalent to
converting to "proper frequency" - but I thought I would ask the more (than
me) mathematically gifted members of this lists if I am committing some
grave sin in my simplistic approach?

Thanks!
Ole

[1]
http://www.stable32.com/Outliers%20in%20Time%20and%20Frequency%20Measurements.pdf
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[time-nuts] (no subject)

[Ole Petter Ronningen]

Hello

I just stumbled across this:
https://www.muquans.com/index.php/products/mclock

A commercially available cold atom rubidium clock! My apologies if this has
already been reported on the list.

Ole
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Re: [time-nuts] gLAB PPP noisy clock residuals

[Ole Petter Ronningen]

>
> I did a comparison of a few PPP results some years ago, maybe you saw it
> already
> http://www.anderswallin.net/2013/12/comparing-gps-ppp-solutions/


Ah, yes I forgot about that! Nice, I'll revisit RTKlib again.


> For the web-service running NrCAN, there was an URL API that allows running
> the filter/algorithm forward and backward ("filtfilt" in matlab or numpy),
> to get rid of the initial transient in only the forward solution. You could
> ask the maintainers, or I can try to dig in my archives (I should have
> python code that submits RINEX to the service and retrieves the results).
>

 That could be an option, I will contact the maintainers.

if you dig in the ESA gLAB settings, can you set the ZTD-model identically
> and see what happens?
>

I will investigate the  TZD-model, thanks for the tip. I was trying to wrap
my head around differential code biases; It seems NrCAN PPP applies
corrections, but I believe gLAB does not by default (and it crashes when I
give it -model:dcb:p1c1 strict). Not sure if DCB would show up as an issue
at the level I am looking at now, though.

If you post your RINEX:es and other relevant data I can try processing also
> and see what I get.


Appreciate the offer! :) Link to a recent RINEX that gives a reasonable
result from NRcan PPP:
https://www.dropbox.com/s/er9o6lfg4gva486/2017.05.21.zip?dl=0

Thanks!
Ole
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[time-nuts] gLAB PPP noisy clock residuals

[Ole Petter Ronningen]

Hi, all

Not sure if this is 100% within scope of the list, but still: I am trying
to get some good stability measurements of my hydrogen maser, using GPS
L1/L2 and PPP. I collect L1/L2 code and phase observables continously, and
process daily RINEX-files with PPP software and IGS corrections.

I've used the NrCAN-PPP online service, which gives reasonably good
results. The issue with NrCAN is that it only process in the forward
direction (at least, this is what I assume, looking at the results.) So I
want to run the processing locally so that I can run it both forward and
reverse.

I have not been able to get a copy of the nrcan-ppp softwarepackage, so I
am looking elsewhere. ESA gLAB looks like it might fit the bill. The
problem, in short, is that the data I get from  postprocessing with gLAB is
much, _much_ noisier than the results I get from submitting the RINEX files
to NrCAN-PPP online service.

(see attached screenshot - note I've cut away the first 2-3 hours of noisy
data from nrcan)

I've tested this on both a Trimble NetRS and a Novatel OEMV3, and I get
comparable results from both: nice smooth data from NrCAN (except the first
2-3 hours), jagged noisy data from gLAB.

(The Novatel required jumping through MANY hoops before I could get any
usable data, including writing a RINEX-converter. In case someone wants to
play along..)

I'd be tempted to think NrCAN applies smoothing somewhere, but the .sum
file contains "Parameter smoothing: NO"

I am running gLAB with 5-second interval observations, IGS Rapid products
(*.sp3, 10 degree clock interpolation), forward/reverse, throw away the
forward, grab clock offset from the FILTER output, convert to ns - as A.
Wallin is doing in ppp-tools.

So, in summary; does anyone know what is going on? Am I missing some step
in the gLAB processing?

Thanks for any insight.

Ole
[image: Inline image 1]
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[time-nuts] LEA-6T effect of position hold

[Ole Petter Ronningen]

Hi, all

The subject of position hold mode in GPS receivers pops up every now and
then. Here is a plot that may be of interest to some. Nothing new, but I
thought it a nice visualisation of the difference between position hold and
"not position hold".

I was measuring EFOS 3 against the PPS of a U-blox LEA-6T to get a coarse
indication of the frequency. I have not got around to mounting permanent
antennas in my new lab, so this was a bare board with a patch-antenna on my
desk - no great precision needed nor expected. I fired up the receiver and
made the measurements while it was still surveying - about half way through
it switched to position hold mode. The position is reported with a standard
deviation of 15 meters, so not a great fix. However, I thought the phase
plot was interesting.

Thinking about a GPSDO, it is easy to see the difference between using the
first half of the plot to discipline an oscillator versus the second half.

In case the attachment does not make it though, it is also here:
http://www.efos3.com/images/AHM%20v%20PPS%20pos%20hold.PNG

Ole
[image: Inline image 1]
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Re: [time-nuts] Thermal effects on cables

[Ole Petter Ronningen]

I should have mentioned this in the original post - the measurements were
not taken on the same cable length. Beware, and consult paper.

Ole

On Fri, Jan 13, 2017 at 7:52 AM, Ole Petter Ronningen <opronnin...@gmail.com
> wrote:

> Hi, all
>
> The question of phase shifts in cables pops up every now and then on this
> list - I stumbled across a good table of measured phase shifts with
> temperature in different cable types in this paper:
> http://www.ira.inaf.it/eratec/gothenburg/presentations/ERATEC_2014_
> PresentationWSchaefer.pdf that I though would be of interest to others.
>
> A quick summary given below, see pdf for full details. Lots of other
> interesting stuff in there also.
>
> Values in ppm/K, for 10 Mhz except when otherwise stated. (The paper gives
> values for 5, 10 and 100Mhz)
>
> Huber-Suhner Multiflex 141: -6
> RG-223: -131.9
> Semiflex Cable: -11.5
> Huber-Suhner: -8.6
> Times Microwave LMR-240: -3.4
> Times Microwave SFT-205: 7.7
> Meggitt 2T693 SiO2: 30.6
> Andrew FSJ-1 (@5Mhz): 25
> Andrew FSJ-4 (@5Mhz): 10
> Andrew LDF-1P-50-42: 2.8
> Andrew LDF4-50A: 4.7
> Times Microwave TF4FLEX (@100Mhz):6.4
> Phasetrack PT210 (@100Mhz): 2
>
> Ole
>
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[time-nuts] Thermal effects on cables

[Ole Petter Ronningen]

Hi, all

The question of phase shifts in cables pops up every now and then on this
list - I stumbled across a good table of measured phase shifts with
temperature in different cable types in this paper:
http://www.ira.inaf.it/eratec/gothenburg/presentations/ERATEC_2014_PresentationWSchaefer.pdf
that I though would be of interest to others.

A quick summary given below, see pdf for full details. Lots of other
interesting stuff in there also.

Values in ppm/K, for 10 Mhz except when otherwise stated. (The paper gives
values for 5, 10 and 100Mhz)

Huber-Suhner Multiflex 141: -6
RG-223: -131.9
Semiflex Cable: -11.5
Huber-Suhner: -8.6
Times Microwave LMR-240: -3.4
Times Microwave SFT-205: 7.7
Meggitt 2T693 SiO2: 30.6
Andrew FSJ-1 (@5Mhz): 25
Andrew FSJ-4 (@5Mhz): 10
Andrew LDF-1P-50-42: 2.8
Andrew LDF4-50A: 4.7
Times Microwave TF4FLEX (@100Mhz):6.4
Phasetrack PT210 (@100Mhz): 2

Ole
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Re: [time-nuts] hm H Maser

[Ole Petter Ronningen]

Add to this ion-pumps (in the case of EFOS type masers 2 every ~2 years),
plus substantial tooling (turbomolecular vacuum pump, anyone?) to service
the thing - unless you want the manufacturer to do so..

Ole

On Tue, Jan 10, 2017 at 11:12 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> On 10 January 2017 at 15:35, Ole Petter Rønningen 
> wrote:
>
> > ... having said that, I for one think I'm with Bob on this one. The thing
> > about masers are that they are big. At least active masers. And they
> > require a substantial volume be kept at ultra high vacuum - which is not
> > trivial, especially not in a homeshop. The cavity needs to be kept at a
> > temperature stable to 0.001 degree C. With 4-5 magnetic shields. Add to
> > this costly pumps to keep the vacuum this low even if you succeed at
> > reaching that vacuum.. There's easily 1-2KUSD running cost per year just
> to
> > keep the maser running.
> >
>
> Looking at the Microsemi MHM 2010 Active Hydogen Maser data sheet, the
> maser has a peak power of 150 W and an operating power of 75 W.  Based on a
> power consumption of 75 W, that is 657 kW hr / year of energy. I pay around
> £0.20 (GBP) per kW hr for electricity, so that's £131 (GBP) annually. I
> believe electricity is cheaper in the USA than here in the UK, but
> converting £131 (GBP) to USD, that's around $161/year in electricity. So
> running costs don't seem to be an issue.
>
> But I must admit, the thought of spending a lot of time/money to build
> something I could have bought for a lot less with higher performance is not
> that attractive, although of course there would be a satisfaction from
> building it yourself.
>
> Dave
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Re: [time-nuts] hm H Maser

[Ole Petter Ronningen]

Not sure how relevant that particular example is. PHM on Galileo was new
science (at least the sapphire loaded cavity), and *very* different
reliability engineering.

AHM's are nothing new, the science hace been done, the construction is
known, down to exact drawings and circuit diagrams. There are numbers from
1982 that can possibly be used as a startingpoint for estimating an amateur
project in https://library.nrao.edu/public/memos/vlba/main/VLBA_65.pdf

As a side note, I am also not convinced that sourcing the fused quartz
teflon coated bulbs would be a show stopper for a limited number (<5) of
masers, I for one have one on my shelf. It is quite possible that old bulbs
for previous designs exists with the current manufacturers that they might
be willing to part with.

They are also still manufactured, Vremya or one of the others might be
willing to sell them - although I have no idea about the cost.

As another side note, on a trip to Switzerland I was allowed a glimpse of a
couple of the PHM's for Galileo in person. Impressive.

Ole

On Tue, Jan 10, 2017 at 2:18 PM, ewkehren via time-nuts 
wrote:

> Do we know what the PHM development for Galileo cost?
>
>
>
>
> Sent from Samsung tabletBob Camp  wrote:Hi
>
> > On Jan 10, 2017, at 2:45 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkir...@kirkbymicrowave.co.uk> wrote:
> >
> > Once 9 Jan 2017 12:59, "Bob Camp"  wrote:
> >>
> >> Hi
> >>
> >> Ok here are some rough numbers:
> >>
> >>> On Jan 9, 2017, at 4:35 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> > drkir...@kirkbymicrowave.co.uk> wrote:
> >
> >>> It would be interesting to see your breakdown of the costs and man
> hours
> >>> for an H2 maser. I suspect that others would find cheaper/faster
> > solutions.
> >>
> >> $100M for the H2
> >>
> >> $25M for the Rb
> >
> > With all due respect,  and I apprectiate you have a good knowledge of
> this
> > field, but that's not a breakdown of costs or man hours I wanted to see,
> > but a cost which appears to be plucked from the air.
>
> Hardly plucked from the air. The last Rb design that I was involved with
> was
> roughly 5X that expensive.
>
> >
> > There's a BIG difference between a volunteer effort where
> >
> > * Salaries are not paid
> > * Items of test equipment are likely to be borrowed or people provide
> > access to them for no charge etc,
> > * Academics are likely to provide consultancy for free, in return for
> being
> > on papers published.
> > * Software licenses could probably be obtained free,  or enough people
> get
> > trials.
>
> That’s where the 5:1 cost reduction comes from.
>
> >
> > compared to a commercial company building a maser where
> >
> > * Salaries are paid
> > * All equipment is purchased new
> > * Bench power supplies with 3.5 digit displays are sent out for
> calibration
> > each year.
> > *  No outside body will do anything except at a commercial rate.
> > * Flights are booked for meetings which could be done over the Internet.
> > * High end software licenses are huge.
> >
> >> $500M for the fountain.
> >
> > But on what basis do you arrive at that figure?
>
> The numbers that the people who have done it come up with when you talk to
> them.
>
> >
> >> To get sponsorship for anything remotely close to those numbers, you
> >> need to have some massively good credentials.
> >>
> >> Bob
> >
> > Yes agreed at $500M. But someone like Tom, who does have massively good
> > credentials, could perhaps get $500,000, and perhaps that wisely spent
> > could get a fountain built.  Without knowing how you arrive at $500M, it
> is
> > not possible for anyone to look at ways of shaving that cost.
>
>
> This is *not* a cheap field to be doing things in ….
>
> Bob
>
> >
> > The Lovell Telescope at Jodrell Bank in the UK was built on a shoestring
> > budget. It was at the time the world's  largest steerable radio
> telephone.
> > Half a century later only 2 larger ones have been built.
> >
> > Maybe I am too nieve.
> >
> > Dave.
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Re: [time-nuts] EFOS 3 online

[Ole Petter Ronningen]

I suspect it is no longer doing 1e-13 at 1 second tau - it was a long drive
from Neuchatel, and lots of stuff shifting! Not to mention my less than
optimal temperature stability (or lack thereof). But it should still be
good enough for a house standard! :)

I casually mentioned the difficulty measuring the maser to the wife,
starting to outline a possible solution involving other masers - it seems
"we" feel a single maser is sufficient!

Ole

On Sat, Jan 7, 2017 at 11:42 PM, John Miles  wrote:

> > Inspired by Corbys post, I thought I'd follow up with putting the
> > telemetry-data from EFOS 3 on the web, for those with any interest in
> these
> > things. There is also a small picture gallery. Can be found on
> > www.efos3.com.
> > If I got the scheduling right, weekly plots should update every 5
> minutes..
>
> 1E-13 at t=1s in your plot at http://www.efos3.com/efos3.html is looking
> great.  I think you have it working as well as it possibly can, at least in
> the short term.  You just need two more of them to be sure. :)
>
> -- john, KE5FX
> Miles Design LLC
>
>
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[time-nuts] EFOS 3 online

[Ole Petter Ronningen]

Hello

Inspired by Corbys post, I thought I'd follow up with putting the
telemetry-data from EFOS 3 on the web, for those with any interest in these
things. There is also a small picture gallery. Can be found on www.efos3.com.
If I got the scheduling right, weekly plots should update every 5 minutes..

BR,
Ole
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Re: [time-nuts] Trimble UCCM survey results

[Ole Petter Ronningen]

Possibly the z3801 reports heigh as MSL, whereas the UCCM use some other
reference frame.

Ole

On Tue, Dec 20, 2016 at 7:28 AM, Tom Curlee  wrote:

> A couple of questions:
> I've just started using  LH 5.0 with my 2  GPSDO units (Thanks Mark!) - a
> Trimble UCCM and a Z3801A.  Oddly, I'm very getting different survey
> altitude values.  The Z3801A is around 81 M, which agrees within 1 or 2
> meters with Google maps (not a perfect source, but close), but the UCCM is
> usually around 48M to 53M depending on which survey I want to believe.
> Both receivers are locked and both are fed off the same antenna through a
> splitter.  I admit that the antenna placement is very poor - anything below
> 60 degrees elevation to the north is blocked (LH is great for antenna
> placement analysis).  Anyone have any ideas?
> A question on LH usage.  When the UCCM is in the position hold mode, what
> happens when a precision survey is run?  Looking at the .lla file shows
> that every position, including the final processed location,  is the same
> as that shown as the position hold location on the main LH screen.  Do you
> need to take the receiver out of the hold mode to run a precision survey?
> How?  How is the position scatter plot used with a survey?  I usually don't
> see any positions plotted, certainly not when running a precision survey.
> I think I saw data plotted when I did an internal survey.
> Many thanks for any info.  And thanks again to Mark and John for all the
> work.
> Tom
>
>
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Re: [time-nuts] Hydrogen maser spin exchange

[Ole Petter Ronningen]

There is indeed a quad- or hexa-pole state selection magnet between the
dissociator and the cavity, required to select the atoms of the correct
state to allow a population inversion resulting in oscillation.

My understanding is that the spin-exchange of interest takes place between
atoms already bouncing around inside the cavity - having passed that
particular obstacle.

And while on that subject, if anyone could elaborate on the difference
between the two (quad or hexa-pole), that would be interesting. I have not
found a clear explanation for why one might choose one over the other.

Ole

On Fri, Jun 17, 2016 at 11:35 PM, paul swed <paulsw...@gmail.com> wrote:

> Ole,
> Quite looking forward to the replies. Though no intention to own a maser
> currently.
> I thought there was a method of rejecting or reducing types of spin.
> Therefore reducing the impact you mention. Essentially a state selector.
> Pretty sure that thought will get corrected pretty quickly.
> Regards
> Paul
> WB8TSL
>
> On Fri, Jun 17, 2016 at 3:33 PM, Ole Petter Ronningen <
> opronnin...@gmail.com
> > wrote:
>
> > Hi. Apologies for a long post.
> >
> > I'm trying to read up on the "care and feeding of hydrogen masers". While
> > they are conceptually simple from a distance, there's quite a bit going
> on
> > in the quantum mechanics department when looked at up close. Somewhat
> > frustratingly, I am not mentally equipped to really grasp the finer (or
> > even coarser) points of that particular department. The topic of this
> post
> > is the concept of spin exchange, and it's relation to cavity (auto)
> tuning.
> > I've read papers on the subject, but I am having difficulties building a
> > "workable intuition", so I turn to the group.
> >
> > Here's what I think I understand, and I respectfully ask for corrections
> if
> > I am way off base here..
> >
> > Spin-exchange in a hydrogen maser happens when two atoms collide, and
> > exchange spin, as it were.. (Hazy on the details here..) The number of
> > spin-exchange collisions is directly proportional to the density of atoms
> > in the cavity. These collisions *will* happen, but is a problem in
> hydrogen
> > masers for two reasons: 1) it takes away energy from the cavity,
> resulting
> > in lower signal output power, which degrades stability, and, 2) more
> > significantly, it results in a frequency shift.
> >
> > The frequency shift, as far as I can gather, is directly related to the
> > cavity resonant frequency - there is no way to *stop* spin exchange
> taking
> > place (apart from reducing the hydrogen density to a level where
> collisions
> > are rare, in which case the density will be too low for oscillation to
> take
> > place), but it is possible to reduce the impact the spin exchange has on
> > the output frequency.
> >
> > While the resonant frequency obviously influences the output power of the
> > maser cavity, the "mistuning" of the cavity also increases the effect
> spin
> > exchange has. In other words, in a perfectly tuned cavity, spin exchange
> > does not result in a frequency shift. In a badly tuned cavity, increasing
> > or decreasing the hydrogen flux (thereby increasing or decreasing the
> > number of collisions taking place) results in a corresponding
> > increase/decrease of the output frequency. Since the cavity ages, and the
> > cavity resonant frequency follows that aging, the long term stability of
> > the maser is degraded unless the aging can be compensated for. Which is
> > what cavity auto-tuning is all about.
> >
> > From my understanding, there are a few ways to implement cavity
> > auto-tuning:
> > 1. From the above, it follows that a modulation of the hydrogen flux
> into a
> > mis-tuned cavity will result in a frequency shift following the
> modulation
> > frequency. Using a stable reference, this shift can be measured, and
> > corrections can be made to the cavity varactor voltage. Once the output
> > frequency no longer shifts in response to the changes in hydrogen flux,
> the
> > cavity is correctly tuned.
> >
> > 2. It is also possible to modulate the cavity varactor voltage. By
> > measuring the output power of the cavity, an error signal can be obtained
> > and used to correct the average varactor voltage. A square wave of i.e.
> > 100hz, centered on the approximate correct varactor voltate is put in the
> > varactor, and cavity output power is measured. If the output power
> measured
> > on the "low" of the square wave is lower than the signal measured when
> the
> > &quo

[time-nuts] Hydrogen maser spin exchange

[Ole Petter Ronningen]

Hi. Apologies for a long post.

I'm trying to read up on the "care and feeding of hydrogen masers". While
they are conceptually simple from a distance, there's quite a bit going on
in the quantum mechanics department when looked at up close. Somewhat
frustratingly, I am not mentally equipped to really grasp the finer (or
even coarser) points of that particular department. The topic of this post
is the concept of spin exchange, and it's relation to cavity (auto) tuning.
I've read papers on the subject, but I am having difficulties building a
"workable intuition", so I turn to the group.

Here's what I think I understand, and I respectfully ask for corrections if
I am way off base here..

Spin-exchange in a hydrogen maser happens when two atoms collide, and
exchange spin, as it were.. (Hazy on the details here..) The number of
spin-exchange collisions is directly proportional to the density of atoms
in the cavity. These collisions *will* happen, but is a problem in hydrogen
masers for two reasons: 1) it takes away energy from the cavity, resulting
in lower signal output power, which degrades stability, and, 2) more
significantly, it results in a frequency shift.

The frequency shift, as far as I can gather, is directly related to the
cavity resonant frequency - there is no way to *stop* spin exchange taking
place (apart from reducing the hydrogen density to a level where collisions
are rare, in which case the density will be too low for oscillation to take
place), but it is possible to reduce the impact the spin exchange has on
the output frequency.

While the resonant frequency obviously influences the output power of the
maser cavity, the "mistuning" of the cavity also increases the effect spin
exchange has. In other words, in a perfectly tuned cavity, spin exchange
does not result in a frequency shift. In a badly tuned cavity, increasing
or decreasing the hydrogen flux (thereby increasing or decreasing the
number of collisions taking place) results in a corresponding
increase/decrease of the output frequency. Since the cavity ages, and the
cavity resonant frequency follows that aging, the long term stability of
the maser is degraded unless the aging can be compensated for. Which is
what cavity auto-tuning is all about.

>From my understanding, there are a few ways to implement cavity auto-tuning:
1. From the above, it follows that a modulation of the hydrogen flux into a
mis-tuned cavity will result in a frequency shift following the modulation
frequency. Using a stable reference, this shift can be measured, and
corrections can be made to the cavity varactor voltage. Once the output
frequency no longer shifts in response to the changes in hydrogen flux, the
cavity is correctly tuned.

2. It is also possible to modulate the cavity varactor voltage. By
measuring the output power of the cavity, an error signal can be obtained
and used to correct the average varactor voltage. A square wave of i.e.
100hz, centered on the approximate correct varactor voltate is put in the
varactor, and cavity output power is measured. If the output power measured
on the "low" of the square wave is lower than the signal measured when the
"high", lower the offset by some mV, and vice versa. Suitable filtering
would of course be required.

The idea is that this method should not result in appreciable degradation
of the short/medium term stability of the maser, because the frequency of
the atoms interacting with the electromagnetic field in the maser cavity
takes time to respond to the changes in the resonant frequency, but the
output power responds "instantly". (Hazy on those details as well..) By
modulating the cavity varactor voltage (much) faster that the time constant
of the maser cavity, the modulation is effectively filtered out.

I am very interested in this method, as it seems to me that it would be
easy (feasible) to retrofit this to older masers never equipped with cavity
auto tuning.

There is at least one more way, which involves injecting a signal into the
maser cavity through a second coupling loop. At least one vendor I know of
does this in their newest design. I do not understand even the basics of
this method.

Any insights and/or corrections of my understanding is most welcome.

Thanks,
Ole
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Re: [time-nuts] Generating a solid PPS from 10Mhz source

[Ole Petter Ronningen]

Sounds like a PICDIV is just about right:
http://www.leapsecond.com/pic/picdiv.htm

Ole

On Wed, Jan 13, 2016 at 10:22 AM, Jerome Blaha 
wrote:

> Hey Guys,
>
> Is there an easy circuit to build that can consistently deliver a 1 PPS
> from a 10MHz source with excellent resolution and repeatability?  My first
> application is to test different 10MHz oscillators without a TIC always
> attached and then compare the PPS output change over time against a master
> GPSDO PPS with an HP53132A.
>
> The circuit used for PPS generation would have to deliver consistent PPS
> output with preferably not more than 100ps noise or jitter, assuming a
> perfect source.  I'm totally guessing that for this resolution, the PPS
> would have to be generated and accurate to within 0.001Hz every second.  If
> this is too difficult, maybe the integration time can be increased to
> generate one pulse every 10second or every 100,000,000.00 cycles?
>
> Finally, is a square 10Mhz reference any better in this case than a
> sinusoidal input for generating the PPS?
>
> Thanks,
> Jerome
>
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[time-nuts] Public lecture on atomic and optical clocks

[Ole Petter Ronningen]

Hello

There is a relatively recent (november 2015) public lecture by David
Wineland on Youtube, titled "Keeping Better Time: The Era of Optical Atomic
Clocks". I thought it an interesting, clear overview for the non-expert.

Link: https://youtu.be/LxbkyuzXst4

I searched the archives, but could not find it - apologies if this has
already been reported.

Ole
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Re: [time-nuts] Novatel ProPak-V3 GPSDO

[Ole Petter Ronningen]

Bob,

Perhaps my subject line should have been "Novatel ProPak-V3 and TAIPPP" - I
got the unit primarily to play around with PPP and time transfer. I was
unaware of the GPSDO-functionality when I got it, but I thought it was kind
of neat and at least worth testing. Will report back if I get any useful
results on that front.

But, as you rightly point out, the licenses to get L1/L2/L5 GPS+GLONASS and
so on are *not* cheap - and I am not at all clear on exactly which (if any)
firmware options are required to get PPP working properly in a timing
context.

I am therefore exploring the possibility to get useful performance on
L1-only - and there is at least a couple of papers[1] on that subject. It
would seem that L1 code+carrier tracking, combined with SBAS (or,
preferably, other precise corrections) in post processing will get the
PPP-solutions a lot closer to L1/L2 than I would have expected!

I assume that this accuracy in position will directly transfer over to
solving for time. If this is indeed the case, anyone with a cesium (or
perhaps even a rubidium) and one of these receivers could compare their
frequency-sources to e.g. USNO. It might take several days or weeks to get
any meaningful precision, and it would be post-processing all the way, but
still useful if the frequency source is stable enough. (And if not
particularly useful, then at least interesting!)

It is quite possible that other (more reasonably priced) receivers will
also produce useful precision in this setting. The referenced paper makes a
point that the reported levels of accuracy depend on "high grade equipment"
- but I am not clear on which properties distinguish "high grade" from "low
grade" in this context - multipath is mentioned. I have a uBlox that will
output raw measurements, and I may try to compare the two.

The receivers used in time transfer needs to be code+carrier tracking. It
needs to be driven by the frequency source to be calibrated, and according
to what scant information I have found, also needs a PPS input from the
local clock. I am unsure about that last requirement, I do not fully
understand the reasoning - but I *think* it is required to align "time" (as
opposed to only frequency). It may be that lack of PPS input on the
receiver can be compensated for with an external TI counter. It may also be
that it is possible to "calibrate" only frequency, and leave the PPS to its
own devices.

But we'll see how it progresses - away from the "lab" at the moment, so
it's all based on reading papers and guessing. (Which is at least half the
fun!)

BR,
Ole

1. Wanninger, L. Hesselbarth, A., "SBAS Based Single and Dual Frequency
Precise Point Positioning" and "SBAS Orbit and Satellite Clock Corrections
for Precise Point Positioning"


On Fri, Dec 25, 2015 at 6:19 PM, Bob Camp <kb...@n1k.org> wrote:

> Hi
>
> I think you will find the Novatel OEM cards inside a number of L1/L2
> timing receiver designs. The
> cost for the basic card is not crazy if bought surplus. Doing the *full*
> set of firmware / software
> upgrades to make them “work right’ is more expensive than some new
> automobiles. If you
> decide to go that way, it’s almost as cheap to buy the brand new V6 board
> plus the software as
> to upgrade an old one. The advantage is that the new boards have a bit
> more processing
> horsepower on them.
>
> If you run them as “L1 only” devices, the Novatel cards do not have much
> (if any) advantage
> over the other boards out there. Since they fetch a premium price surplus,
> their bang for the
> buck factor on L1 is not very good. Something like a TBolt is a cheaper /
> “at least as good”
> alternative.
>
> I do not know of any of the precision timing people who use the charge
> pump output of the
> board for their systems. They pretty much all team the board up with some
> sort of cpu board
> (single board computer) and let it do the heavy lifting and data
> collection. The full implementation
> then is the Novatel card, the CPU card, and a custom board for the GPSDO /
> measurement
> system.
>
> This is by no means a knock on the Novatel cards. They are *very* good
> devices. The gotcha
> is the fact that they need a lot of firmware “unlocks” to do all the good
> stuff they are capable of.
> With the *full* set of unlocks the newest cards are (when they come out)
> likely the best thing you
> can buy for this sort of thing when teamed up with a capable computer.
>
> Bob
>
>
> > On Dec 25, 2015, at 6:35 AM, Ole Petter Ronningen <opronnin...@gmail.com>
> wrote:
> >
> > Hello
> >
> > I'm sure many of you have noticed quite a few surplus NOS Novatel OEM-V3
> > L1-only units appearing on eBay lately. Reading the firmware manual, it
> > seems the ProP

Re: [time-nuts] Novatel ProPak-V3 GPSDO

[Ole Petter Ronningen]

Hi, Pete

An example is eBay item number:281892200243

On Fri, Dec 25, 2015 at 6:23 PM, Pete Lancashire <p...@petelancashire.com>
wrote:

> I just looked at current and past sale, do you have an example ?
>
> I only see two Propacks  1's  that someone has been trying to sell for
> quite a long time, and one V3
>
>
>
> On Fri, Dec 25, 2015 at 3:35 AM, Ole Petter Ronningen <
> opronnin...@gmail.com
> > wrote:
>
> > Hello
> >
> > I'm sure many of you have noticed quite a few surplus NOS Novatel OEM-V3
> > L1-only units appearing on eBay lately. Reading the firmware manual, it
> > seems the ProPak is capable of steering an external oscillator with the
> > addition of a filtered chargepump circuit. Has anyone made any
> experiments
> > using this functionality?
> >
> > Also, a couple of labs (APL and USNO) use ProPak-V3 receivers to
> > participate in TAI, by the use of PPP. BIPM has a little information
> about
> > the ProPak (calibration procedures), but other than that I have not found
> > much information about the configuration of the receiver in this
> particular
> > setting. Any clues would be appreciated.
> >
> > (In case anyone is interested - the receiver can be software upgraded to
> > also track L2 - the license is north of USD2K..)
> >
> > Thanks,
> > Ole
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[time-nuts] Novatel ProPak-V3 GPSDO

[Ole Petter Ronningen]

Hello

I'm sure many of you have noticed quite a few surplus NOS Novatel OEM-V3
L1-only units appearing on eBay lately. Reading the firmware manual, it
seems the ProPak is capable of steering an external oscillator with the
addition of a filtered chargepump circuit. Has anyone made any experiments
using this functionality?

Also, a couple of labs (APL and USNO) use ProPak-V3 receivers to
participate in TAI, by the use of PPP. BIPM has a little information about
the ProPak (calibration procedures), but other than that I have not found
much information about the configuration of the receiver in this particular
setting. Any clues would be appreciated.

(In case anyone is interested - the receiver can be software upgraded to
also track L2 - the license is north of USD2K..)

Thanks,
Ole
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Re: [time-nuts] Digital Phasae Lock Loops

[Ole Petter Ronningen]

Quartzlock makes a couple of interesting digital PLL-modules, marketed
specifically as ultra low noise cleanup loops. The datasheets contain a lot
of interesting and useful information about the software architecture - not
enough that *I* can recreate it, but perhaps someone more skilled than me
can.

Very interesting stuff:
http://quartzlock.com/product/timing-modules/digital-phase-lock-loop

Does anyone know of a reference where more information about this approach
can be found? I am impressed they can do all that in a PIC 16F689..

On Sat, Oct 17, 2015 at 4:48 PM, Jim Lux  wrote:

> On 10/17/15 6:17 AM, Alex Pummer wrote:
>
>>
>> actually, that is a ketch 22, if the loop bandwidth is to low, you will
>> have low noise , but it may will not lock at all, an other way to try to
>> filter out the noise, also you may make the loop filter digital, but
>> leave the the PLL analog, that could have  the possibility to have the
>> advantage to be able to change the loop bandwidth  increase for locking,
>> and reduce after the detected locking
>>
>
> changing  loop bandwidth between acquisition and tracking, or, similarly,
> (effective) loop bandwidth that changes with SNR are pretty common
> strategies.
>
> In the deep space transponder world (where you are acquiring and tracking
> a very narrow carrier at -155 or -160 dBm against noise of -170dBm/Hz) you
> also want to know what order filter you should be using in the tracking
> loop.  If there's an expectation that the frequency being tracked is
> changing (e.g. Doppler), then a low order loop may not be the best choice.
>
>
>
>
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Re: [time-nuts] LAN/USB to GP-IB/HP-IP Adapters

[Ole Petter Ronningen]

I have both a chinese clone 82357b and two NI GPIB-USB-HS. If you will
write your own software for aging test-equipment, my experience is that a
clean NI solution with GPIB-USB-HS and NI 488.2 is a *lot* less painful
than trying to get Agilent GPIB to play nice with the NI software-stack.
Speaking for myself I could never get it to work satisfactorily on Windows
(never bothered to try another OS), just lots of weird unexplained
problems; sometimes working, sometimes hanging, sometimes requiring the
sacrifice of a chicken. Might be the chinese clone adapter, though, I never
tried a genuine Agilent 82357. Come to think of it, the NI's came out of
china as well, so might also be clones. Just way better clones. :)

Ole

On Fri, Sep 11, 2015 at 1:16 PM, cfo  wrote:

> On Thu, 10 Sep 2015 14:58:41 -0700, Brooke Clarke wrote:
>
> >so I'm looking for an adapter that runs
> > from LAN or a USB port.
> >
> > Can anyone comment on what's available?
> >
>
> Hi Brooke
>
> Afaik the Agilent USB GPIB adapter can "Speak VISA on Windows" with
> Agilents windows driver. But no VISA support for Agilents under Linux, as
> Agilent doesn't make drivers for linux :-(
>
> See this Agilent PDF
> http://cp.literature.agilent.com/litweb/pdf/5990-3731EN.pdf?cmpid=1273CN
>
>
> And have a look on *bay for :
> "Agilent 82357B USB-GPIB Interface"
>
>
> According to this thread , even the "real ones" are clones (work ok)
> http://www.eevblog.com/forum/testgear/flood-of-new-agilent-82357b-gpib-
> usb-adaptors-on-ebay-the-real-deal/
>
>
> I have a Beiming and an Agilent (prob a clone) , both works fine with
> liunx-gpib.
>
> CFO
> Denmark
>
> --
> E-mail:xne...@luna.dyndns.dk
>
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Re: [time-nuts] Troubleshooting Fluke PM6681

[Ole Petter Ronningen]

Fantastic, just what I needed. Thank you!

On Sun, Aug 16, 2015 at 9:16 PM, Magnus Danielson 
mag...@rubidium.dyndns.org wrote:

 Ole,

 I checked with a former Pendulum employee, and free off memory, he
 recommend trimming up the 100 MHz until Error 2 does not show. Sensing it
 directly can be difficult, FET-probe essentially mandatory. Indirectly a 10
 MHz is possible. A problem is that trimming with the hood off causes a
 different thermal setup than when the hood is on. If you dare, make a hole
 in the hood so that you can trim it with the hood on, that is what they did.

 CMOS backup battery eventually fails, and then you need to replace it and
 re-calibrate it. I have the details jotted down, but it seems that this is
 not your issue.

 Cheers,
 Magnus


 On 08/16/2015 12:20 PM, Ole Petter Ronningen wrote:

 Hello.

 I have a Fluke PM6681 that has issues. When I got it, it gave results all
 over the place, but after adjusting the 100Mhz multiplier-chain, it seems
 to be much better; at least I get std.deviationwell within spec using a
 split pulse to input A and B, 100 samples. I'd like to get it
 professionally calibrated, but I don't want to send it in with known
 issues
 - the cost of calibration will not be refunded if the instrument can not
 be
 calibrated, and I believe it is no longer repairable.

 So, the issue is that it fails the ASIC test (test 6), with err 2.The
 service-guide lists a number of signals to be checked in test-mode, but I
 am not able to see any of them. Since the counter seems to function, I can
 only conclude that the signals are not present due to this error.. (Or
 that
 I am mistreading the guide and looking in the wrong place, probably at
 least as likely..)

 Anyway, I cant seem to find a description of this particular error, does
 anyone know what it means?

 Thanks,
 Ole
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[time-nuts] Troubleshooting Fluke PM6681

[Ole Petter Ronningen]

Hello.

I have a Fluke PM6681 that has issues. When I got it, it gave results all
over the place, but after adjusting the 100Mhz multiplier-chain, it seems
to be much better; at least I get std.deviationwell within spec using a
split pulse to input A and B, 100 samples. I'd like to get it
professionally calibrated, but I don't want to send it in with known issues
- the cost of calibration will not be refunded if the instrument can not be
calibrated, and I believe it is no longer repairable.

So, the issue is that it fails the ASIC test (test 6), with err 2.The
service-guide lists a number of signals to be checked in test-mode, but I
am not able to see any of them. Since the counter seems to function, I can
only conclude that the signals are not present due to this error.. (Or that
I am mistreading the guide and looking in the wrong place, probably at
least as likely..)

Anyway, I cant seem to find a description of this particular error, does
anyone know what it means?

Thanks,
Ole
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Re: [time-nuts] Modified Allan Deviation and counter averaging

[Ole Petter Ronningen]

*Very* much looking forward to some insight on this method - I've done
pretty much the same experiment with an E1740A (48.8ps resolution); trigger
from a z3805A PPS, start TI measurement on the first rising edge of the
z3805A 10Mhz (on channel 1) following the trigger, stop the TI measurement
on (i.e.) the 30th rising edge on whatever signal is on channel 2.  Capture
100 samples gap-free every trigger, and average as described.  It is
severely bandwidth-limited by the GPIB interface as to the number of
samples that can be collected on a per second basis, but the E1740A can
store up to ~500k samples, so it can all be batch processed after the
measurement is complete. It will be very interesting to see if the method
has any merit.

Ole

On Tue, Jul 28, 2015 at 11:51 PM, Poul-Henning Kamp p...@phk.freebsd.dk
wrote:

 Sorry this is a bit long-ish, but I figure I'm saving time putting
 in all the details up front.

 The canonical time-nut way to set up a MVAR measurement is to feed
 two sources to a HP5370 and measure the time interval between their
 zero crossings often enough to resolve any phase ambiguities caused
 by frequency differences.

 The computer unfolds the phase wrap-arounds, and calculates the
 MVAR using the measurement rate, typically 100, 10 or 1 Hz, as the
 minimum Tau.

 However, the HP5370 has noise-floor in the low picoseconds, which
 creates the well known diagonal left bound on what we can measure
 this way.

 So it is tempting to do this instead:

 Every measurement period, we let the HP5370 do a burst of 100
 measurements[*] and feed the average to MVAR, and push the diagonal
 line an order of magnitude (sqrt(100)) further down.

 At its specified rate, the HP5370 will take 1/30th of a second to
 do a 100 sample average measurement.

 If we are measuring once each second, that's only 3% of the Tau.

 No measurement is ever instantaneous, simply because the two zero
 crossings are not happening right at the mesurement epoch.

 If I measure two 10MHz signals the canonical way, the first zero
 crossing could come as late as 100(+epsilon) nanoseconds after the
 epoch, and the second as much as 100(+epsilon) nanoseconds later.

 An actual point of the measurement doesn't even exist, but picking
 with the midpoint we get an average delay of 75ns, worst case 150ns.

 That works out to one part in 13 million which is a lot less than 3%,
 but certainly not zero as the MVAR formula pressume.

 Eyeballing it, 3% is well below the reproducibility I see on MVAR
 measurements, and I have therefore waved the method and result
 through, without a formal proof.

 However, I have very carefully made sure to never show anybody
 any of these plots because of the lack of proof.

 Thanks to Johns Turbo-5370 we can do burst measurements at much
 higher rates than 3000/s, and thus potentially push the diagonal
 limit more than a decade to the left, while still doing minimum
 violence to the mathematical assumptions under MVAR.

 [*] The footnote is this: The HP5370 firwmare does not make triggered
 bust averages an easy measurement, but we can change that, in
 particular with Johns Turbo-5370.

 But before I attempt to do that, I would appreciate if a couple of
 the more math-savy time-nuts could ponder the soundness of the
 concept.

 Apart from the delayed measurement point, I have not been able
 to identify any issues.

 The frequency spectrum filtered out by the averaging is wy to
 the left of our minimum Tau.

 Phase wrap-around inside bursts can be detected and unfolded
 in the processing.

 Am I overlooking anything ?


 --
 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] FTS 8400

[Ole Petter Ronningen]

Hi, all.

The FTS-8400 arrived today, with a manual. I might scan it for posterity,
but it seems to be a bit less useful than I hoped for - I figured I might
be able to use it as a disciplined oscillator to an external PPS, but it
does not look like it is capable of that.

Anyway. just though someone might be interested, the high stability
oscillator option is indeed a 5Mhz FTS-1000A.

Ole

On Tue, May 26, 2015 at 3:31 AM, Gregory Beat w...@icloud.com wrote:

  Ole -
 
  These became obsolete in 1999.  Actually led to development of TAC-2
 board (TAPR) in 1996.
  Tom Clark, K3IO could tell you about the FTS 8400 usage with the
  VLBI large dish array in 1980s and 1990s.
 
  Scroll down the TAC32Plus software notes for discussion on Trimble FTS
 8400.
  https://www.cnssys.com/cnsclock/Tac32PlusSoftware.php
 
  Greg
  w9gb
 
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[time-nuts] Some questions related to time-interval measurements and modulation domain analysis

[Ole Petter Ronningen]

Hello, all!

This will be a long post, my apologies..

A while back I scored a HP E1740A time interval analyser. This unit has a
48.8 pS resolution, which is great, but it can only measure up to 3.2uS
with that resolution, which is a bit limiting. It can also store up to 500K
readings internally, so it can measure pretty fast.

While thinking about interesting things to use the instrument for, I
stumbled across modulation domain analysis - which this counter should be
perfect for. I am just starting to scratch the surface of the topic, but I
ran a couple of experiment that surprised me. That is, the results are far
better, or at least far more sensitive, than I would have expected. So I
am looking for advice on what I may have done wrong..

The setup is basically this: a RohdeSchwartz SMIQ-03B RF generator
provides the signal. The generator has a decent OCXO reference. The signal
was a 10Mhz sine at 7dBm, AM modulated at 10KHz, 0.5%(!) modulation. I
verified the signal on an HP8563A, and observed a nice, low peak 10Khz from
the carrier, as expected. Repeat on a Rigol DSA-815, same result.

The e1740A was configured to take 200k time interval measurements of the
signal on channel 1, paced at 25 edges, triggerlevel 0v. I.e. I should get
200K measurements of how much time has elapsed from one rising edge, to the
25th following rising edge. These measurements are back-to-back, i.e. the
stop-edge of one measurements is the start-edge of the next measurement. So
the counter captured a gap-free time-record totalling 500mS.

I (slowly!) downloaded the samples to my computer, and basically did an
FFT. The resulting spectrum showed a clear peak at 10KHz, growing and
shrinking as the AM modulation index was varied. Only the first 1/5 or so
of the spectrum gave much information, as the noise grew pretty quickly on
higher fourier frequencies.

So here is my first question - since this signal is amplitude modulated,
the only way this can (should) show up on the counter is if the triggering
is not perfect - that is, it does not trigger at precisely 0v + whatever
DC offset may or may not be on the signal. Is my undestandig here correct?
A perfect zero-crossing detector would be immune to AM?

If so, this was a very valuable lesson in AM/PM conversion, I think. I
would not have expected to so clearly see AM as little as 0.5%..

But there is a second conondrum in my experiment. I also saw an unexpected
much bigger peak at 64KHz in the spectrum.

In order to verify my methodology, I repeated the measurement on an Agilent
53230A, continous timestamp at 100Khz samplerate, and FFT the result. The
resulting spectrum was pretty much identical, including the large peak at
64KHz. This was also a little surprising, since the resolution of the
53230A is a lot better, but I suppose resolution is less important with so
many datapoints.

There was also a much bigger peak at 50KHz which I suspect is originating
inside the 53230A, since it does not show up on the e1740, nor on the
8563a. I plan to investigate this spur further.

I stuck the signal back on the spectrum analyser, to see if the 64Khz
signal was in fact real, or an artifact of my measurement setup, which I
was suspecting. Nothing on the DSA-815 nor on the 8563a. Not untill I have
set RBW 30Hz, videoaveraging 80+ measurements on the 8563a do I see a peak
at 64Khz from the carrier, at around -80dBc. So the signal seems to really
be there.

I suspected a switching power-suppy might be coupling on to my cables, so i
switched the RG-58 out for double shielded LMR-240, with no difference at
all in the measurements. The peak was there both on the e1740A and the
53230A. So I am lead to believe the 64Khz spur is real, and originates in
the signal generator, since is is visible on three separate instruments,
and two separate measurement methods.

My question is this - how in the world can the counter pick up such a TINY
signal?? Does this make sense at all?

I suppose it is possible that the spur originates in my lab somewhere, and
is in fact quite strong, strong enough to couple into the counters with a
more reasonable signal - and only appearing to be weak on the 8563a because
it is better shielded?

Thanks for any insight!

Ole
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[time-nuts] FTS 8400

[Ole Petter Ronningen]

Hello, all

I recently came across a FTS 8400 Satellite Timing Receiver, and while I
await delivery, I am trying to dig up some more information about it. I
haven't been able to find much on line, but from what little I have found
they've been used in some pretty high end setups  - which leads me to HOPE
there may be a nice high stability oscillator in there. This particular
unit supposedly has the option for High stability internal oscillator.
You may guess what I am hoping for, given the name plate..

I do not have much hope for it to function as a GPSDO (although I might get
lucky), but it looks like a pretty interesting device all the same. Does
anyone have any information about these units?

Thanks.
Ole
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Re: [time-nuts] 53230A noise floor

[Ole Petter Ronningen]

Tangetially relevant; I made a patch for TimeLab to use the gap-free
frequency measurement-mode for the 53230A, if anyone is interested.

On Fri, Apr 3, 2015 at 4:34 PM, Tom Van Baak t...@leapsecond.com wrote:

  There is probably a good explanation for the ADEV-level in standard
  (pi-counting?) reciprocal frequency counter mode as well as the roughly
  1/sqrt(10) enhancement in ADEV when increasing the gate-time 10-fold.

 Anders,

 See the part the end that shows why averaging breaks ADEV:
 http://leapsecond.com/pages/adev-avg/

  I collected the data with a simple program that just calls the READ?
 function
  repeatedly, which does result in some dead-time between measurements.

 Yes, that's the easy way. But for more valid results use gap-free
 continuous mode (SENS:FREQ:MODE CONT). From the manual:

 CONTinuous configures the instrument to make continuous
 resolution-enhanced, gap-free measurements.  This mode should be selected
 for true Allan deviation computation (CALCulate:AVERage subsystem).  In
 this mode, all samples for a each trigger are started by a single gate open
 (instead of gate open/close per sample), and the measurements are computed
 back-to-back with no dead time.  CONTinuous can only be used for frequency
 and average period measurements. Available only on the Agilent 53230A.

 /tvb
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Re: [time-nuts] Mini-time lab cost and maintenance

[Ole Petter Ronningen]

Every timelab needs a time interval counter. I'd say look for a HP 5334B
with option 010. I've picked up two from ebay for about USD100 each, and
that comes with a decent 18011. After that, watch your cash disappear as
you discover a need for faster/better/more accurate instruments, not to
mention better and better oscillators..

Ole

On Tue, Apr 7, 2015 at 12:33 AM, Chris Albertson albertson.ch...@gmail.com
wrote:

 You can do a lot for $200 if you can build electronics yourself.
 Decent GPS with PPS starts at under $20 on eBay.  Same for surplus
 10MHz oscillators.  People have build usable counters for cheap
 microprocessor development boards and software.But it all depends
 on what you want to measure

 On Mon, Apr 6, 2015 at 9:30 AM, Adam Blakney akblak...@gmail.com wrote:
  I was wondering how expensive it would be to have even a small and lower
  level time lab. What are some less expensive models of machinery i would
  need, and how much maintenance is required?
 
  Thanks, Adam
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 --

 Chris Albertson
 Redondo Beach, California
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Re: [time-nuts] Austron 1250A Tuning tool

[Ole Petter Ronningen]

Fantastic, just what I needed. A little gentle persuasion with a knife
coaxed one of my crappy screwdrivers blade to become long enough (or
rather, the handle short enough..) to fit. 5 minute job once I knew what is
on the other end. Thank you!

OleP
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Re: [time-nuts] Austron 1250A

[Ole Petter Ronningen]

Thanks all

I decided to replace the batteries, expecting delivery any minute now.
Surprisingly expensive to replace those NiCd's.. Anyway, after looking at
the schematics a bit, I was able to stop the relay chatter by setting the
unit to charge, and holding down the reset switch for a couple of minutes.
That gave the batteries enough charge to power the base of the transistor
that holds the relay.

Ole
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[time-nuts] Austron 1250A Tuning tool

[Ole Petter Ronningen]

Hello

My 1250A has drifted outside the range of the front panel control, so the
coarse adjust needs some fiddling. The manual makes mention of a special
tool to be used for this. I don't have the tool, the closest I can get is a
10 bamboo stick that I cunningly liberated from my wifes sushimaking mat!
I wondered if anyone else on the list has this tool, and can send me a
description/photo of the tip? I tried widdling the tip of my stick to
various shapes, but not knowing what it is supposed to mate with, it is a
bit frustrating..

Thank you all
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[time-nuts] KS-24361 adjustable PLL time-constant

[Ole Petter Ronningen]

I know these has been discussed to death here, so my apologies for that.
Also, apologies if this has already been reported; i did not find it in the
archives..

It might be of interest to some that it appears that the KS-boxes has an
adjustable PLL time constant:

:SYST:LANG PFORTH
pll_rep
start ptr = 0stop_ptr = 0
max loop time = 700
ffom = 1
tfom = 1.0e-06 secs
1000 loop_time
pll_rep
start ptr = 0stop_ptr = 0
max loop time = 1000
ffom = 1
tfom = 1.0e-06 secs

Looks like a teakable PLL parameter, but I don't have the measurements to
back it up. Yet.

Also, there is a command to report on the L1-status, which might make life
easier for those who try to get the boxes going separately by manipulating
the J5-port:

On REF-0
print_l1
mode: locked, duration: 1152
locked duration: 1153, learning exceeded: 0
ready: 1, critical failure: 0
shutdown failure: 0
GPS locked once: 1
GPS found once: 1
Flywheel capable state: 0, time: 3600 sec
Other flywheel capable state: 2, time: 28800 sec
flywheel ready mode: idle
Other GPS locked once: 1
other on: 1, delayed other on: 1

Monitor
enable active: 1, ready: 1, hold actref: 1
ext_1pps_dead: 1 ext 1pps valid: 0
gps_1pps_dead: 0 gps 1pps valid: 1

HW lines
cable 1, active in: 0, ready in: 1
Ext locked in: 0, GPS Locked once in 1
ACTREF out: 1, PRI_ACT out: 1
Int power: 0, Ext power: 0
-

on REF-1:
mode: locked, duration: 76342
locked duration: 76343, learning exceeded: 0
ready: 1, critical failure: 0
shutdown failure: 0
GPS locked once: 1
GPS found once: 1
Flywheel capable state: 2, time: 28800 sec
ref duration: 100
other on: 1, delayed other on: 1

Monitor
enable active: 1, ready: 1, hold actref: 0
ext_1pps_dead: 0 ext 1pps valid: 1
gps_1pps_dead: 0 gps 1pps valid: 1

HW lines
cable 1, active in: 1, ready in: 1
ACTREF out: 0, PRI_ACT in: 0
Int power: 0, Ext power: 0


OleP
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[time-nuts] GPS position averaging

[Ole Petter Ronningen]

Hello, all

I have a couple of GPSDOs (KS, z3805a) hooked up to a fixed outdoor antenna
through an HP 58516 splitter. I notice that when I powercycle the GPSDOs
(which I generally try to avoid), the position they come up with differs
from time to time in at least the last three digits (and height in
particular varies with up to 30m).

I would like to get a better idea of what my actualt antenna location is,
so that I can manually set the position in the GPSDOs. For that purpose I
set up a Ublox M8N with logging in U-center, and I've collected about 250K
readings over several days. For each reading I also log number of SV's
used, as well as HDOP, VDOP. PDOP, thinking I would filter the list and end
up with a subset of really good fixes.The idea is then to average the best
readings and use that as my position.

My question is twofold; 1) is this for some reason a bad idea? And 2) How
do I average the numbers? I can not put my finger on it but it feels
wrong to average lat, long and height independently.

Any hints are greatly appreciated.

Thank you!
Ole P
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[time-nuts] Proper way to manually connect Vfc

[Ole Petter Ronningen]

Hello, all

I've started to build up a little collection of various OCXO's, and
measuring various deviations and variances and whatnot. I'm putting them
into proper enclosures, but up untill now I've adjusted them simply using
the Vref through a reasonably low tempco (20-100ppm/C) multiturn pot, with
just a .1uF cap on the Vfc pin to ground. Is this in fact the best way to
do it? Or is there another (reasonably simple) way to improve on that
setup?

I presume the reference-voltage present on most OCXO's are clean enough
to meet spec, but are there improvements to be had by using a separate low
noise regulator, for instance?

How about filtering, is there any reason to spend much effort on that, as
the OCXO's are in separate enclosures, with coax soldered directly onto the
10Mhz output? Not sure where the noise would come from, but I stand to be
corrected..

Sorry if this has been repeatedly answered (as I have a feeling it must
have been), but I failed to find it in the archives (perhaps poorly chosen
search-terms on my part)

Thank you
Ole P
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[time-nuts] Low noise powersupplies

[Ole Petter Ronningen]

Hello, all

I thought it may be of interest to some of the members of this list that TI
is selling evaluation modules for some ultra low noise regulators for $20
in their estore, shipping world wide included. The specs looks pretty
decent to me, and I've ordered up a couple of boards to use as clean up
boxes for my bench-supplies, to use on noise-sensitive projects.

1.4-30v output TPS7A4701EVM-094
3.5µVRMS (10Hz, 100KHz)
25 nV/√Hz (10Hz, 1MHz)
Maximum Output Current of 1A

+-15v version TPS7A30-49EVM-567:
15v rail:
Noise:
 12.7µVRMS (20Hz to 20kHz)
 15.4µVRMS (10Hz to 100kHz)
Power-Supply Ripple Rejection:
 72dB (120Hz)
 ≥ 52dB (10Hz to 400kHz)
Maximum Output Current: 150mA


-15v rail:
Noise:
 14µVRMS (20Hz to 20kHz)
 15.1µVRMS (10Hz to 100kHz)
Power-Supply Ripple Rejection:
 72dB (120Hz)
 ≥ 55dB (10Hz to 700kHz)
Maximum Output Current: 200mA

Ole
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[time-nuts] FTS1000A 05818-501 spec's

[Ole Petter Ronningen]

Hello, all

I went a bit overboard on ebay and ended up with a FTS1000A model
05818-501. I've found the datasheet for the FTS1000 on ko4bb's site, but
the model numbers does not match up. Does anyone know the spec for this
particular model (phasenoise/stability), and if there's reason to suspect
that the pinout is different for this particular model?

Thank you all!
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