[time-nuts] Re: GPS failed

[Andy Talbot via time-nuts]

There is a 3G/4G Supplementary Downlink allocation at 1492MHz in some
countries.   Close enough to cause problems.

Andy
www.g4jnt.com



On Mon, 11 Jul 2022 at 14:40, paul swed via time-nuts <
time-nuts@lists.febo.com> wrote:

> Skipp
> I am aware at least in the US that there is the possibility of 5G
> interference along with newer possible bands that 5G can use. I have read
> several articles in a publication called GNSS.
>
>
> Thats why I am using wwvb at 60 KHz. Humor intended.
> Regards
> Paul
> WB8TSL
>
> On Mon, Jul 11, 2022 at 8:49 AM skipp Isaham via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
> > Hello to the Group,
> >
> > I'd like to get some opinions and war stories regarding GPS reliability
> at
> > high RF level and elevation locations.
> >
> > Background:  Three different hill-top GPS receivers, all different types,
> > using
> > different antennas mounted on an outside fixiture, plain view of the open
> > sky,
> > all stopped working.
> >
> > Test antennas were brought in and placed on a fixture well away from the
> > original antennas, the recevers went back in to capture and lock.
> >
> > From what I understand, the original antennas are what I would call
> > straight
> > preamp with no pre-selection / filtering.
> >
> > The ordered and now inbound replacements are said to contain a SAW filter
> > system. It is the intent of the client to just place these "improved
> > antennas" in
> > to service and get on with life.
> >
> > I would suspect a GPS antenna (and receiver) could be subject to RF
> > overload
> > or blocking, however, we're assuming nothing major has changed at the
> > site, nor
> > any nearby location.  One might think there are more GPS receivers being
> > pushed
> > out of reliable operation by the world around them, I'm just not hearing
> > those stories
> > from a lot of people using them (GPS receivers).
> >
> > Any new install GPS receiver antenna ordered will/should contain some
> > pre-selection
> > to potentially avoid a problem, even some years down the road? Seems like
> > that's
> > where things are going... no more off the shelf, wide band, (hot)
> > preamplified GPS antennas
> > in busy locations?
> >
> > Thank you in advance for any related comments and/or opions ...
> >
> > cheers,
> >
> > skipp
> >
> > skipp025 at jah who dot calm
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe send an email to time-nuts-le...@lists.febo.com
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-le...@lists.febo.com
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-le...@lists.febo.com

[time-nuts] Re: GPS failed

[Andy Talbot via time-nuts]

I have had one, and possibly two, low cost active antennas  go unstable and
start oscillating.  These are the  magnetic car mount type with a ceramic
patch antenna.   The ceramic patch has quite a high Q and determines the
frequency the unstable RF front end takes off at - which is obviously at
1575.42 plus / minus a few tens of kHz.   Needless to say, all local GPS
receivers are jammed

I also heard a case of a GPS antenna going unstable, oscillating and taking
out most of the boats in a marina.   The Radio Communications Agency (as
our enforcement body was then, before it became Ofcom) had to be called
out to identify the problem.

Andy
www.g4jnt.com



On Mon, 11 Jul 2022 at 14:37, Lux, Jim via time-nuts <
time-nuts@lists.febo.com> wrote:

> On 7/10/22 4:19 PM, skipp Isaham via time-nuts wrote:
> > Hello to the Group,
> >
> > I'd like to get some opinions and war stories regarding GPS reliability
> at
> > high RF level and elevation locations.
> >
> > Background:  Three different hill-top GPS receivers, all different
> types, using
> > different antennas mounted on an outside fixiture, plain view of the
> open sky,
> > all stopped working.
> >
> > Test antennas were brought in and placed on a fixture well away from the
> > original antennas, the recevers went back in to capture and lock.
> >
> >  From what I understand, the original antennas are what I would call
> straight
> > preamp with no pre-selection / filtering.
> >
> > The ordered and now inbound replacements are said to contain a SAW filter
> > system. It is the intent of the client to just place these "improved
> antennas" in
> > to service and get on with life.
> >
> > I would suspect a GPS antenna (and receiver) could be subject to RF
> overload
> > or blocking, however, we're assuming nothing major has changed at the
> site, nor
> > any nearby location.  One might think there are more GPS receivers being
> pushed
> > out of reliable operation by the world around them, I'm just not hearing
> those stories
> > from a lot of people using them (GPS receivers).
>
> yes, this happens.  We used to have a Pendulum timing receiver with a
> typical "small white cone" type amplified antenna - if someone was on
> the roof with a cellphone, it lost lock, presumably from the (way out of
> band) emissions.
>
>
> As to where the interfering source is - it doesn't take much, and it
> could be some distance away.  After all, this was the big deal with
> LightSquared - it was moderately high powered terrestrial broadcast
> transmitters in the satellite downlink band next to GNSS.
>
>
> >
> > Any new install GPS receiver antenna ordered will/should contain some
> pre-selection
> > to potentially avoid a problem, even some years down the road? Seems
> like that's
> > where things are going... no more off the shelf, wide band, (hot)
> preamplified GPS antennas
> > in busy locations?
> >
> > Thank you in advance for any related comments and/or opions ...
> >
> > cheers,
> >
> > skipp
> >
> > skipp025 at jah who dot calm
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe send an email to time-nuts-le...@lists.febo.com
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-le...@lists.febo.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-le...@lists.febo.com

[time-nuts] Re: Knowing when the PPS signal is locked to the satellite.

[Andy Talbot via time-nuts]

The status flag in the $GxRMC message tells you if the unit is 'locked'
The PPS appears more-or-less when that flag goes from 'V' to 'A'


Andy
www.g4jnt.com



On Wed, 22 Jun 2022 at 14:23, Dave via time-nuts 
wrote:

> I am using a NEO-6M to provide a PPS signal for an experiment but I need
> to know when it is locked or not.
>
> Does anyone know if there is a way to find out from either the NMEA data
> stream or via the proprietary protocol ??
>
> At the moment I have it programmed to only provide a PPS signal when it
> is locked (or nothing if not) and monitor
> the PPS signal in the microprocessor, but it's not entirely satisfactory
> and I need a better mechanism.
>
> Dave
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-le...@lists.febo.com
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-le...@lists.febo.com

[time-nuts] Re: Ublox M6T -M8T

[Andy Talbot via time-nuts]

Do you mean "even submultiples"?  ie. even division ratios.

Andy
www.g4jnt.com



On Sat, 28 May 2022 at 21:11, Matthias Welwarsky via time-nuts <
time-nuts@lists.febo.com> wrote:

> Hi Rich,
>
> Only frequencies that are even multiples of the internal crystal frequency
> (48MHz) are "clean". Everything else is, as Bob puts it, "drop a pulse,
> add a
> pulse" approximations. However, that's normally easy to filter.
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-le...@lists.febo.com

[time-nuts] Re: measuring tiny devices

[Andy Talbot via time-nuts]

Google (other search engines are available :-)   DISHAL Filter Tuning
Very neat and quick way to tune up a filter using just return loss.
Doesn't even require a VNWA.

Andy
www.g4jnt.com



On Thu, 26 May 2022 at 16:40, Bob kb8tq via time-nuts <
time-nuts@lists.febo.com> wrote:

> Hi
>
> The real answer to the problem is to dig into the bowels of 1940’s
> electronic craft.
> There are various methods for setting up an L/C filter. You short this /
> open that sweep
> to find a dip or a peak. You move it to the “right” place. Just what you
> do depends
> very much on the filter design. Many L/C’s got done this way or that way
> simply
> because they would fit a known alignment method.
>
> While it all sounds very cumbersome and obscure it actually isn’t. Long
> ago I stumbled
> upon a gal setting up very complex L/C IF filters this way. The display
> gyrated this way
> and that way as she did this or that. I don’t think it took her more than
> a minute to get
> the whole thing set up….. to this day, I’m amazed by how fast she was.
>
> Do I have any useful links to actually read up on  this magic? … sorry
> about that.
>
> Bob
>
> > On May 26, 2022, at 4:58 AM, Lux, Jim via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > On 5/25/22 3:16 PM, ed breya via time-nuts wrote:
> >> Thanks Mike, for info on LCR alternatives. It's good to know of others
> out there, if needed. I have an HP4276A and HP4271A. The 4276A is the main
> workhorse for all part checking, since it has a wide range of LCZ, although
> limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and
> good for smaller and RF parts, but very limited upper LCR ranges. I think
> it works, so I can use it if needed, but would have to check it out and
> build an official lead set for it. I recall working on it a few years ago
> to fix some flakiness in the controls, so not 100% sure of its present
> condition.
> >>
> >> The main difficulty I've found in measuring small chokes is more of
> probing/connection problem rather than instrument limitation. For most
> things, I use a ground reference converter that I built for the 4276A many
> years ago. It allows ground-referenced measurements, so the DUT doesn't
> have to float inside the measuring bridge. The four-wire arrangement is
> extended (in modified form) all the way to a small alligator clip ground,
> and a probe tip, for DUT connection, so there is some residual L in the
> clip and the probe tip, which causes some variable error, especially in
> attaching to very small parts and leads. When you add in the variable
> contact resistance too, it gets worse. Imagine holding a small RF can
> (about a 1/2 inch cube) between your fingers, with a little clip sort of
> hanging from one lead, and pressing the end of the probe tip against the
> other lead. All the while, there's the variable contact forces, and effects
> from the relative positions of all the pieces and fingers, and the stray C
> from the coil to the can to the fingers. I have pretty good dexterity, and
> have managed to make these measurements holding all this stuff in one hand,
> while tweaking the tuning slug with the other.
> >>
> >> I had planned on making other accessories like another clip lead to go
> in place of the probe tip, but not yet built. I also have the official
> Kelvin-style lead set that came with the unit, so that's an option that
> would provide much better accuracy and consistency, but the clips are
> fairly large and hard to fit in tight situations, and the DUT must float.
> Anyway, I can make all sorts of improvements in holding parts and hookup,
> but usually I just clip and poke and try to get close enough - especially
> when I have to check a lot of parts, quickly.
> >>
> >> The other problem is that the 4276A is near its limit for getting
> measurements below 1 uH, with only two digits left for nH. The 4271A would
> be much better for this, with 1 nH vs 10 nH resolution.
> >>
> >> If I get in a situation where I need to do a lot of this (if I should
> get filter madness, for instance), then I'll have to improve the tools and
> methods, but I'm OK for now, having slogged through it this time.
> >
> >
> > You might check out the NanoVNA - people have made a variety of novel
> fixtures for measuring small parts (i.e. 0604 SMTs)
> >
> > It certainly has the measurement frequency range you need. The trick is
> figuring out whether you want to do a series or shunt measurement, and that
> sort of depends on the reactance of your device at the frequency of
> interest.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe send an email to time-nuts-le...@lists.febo.com
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-le...@lists.febo.com
___
time-nuts mailing list -- time-nuts@lists.febo.com

[time-nuts] Re: Effect of temperature on cheap puck style GNSS antennas?

[Andy Talbot]

"During sunrise"
Isn't it more likely to be due to changes in the ionosphere during
sunrise/set that causes the timing discrepancies.   Any changes to the
antenna / LNA due to temperature will affect the reception of all
satellites so should cancel out.

Andy
www.g4jnt.com



On Thu, 12 May 2022 at 08:33, Matthias Welwarsky 
wrote:

> Dear list members,
>
> My DIY GPSDO has a rather well defined dependence to the environmental
> temperature, which correlates almost linearly with a frequency shift of
> the
> OCXO. However, at times I see the error against the GNSS reference
> increasing
> with its case temperature not warranting such effect.
>
> My antenna is one of those cheap, magnetic, active antennas you'd put on a
> car
> roof. It's facing south and has full exposure to the sun, obviously.
>
> During sunrise I see the TIC error increasing 20ns-30ns over lets say 2000
> seconds. The GPSDO case temperature rises, too, during that time as the
> room
> temperature increases, but it is only by 0.3°C.
>
> I'm wondering if the temperature of the antenna, which of course rises
> much
> faster than the room temperature, can have an effect of this magnitude?
>
> Best regards,
> Matthias
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-le...@lists.febo.com
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-le...@lists.febo.com

[time-nuts] Re: RAGA - was Re: Re: Low Phase Noise70 10 MHz bench signal source sought

[Andy Talbot]

I have encountered GPS active antennas that are unstable and oscillate,
especially when not mounted on a metal backing.One even oscillated
occasionally when it did have a ground plane.   Because the ceramic patch
antenna is narrowband and has a high Q, the spurious oscillation is
relatively stable in frequency, and of course very close to 1575MHz where
patch resonates.
One such faulty antenna I had once jammed every other GPS receiver in the
house - although they were all the old 2nd generation type receivers of two
decades ago

Andy
www.g4jnt.com



On Sat, 2 Apr 2022 at 19:27, Lux, Jim  wrote:

> I encountered a weird problem when I hooked up 4 OEM GPS modules to 4
> Beaglebones.. Side by side, they wouldn't all get GPS lock. It turns out
> the (unshielded) receivers radiate enough stuff to foul up adjacent
> receivers.   Move them several meters apart and no problems.  I didn't
> get around to seeing if there is some effect on the timing performance,
> even if they "get lock", but I'll bet there is.  A
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: One-night experiment: empirically verifying that the west coast power grid is actually interconnected

[Andy Talbot]

It ought  to be possible to build inertia, electronically, into inverters.
 The maths can't be difficult to fathom-out, then DSP can do the rest.
 BUT to allow this to be possible, in normal usage the solar/wind/whatever
source must be operating at a level significantly below what it can give
out, in order to be able to push out more energy in a hurry when, say,
frequency drops too much.
The operators of such systems will have to be mandated or incentivised to
run backed off at all times in case their extra capability is needed for
emergencies.

Andy
www.g4jnt.com



On Wed, 9 Mar 2022 at 08:58, Poul-Henning Kamp  wrote:

> 
> Jeremy Elson writes:
>
> > Wow! I was not expecting the two curves to match up so well. What a
> beautiful result!
>
> The effective impedances of the power grid are very low, so frequency
> discrepancies are almost physically impossible.
>
> If you want to see the real trouble, you need to GPS referenced high
> resolution phase measurements in two or more locations, and then
> plot the RMS of their differences.
>
> Traditionally the grid frequency has been stabilized by the inertia
> in the (huge!) rotors in centralized power plant's turbo generators.
>
> Solar power generation is instantaneous and contribute no inertia.
>
> Wind power has lots of small generators, but they are behind electronic
> "frequency converters", (AC->DC->AC conversion) which attenuates and
> delays the response from their generators inertia[1].
>
> With solar and wind taking over, for instance 60% of planned new
> generating capacity in USA next year will be solar and batteries,
> "low inertia situations" have become a real worry.
>
> The UK's grid collapse a couple of years ago is the first documented
> case where "low inertia" was "but for" factor.
>
> The big-iron-wound-with-copper manufacturers have started hawking
> "inertia generators" as a solution:  Huge spinning lumps of iron
> connected to a motor-generator.
>
> Other solutions are to mandate local battery-storage and inertia
> supplying control algorithems at large VE deployments.
>
> NREL has a good article called:
>
> Inertia and the Power grid: A Guide without the Spin
>
> https://www.nrel.gov/docs/fy20osti/73856.pdf
>
> Poul-Henning
>
> [1] Different control-algorithms in different wind generators on
> the same grid-radial could cause frequency oscillations, if the
> interactions are not taken into account.  This mandates quite
> conservative control strategies, which further attenuates the
> "inertia contributions".
>
> [2] https://www.eia.gov/todayinenergy/detail.php?id=51518
>
> --
> 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.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Phase coherence with 2X GPSDO

[Andy Talbot]

Where are the GPS antennas wrt. you 'moving around'?
Could it be that while you were watching the paint drying, you didn't move
much.   But when you moved away, the RF pattern as a result of local
reflections of the signal from the satellites (from you) were enough to
upset the receiver to give the phase shift.


Andy
www.g4jnt.com



On Tue, 8 Mar 2022 at 14:55, Bob kb8tq  wrote:

> HI
>
> > On Mar 8, 2022, at 2:31 AM, ed breya  wrote:
> >
> > Just an interesting observation. Last night, shortly after I wrote about
> my dual GPSDO system, I decided to take a look at it, with the usual scope
> setup looking at both 10 MHz outputs. It looked like one of those
> reasonably good times, where the phase between them seemed very stable
> during fairly long observation time. They were nearly in quadrature,
> drifting very slightly back and forth, over maybe an hour of occasional
> observation. This is akin to the proverbial "watching paint dry" - nothing
> new to report, over a long time, blah blah blah.
> >
> > I went inside for at most a couple minutes to look at something, and
> when I returned to the garage, I noticed they were nearly in-phase, all of
> a sudden. Over the next half hour or so, I could see the phase drift back
> to about where it was before. During that brief moment when I was gone, I
> had missed what was probably a DAC value update, when one of the units
> decided it was time to make a change.
> >
> > The change of one or some LSBs must have had a relatively instantaneous
> effect in the time scale involved, and I missed it, but I did see the
> aftermath. So, you can add that sort of effect in the time/frequency
> situation. The temperatures and drifts of various parts, and the SW
> figuring out what to do about it, tend to go quite slowly, but once the
> decision is made to change a value, there's a step function involved.
> >
> > As I understand, the tuning DAC may be updated once a second at most (if
> comparing to the 1PPS), in small increments, as the DO part tries to keep
> everything right according to the GPS part.
>
> In the case of most GPSDO’s running with most firmware:
>
> The updates are indeed once a second. The math does it’s thing on each PPS
> and comes up with a “new guess” each time. The delta with most DAC’s is in
> the
> “several to many” LSB's range. A lot depends on what’s going on with the
> oscillator
> and the rest of the “stuff”.
>
> While we tend to blame everything on the poor OCXO in the typical OEM
> module,
> that may not be the problem. The Vref or even the tempco of the DAC could
> easily
> be getting into the mix. There are some well known GPSDO’s that a lot of
> us have
> where this is the case.
>
> Since I’m sure “why” will be the next question ….
>
> If the device is targeted at a very long lifespan (10, 20, ….. years ) the
> trim range is
> going to be non-trivial. Just how large it is depends a bit on how
> conservative the
> folks who did the oscillator / GPSDO felt when they did it all up.  Could
> you use
> a $50 Vref and a $90 DAC? That’s really going to destroy your budget ….
>
> Bob
>
>
> > With my simple setup and observations, I can't tell really how big, or
> how often these adjustments are made, but whatever this was, it was quite
> obvious. The most interesting things tend to happen when you're not looking.
> >
> > Ed
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Testing GPSDOs

[Andy Talbot]

Yes, 1Hz observed is 1Hz on the multiplied up signal, which at 5GHz is
2E-10 on the reference causing it

The FFT process does indeed smear out faster transitions, so you need to
flip between different  FFT sizes to see fully what is happening.

If you use a prog like SPECTRAN to view the audio beat note, it's quite
feasible to have several instances of that software open at the same time,
all fed from the same soundcard source.   Set each instance to a different
FFT resolution, one wide, one narrow and others as you like, and watch what
happens


Andy
www.g4jnt.com



On Mon, 21 Feb 2022 at 08:38, Erik Kaashoek  wrote:

> Andy,
> Thanks for these references
> Using two 5GHz PLL's, one hard referenced to the in-house standard and
> the other to the TCXO under test and the outputs of the PLL's send into
> a mixer producing a 10kHz output send into a PC for FFT analysis made
> the performance of the TCXO very visible.
> Can I assume 1 Hz variation of the audio signal is 2e-10 variation on
> the 10MHz signal?
> My concern with the high resolution FFT is the length of the FFT, does
> this not hide fast frequency variations? Or will these variation become
> visible through blurring of the peak and as long as the peak is nice an
> sharp one can assume the signal is stable over the FFT length?
> Erik.
> On 20-2-2022 18:38, Andy Talbot wrote:
> > Dunno if this will do what you want ...
> >
> > Get hold of some PLL Fract-N synthesizers, like the ubiquitous ADF4351,
> so
> > you can multiply up from two sources. Mix the outputs and look at the
> > frequency deviation over time.
> > My tests using this technique can be seen at
> > http://g4jnt.com/10MHz_Reference_Source_Stability.pdfand
> > http://g4jnt.com/ShortTermStabilityLeoBodnarGPSDO.pdf
> >
> > I used synths I had to hand, but anything that will multiply up your test
> > and reference signals to a pair of frequencies separated by a few kHz, so
> > you can look at the beat note using soundcard software.
> >
> >
> > Andy
> > www.g4jnt.com
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Testing GPSDOs

[Andy Talbot]

Dunno if this will do what you want ...

Get hold of some PLL Fract-N synthesizers, like the ubiquitous ADF4351, so
you can multiply up from two sources. Mix the outputs and look at the
frequency deviation over time.
My tests using this technique can be seen at
http://g4jnt.com/10MHz_Reference_Source_Stability.pdfand
http://g4jnt.com/ShortTermStabilityLeoBodnarGPSDO.pdf

I used synths I had to hand, but anything that will multiply up your test
and reference signals to a pair of frequencies separated by a few kHz, so
you can look at the beat note using soundcard software.


Andy
www.g4jnt.com



On Sun, 20 Feb 2022 at 17:10, Erik Kaashoek  wrote:

> I'm trying to check the short term stability of a TCXO, for tau below 1
> second
> With my frequency counter and timelab the shortest tau usable is 0.02
> seconds but the decrease of accuracy of the counter with this small tau
> starts to limit the measurement. But with Vtune of the TCXO at min or
> max the frequency deviation is well below 0.5e-9. In between Vtune
> produce bigger frequency deviations, don't understand why but if there
> is digital stuff inside the TCXO anything is possible I recently learned.
> So I'm trying to use an SA/Modulation analyzer to look at the spectrum
> of overtones  with 1Hz resolution or watch the FM modulation analysis
> The FM modulation analysis does not give understandable information. At
> the fundamental of the 10MHz the frequency deviation is reported as
> 25Hz, for the harmonics of the 10MHz the frequency deviation increase
> with the harmonic so the 25Hz may be correct.
> But the measured modulation frequency is 10kHz so I tried to output the
> demodulated FM into a good PC audio card and use audio FFT SW so see if
> there is anything recognizable but I can not see any peak above the
> noise. Listening to the demodulated FM also does not reveal a lot, just
> a very faint wistle of some tones.
> The small span scans on the SA show 50 Hz sidebands, even when the whole
> TCXO is running on battery power so I'm confused.
> In short, this requires still a lot of time to learn how to measure and
> to create understanding.
> And investing in a timepod is currently not feasible.
>
> Is there any reference material to be found on how to do these short tau
> stability measurements?
> The method with the mixers Bob was referring to?
> Erik.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: 10 MHz TCXO periodically jumping 20 mHz up and down

[Andy Talbot]

At that time the synth was set to one frequency and the code went into
sleep , so any buffering resistors etc would have served no purpose.
The TCXO really was hopping over four frequencies in a PN way at intervals
of a little under one second per hop.

Andy
www.g4jnt.com



On Sat, 19 Feb 2022 at 20:46, glen english LIST 
wrote:

> Andy, do you have the PIC and the synthesiser chip data control lines
> well buffered/isolated (nice big resistors etc on the data lines ?)
>
> Any sort of current you inject into the synth chip will find its way
> onto the output
>
> On 19/02/2022 7:55 pm, Andy Talbot wrote:
> > A while back I purchased a low cost TCXO which I then used as the
> reference
> > for a synthesizer generating 10GHz.  Listening to the output on an SSB
> > radio, the tone was hopping in a random fashion over four frequencies,
> > spaced a few tens of Hz apart.   This was surreal!  I had, at that time,
> > been building Multifrequency Shift Keyed data sources ( for WSJT modes)
> by
> > programming synths directly, but this wasn't the case here.   Yet the
> > hopping tones sounded just like the modulation I woul
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: 10 MHz TCXO periodically jumping 20 mHz up and down

[Andy Talbot]

A while back I purchased a low cost TCXO which I then used as the reference
for a synthesizer generating 10GHz.  Listening to the output on an SSB
radio, the tone was hopping in a random fashion over four frequencies,
spaced a few tens of Hz apart.   This was surreal!  I had, at that time,
been building Multifrequency Shift Keyed data sources ( for WSJT modes) by
programming synths directly, but this wasn't the case here.   Yet the
hopping tones sounded just like the modulation I would eventually be adding.
Double checking, then again, then again. that I hadn't inadvertently
programmed the synth controller PIC with the wrong code, had to come to the
conclusion it was the TCXO using a PRN sequence to effect digital
temperature/frequency compensation.At its 10MHz fundamental, each hop
would have been a few tens of millihertz.

But it was very weird at first, hearing what sounded like a familiar
modulation on a synth that wasn't programmed to generate it.  There were
four tones hopping in a (presumably pseudo) random manner, and the WSJT
mode I was going to use, JT4, had... four tones that hop around.

Andy
www.g4jnt.com



On Fri, 18 Feb 2022 at 10:19, Erik Kaashoek  wrote:

> During long term testing of some 10 MHz TCXO  the output frequency seems
> to jump within one second 20 mHz ( millihertz) up in frequency  every
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Garmin GPS 25 Module

[Andy Talbot]

Yes, I had to disable the GSV sentence to get the data flow down to a level
that could be sent at the lower speed.
I'm only using  GPRMC, so all the others could be removed as well, but as
GPRMC comes first in the block every second, there's nothing to be gained
from killing any of the others sentences.

I did fall foul once of a changed format.   Originally I wrote for an RMC
string that just gave integer seconds.   On using my code with a later
module it failed, and I spotted that it was sending decimal seconds, so had
to rewrite my PIC code to cope with that.
Then later, using other module types, GPRMC became GNRMC to cope with
Glonass etc. so that was another change needed.

Andy
www.g4jnt.com



On Wed, 9 Feb 2022 at 15:49, Bob kb8tq  wrote:

> Hi
>
> In terms of upgrading the GPS module(s):
>
> You might want to look at just *what* NMEA messages are being used.
> While the format is “standard” it’s not quite dead nuts in some cases.
> Vendors get to add this and that and it still is NMEA. Converting from
> one family to another is not always easy.
>
> I would also want to check the GPS antenna at the remote site. They
> don’t last forever. Flakey sat signals can drive a module a bit nuts.
>
> GPS modules have gotten pretty cheap over the years. If this is a long
> drive / crazy access sort of thing, redundancy is not as expensive on
> the module (or antenna) side as it once was.
>
> Bob
>
> > On Feb 9, 2022, at 4:36 AM, Andy Talbot  wrote:
> >
> > I run a set of microwave beacons on a remote site that transmit data
> modes
> > whose Tx timing is controlled from GPS.   They were installed some 20
> years
> > ago and used a Garmin GPS25-LVS module to deliver NMA and 1 PPS signals
> to
> > all five individual controllers.
> >
> > After a power outage that lasted a couple of days, the beacons fired up
> but
> > it was clear, after a couple of days timing was corrupted.  Each beacon
> has
> > slightly different controller firmware, and by monitoring the resulting
> > corrupted modulation it could be determined what was wrong.No PPS
> > signal was present - which killed modulation on two of them. NMEA timing
> > data was present but the time being reported was out by several seconds,
> > rendering the data signal transmitted undecodable by most people.
> >
> > I went up to the remote site to recover the old hardware and am in the
> > process of replacing the timing source using a Ublox NEO-6.   Since all
> the
> > beacons were originally designed based on 4800 baud NMEA, the Ublox was
> set
> > for this for backwards compatibility with the Garmin and the
> configuration
> > saved in NV ram.
> >
> > Now the query I have.   I had assumed it was a 1024 week rollover that
> > killed the Garmin, but on testing teh module when I returned home, after
> a
> > longer than normal initialisation period it DID start outputting the
> > correct date and time, with PPS present.   So the initial reboot failed,
> > even after a couple of days attempt, but after a power cycle it worked.
> >
> > I'm puzzled by that behaviour.  Is anyone here familar with the GPS25
> > family, dating from the turn of the millennium?
> >
> > As an aside, a Jupiter TU60 GPS module was also in use on site,
> delivering
> > a GPS locked 10kHz signal.   This I used to lock a 10MHz reference in
> > "Probably the Simplest GPSDO Possible"  http://g4jnt.com/SimpleGPSDO.pdf
> > That module, which is not a lot newer than the Garmin, did appear to have
> > survived the reboot as the resulting frequencies of the beacons were
> > spot-on when they returned with their modulation faults.  However, in the
> > spirit of doing the job properly, it too is being replaced with a
> > Leo-Bodnar mini GPSDO.
> > All beacon details at scrbg.org
> >
> >
> > Andy
> > www.g4jnt.com
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Garmin GPS 25 Module

[Andy Talbot]

I run a set of microwave beacons on a remote site that transmit data modes
whose Tx timing is controlled from GPS.   They were installed some 20 years
ago and used a Garmin GPS25-LVS module to deliver NMA and 1 PPS signals to
all five individual controllers.

After a power outage that lasted a couple of days, the beacons fired up but
it was clear, after a couple of days timing was corrupted.  Each beacon has
slightly different controller firmware, and by monitoring the resulting
corrupted modulation it could be determined what was wrong.No PPS
signal was present - which killed modulation on two of them. NMEA timing
data was present but the time being reported was out by several seconds,
rendering the data signal transmitted undecodable by most people.

I went up to the remote site to recover the old hardware and am in the
process of replacing the timing source using a Ublox NEO-6.   Since all the
beacons were originally designed based on 4800 baud NMEA, the Ublox was set
for this for backwards compatibility with the Garmin and the configuration
saved in NV ram.

Now the query I have.   I had assumed it was a 1024 week rollover that
killed the Garmin, but on testing teh module when I returned home, after a
longer than normal initialisation period it DID start outputting the
correct date and time, with PPS present.   So the initial reboot failed,
even after a couple of days attempt, but after a power cycle it worked.

I'm puzzled by that behaviour.  Is anyone here familar with the GPS25
family, dating from the turn of the millennium?

As an aside, a Jupiter TU60 GPS module was also in use on site, delivering
a GPS locked 10kHz signal.   This I used to lock a 10MHz reference in
"Probably the Simplest GPSDO Possible"  http://g4jnt.com/SimpleGPSDO.pdf
That module, which is not a lot newer than the Garmin, did appear to have
survived the reboot as the resulting frequencies of the beacons were
spot-on when they returned with their modulation faults.  However, in the
spirit of doing the job properly, it too is being replaced with a
Leo-Bodnar mini GPSDO.
All beacon details at scrbg.org


Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: electronics question or how not to fry my raspberry pi

[Andy Talbot]

Those diodes are so robust that a PIC connected the wrong way to a 5V 1 Amp
PSU was protected by all these diodes conducting in parallel and current
limiting the PSU.   The PIC appeared to have survived (although I chucked
it anyway, just in case)

Andy
www.g4jnt.com



On Sat, 29 Jan 2022 at 18:56, Robert Atkinson via time-nuts <
time-nuts@lists.febo.com> wrote:

>  You can run the PicDiv on 3.3 V and connect the 5V signal to the PicDiv
> input via a series resistor between 1k and 10k. Put the resistor at the
> PicDiv end of the connection.
> The PIC has protection diodes on it's input These clamp the input to the
> supply. The series resisor limits the current. This is robust. There are
> thousands of devices out there with a pin conneted to the mains with just a
> series resistor. t's used for zerocrossing detection or monitoring the
> mains frequency.
> Robert G8RPI.
>
> On Friday, 28 January 2022, 20:06:20 GMT, folkert <
> folk...@vanheusden.com> wrote:
>
>  Hi,
>
> I bought a GPSDO. It outputs somewhere around 3V. This is connected to a
> picdiv and then to a raspberry pi. The picdiv is happy with 3.3v, the rpi
> as well. All good.
>
> Now I bought a "Square Wave Amplifier" by BG7TBL (
> https://www.aliexpress.com/item/4000192799858.html?gatewayAdapt=glo2nld=a2g0o.9042311.0.0.3d764c4dMZPAX8
> ). Documentation I could find was a bit vague about the
> output voltage but I measured 5v with a scope (see
> https://vanheusden.com/permshare/scope.png - the scope software says
> 2MHz but output is really 10MHz).
>
> I did not study electronics, am only a electronics-hobbyist so bare with
> me when this is a dumb question.
>
> The RPI doesn't like 5v on its GPIO pins.
> So I wonder:
> - can I feed the picdiv 5v on its GPIO pin while giving it a 3.3v
>   voltage so that it outputs 3.3v as well to the rpi pins?
> - or should I use a voltage divider? I was thinking of a 4.7k ohm and
>   8.2k ohm resistor giving slightly less than 3.2v - will that work? or
>   will that attenuate the signal too much? The 50 ohm bnc cable between
>   the amplifier and the rpi is 3m long. Anything else I should be aware
>   of?
>
>
> Regards,
>
> Folkert van Heusden
> PD9FVH
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: My AC measurement project & question

[Andy Talbot]

But do you want to measure anything other than mains frequency?   IF not,
waveform distortion in immaterial.
Or am I missing something here?

My mains monitor uses an old wall wart with 9V rectified but unregulated DC
out - 5V regulator on the display board.  I added an extra wire to one side
of the transformer winding which goes via a DC block capacitor and resistor
of a few kΩ to the Schmitt timer input of the PIC microcontroller.   At
several volts peak to peak, it's more than sufficient to take the Schmitt
well beyond its two switching thresholds.  Clamp diodes to Vdd and GND
within the PIC keep it to safe limits.


Andy
www.g4jnt.com



On Sun, 23 Jan 2022 at 10:44, Dave B via time-nuts 
wrote:

> On 23/01/2022 08:30, time-nuts-requ...@lists.febo.com wrote:
> > Stick with the transformer. The use of a capacitive divider is
> predicated on the line waveform always being a sine wave. Dream on! All it
> takes is one good spike down the line, maybe only 20-30V amplitude, and
> your capacitive divider passes it right on to that ADC that has a much
> lower (3.3V?) limit. Guess what goes poof?
> > 
>
> Transformers distort the waveform, unless specifically designed for that
> need.
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Where do people get the time?

[Andy Talbot]

And here in the UK, after dialling 123  it was originally "At the third
stroke the time will be HH MM and S0 seconds"
Later, after privatisation, it became   "At the third stroke the time
sponsored by Accurist will be HH MM and S0 seconds"

I don't know if it still operates on landlines; on my mobile network '123'
gets voicemail.

Andy
www.g4jnt.com



On Fri, 7 Jan 2022 at 09:18, Bryan _  wrote:

> , and only after asking those on the "party line" to hang up, only
> those over 55 would know what I am talking about.
>
> -=Bryan=-
>
> 
> From: Chris Howard 
> Sent: January 6, 2022 6:56 PM
> To: time-nuts@lists.febo.com 
> Subject: [time-nuts] Re: Where do people get the time?
>
>
> When I was a kid in the 1960's we got the time by calling a phone number.
>
> "Bankers Trust time ten fifty three; temperature 46"
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Where do people get the time?

[Andy Talbot]

In the UK, the BT speaking clock, apparently, is still operational.But
at a cost of 50p per minute, I doubt it gets much use.
I'm not going to waste 50p by dialling 123 from the landline to test it
still goes, and it doesn't work on mobiles.

Andy
www.g4jnt.com



On Mon, 27 Dec 2021 at 20:28, Raven L  wrote:

> For what it's worth, my google pixel on AT's network in the US is almost
> always at least a second off UTC - at the moment, it shows -1.77s (courtesy
> of the ClockSync app). Seeing it within 0.5s is actually mysteriously rare.
>
> On Mon, Dec 27, 2021, 2:16 PM Adam Space  wrote:
>
> > As a younger person I appreciate this write-up. It is interesting to see
> > the progression. Nowadays, phones are synchronized to within a second
> > easily, and probably within 10ms at least once per day (this is what I
> > suspect from occasionally checking the offset on my phone). With
> computers
> > too, I would bet that most come out of the box with some sort of NTP
> setup
> > that at the very least keeps them within a few seconds, depending on how
> > often the default polling interval is. The idea of having to go to great
> > lengths to get access to an accurate time signal seems foreign today, but
> > it's interesting hearing about that being the case in the past.
> >
> > On Sat, Dec 25, 2021 at 8:07 PM Attila Kinali  wrote:
> >
> > > On Sat, 25 Dec 2021 15:27:51 -0800
> > > Hal Murray  wrote:
> > >
> > > > How good are cell phones?  I remember comments about them being way
> > > off.  But
> > > > that was a long time ago.
> > >
> > > Cellphone network time distribution is something rather new
> > > and didn't exist until EDGE (or was it HSDPA?) came along.
> > > But once it was available, it was "good enough", i.e. the
> > > time offset was low enough to be not perceivable (~100ms).
> > > At least in Europe.
> > >
> > > I know from other countries, that back in 2005, network time
> > > was off by a few minutes. This has probably improved now, because
> > > UMTS requires the cells to be synchronized to UTC to within
> > > a few 10s of µs. (I don't remember the details, Magnus can
> > > provide a more accurate picture) And by already having accurate
> > > time in the network, providing that to the cellphones is easy
> > > and the obvious way to go about.
> > >
> > >
> > > > If I was doing it now, I would probably setup one of the battery
> > powered
> > > > clocks that listens to WWVB.  When were they first widely available?
> > >
> > > Hmm... Let me give you a quick history of how time aquisition
> > > evolved through the eyes of a fledgling time-nut :-)
> > >
> > > Disclaimer: This is how I experienced things as I grew up in
> > > Switzerland. It was probably quite similar throughout western
> > > Europe, but I didn't travel enough until early/mid 90s to say
> > > anything beyond the countries I visited regularly. Not to
> > > mention that a toddler who can't read a watch wasn't much
> > > interested in how to get accurate time in the first place...
> > > That said, Swiss were and still are quite a bit more obsessed
> > > with time than the rest of Europe. So my view might be a bit
> > > skewed.
> > >
> > > In the 80s virtually all watches and clocks were quartz movements.
> > > I.e. they kept time accurately enough for most things. There were
> > > still some mechanical watches around, but they were mostly a
> > > thing of the past and kind of a fashion statement... Or a watch
> > > gifted by a relative decades ago. Most people set their watches
> > > at least every 6 months, when dailight saving switched. I had
> > > (and lost) a Swatch Flick Flak (
> > > https://www.newlyswissed.com/wp-content/uploads/2015/08/Flik-Flak.jpg
> ),
> > > two Pop Swatch ( https://www.uhrenkosmos.com/30-jahre-pop-swatch/ )
> > > and two Tissot Two-timer (pretty much this model
> > >
> >
> https://watchcharts.com/listing/1084976/tissot-twotimer-timer-analog-digital-watch
> > > ).
> > > as my watches as a kid during kindergarten and elementary school.
> > > The Tissot I used until I broke its wristband holder a week before
> > > I graduated from high-school, which had a pretty deep gouge in the
> > > glass through the whole watch face when I fell on some gravel path
> > > in 4th grade.
> > >
> > > None of these watches were special for a child in Switzerland.
> > > Even the Tissot Two-timer, which was IIRC CHF 80-100 back in
> > > the late 80s (probably around 200 USD in today's money), was a
> > > relatively common watch to have as an elementary/middle school
> > > student. And even a first grade student was expected to have
> > > some form of a watch, either on his wrist or in his pocket.
> > > And that, even though there was a clock somewhere in sight virtually
> > > everywhere in Switzerland  as there were plenty of watch/clock shops
> > > and a lot of stores had a clock somewhere around the entrance.
> > >
> > > The way to get time was usually TV and radio broadcast or church
> > > bell towers. One popular way was 

[time-nuts] Re: Why do have OCXO a Vref output? (was: help reviving Trimble UCCM-LPS GPSDO)

[Andy Talbot]

In the (very) few OCXO circuits I've seen, voltage at both ends of the
tuning varactor are derived from the same internal voltage reference.  So
any drift in this will, partially at least, cancel out.I too was
surprised to see nothing more than a Zener being used in one case, but
bearing in mind this was in a temperature controlled environment is not as
bad as a Zener in open air

Andy
www.g4jnt.com



On Sat, 25 Dec 2021 at 16:26, Poul-Henning Kamp  wrote:

> Being also a bit of a volt-nut, I played a bit with the Vref output
> from some of my OCXO's and must sadly report that they were not
> spectacular, seen from a volt-nut perspective.
>
> In at least once case, an admittedly pretty old OCXO design, the
> voltage reference was not located in the most well-regulated part
> of the oven and the chosen chip had pretty bad tempco at the elevated
> temperature.
>
> --
> 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.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Why do have OCXO a Vref output? (was: help reviving Trimble UCCM-LPS GPSDO)

[Andy Talbot]

I've always assumed this is because they need to know the reference is
clean and under the OCXO manufacturer's control if it's to meet specs.  If
the user had to supply the reference there's no knowing how clean it is.

Andy
www.g4jnt.com



On Thu, 23 Dec 2021 at 17:47, Attila Kinali  wrote:

> On Thu, 23 Dec 2021 14:42:27 +0100
> Wilko Bulte  wrote:
>
> > A quick experiment learned that the OCXO freq responds to the EFC
> voltage.
> > So, looks like the Vref circuit in the OCXO has died.
>
> A stupid side question: Why do have OCXO a Vref output in the
> first place?
>
> I can see that some form of reference might make stabilizing
> the power in the crystal easier, but that still wouldn't make
> it necessary to have an actual reference output.
>
> And related to that: Would supplying the voltage reference
> externally, in case of a broken Vref output, work for whatever
> is inside that needs this reference voltage?
>
> Attila Kinali
>
> --
> The driving force behind research is the question: "Why?"
> There are things we don't understand and things we always
> wonder about. And that's why we do research.
> -- Kobayashi Makoto
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: local WWVB ?

[Andy Talbot]

To "transmit" on 60kHz and radiate ANY reasonable power needs a very large
antenna.   I used to transmit on 73kHz when we briefly had an amateiur band
there, have  7 metre high antenna with a substantial capacity hat, was
putting 200 Watts into it but was getting an estimated radiated power of
just a few milliwatts.  It was detected at 400km distance, but only in an
ultra narrow bandwidth DSP based receiver, far too narrow for 1s timing
window

The small transmitters you are talking about for relays operate using a
magnetic loop that couples only (well, very nearly only) the magnetic H
field from the source.   The H field falls off not as the square of
distance, as the radiated field normally associated with a radio
transmission does, but as the sixth power of distance.   SO once you get
beyond a few metres of a small loop antenna  with a few milliwatts being
put into it, any signal will have dropped below the noise and cannot be
considered to be "transmitted"



Andy
www.g4jnt.com



On Sat, 11 Dec 2021 at 16:11,  wrote:

> Although not advisable a search of the Internet will turn up several.
> There is a well know Raspberry PI version. The range of the transmitters
> is only a couple of feet so if placed next to your clock it will work.
> Anything that would cover your entire house would certainly not be
> advised.
>
> There is also a smart phone app that does the same thing. It uses the
> phone speaker somehow to generate a harmonic (probably 3rd of 20 kHz).
> The watch or clock has to be placed next to the phone speaker for it to
> work.
>
> Ray, AB7HE
>
>
> On 2021-12-11 06:43, Attila Kinali wrote:
> > On Fri, 10 Dec 2021 15:54:55 -0500
> > "Lawrence Brandt"  wrote:
> >
> >> Has anyone designed and/or sold a "WWVB repeater" device? I can
> >> picture a
> >> Raspberry Pi which had software to get NTP data or GPS-referenced
> >> time, and
> >> a small 60 kHz transmitter, which would send the proper WWVB timecode
> >> data
> >> to the several "atomic clocks" I have around the house.
> >
> > Today, with all the non-licensed wireless stuff we have as
> > gadgets, it doesn't seem to be as obvious as it once was, but:
> > Transmitting on a frequency you don't have the explicit license
> > for is forbidden. And there are some quite hefty fines for that.
> > Especially transmitting on a widely used frequency of an
> > infrastructure service like WWVB might not be looked kindly upon.
> >
> > If you want to lock WWVB clocks that are placed somewhere, where
> > the reception is not good enough. Then you should inject the signal
> > directly into the clock. This way you avoid transmitting.
> >
> > Alternatively, replace the electronics with some 802.15.4 system
> > (e.g., 6LowPan) and distribute time in this network. There are
> > plenty of developer boards available for this kind of stuff,
> > just check adafruit and sparkfun.
> >
> >   Attila Kinali
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Lowest noise (phase noise and ADEV) method to achieve 10 MHz signal from 5 MHz input

[Andy Talbot]

Your push-pull doubler is much nicer than my full-wave rectifier with
Schottky diodes
http://g4jnt.com/10MHzDist.pdf

Andy
www.g4jnt.com



On Mon, 29 Nov 2021 at 15:42, Wilko Bulte  wrote:

> For those interested, Dave PA5DOF and your's truly are working to get the
> doubler implemented that Luciano has on his website. The first PCB
> prototype is in and has been built and works OK. Some minor tweaks/fixes
> will be added to a V0.2 PCB. If there is interest I can share the Gerber
> files.
>
> The doubler is intended to be hooked up to an Efratom MRK-HLN 5MHz Rb. Our
> shack T equipment for the best part requires a 10MHz reference.
>
> Wilko
>
> > On 29 Nov 2021, at 10:35, tim...@timeok.it wrote:
> >
> > 
> >   you can use this:
> >
> >
> http://www.timeok.it/wp-content/uploads/2015/08/high-performance-frequency-doublerv1-31.pdf
> >
> >   Luciano P. S. Paramithiotti
> >   tim...@timeok.it
> >   www.timeok.it
> >
> >   Da "Matt Huszagh" huszaghm...@gmail.com
> >   A time-nuts@lists.febo.com
> >   Cc
> >   Data Sun, 28 Nov 2021 19:29:58 -0800
> >   Oggetto [time-nuts] Lowest noise (phase noise and ADEV) method to
> achieve 10 MHz signal from 5 MHz input
> >   Hi,
> >
> >   I've got a 10 MHz distribution amplifier and am considering purchasing
> a
> >   5 MHz reference. Most (not all) of my equipment accepts a 5 MHz
> >   reference, but I'd like to be able to use the existing distribution
> >   amplifier I have if possible. Therefore, I'm considering ways I might
> >   generate a low-noise 10 MHz signal from the 5 MHz reference.
> >
> >   An obvious way is to use a doubler. However, as I understand it, even
> an
> >   ideal doubler will add 20log(2)=6 dB of phase noise to the 10 MHz
> >   signal. It seems like a possibly more expensive, but lower noise way
> >   would be to use a PLL with a divider that locks the divided 10 MHz
> >   signal to the 5 MHz input. If the time constant of the loop filter is
> >   set long enough, does this avoid the phase noise multiplication issue?
> >   From what I've gathered, this is a technique HP used in some of their
> >   gear. For example, the 8566 and 8340/1 lock a 100 MHz VCXO to an
> >   external reference with a PLL.
> >
> >   Any other thoughts on this?
> >   Matt
> >   ___
> >   time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> >   To unsubscribe, go to and follow the instructions there.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Andy Talbot]

I forgot the URL
http://g4jnt.com/10MHzDist.pdf

Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 18:39, Andy Talbot  wrote:

> The way I look at short term stability is to multiply up to microwave
> frequencies then mix the two and look at the resulting beat note.   The
> popular ADF4351 Fract-N synthesizer is ideal for this.  Take two of them,
> and programme for two frequencies in the GHz region a 1kHz or so apart when
> driven by the two 10MHz freqs that are being comparedApply the two
> multiplied signals to a mixer, and look at the resulting IF product with a
> PC soundcard input.   Using spectral analysis software with a waterfall
> display, such as Spectran or Spectrum Lab you can look at the multiplied
> frequency instability in real time.
>
> An example of the techniques used on a range of 10MHz reference sources
> can be found here (I used a different Fract-N synth with a smaller setting
> grid possible than the ADF4351 can give, but the same idea applies)
>
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 28 Nov 2021 at 18:19, Erik Kaashoek  wrote:
>
>> As the collection of frequency sources and counters in my home lab is
>> growing I'd like to understand the performance of the frequency sources.
>> Two different GPSDO do help to check long term stability.
>> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly
>> unknown and seemingly not of good reputation, more specifically its
>> (very) short term stability is doubted.
>> So how best to check very short term  (below 1s) frequency stability.
>> The frequency counters available loose resolution quickly when the gate
>> time is reduced below 1 second and high performance phase noise
>> measurement equipment is not available so google helped with a search
>> for alternative measurement methods.
>> What I found was a method using two frequency sources, one of the two
>> being  a VCO, a mixer and some filters and amplifiers.
>> By weak locking (large time constant)  the VCO source using the mixer as
>> phase detector to the other source, the output of the mixer's IF port
>> should carry a voltage real time proportionally to the phase difference
>> and by filtering and amplifying it should be possible to check for
>> variations in the 1ms-1s range.
>> Maybe even a scope can see the variations.
>> When you know the amplification and the full range voltage you can even
>> do an absolute measurement.
>> Would this method work?
>> Any specific concerns to take note of when doing the measurement?
>> Removing the DC component (or locking the VCO such that there is no DC
>> component) will be crucial I guess but given the slow speed of the loop
>> even an ADC->computer->DAC->VCO setup can work.
>> Any suggestion is welcome.
>> Erik.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Andy Talbot]

The way I look at short term stability is to multiply up to microwave
frequencies then mix the two and look at the resulting beat note.   The
popular ADF4351 Fract-N synthesizer is ideal for this.  Take two of them,
and programme for two frequencies in the GHz region a 1kHz or so apart when
driven by the two 10MHz freqs that are being comparedApply the two
multiplied signals to a mixer, and look at the resulting IF product with a
PC soundcard input.   Using spectral analysis software with a waterfall
display, such as Spectran or Spectrum Lab you can look at the multiplied
frequency instability in real time.

An example of the techniques used on a range of 10MHz reference sources can
be found here (I used a different Fract-N synth with a smaller setting grid
possible than teh ADF4351 can give, but the same idea applies)


Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 18:19, Erik Kaashoek  wrote:

> As the collection of frequency sources and counters in my home lab is
> growing I'd like to understand the performance of the frequency sources.
> Two different GPSDO do help to check long term stability.
> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly
> unknown and seemingly not of good reputation, more specifically its
> (very) short term stability is doubted.
> So how best to check very short term  (below 1s) frequency stability.
> The frequency counters available loose resolution quickly when the gate
> time is reduced below 1 second and high performance phase noise
> measurement equipment is not available so google helped with a search
> for alternative measurement methods.
> What I found was a method using two frequency sources, one of the two
> being  a VCO, a mixer and some filters and amplifiers.
> By weak locking (large time constant)  the VCO source using the mixer as
> phase detector to the other source, the output of the mixer's IF port
> should carry a voltage real time proportionally to the phase difference
> and by filtering and amplifying it should be possible to check for
> variations in the 1ms-1s range.
> Maybe even a scope can see the variations.
> When you know the amplification and the full range voltage you can even
> do an absolute measurement.
> Would this method work?
> Any specific concerns to take note of when doing the measurement?
> Removing the DC component (or locking the VCO such that there is no DC
> component) will be crucial I guess but given the slow speed of the loop
> even an ADC->computer->DAC->VCO setup can work.
> Any suggestion is welcome.
> Erik.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Andy Talbot]

 >>
> >> For more information see the Project G.R.E.A.T. 2005 page:
> >>
> >> http://leapsecond.com/great2005/
> >>
> >> Better yet, these two recent talks from 2018 and 2020 cover all 3
> >> GREAT
> >> experiments:
> >>
> >> <http://web.stanford.edu/group/scpnt/pnt/PNT18/presentation_files/I08
> >> -VanBaak-GPS_Flying_Clocks_and_Relativity.pdf>
> >>
> >> <http://leapsecond.com/ptti2020/2020-PTTI-tvb-Atomic-Timekeeping-Hobb
> >> y.pdf>
> >>
> >> Lots of time nutty photos in both of those!
> >>
> >> /tvb
> >>
> >>
> >> On 11/27/2021 7:33 AM, Andy Talbot wrote:
> >>> Just been reading your adventures with 3 Cs clocks, a mountain and 3
> >>> kids, but I can't make the estimate of time dilation work out.
> >>> You measured ~ 23ns and say it agrees with calculation
> >>>
> >>> The equation quoted in a related reference, for "low elevations" is
> >>> g.h/c² which if you plug in g = 9.81 m/s²  and h = 4300m for Mt
> >>> Rainer gives an expected value of 4.7 * 10^-16.
> >>> Over 2 days, 2 * 86400s, that would be 81 ns in total, four times
> >>> your value
> >>>
> >>> What am I missing?
> >>>
> >>> Was just speculating what Ben Nevis at a mere 1340m height might
> >>> offer
> >>>
> >>> Andy
> >>> www.g4jnt.com
> >>> ___
> >>> time-nuts mailing list --time-nuts@lists.febo.com  -- To unsubscribe
> >>> send an email totime-nuts-le...@lists.febo.com To unsubscribe, go to
> >>> and follow the instructions there.
> >> ___
> >> time-nuts mailing list --time-nuts@lists.febo.com  -- To unsubscribe
> >> send an email totime-nuts-le...@lists.febo.com To unsubscribe, go to
> >> and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list --time-nuts@lists.febo.com  -- To unsubscribe
> > send an email totime-nuts-le...@lists.febo.com To unsubscribe, go to
> and follow the instructions there.
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and
> follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Andy Talbot]

No, there's no route to the top of Ben Nevis other than a clamber on a
rocky path - I did it once in years gone by.  You'd have to be young and
Special Forces trained or similar to get a 5071 with power up there!

You may be thinking of Mt Snowdon in Wales, that has a rail route to the
top.

Tom, ah I see, so your delta H is much smaller than I'd assumed.
Coincidently the same as the height of Ben Nevis ASL - for which I
calculated ~20ns

Andy
www.g4jnt.com



On Sat, 27 Nov 2021 at 20:04, Hal Murray  wrote:

>
> j...@luxfamily.com said:
> >> Was just speculating what Ben Nevis at a mere 1340m height might offer
>
> > Considering the parking lot is around 200m, carrying the clocks and
> power to
> > the top might be moving from a moderate walk to the strenuous  category.
> One
> > might also want to do this in summertime, so you've got a  few months to
> plan
> > the expedition.
>
> > I wonder what the highest road in the UK is?
>
> There is a tourist train to the top of Ben Nevis.
>
>
> --
> These are my opinions.  I hate spam.
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Leap indicator set to 1 !

[Andy Talbot]

A leap second is due 31 December.   I'm sure I've seen reference to a "leap
second pending" flag in some reference to time keeping somewhere.

Andy
www.g4jnt.com



On Sat, 27 Nov 2021 at 15:23, Steven Sommars 
wrote:

> FYI.
>
> At 2021-11-27 00:00:00 UTC many public NTP servers began setting the leap
> indicator to 1.
> This may be gpsd related
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: QM10 Quartz chronometer

[Andy Talbot]

Some years ago, before we had locked LOs for transverters, the Am.
Microwave community used clip-on crystal heaters.  These were a PTC
thermistor with a turnover around 35 - 40C.   They were usually used on
5th or 7th overtone crystals around 100MHz  designed for 20C operation, so
weren't ideal, but could maintain a crystal more on frequency that just
open to the the air temp.
Perhaps used on a watch crystal thay would work more effectively.

Not sure where you'd get them from now, though.

Andy
www.g4jnt.com



On Fri, 26 Nov 2021 at 16:46, David G. McGaw 
wrote:

> But not in a chronometer.  They usually use something in the MHz range.
>
> 32kHz crystals are not very stable over temperature.  Watches rely on
> you wearing it for much of the day, keeping it at a nearly constant
> temperature and putting it on your bed stand at night, also presumably
> fairly constant.  Unfortunately they have been adopted for computer Real
> Time Clocks, which is why most computers do not keep very good time.
>
> David N1HAC
>
> On 11/26/21 9:14 AM, Scott McGrath wrote:
> > Usually in analog quartz clocks oscillator frequency is around 32khz
> >
> > Content by Scott
> > Typos by Siri
> >
> > On Nov 26, 2021, at 9:09 AM, Peter Torry via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > Hello list,
> >
> > I am restoring a Seiko Quartz QM10 Marine Chronometer that is currently
> inoperative. Preliminary investigations would indicate that the oscillator
> (TO5 header) isn't functioning therefore I am seeking any information as to
> its nominal frequency and whether it is just a crystal or an oscillator. I
> can follow the cmos dividers OK but a schematic diagram would be most
> useful.
> >
> > Any help or pointers much appreciated.
> >
> > Kind regards
> >
> > Peter   UK
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: function generator

[Andy Talbot]

But you don't need a DDS route to get 1 PPS from any frequency that is an
exact multiple of 1Hz.
I clock a PIC with 10MHz from a master reference.  An interrupt is
generated at an exact submultiple of this, and additional code outputs a
pulse every 25 clocks (clock freq = Fosc / 4)

Or from 10MHz, four 74AC390 CMOS counters will do it

Or am I missing some fundamental issue here?

Andy
www.g4jnt.com



On Mon, 22 Nov 2021 at 18:20, Gerhard Hoffmann 
wrote:

>
>
> Am 22.11.21 um 18:31 schrieb Erik Kaashoek:
> > Some time ago I needed a output at 10,00.001Hz so I tried to do that
> > with a SI5351.
> > Using pure integer math (as the PLL and divider register are integers) i
> > search for a combination of 3 divider/multipliers that gave the least
> > error.
> > If the reference frequency is not integer related to the internal PLL
> > frequency and  multiplier/divider registers you always will have limited
> > accuracy as there is a fractional error.
> > The amount of error will depend on the number of digits in the
> > multiplier/divider register lengths and the care you take to search for
> > the best solution.
> > If the DDS has a PLL driven clock this could be the cause.
>
> There once was a BCD DDS chip made by Standard Telecom.
> Doing that in an FPGA would be an easy exercise.
>
> Cheers, Gerhard
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: function generator

[Andy Talbot]

The frequency setting error is the clock frequency divided by the
accumulator length, at least in a DDS
If it has a 32 bit NCO clocked at 200Mhz, the setting error will be
200MHz/2^32 = 0.046Hz.
Max possible error will be 2^-32 of te hclock.

Not sure how that AWG would be set up, but if you can choose your buffer
length, then make sure you get one that allows an exact integer division
from your clock.   If you can't choose a buffer length and are forced to
take a fixed value, then frequency generation errors are inevitable.



Andy
www.g4jnt.com



On Mon, 22 Nov 2021 at 17:14, Jeremy Elson  wrote:

> Andy,
>
> I was thinking in the same direction - the device can create arbitrary
> waveforms so they're almost certainly using DDS. So I assumed it was some
> sort of round-off error. I just can't quite convince myself of this because
> it seems like round-off errors would be bigger, i.e. an error of one part
> in 1E11 suggests a buffer of length 1E11 which seems unlikely.
>
> On Mon, Nov 22, 2021 at 9:06 AM Andy Talbot  wrote:
>
>> Could the Rigol be using a DDS / NCO lookup approach to its frequency
>> generation?  In which case you'll be subject to rounding errors on the DDS
>> increment, whose maximum magnitude will be  dependent on the register
>> length.
>>
>> Andy
>> www.g4jnt.com
>>
>>
>>
>> On Mon, 22 Nov 2021 at 16:53, Jeremy Elson  wrote:
>>
>> > I did not see any such setting in the Rigol, but I'll check again. in
>> April
>> > I did write to Rigol to report the problem and had the following
>> (abridged)
>> > conversation with support:
>> >
>> > Me:
>> >
>> > "I recently tried to use your DG1022Z signal generator to generate one
>> > pulse-per-second (pulse mode, frequency 1.00hz, width 10
>> microseconds).
>> > However, it appears there is a small frequency error of one part in
>> 1e11,
>> > i.e. the pulse per second gets later by about 6 nanoseconds every 1,000
>> > seconds." [More technical description abridged, including a link to a
>> > graph.]
>> >
>> > Rigol:
>> >
>> > "Please find the following datasheet for DG1000Z, the accuracy is
>> +/-1ppm.
>> > If your pulse is 1second with 10us width, 6ns per 1000s is in the
>> accuracy
>> > range."  [They attached an image of a page from the DG1000Z datasheet,
>> > showing a line that said "Accuracy: +/- 1ppm of the setting value"]
>> >
>> > Me:
>> >
>> > "Is this the specification even when the unit is provided with an
>> accurate
>> > external clock?"
>> >
>> > Rigol:
>> >
>> > "I would say Yes. The internal processing circuit will effect the clock
>> > signal,  harmonics and phase noise will result the frequency variance."
>> >
>> > -Jeremy
>> >
>> > On Sun, Nov 21, 2021 at 11:54 PM Poul-Henning Kamp 
>> > wrote:
>> >
>> > > 
>> > > Jeremy Elson writes:
>> > >
>> > > > [...] I plugged an RbXO into the DG1022Z and simply asked the
>> > > > DG1022Z to divide it down to a 1pps signal. That is, I configured
>> it to
>> > > > create a pulse with a small duty cycle and 1hz frequency using the
>> > > external
>> > > > clock as a reference. To my surprise, it introduces a small but
>> > > > measurable error of one part in 1E11 in the dividing-down. You can
>> read
>> > > the
>> > > > full story of this in my post from earlier this year:
>> > >
>> > > When you feed such instruments an external clock, you often have to
>> > change
>> > > one or more calibration constants for the internal (OC)XO's offset to
>> > zero.
>> > >
>> > > Another problem is that if you use the square wave output of a DDS
>> based
>> > > generator, they often produce the square from the sine output of
>> > > the DDS chip with a schmitt-trigger, which causes lousy jitter.
>> > >
>> > > --
>> > > 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.
>> > >
>> > ___
>> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send
>> > an email to time-nuts-le...@lists.febo.com
>> > To unsubscribe, go to and follow the instructions there.
>> >
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: function generator

[Andy Talbot]

Could the Rigol be using a DDS / NCO lookup approach to its frequency
generation?  In which case you'll be subject to rounding errors on the DDS
increment, whose maximum magnitude will be  dependent on the register
length.

Andy
www.g4jnt.com



On Mon, 22 Nov 2021 at 16:53, Jeremy Elson  wrote:

> I did not see any such setting in the Rigol, but I'll check again. in April
> I did write to Rigol to report the problem and had the following (abridged)
> conversation with support:
>
> Me:
>
> "I recently tried to use your DG1022Z signal generator to generate one
> pulse-per-second (pulse mode, frequency 1.00hz, width 10 microseconds).
> However, it appears there is a small frequency error of one part in 1e11,
> i.e. the pulse per second gets later by about 6 nanoseconds every 1,000
> seconds." [More technical description abridged, including a link to a
> graph.]
>
> Rigol:
>
> "Please find the following datasheet for DG1000Z, the accuracy is +/-1ppm.
> If your pulse is 1second with 10us width, 6ns per 1000s is in the accuracy
> range."  [They attached an image of a page from the DG1000Z datasheet,
> showing a line that said "Accuracy: +/- 1ppm of the setting value"]
>
> Me:
>
> "Is this the specification even when the unit is provided with an accurate
> external clock?"
>
> Rigol:
>
> "I would say Yes. The internal processing circuit will effect the clock
> signal,  harmonics and phase noise will result the frequency variance."
>
> -Jeremy
>
> On Sun, Nov 21, 2021 at 11:54 PM Poul-Henning Kamp 
> wrote:
>
> > 
> > Jeremy Elson writes:
> >
> > > [...] I plugged an RbXO into the DG1022Z and simply asked the
> > > DG1022Z to divide it down to a 1pps signal. That is, I configured it to
> > > create a pulse with a small duty cycle and 1hz frequency using the
> > external
> > > clock as a reference. To my surprise, it introduces a small but
> > > measurable error of one part in 1E11 in the dividing-down. You can read
> > the
> > > full story of this in my post from earlier this year:
> >
> > When you feed such instruments an external clock, you often have to
> change
> > one or more calibration constants for the internal (OC)XO's offset to
> zero.
> >
> > Another problem is that if you use the square wave output of a DDS based
> > generator, they often produce the square from the sine output of
> > the DDS chip with a schmitt-trigger, which causes lousy jitter.
> >
> > --
> > 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.
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: NTP servers

[Andy Talbot]

GPS with any serial port can be used (along with PPS) for accurate time.
You write a routine for a microcontroller that maintains time  keeping and
clock it from the 1 PPS signal.  That gives you correct display of accurate
time.   You read the NMEA from the GPS and use it to set your registers on
a regular basis.  I usually do every minute, at second number 58.  The NMEA
read can be done in time so the next PPS increments to the correct
setting.   NMEA string is always less than one second long

The only time this falls over is for leap seconds when they don't show on
the display for up to one minute after they happened.

Andy
www.g4jnt.com



On Mon, 22 Nov 2021 at 10:42, Hal Murray  wrote:

> time.isan...@gmail.com said:
> > but I am curious to see if I could sync up with some of you guys who
> seem to
> > have some pretty cool set-ups.
>
> GPS has taken over the time-distribution business.
>
> If you want to use GPS, there are 2 ways to go.
>
> You can get a simple GPS receiver and plug that into your PC.  For decent
> time, you need a PPS signal and a real serial port, not USB.
>
> The other approach is to get a GPSDO -- GPS Disciplined Oscillator.
> That's a
> box with a GPS receiver and a good crystal and some software.  It smoothes
> out
> the rough edges in the timing from the GPS signal and/or keeps going
> (holdover) when the GPS signal fades or dies.
>
> GPS is very very good in the long term but noisy in the short term.  Short
> means seconds to minutes.  Long means days/months.  A GPSDO will get rid
> of
> most of the short term noise.
>
> There are/were several models available at relatively low cost after they
> were recycled from cell phone towers.  HP Z3801A and Trimble Thunderbolt
> are popular.  "GPSDO" will get lots of hits on eBay.  I don't know how good
> the recent ones are.
>
> Just reading the info available can be fun if you like that stuff.
>   http://www.realhamradio.com/GPS_Frequency_Standard.htm
> The Z3801A manual is a good read.
>   http://www.leapsecond.com/museum/z3801a/097-z3801-01-iss-1.pdf
> Time sink warning!
>
> GPS works much better if you have a good antenna location.  Modern GPS
> receivers are sensitive enough that they sometimes/often work indoors,
> maybe better on a window sill, maybe even better if the window faces
> south.  Just because it's working now doesn't mean it won't glitch often
> enough to cause problems.  Mumble.  Try it and see what happens.
>
> -
>
> There is actually a 3rd way: buy a box that does it all.  But that's not
> much
> fun, at least for most of the people on this list.
>
> --
>
> > there are plenty of good stratum 1 NTP servers open to the public (e.g.
> > NIST's servers),
>
> If you have a good local NTP setup, you can measure how good other servers
> are, or more likely how good the network connection is.  NTP assumes the
> network delays are symmetric.  Often, that's not true.  So "how good" turns
> into measuring network (a)symmetries.
>
>
> --
> These are my opinions.  I hate spam.
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] 5/10MHz Doubler and Distribution

[Andy Talbot]

Several people have asked for the Gerbers for my  5/10MHz doubler and
distribution amp, that I've now made them available for direct download

Get the latest version of http://g4jnt.com/10MHzDist.pdf just updated
(refresh your browser if it's already in cache) and the link for the
download is given.


Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: 1 pps

[Andy Talbot]

You seem to have gone to extraordinary lengths to trap out each unwanted
product, yet  the final spectrum shows only -50dBc products.   That seems a
poor return for that effort in filter design.

I made a 5MHz doubler plus distribution for my HP5061. You can see the
design at http://g4jnt.com/10MHzDist.pdf  The doubler is a full wave
rectifier and the filter a three section top capacitor coupled LC
resonator.I achieved better than -80dBc rejection of the 5MHz
fundamental and something like  -75dB at 15MHz but this far down,
measurement is quite a challenge.

For most practical purposes these levels are more than adequate, but I do
sometimes directly multiply up to 10GHz or higher, using this 10MHz source
as the reference input to a PLL synthesizer.   I think I've seen evidence
that even -80dBc at 5MHz can introduce spurii at this level of
multiplication, so really ought to be aiming at -100dBc - but that woul dbe
impossible to measure with any test equipment I have.   Even seeing -80dBc
was a challenge.

Andy
www.g4jnt.com



On Thu, 11 Nov 2021 at 00:53, Gerhard Hoffmann 
wrote:

>
>
> Am 10.11.21 um 23:56 schrieb B Riches via time-nuts:
> > Any ideas on how to get a useable 1 pps output sig out of a Lucent
> KS-24361 to use with SL sampling rate detector.
> > I am using the 1 pps output from a Jackson unit but would like to use
> the Lucent if I can since that is my gps standard.
> > 73
> > Bill, WA2DVUCape May, NJ
>
> There are some pics with red arrows herein:
>
> <   http://www.hoffmann-hochfrequenz.de/downloads/DoubDist.pdf  >
>
> The board I made was home-etched, so there are no left-overs,
> but you or whoever can get the Altium or Gerber files.
> Should be less than 20 bucks for 10 boards from JLCPCB,
> including postage.
>
> Cheers, Gerhard
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Ryzen mobos with serial port for Garmin GPS?

[Andy Talbot]

Well, yes.   No one would rely on a windows PC for timing accuracy, surely
This is what I did to get a fully coherent timing and frequency locked
system for a narrowband LF receiver using an FTDI interface to a PC.
http://g4jnt.com/Coherent_LF_Receiver.pdf

Andy
www.g4jnt.com



On Fri, 5 Nov 2021 at 18:44, Bill Dailey  wrote:

> There is significant jitter using USB for timing.  Has been done poorly
> for a long time.  Well known.
>
> Bill Dailey
>
> Negativity always wins the short game. But positivity wins the long game.
> - Gary Vaynerchuk
>
> Don’t be easy to understand,
> Be impossible to misunderstand
> - Steve Sims
>
> > On Nov 5, 2021, at 1:33 PM, Andy Talbot  wrote:
> >
> > Use FTDI USB serial ports - you can't go wrong with them.
> > https://ftdichip.com/
> >
> > I have, at the last count, used something like 200 of their FT232 device
> in
> > one form or another on the shack PC.   I know that, because device
> manager
> > has registered up to COM200.  Every time a new one is plugged in, a new
> COM
> > port is set up.
> >
> > Andy
> > www.g4jnt.com
> >
> >
> >
> >> On Fri, 5 Nov 2021 at 18:26, Alec Teal 
> wrote:
> >>
> >> A friend of mine who lives and breaths this stuff (I wont tell you what
> >> he does - but suffice to say he's authoritative) basically said to me on
> >> something about serial ports that you can't go wrong with USB stuff,
> >> even on Linux.
> >>
> >> Would that work?
> >>
> >> Serial ports certainly are getting scarce! You'd get 2 to a board an
> >> embarrassingly long time ago!
> >>
> >>> On 05/11/2021 06:10, Darren Freeman wrote:
> >>> On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
> >>>> However, mobos with a serial port are becoming harder to find.
> >>> That's not really been my experience, they just moved it to a header.
> >>> You will need to supply a DE9 to ribbon cable, say on a bracket, or
> >>> installed in a cutout elsewhere in the case.
> >>>
> >>> This is the first one that I checked, and it has such a port labelled
> >>> COMA, along the left/bottom edge.
> >>> https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
> >>>
> >>> Also note that the Linux PPS driver supports the standard PC parallel
> >>> port, which you can usually find as a header. If you are having
> >>> performance issues with one, try the other. (But you may need to supply
> >>> negative-going edges to the parallel port.)
> >>>
> >>>
> >>> Have fun,
> >>> Darren
> >>> ___
> >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> >> send an email to time-nuts-le...@lists.febo.com
> >>> To unsubscribe, go to and follow the instructions there.
> >>>
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send
> >> an email to time-nuts-le...@lists.febo.com
> >> To unsubscribe, go to and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Ryzen mobos with serial port for Garmin GPS?

[Andy Talbot]

A bit more :
I think the serial interface, via an FTDI chip device, makes for one of te
most versatile interfaces you could go for.  Serial ports are supported in
every programming language so are generally easy to set up in software
without having to install DLLs.
The FTDI devices will run at up to 300 Baud, whereas the original
'real' RS232 was only ever 115200 baud max.
I have even used mine for 10 bit digitised audio at sampling-card rates
sent on  RS422 twisted pair .  It was simpler to programme than using a
soundcard would have been.

One FTDI device allows 8 bit parallel access that 'looks' to the PC like a
serial port.  Never tried this myself, but a number of manufacturers have
implemented PC interfaces using this route.

Andy
www.g4jnt.com



On Fri, 5 Nov 2021 at 18:32, Andy Talbot  wrote:

> Use FTDI USB serial ports - you can't go wrong with them.
> https://ftdichip.com/
>
> I have, at the last count, used something like 200 of their FT232 device
> in one form or another on the shack PC.   I know that, because device
> manager has registered up to COM200.  Every time a new one is plugged in, a
> new COM port is set up.
>
> Andy
> www.g4jnt.com
>
>
>
> On Fri, 5 Nov 2021 at 18:26, Alec Teal 
> wrote:
>
>> A friend of mine who lives and breaths this stuff (I wont tell you what
>> he does - but suffice to say he's authoritative) basically said to me on
>> something about serial ports that you can't go wrong with USB stuff,
>> even on Linux.
>>
>> Would that work?
>>
>> Serial ports certainly are getting scarce! You'd get 2 to a board an
>> embarrassingly long time ago!
>>
>> On 05/11/2021 06:10, Darren Freeman wrote:
>> > On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
>> >> However, mobos with a serial port are becoming harder to find.
>> > That's not really been my experience, they just moved it to a header.
>> > You will need to supply a DE9 to ribbon cable, say on a bracket, or
>> > installed in a cutout elsewhere in the case.
>> >
>> > This is the first one that I checked, and it has such a port labelled
>> > COMA, along the left/bottom edge.
>> > https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
>> >
>> > Also note that the Linux PPS driver supports the standard PC parallel
>> > port, which you can usually find as a header. If you are having
>> > performance issues with one, try the other. (But you may need to supply
>> > negative-going edges to the parallel port.)
>> >
>> >
>> > Have fun,
>> > Darren
>> > ___
>> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> > To unsubscribe, go to and follow the instructions there.
>> >
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Ryzen mobos with serial port for Garmin GPS?

[Andy Talbot]

Use FTDI USB serial ports - you can't go wrong with them.
https://ftdichip.com/

I have, at the last count, used something like 200 of their FT232 device in
one form or another on the shack PC.   I know that, because device manager
has registered up to COM200.  Every time a new one is plugged in, a new COM
port is set up.

Andy
www.g4jnt.com



On Fri, 5 Nov 2021 at 18:26, Alec Teal  wrote:

> A friend of mine who lives and breaths this stuff (I wont tell you what
> he does - but suffice to say he's authoritative) basically said to me on
> something about serial ports that you can't go wrong with USB stuff,
> even on Linux.
>
> Would that work?
>
> Serial ports certainly are getting scarce! You'd get 2 to a board an
> embarrassingly long time ago!
>
> On 05/11/2021 06:10, Darren Freeman wrote:
> > On Thu, 2021-11-04 at 22:36 -0700, Rich Wales wrote:
> >> However, mobos with a serial port are becoming harder to find.
> > That's not really been my experience, they just moved it to a header.
> > You will need to supply a DE9 to ribbon cable, say on a bracket, or
> > installed in a cutout elsewhere in the case.
> >
> > This is the first one that I checked, and it has such a port labelled
> > COMA, along the left/bottom edge.
> > https://www.gigabyte.com/Motherboard/B450-AORUS-M-rev-1x/sp#sp
> >
> > Also note that the Linux PPS driver supports the standard PC parallel
> > port, which you can usually find as a header. If you are having
> > performance issues with one, try the other. (But you may need to supply
> > negative-going edges to the parallel port.)
> >
> >
> > Have fun,
> > Darren
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: constructing a moon base

[Andy Talbot]

When things get that big they could put a series of location satellites
around the Moon, so it has its own ... err... not GPS, but MPS perhaps?

Andy
www.g4jnt.com



On Wed, 29 Sept 2021 at 15:31, Chris Howard  wrote:

> My employment involves the design and manufacturing of construction
> equipment.
>
> I had a conversation today about what will be needed for
> time/positioning when GPS is not in sight, like road-building on the far
> side of the moon.
> The context was timestamp coordination between multiple data sources in
> the vehicle environment, ntpd, and similar things.
>
> No GPS probably means cesium on the road grader?
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: ammonia, cesium, masers, etc.

[Andy Talbot]

It ought to be possible to find the resonance with off the shelf equipment
An ADF5355 synthesizer is capable of small frequency steps and will
generate up to 13.6GHz.  Use it's 2nd harmonic leakage (4th harm of the
VCO), there is a bit coming out at 24GHz.   If the synth  reference input
is derived from a 48 bit DDS like an AD9852, it can be tuned in really
small frequency steps, far below the 1Hz steps that ought to be enough to
spot the absorbtion.   Isn't Caesium about 1Hz wide ?

For detection, an amateur 24GHx converter is close enough to use.
Copper water pipe that has been hammered into an oval can support TE01
modes reliably enough if you need to suppress polarisation rotation.

Andy
www.g4jnt.com



On Mon, 20 Sept 2021 at 18:14, Andy Talbot  wrote:

> What's the exact resonance frequency of ammonia?   To as many sig figures
> as it's been calculated.
> Googling just seems to throw up "approximately 23.8GHz"
>
> Andy
> www.g4jnt.com
>
>
>
> On Mon, 20 Sept 2021 at 18:10, paul swed  wrote:
>
>> Well at the very next MIT flea I will grab some 23 GHz waveguide. Maybe
>> Nearfest in October. Another trick I have actually used on 10 GHz id 3/4"
>> copper tube as waveguide. Its quite low loss but circularly polarized. So
>> to use it I needed to rotate the coupling in the shack for best return
>> loss. So perhaps 1/2" or 1/4" would be the same. At least in the earliest
>> Amonia system they simply seemed to have filled the waveguide with amonia.
>> Then launched 23 GHz down the length of it. Good thing about amonia if you
>> have a wave guide leak you would know it.
>> Indeed there is a ton of modern 23 GHz technology available. I was going
>> to
>> make some comments on system oscillators and deleted them. I haven't
>> looked
>> at what types of oscillators or multipliers are out there at a cheap cost.
>> All this being said its a curious possibility. But if its no better then a
>> Cesium not worth any effort. Its one serious advantage is you could refill
>> the amonia. Not really sure what would get used up. I think as mentioned
>> here the amonia H would disassociate.
>> Regards
>> Paul
>>
>> On Mon, Sep 20, 2021 at 11:07 AM Lux, Jim  wrote:
>>
>> > On 9/20/21 7:17 AM, Poul-Henning Kamp wrote:
>> > > 
>> > > paul swed writes:
>> > >
>> > >> Though honestly bending 23 GHz waveguide might be tricky. Or simply
>> > leave it
>> > >> straight after all it Amatuer grade.
>> > > I seem to recall that there was about 10-ish meter coiled up in the
>> > > one on the famous old picture.  That might be a bit unwieldy.  On the
>> > > other hand, that was probably not waveguide as much as just plain
>> > > copper-tubing ?
>> >
>> > That would depend on whether you want to control moding. (the picture
>> > says rectangular) Bending WG is pretty easy if the radius is large
>> > compared to the size of the WG - it's very soft copper, so you just need
>> > an appropriate form around which to bend it. The trick of filling it
>> > with sand also helps.  At 23 GHz, you probably want to use WR34 or WR42
>> > (Hmm, probably the bigger, so you're farther from cutoff, 17 and 14 GHz
>> > respectively).
>> >
>> > >
>> > >> Lastly they discussed an Amonia maser. Never knew. Wonder if it
>> actually
>> > >> vented amonia slowly. Sort of sounds that way.
>> > > I would suspect the main problem with an amonia maser is that the
>> > > Amonia disassociates and the hydrogen leaks out though the metal ?
>> > >
>> > I wonder, though, if you were "building your own atomic clock" whether
>> > ammonia might not be easier than Cs or Rb, for instance. These days a 23
>> > GHz oscillator and other parts are fairly easy to come by, and ammonia
>> > is somewhat easier to handle than Cs or Rb. I would normally think you
>> > can get any of them by just ordering them, but since ammonia is used in
>> > synthesis of methamphetamine, it may not be so easy to get a small
>> > bottle of ammonia gas.
>> > ___
>> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send
>> > an email to time-nuts-le...@lists.febo.com
>> > To unsubscribe, go to and follow the instructions there.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: ammonia, cesium, masers, etc.

[Andy Talbot]

What's the exact resonance frequency of ammonia?   To as many sig figures
as it's been calculated.
Googling just seems to throw up "approximately 23.8GHz"

Andy
www.g4jnt.com



On Mon, 20 Sept 2021 at 18:10, paul swed  wrote:

> Well at the very next MIT flea I will grab some 23 GHz waveguide. Maybe
> Nearfest in October. Another trick I have actually used on 10 GHz id 3/4"
> copper tube as waveguide. Its quite low loss but circularly polarized. So
> to use it I needed to rotate the coupling in the shack for best return
> loss. So perhaps 1/2" or 1/4" would be the same. At least in the earliest
> Amonia system they simply seemed to have filled the waveguide with amonia.
> Then launched 23 GHz down the length of it. Good thing about amonia if you
> have a wave guide leak you would know it.
> Indeed there is a ton of modern 23 GHz technology available. I was going to
> make some comments on system oscillators and deleted them. I haven't looked
> at what types of oscillators or multipliers are out there at a cheap cost.
> All this being said its a curious possibility. But if its no better then a
> Cesium not worth any effort. Its one serious advantage is you could refill
> the amonia. Not really sure what would get used up. I think as mentioned
> here the amonia H would disassociate.
> Regards
> Paul
>
> On Mon, Sep 20, 2021 at 11:07 AM Lux, Jim  wrote:
>
> > On 9/20/21 7:17 AM, Poul-Henning Kamp wrote:
> > > 
> > > paul swed writes:
> > >
> > >> Though honestly bending 23 GHz waveguide might be tricky. Or simply
> > leave it
> > >> straight after all it Amatuer grade.
> > > I seem to recall that there was about 10-ish meter coiled up in the
> > > one on the famous old picture.  That might be a bit unwieldy.  On the
> > > other hand, that was probably not waveguide as much as just plain
> > > copper-tubing ?
> >
> > That would depend on whether you want to control moding. (the picture
> > says rectangular) Bending WG is pretty easy if the radius is large
> > compared to the size of the WG - it's very soft copper, so you just need
> > an appropriate form around which to bend it. The trick of filling it
> > with sand also helps.  At 23 GHz, you probably want to use WR34 or WR42
> > (Hmm, probably the bigger, so you're farther from cutoff, 17 and 14 GHz
> > respectively).
> >
> > >
> > >> Lastly they discussed an Amonia maser. Never knew. Wonder if it
> actually
> > >> vented amonia slowly. Sort of sounds that way.
> > > I would suspect the main problem with an amonia maser is that the
> > > Amonia disassociates and the hydrogen leaks out though the metal ?
> > >
> > I wonder, though, if you were "building your own atomic clock" whether
> > ammonia might not be easier than Cs or Rb, for instance. These days a 23
> > GHz oscillator and other parts are fairly easy to come by, and ammonia
> > is somewhat easier to handle than Cs or Rb. I would normally think you
> > can get any of them by just ordering them, but since ammonia is used in
> > synthesis of methamphetamine, it may not be so easy to get a small
> > bottle of ammonia gas.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send
> > an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Query about List and about 10 MHz Distro

[Andy Talbot]

Hence my observation that balanced twisted pair might be a better solution
than coax for 10MHz distribution
Removes all possibility of ground loops

Andy
www.g4jnt.com



On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:

> I believe that a significant problem in my case was not leakage through the 
> shield,
> but
> rather common-mode currents on the cable.  My experiences were with RG-6 style
> cable,
> namely a cable that mostly went around the outside of the house for TV
> distribution.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Query about List and about 10 MHz Distro

[Andy Talbot]

When I asked about this on another Group a while back, I was told the phase
noise made it an undesirable solution.

Although I never tried it, I would imaging balanced shielded twisted pair
would be a better way to go.   Immune from ground loop problems than can
beset coax distribution and a whole raft of ICs support the medium, from
RS422 to CAN bus drivers and receivers.


Andy
www.g4jnt.com



On Sat, 28 Aug 2021 at 17:51, AC0XU (Jim)  wrote:

> I am hoping that you can help me about a couple of things:
>
> 1) My time-nuts summaries sometimes appear unformatted and unreadable. All
> the text from all the postings is crammed together without spacing. How can
> I fix it?
>
> 2) I want to distribute 10 MHz references by fiber. There are
> RF-over-Fiber products available, but too expensive for me (thousands of
> $$$ per xmit/rcv set).  I am thinking that it should be possible to use
> fiber Ethernet components to do this. I don't mean IEEE 1588 but a much
> simpler, no-computer-required, solution. Possibly just converting sine wave
> (coax) to square wave (fiber) to sine wave (coax). I am looking for a low
> cost solution. Any thoughts or recommendations??
>
> Thanks!
>
> Jim
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Testing a GPS mag mount antenna

[Andy Talbot]

The first generation GPS were, IIRC, 50 Watts, +17dBW  EIRP.   The latest
one are higher power at up to 200W, or 23dBW EIRP
If you go through the link budget calculations, and assume a receiver with
a good noise figure, you can show that with a ground station antenna of
more than about 36dBi gain you can see the GPS signal above receiver
noise.That gain corresponds to a dish of about 4.5 metres diameter at
1575MHz.   Bigger than one most radio amateurs are likely to fit in their
back garden, although there are a few moonbouncers around the World with
dishes that big.Quite a few have 3m dishes.

Andy
www.g4jnt.com



On Fri, 20 Aug 2021 at 22:33, Gerhard Hoffmann 
wrote:

>
> Am 20.08.21 um 22:14 schrieb skipp isaham via time-nuts:
> >
> > Hello to the Group,
> >
> > I picked a box of used (removed from commercial radio APRS type
> > service) mobile/vehicle GPS Antennas. They are mostly the classic
> > square molded, black plastic magnetic mount type, about the size of a
> > bar of soap when cut to square (2/3 the size of a large bar of soap).
> > The coax length terminates to an SMA connector.
> >
> > I'd like to use some of these unmarked (obviously also unbranded)
> > antennas for a few projects. The initial goal is to first set up a
> > system to test (good/bad) the antennas, then determine their operation
> > voltage, I suspect them to be 3.x to 5.x Volts. They are probably not
> > "new enough" to be the type to operate of 3 or 5 Volts DC.
> >
> > For testing... I purchased a nice NOS Mini-Circuits bias-Tee.
> >
> > The intent is to now operate the antenna through the bias-tee, in to
> > an analyzer. I would initially start the bias supply off at 3 Vdc,
> > while also monitoring current.  If I don't receive an adequate/valid
> > GPS signal off air, I could increase the bias up to 5 Vdc (rinse/repeat).
> >
> > Should I be able to "see something" on or around the GPS frequency
> > other than what I suspect will be something visual looking like a
> > noise/pulse source/signal?
>
> You won't see anything interesting on the spectrum analyzer. The
> signal(s) look like noise, and they are buried in the real noise.
>
> Deeply!  In a real receiver, there are probably just 1 bit ADCs, aka
> comparators, and the receiver  needs to know the pseudo random
>
> polynomial that was used to blow up the bandwidth of the 50 baud message
> to some MHz in order to reverse that effect.
>
> And you have to know which part of the polynomial is currently used.
> This is done by search & correlation tries. Sloppy wording, I know.
>
> Only when that reversal is done you have a positive signal/noise ratio.
> GPS receivers are 95% math, the rest is electronics
>
> and packaging.
>
> You may see a noise molehill at the nominal frequencies, but that means
> only that the pre-amplifier and maybe some filtering works.
>
> And there is a hefty preamplifier to make up for 5 meters of El Cheapo
> RG-174  coax. The GPS pseudo-noise is only
>
> 1 promille of that what you see.
>
> Disclaimer: Last time I was involved in this was with the Plessey
> 1010/2010 chip set in a previous life, for GPS/Glonass combined,
>
> which was new then.
>
>
> Gerhard, DK4XP
>
>
>
>
>
> > I don't yet have a GPS receiver with a signal strength indicator, else
> > I could probably not have to send this post.  But, I do have access to
> > an analyzer, I bought the bias-tee (was reasonable in price) and I'd
> > like to test these 30 antennas to see if they work and determine if
> > 3.x volts is enough... or 5 volts is required.
> >
> > Thank you in advance for any replies and comments.
> >
> > cheers,
> >
> > skipp
> >
> > skipp025 at yahoo.com
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> > send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: HP5061 offline management.

[Andy Talbot]

I have a 5061A that has been sitting in my shack for over 25 years.   I
keep it in  standby, using just the OCXO as a casual reference, good for
less than 1 PPM.  I check the 1PPS output against GPS using a counter timer
and tweak the front panel pot a few times a year to keep it spot on.
When high accuracy is needed, perhaps a few times a year, Cs is activated
and it typically comes up to satisfactory accuracy is around an hour - I
usually leave it two hours.

Yes it consumes a few tens of watts, but I'm quite prepared to spend the
few pence per day that costs :-) to keep the tube fully pumped and ready to
go.

I replaced the NiCd battery pack which was completely dead when I got the
unit with a LM317 and float charged 24V lead acid batteries.

Andy
www.g4jnt.com



On Thu, 5 Aug 2021 at 23:26, paul swed  wrote:

> Was talking with another time-nut on the best way to use the HP5061 Cesium
> to protect the tube. I have read over the years that some people let the
> system run but with the CS oven off.
> This consumes 19.4 watts or about 14KWH/month.
> But has the advantage of a nice local reference and the tube is pumped
> down.
> I however leave my units completely off and run them every 2 months. The
> downside of this is that when the ion pump clears the tube when the CS oven
> is turned on there is a crud burst and the ion current reading can go
> significantly up. Then has to pump back down a number of times.
> There is a better way.
> Leave just the 3500V supply run. Disconnect it from the internal power add
> a resistor and cap powered by a external switching wallwort in the 1 watt
> range. Brand new meanwell  units are $11. These are medical grade not that
> its required. The resistor is about 470 ohms a 1/4 watt. Dropping 24V to
> 19V. Use a 470 uf cap on the side of the resistor connected to the 3500V
> supply. Ground the negative to the chassis so the I pump meter works.
> Taking this approach drops power consumption to .31 Watts. Larger higher
> current supplies will draw higher power wasting idle currents.
> I was going to drill out a hole and mount a small powerjax. But just really
> didn't so brought out a pigtail to a powerjax. No change to the chassis.
>
> Operating this way the 3500V supply is always running. When I want the CS
> to run I plug the original power cord in. After the ovens warm up in
> business. No waiting for the ion pump to do its job and the best benefit No
> crud burst as the tube is clean.
>
> The same adapter will easily power many 3500 V supplies. I have 3 5061s
> that will be modified. Good news each 5061 consumes about 10 ma.
>
> Lastly 5061s do make noise around 2 KHz somewhat annoying.
> Its easy enough to use a wall time and run just at night and switch the
> supply on when actually using the Cesium. But a timer just multiplied power
> consumption a lot.
> A greener HP 5061 Did I just say that. Sorry.
> Regards
> Paul
> WB8TSL
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Antenna return loss

[Andy Talbot]

Much talk about source return loss and splitters.
All active GPS antennas I've met have masses of gain at the top end, 40dB
or more.   Most of the small puck ones come with several metres of RG174
thin coax.

This is so lossy at 1.6GHz that that several metres may have perhaps 10 -
15dB loss.   So there's your good source impedance for the splitter 20 -
30dB RLoss without even considering the head amp itself.

Even several metres of UR43 should have enough loss to constitute a decent
match.

Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Subject: Re: Tbolt

[Andy Talbot]

I get a proper picture

Andy
www.g4jnt.com



On Fri, 23 Jul 2021 at 18:41, Dave B via time-nuts 
wrote:

> From: Gerhard Hoffmann 
>
> Subject: [time-nuts] Re: Tbolt
>
> > I can only offer an opened Morion MV-89A.
> > The 10 MHz version is really 5 MHz + doubler.
> > It stopped oscillating with Vtune > 0.6V, so it was a natural candidate
> > for forensic medicine.
> >
> > <
> >
> https://www.flickr.com/photos/137684711@N07/49585174873/in/album-72157662535945536/
>
> >  >
> >
> > and some pictures following the RIGHT arrow.
>
> 
>
> All I get, is a child and a panda, + a message to logout!
>
> Guess not a public page.
>
> Dave G8KBV.
>
>
>
>
> --
> Created on and sent from a Unix like PC running and using free and open
> source software:
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Thunderbolts ...

[Andy Talbot]

The LB uses a modern, third generation GPS module , Ublox 7 or 8 that has
the weak signal performance of its generation. Streets ahead of the old
Trimbles , Motorola and Garmins we used to love.
Here I use a passive patch antenna on mine in the shack and it stays
locked.


On Tue, 20 Jul 2021 at 20:34, David G. McGaw 
wrote:

> I have been using several versions of the UCCM units (Trimble,
> Symmetricom and Samsung) with mostly good results, both bare and
> packaged, as well as having several Thunderbolts.  The one thing that
> the Bodinar unit has which is nice is the synthesizer built in.  The
> Thunderbolts and UCCMs do not have this.  On the other hand, as has been
> said, the Bodinar unit has poor hold-over performance if you lose GPS
> lock, which here in NH amongst the trees and hills can happen fairly
> frequently.  As a result, I use OXCO GPSDOs with an external synthesizer.
>
> David N1HAC
>
> On 7/20/21 1:32 PM, N1BUG wrote:
> > Good question on the Leo Bodnar comparison. That's what I am using now
> > and I am sure it is good enough for my purposes but I really want
> > something I can use with LH and maybe the KO4BB Thunderbolt Monitor. I
> > also inquired about the Thunderbolts and hope there's enough supply
> > that I can grab one. I've been looking for a while but am hesitant on
> > eBay units.
> >
> > Paul N1BUG
> >
> >
> >
> > On 7/20/21 1:11 PM, Bob Darlington wrote:
> >> Same.  He probably got 250+ requests in short order.  I'm curious how
> >> the
> >> Leo Bodnar GPSDOs compare.   I'm considering one of these over a
> >> thunderbolt for field use for ham radio EME work.
> >>
> >> -Bob N3XKB
> >>
> >> On Tue, Jul 20, 2021 at 10:59 AM Wes  wrote:
> >>
> >>> I wrote Tom, at the address he gave, on Saturday with a query.  So
> >>> far, no
> >>> reply.
> >>>
> >>> Wes  N7WS
> >>>
> >>>On 7/19/2021 4:59 PM, John Miles wrote:
>  If you're looking for a low cost surplus GPSDO, the ones Tom
>  mentioned in
>  his post on Saturday are the ones you want.  Not a Thunderbolt-E,
>  and not
>  something from the China surplus/e-waste market.
> 
>  -- john, KE5FX
> 
> >>> ___
> >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> >>> send
> >>> an email to time-nuts-le...@lists.febo.com
> >>> To unsubscribe, go to and follow the instructions there.
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> >> send an email to time-nuts-le...@lists.febo.com
> >> To unsubscribe, go to and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> > send an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.

-- 
Andy (out keeping fit)
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Thunderbolts ...

[Andy Talbot]

If you're interested in the Short Term Stability of the LB GPSDO.

http://g4jnt.com/ShortTermStabilityLeoBodnarGPSDO.pdf

Andy
www.g4jnt.com



On Tue, 20 Jul 2021 at 18:12, Bob Darlington  wrote:

> Same.  He probably got 250+ requests in short order.  I'm curious how the
> Leo Bodnar GPSDOs compare.   I'm considering one of these over a
> thunderbolt for field use for ham radio EME work.
>
> -Bob N3XKB
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: GPS Splitter for L1, GNSS, etc?

[Andy Talbot]

I once saw a design for a GPS antenna splitter that comprised a four-way
Wilkinson splitter on PCB microstrip, so had DC continuity between all
ports   At each output port was a capacitor to pass the RF, shunted by a
small diode.   That way any GPS receiver that put DC on its antenna port
would be isolated by the diodes  from all the other receivers.  The
receiver delivering the highest antenna supply voltage would  'win' and end
up supplying the active antenna via its diode in the splitter.

Andy
www.g4jnt.com



On Wed, 2 Jun 2021 at 10:14, shouldbe q931  wrote:

> On Wed, Jun 2, 2021 at 10:09 AM shouldbe q931 
> wrote:
> >
> > On Wed, Jun 2, 2021 at 5:21 AM W7SLS  wrote:
> > >
> > > Hello,
> > >
> > > Looking for group wisdom to avoid newbie mistakes with a GPS splitter.
> > >
> > > For context, I’m a home- not National- or University-Lab.
> > > That said, I have a non-zero budget.
> > >
> > > Today:
> > > Antenna
> > > 1- CORS RTK GNSS Survey Antenna high gain measurement GNSS GPS
> GLONASS BDS 
> > > 2 - patch antenna - works really well with Time Hat, even a
> few meters way from window
> > >
> > > Splitter
> > > 1 - Symmetricom 58536A
> > >
> > > Devices
> > > 1 - Auction Site GPSDO
> > > 2 - Leo Bodnar GPSDO
> > > 3 - Time Hat <— wow!  a fan!
> > > 4 - (on the way) 2nd Time Hat
> > >
> > > Site
> > > - suburban, forest to the S, hill to the N
> > >
> > > Challenge:
> > >
> > > Existing  splitter is L1 only (I think), which blocks the many
> newer GPS satellites.
> > > With my compromised (for GPS) location, that’s not so good.
> > >
> > > I need / want a wider band GPS Splitter
> > >
> > > 1 - some posts talk about removing the bandpass filters in an
> existing splitter
> > > OK, but (a) it nukes any value of that splitter, and
> (b) those filters also eliminate other interference (yes?)
> > >
> > > 2 - new choices seem to be in the $1000 and way above, outside
> of my budget
> > >
> > > 3 - more interested in ‘ready to use’ than ‘have to add on
> bypasses' to power the antenna (e.g., Cable TV splitter)
> > >
> > > 3 - auction site has numerous options, but I’m not sure how to
> 'separate wheat from chaff’
> > >
> > > LOL, some of you may be the sellers :)
> > >
> > > several items $500+  <— more than I want to spend
> > > several items $30 -   <— I’d rather not get  aTV
> antenna splitter and a hobby to make it work
> > >
> > > 324575653743  GPS Source S14 $175
> > >
> > > 153359161105  GPS Antenna Splitter GPS/GLONASS L1
> GALILEO E1 BEIDOU B1- FedEx Fast Ship SV1AFN $120
> > >
> > >
> > > Thoughts?   Thanks for the group bandwidth.
> > >
> > > Scott W7SLS
> > >
> > > PS:  yes the Symmetricom 58536A will be for sale after I replace it.
> > > ___
> > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send an email to time-nuts-le...@lists.febo.com
> > > To unsubscribe, go to and follow the instructions there.
> >
>
> And now for the complete email...
>
> One might consider something like 40252864 combined with Bias Tee
> DC blocks such as 124130508678 for all bar one of the receivers, which
> is used to power the antenna.
>
> Not a one box solution, but very simple to put together with some SMA
> to SMA cables.
>
> Cheers
>
> Arne
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Ublox NEO-M8T-0-10​as a LO question

[Andy Talbot]

More to do with amateurs using narrow band modulations, and the LB GPSDO
being moderately good close in.   Phase noise out beyond a few kHz goes
more or less unnoticed on SSB

Andy
www.g4jnt.com



On Wed, 31 Mar 2021 at 13:35, Dana Whitlow  wrote:

> Chris,
>
> It may be that the modulation and subsequent demodulation scheme used for
> satellite TV and the
> like is rather more robust than many people give it credit for.
>
> Dana
>
>
> On Wed, Mar 31, 2021 at 7:09 AM Chris Wilson  wrote:
>
> > Hello everyone
> >
> >  Monday, March 29, 2021
> >
> >  Thanks for the replies, some went a little over my head, which is not
> > hard :) I am wondering how people successfully use a Leo Bodnar
> > programmable GPS source to provide an external LO for an LNB as opposed
> to
> > its internal xtal. What is different, in simple terms please, between my
> > Ublox output and the Leo Bodnar one?
> >
> >
> > Best regards,
> >  Chrismailto:ch...@chriswilson.tv
> >
> >
> > LJ> On 3/29/21 10:14 AM, John Ackermann N8UR wrote:
> > >> That's probably a really bad idea.  The phase noise from the TIMEPULSE
> > >> output is pretty bad compared to a "real" RF source, and by the time
> > >> it's multiplied up to 10 GHz you'll have more noise than signal.
> > >> Attached are some phase noise plots and a couple of spectrum analyzer
> > >> captures to give you some idea what to expect.
> >
> > >> BTW, even the Bodnar unit may not look too good at 10 GHz -- remember
> > >> that you increase phase noise by 20 dB for 10 times multiplication.
> >
> > >> John
> >
> > LJ> What's the signal bandwidth from Es'Hail?
> >
> > LJ> The optimum strategy is a *very quiet* crystal oscillator that you
> > LJ> discipline with the 1pps, and choose that oscillator so its frequency
> > is
> > LJ> what you need.
> >
> > LJ> What we've done in the past is use the reference to clock a NCO in
> > FPGA,
> > LJ> and use one of the well known spur reduction techniques that pushes
> the
> > LJ> spurs away from the center before running it to the DAC. This
> degrades
> > LJ> the performance at, say, 100kHz away, but improves the performance
> > LJ> within 1 kHz. This relies on knowing what the loop bandwidth is in
> your
> > LJ> 10GHz LO PLL, since inside that bandwidth it's the reference, but
> > LJ> outside it's the DRO or GaAs oscillator.
> >
> >
> > LJ> There might be some DDS chips that implement this kind of thing - the
> > LJ> latest chips from ADI are pretty sophisticated.
> >
> >
> >
> >
> >
> > >> On 3/29/21 12:25 PM, Chris Wilson wrote:
> >
> >
> > >>>29/03/2021 17:20
> >
> > >>> Can I use my Ublox NEO-M8T-0-10​  as a LO for  a  modified satellite
> > >>> LNB on 10 GHz? It needs 25 MHz and the Ublox is my only GPS locked
> > >>> source for such a frequency. I want to receive the Es Hail downlink
> > >>> with excellent stability. I can lock the receiver to 10 MHz which is
> > >>> available from my Trimble Thunderbolt. If the Ublox would do I would
> > >>> not have to buy something like the Leo Bodnar GPS. Thanks.
> >
> >
> > >> ___
> > >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> > send an email to time-nuts-le...@lists.febo.com
> > >> To unsubscribe, go to and follow the instructions there.
> >
> > LJ> ___
> > LJ> time-nuts mailing list -- time-nuts@lists.febo.com -- To
> > LJ> unsubscribe send an email to time-nuts-le...@lists.febo.com
> > LJ> To unsubscribe, go to and follow the instructions there.
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send
> > an email to time-nuts-le...@lists.febo.com
> > To unsubscribe, go to and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Grandfather clock sync'd to 1PPS

[Andy Talbot]

>
> G3PLX did something similar, synchronising his GF clock to GPS.   But
> wanting to make no modifications to the pendulum, IIRC he placed a
> solenoid near the pendulum and used eddy current loss to slow it down.
>
> Andy
> www.g4jnt.com
>
>
>
>
> 
>  Virus-free.
> www.avg.com
> 
> <#m_7271374846254809346_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
> On Thu, 11 Mar 2021 at 11:16, Peter Torry via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
>> Hello Paul,
>>
>> You will still need to power the clock by winding it up when required.
>> The pendulum does not drive the clock, it regulates how the power is
>> allowed to escape from the driving force through a mechanism called the
>> escapement.
>>
>> As far as regulation goes the traditional was is to fis a soft Iron pole
>> piece to the pendulum about  a quarter of the way down from the
>> suspension and mount a coil of wire adjacent to this such that the pole
>> piece enters the coil on the excursion of the pendulum. The control
>> mechanism inserts a current through the coil in 100 micro amp steps to
>> bring the clock to time. The best way to monitor the timekeeping is by
>> using an optical detector and feeding the result back into the coil.
>>
>> There will still be variations from second to second because of
>> escapement error so it would be best to start with a clock using a dead
>> beat escapement or better.
>>
>> Enjoy the experiment.
>>
>> Regards
>>
>> Peter
>>
>>
>> On 11/03/2021 02:28, paul swed wrote:
>> > Like you all, I have always thought it would be fun to mess with a
>> > pendulum clock. Since I have one already what stands in the way? Well my
>> > Wife might think very differently about a few screws and wires in that
>> > clock. At the other end of the spectrum is Bill S. beautiful clocks he
>> has
>> > built. Not going to be anything like that. So will have to settle for a
>> > magical deal some day. Though for now Fleas and other gatherings are
>> out.
>> > I was wondering about winding the clock. And I see its still needed. I
>> had
>> > thought by driving the pendulum the clock would not need the drive
>> weight.
>> > Am I wrong about that? Or simply they are two different and separate
>> issues.
>> > Want to thank Gerald for sharing what he did and starting a great
>> thread.
>> >
>> > Regards
>> > Paul
>> > WB8TSL
>>
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

Re: [time-nuts] Mains Frequency -again

[Andy Talbot]

Well, I do everything in PICs with a assembler, but you have a point.  A
flash memory chip is one route.  An FTDI Vinculum and USB memory stick,
another.
Andy
www.g4jnt.com



On Wed, 24 Feb 2021 at 14:05, Dan Kemppainen  wrote:

> Andy,
>
> Perhaps one of the little openlog units from sparkfun, or one of the
> clones would work for logging?
>
> https://www.sparkfun.com/products/13712
>
> Honestly, I have two and a pair of 32Gb Cards, but have not tried them
> yet. Seems like a good solution for a project like this. I don't know
> how they buffer writes to the microSD, or what the write life on an
> SDcard would be like.
>
> Dan
>
>
> On 2/24/2021 7:35 AM, time-nuts-requ...@lists.febo.com wrote:
> >
> > My monitor uses a 16F628A PIC device clocked from a 10MHz TCXO.   50Hz
> > mains is fed to the  capture/compare module which is set to measure the
> > number of periods of the prescaled clock in every fourth cycle of the
> > mains.  A simple integer division and the answer is the mains frequency
> in
> > milliHz units..  I only measure to about 0.002Hz resolution as the
> > variation is so wide (~~ 0.2Hz RMS) this is quite enough .
> > Completely separately, a four bit counter is incremented by this divided
> > mains signal every 80ms, and also decremented every 80ms by the divided
> > down clock.   Software is written so that increment and decrement cannot
> > clash.
> >
> > The result is a 32 bit twos-complement count, to 80ms resolution, of
> mains
> > timing difference from that of the TCXO.   A bit of arithmetic and the
> > answer can be shows as a timing discrepancy in seconds on the display.
> >
> > It would be a matter of just a few minutes of extra code writing to add a
> > serial output to transfer data to a logger .   Which I may yet do, but
> that
> > would require getting an old laptop out of storage and leaving it on 24/7
> > to do the logging - don't keep my main PCs on continuously.
> >
> > Not sure this list passes-through attachments;  if not the oicture is
> here
> > http://www.g4jnt.com/DropF/img2783.JPG
> >
> > Andy
> > www.g4jnt.com
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] Mains Frequency -again

[Andy Talbot]

Since building my real time mains monitor, I've noticed just how far the
mains timing drifts, for days at a time.   Friday evening last week (10
days ago)  timing was running at [plus] +50 seconds, and was slowly dragged
back over the weekend to about +7s on teh Monday.  Over the week it wobbled
around, but on a slow downward trend.  By Friday evening (2 days ago) it
was -17s  and I watched it drop further.  Now, Sunday morning, it is -56
seconds

So in the space of eleven days the mains timing has drifted a total of
nearly two minutes.

There doesn't seem to be, anywhere,   a long term record of mains timing
error.  You can download frequency from the Gridwatch site, but not
timing.   And I wouldn't trust integration over such extended periods to
derive timing error.
perhaps it's time to add a serial output to my monitor and couple up an old
obsolete laptop

Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mains Frequency

[Andy Talbot]

The mains timing error was still running ~50 seconds fast at midnight
yesterday, and this morning was still at +40 or so seconds.   But over
Saturday the frequency has dropped lower than I've seen it go for several
days, at one point it must have dropped to 48.8Hz, below scale on my
display and that is flagged.  It's caught up now  Mains timing is now just
0.7 seconds fast - and 2s of that was over the last hour or two.

Andy
www.g4jnt.com



On Fri, 12 Feb 2021 at 11:12, Andy Talbot  wrote:

> I maintain a real time display of mains frequency, and the cumulative
> timing offset from real time.   It was last reset 10 days ago when we had a
> brief power outage (HV fault a mile or so away).
>
> Since then, for the first few days the timing discrepancy kept within
> plus/minus perhaps 20 seconds.  But in the last couple of days is has crept
> up and is now sitting at +48 seconds.   On average the frequency will have
> been running about 0.013Hz high to give that.
>
> Given Nat. Grid still aim to average out to exactly 50Hz, does anyone know
> if there is a time scale associated with that long-term average?
>
> Andy
> www.g4jnt.com
>
>
>
> <http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail>
>  Virus-free.
> www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail>
> <#m_512226393731185000_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mains Frequency

[Andy Talbot]

It's still +47 seconds.Perhaps they'll correct over the weekend.
Wind generation is high at the moment, contributing 13.64GW to the 34GW UK
total demand (it it 22:100 as I write).  Perhaps the high wind generation
level is the reason for the extended high frequency session.

Andy
www.g4jnt.com




Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Fri, 12 Feb 2021 at 21:38, Alex Pummer  wrote:

> at the time I grew up in Eastern Europe -- "communist time" -- they kept
> he clocks using the line frequency as reference -- by counting the
> periods during the day and week and for longer time for equal time
> interval the "provided" equal number of line frequency periods, as
> longer the time interval was as more precise was the time.  That way the
> clocks were relative accurate. They could do it since everything was
> "central governed".
>
> On 2/12/2021 9:24 AM, Lux, Jim wrote:
> > On 2/12/21 8:23 AM, Thomas D. Erb wrote:
> >> "I would think they try to hold it over 1 day, so that mains driven
> >>
> >> clocks don't run slow or fast.? That being said, I wonder how many
> >>
> >> clocks are still being built using a synchronous motor drive? Given that
> >>
> >> all the clocks on appliances in my kitchen have drifted apart, I'll bet
> >>
> >> they use their internal microcontroller crystal as a reference."
> >>
> >> Actually I think all of my kitchen appliances use line frequency for
> >> time reference - it's so easy to count.
> >
> >
> > Maybe.. you've got to condition the AC from the secondary side of the
> > transformer and use a pin to bring it in on, which requires at least 2
> > or 3 passive components, and you already have a crystal for the
> > microcontroller (thinking here of oven timers and the like, which have
> > a numeric display).  These applications are super price sensitive, and
> > those 2 or 3 components cost money, in components, in board space, and
> > in assembly costs. Pennies to be sure, but...
> >
> > And the fact that my appliances drift on the order of a minute in a
> > month, differently. So maybe some count cycles and some have a rock.
> >
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> >
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mains Frequency

[Andy Talbot]

Mine peaked at +50s earlier today, it may have gone higher but didn't see.
 Now down to +44s.
There may be a longer term offset, since this monitor was set arbitrarily
265.3 hours ago, and who knows what the official offset was at that point

Andy
www.g4jnt.com




Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Fri, 12 Feb 2021 at 18:55, Joseph B. Fitzgerald 
wrote:

> It seems the Swiss are in charge of regulating the frequency of the grid
> in Europe.   According to
> https://www.swissgrid.ch/en/home/operation/regulation/frequency.html
> European clocks are running 21.064 s fast as of this writing.
>
>
> As mentioned earlier trading affects the frequency.  You can see the
> effects of changing electricity providers especially at the top of the hour
> on  https://gridradar.net/
>
>
> -Joe Fitzgerald
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mains Frequency

[Andy Talbot]

Why should the microcontroller have a crystal at all?
Many have factory trimmed RC oscillators, typical 1% accuracy, because
accurate timing for other than timekeeping is rarely needed.
A minute per month is 10ppm, typical of a bog standard crystal, and given
the choice of that or mains timing for a clock, I'd use the latter any day.

Re the power supply, they may use direct rectification from mains
nowadays.   Capacitive dropper and bridge with a few smoothing and surge
suppression components.
My 20+ year old  microwave doesn't though - that has a real small
transformer in it that audibly hums .

Andy
www.g4jnt.com



On Fri, 12 Feb 2021 at 18:06, Lux, Jim  wrote:

>
> Maybe.. you've got to condition the AC from the secondary side of the
> transformer and use a pin to bring it in on, which requires at least 2
> or 3 passive components, and you already have a crystal for the
> microcontroller (thinking here of oven timers and the like, which have a
> numeric display).  These applications are super price sensitive, and
> those 2 or 3 components cost money, in components, in board space, and
> in assembly costs. Pennies to be sure, but...
>
> And the fact that my appliances drift on the order of a minute in a
> month, differently. So maybe some count cycles and some have a rock.
>
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>


Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mains Frequency

[Andy Talbot]

Streetlights now use radio control from a master, using, at least round
here, a GSM type of protocol on a dedicated frequency, so every individual
light can be set, at different brightness levels.   And they do do this -
at least on a street basis.  And they monitor every light.

I take the 50Hz in, pass it though a three stage RC filter then into the
TMR1 input of a PIC 16F628 which has a Schmitt input at thresholds of 30%
and 70% of the rails.  , ie 1.5 / 3.5V  so plenty of hysteresis.

Andy
www.g4jnt.com



On Fri, 12 Feb 2021 at 16:57, Adrian Godwin  wrote:

> I wouldn't be surprised to find that streetlight clocks use the same old
> Sangamo or Venner electromechanical timers that they've always used, and
> are far more of a problem to correct than domestic clocks.
>
> Andy, what equipment do you use to monitor the cycle count ?
>
>
> On Fri, Feb 12, 2021 at 2:55 PM Lux, Jim  wrote:
>
> > On 2/12/21 3:12 AM, Andy Talbot wrote:
> > > I maintain a real time display of mains frequency, and the cumulative
> > > timing offset from real time.   It was last reset 10 days ago when we
> > had a
> > > brief power outage (HV fault a mile or so away).
> > >
> > > Since then, for the first few days the timing discrepancy kept within
> > > plus/minus perhaps 20 seconds.  But in the last couple of days is has
> > crept
> > > up and is now sitting at +48 seconds.   On average the frequency will
> > have
> > > been running about 0.013Hz high to give that.
> > >
> > > Given Nat. Grid still aim to average out to exactly 50Hz, does anyone
> > know
> > > if there is a time scale associated with that long-term average?
> >
> >
> > I would think they try to hold it over 1 day, so that mains driven
> > clocks don't run slow or fast.  That being said, I wonder how many
> > clocks are still being built using a synchronous motor drive? Given that
> > all the clocks on appliances in my kitchen have drifted apart, I'll bet
> > they use their internal microcontroller crystal as a reference.
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] Daft idea with the National Grid

[Andy Talbot]

The UK has a standalone frequency locked grid supply, nominal 50Hz, which
typically wanders +/- about 0.15Hz RMS over several minutes , with
occasional short-lived excursions out to 0.2 or 0.3Hz.  Average number of
cycles per period generally is normalised to 50Hz after a few days.
The typical loading for the country ranges over ~25GW to 45GW

Now, I wonder:
I can probably measure the grid frequency to a few micro Hz   over a period
of tens of seconds. So I make a continuous recording of this, averaged over
say 10 second periods.
Now take a 7kW load (the maximum reasonably possible on a domestic circuit)
and switch it on and off at intervals of perhaps 10 minutes, precisely
timed so it can be correlated with the frequency log.  That 7kW load will
be about 0.2ppm of the average for that for the whole of the UK.By post
processing, and some deep correlation covering days worth of cycles of load
on-off with the frequency, I wonder if it would be possible to see the
loading, the mean frequency changing by a few uHz.
Not sure what the time constant of the grid control is, but for* small
signals* I doubt it can be faster than a few minutes.

There was a serious outage on 9 August 2019 that caused frequency to drop
below 49.5Hz and initiate automatic load shedding;   that happened over a
period of a couple of minutes but was a large scale problem.
https://www.ofgem.gov.uk/publications-and-updates/investigation-9-august-2019-power-outage

Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] "Q for dummies"

[Andy Talbot]

MRI machines use superconducting coils to generate a 1T magnetic field over
a volume sufficient for a human body

Andy
www.g4jnt.com



On Tue, 26 Jan 2021 at 21:47, Tom Holmes  wrote:

> I was told that one of the killers of superconductivity is magnetic
> fields. I guess they 'fixed' that.
>
> Tom Holmes, N8ZM
>
> -Original Message-
> From: time-nuts  On Behalf Of Mike Feher
> Sent: Tuesday, January 26, 2021 1:07 PM
> To: 'Discussion of precise time and frequency measurement' <
> time-nuts@lists.febo.com>
> Subject: Re: [time-nuts] "Q for dummies"
>
> I recall back in the late 60’s visiting some friends at BNL. One of them
> took me through the cryogenic lab. In one they had an LC running at near 0
> and it could be heard in a receiver. We know for L, Q in its simplest form
> is Xl/R. At superconductor temperatures R approaches 0 and therefore Q
> approaches infinity. Consequently the circuit oscillated by itself. I was
> amazed. Slightly different, but in the same lab they showed me an
> electromagnet in a superconductor cooled environment. I noticed it was
> wound with uninsulated wire. I inquired about that and was told that
> contact resistance is so much higher than the superconductor resistance,
> and they could get more turns without insulation. Regards – Mike
>
>
>
> Mike B. Feher, N4FS
>
> 89 Arnold Blvd.
>
> Howell NJ 07731
>
> 848-245-9115
>
>
>
> -Original Message-
> From: time-nuts  On Behalf Of Dana
> Whitlow
> Sent: Tuesday, January 26, 2021 9:36 AM
> To: Discussion of precise time and frequency measurement <
> time-nuts@lists.febo.com>
> Subject: Re: [time-nuts] "Q for dummies"
>
>
>
> If anybody can even approach doing justice to the Q concept, including why
> it matters, in just two sentences, that person will have definitely earned
> the "Qulitzer prize" in technical journalism.
>
>
>
> Here's my entry:
>
>
>
> "A circuit's Q is closely related to its internal energy losses compared
> to external energy exchanges.  A high Q can mean better efficiency, better
> conformance with expected performance (especially in filter applications),
> longer ringdown times (wineglass compared to milk glass) and
> (unfortunately) higher price."
>
>
>
> Dana
>
>
>
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] "Q for dummies"

[Andy Talbot]

You could mention it is roughly equivalent to the number of swings you get
for a weight on a rope before it stops swinging.  Or something like that.

Andy
www.g4jnt.com



On Tue, 26 Jan 2021 at 13:14, Ole Petter Ronningen 
wrote:

> Hi, All
>
> I am going to give a presentation to non-nuts, and in one of the slides I
> touch on Q - not wanting to spend more than a sentence or two on the
> subject, I wonder if the following analogy works:
>
> "A quality long-stemmed, thin-walled wine glass will ring for a long time
> after we give it a little tap - this is high Q. A thick-walled, stubby milk
> glass will barely ring at all, just a dull "plink" - this is low Q. The
> energy we put in dies out very quickly."
>
> As I am sure is embarrassingly evident, I have a rather tentative grip on
> the subject myself..
>
> Ole
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Long Wave Radio-Frequency standard testing

[Andy Talbot]

It's a custom LF receiver I put together, a direct conversion downconverter
to 1kHz. Then bandpass sampling to an I/Q data steam, at 12 bit resolution
sent using RS422 o a PC. All frequency conversion and sampling is locked to
a master 10MHz clock.  The interface also includes time stamping from a GPS
module.

PC software takes the data steam, applies a small optional frequency
offset, needed to take out DDS frequency setting resolution, displays raw
input on a vector scope.  It then decimated filters the data down to
sampling rate in teh Hz to sub-Hz region for storage and further analysis
of display.

I originally designed the S/W for use with the  Ebnaut   LF data comms
work, hence the reference to .WAV files with time stamped file names but
its more use as a general tool for monitoroing LF signals.

You can find details here  http://g4jnt.com/Coherent_LF_Receiver.pdf  and
there's a better write up in Jan 2021 edition of RadCom (RSGB Members'
magazine)

Andy
www.g4jnt.com



<http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail>
Virus-free.
www.avg.com
<http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Fri, 15 Jan 2021 at 23:55, paul swed  wrote:

> What was the program that you used for the plot please?
> Regards
> Paul
> WB8TSL
>
> On Fri, Jan 15, 2021 at 5:54 PM Andy Talbot  wrote:
>
> > I did a plot of the phase of the UK 198kHz longwave transmission to me, a
> > path of about 150km, compared against an HP5061A Caesium standard
> > N
> >
> > early 24 hours duration, covering night time and day time propagation in
> > October.
> >
> > You can observe the wild wandering of both phase and amplitude  during
> > night time due to skywave/groundwave interaction as the ionosphere shifts
> > around.
> >
> > Plot also at
> > http://www.g4jnt.com/DropF/droitwichplot2a.bmp
> > if the attachment doesn't get through
> >
> >
> > [image: DroitwichPlot2a.bmp]
> > Andy
> > www.g4jnt.com
> >
> >
> >
> > <
> >
> http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail
> > >
> > Virus-free.
> > www.avg.com
> > <
> >
> http://www.avg.com/email-signature?utm_medium=email_source=link_campaign=sig-email_content=webmail
> > >
> > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >
> > On Fri, 15 Jan 2021 at 21:55, Gilles Clement  wrote:
> >
> > > Hi JF,
> > > DCF77 is more distant, less powerful and probably more polluted
> (77kHz).
> > > Anyhow I would probably not be able to measure better than 10e-11 with
> > > current setup (need a better reference)
> > > Indeed a good and stable phase lock was not easy to reach.
> > > I experienced the day and night huge differences (as documented in
> post)
> > > but nothing specific to phase shifts during sunrise or sunset.
> > > No big difficulties with the ferrite antenna and the receiver design
> > > either (thanks to good stuff from the old radio days probably).
> > > Found that magnetic field antenna (ie: ferrite) appeared much less
> > > sensitive to pollution than electric field antennas.
> > > Naturally bad experience with Led bulbs and vapor gas lamps. You have
> to
> > > chase them all and change to old filament lamps in and around the lab.
> No
> > > issues with computers though.
> > > What I found most challenging (and hence interesting) was the
> following :
> > > - Temperature control, high resolution and high stability (Crystal
> > > oscillator but also for the controller parts, ADC, DAC… )
> > > - PI loop stability (very tricky)
> > > - Matching theory with practice (still work in progress…!)
> > > - Understanding the logic and physics behind behaviors, the real root
> > > cause of problems,
> > > and especially why a « really clever » enhancement - more than often -
> > > actually leads to… performance degradation...
> > > Gilles.
> > >
> > >
> > >
> > > > Le 15 janv. 2021 à 16:57, JF PICARD via time-nuts <
> > > time-nuts@lists.febo.com> a écrit :
> > > >
> > > > Hi,
> > > > 800Kw according to the press release of ANFR. I doubt it is the best
> > > choice : DCF77 is more precise (active hydrogen maser) but a little bit
> > > more distant...
> > > > But the phase lock of a quartz on a VLF signal is not as easy. There
> is
> > > a considerable phase shift in the evening and in 

[time-nuts] Parity Errors

[Andy Talbot]

This morning, I stumbled out of bed still half asleep to make my early
morning coffee and glanced up at the MSF controlled wall clock. 'Wed 3 Jan'
it said.  Shuffled into kitchen and while pouring beans into the grinder
...  " 'ang one, it's not Wednesday!"

Checking the clock again, comparing the time against my GPS clock and
another MSF one it was also showing one minute error in the time.  Clearly
there had been a burst error during the update period and an even number of
bits corrupted.   I've had this before on another MSF clock with various
parts of the decoded time and it's been easy to see which possible pairs of
bits had failed.

The timecode for the minute error must have corrupted when it was receiving
01 or 02, and the units and 2s bit got switched,  (or the units and the
parity, but they're separated so less likely).

The day of week is simpler to visualise the error mechanism.   Sunday is
transmitted as zero, Wednesday as 3.   Two adjacent bits corrupted, so it
will pass the parity check.

Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Radio Controlled Clocks

[Andy Talbot]

No, my GPS clock has it's own timekeeping function, complete with  leap
years and automatic DST setting, clocked from the 1 PPS signal.   All
running in a PIC 16F628  (It uses a Nixie tube display, because I just
happened to have some tubes !) The timekeeping registers are updated every
minute from GPS at the 58 second epoch.  As the NMEA stream carries the
data for the PPS that has *just happened*, then apart from start up,  it
will normally be writing to registers that already contain the same
information.

The only thing that will go wrong is at leap send insertion where it will
indicate the wrong time for 58 seconds after midnight - I don't care about
that.   Suppose I could do the GPS read and update at the :00 second point
which would repair leap seconds for all but the 23:59:60 interval, but it
'felt wrong' to do that at the time of writing the code.

Andy
www.g4jnt.com



On Sun, 27 Dec 2020 at 18:12, David G. McGaw 
wrote:

> A clock that uses an NMEA stream for its display will be a few hundred
> milliseconds slow, dependent on the chosen data products and serial baud
> rate, as NMEA gives the time of the previous second mark.
>
> David N1HAC
>
> On 12/27/20 9:54 AM, Andy Talbot wrote:
> > I've just had a look around the house, and actually have four MSF clocks
> > and an old wristwatch minus its strap (antenna is a small ferrite rod
> > inside).  Forgot I had an old Junghans one as well - that is sitting out
> in
> > the shed as it requires a stronger signal than the more modern ones, and
> > seems to get better reception out there.   It's the only one that shows
> MSF
> > outages as it updates every hour - and the battery seems to last forever!
> >   I never checked to see how close that is to GPS;  if they implement
> proper
> > timing or just a simple delay bodge.
> >
> > Andy
> >
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.g4jnt.com%2Fdata=04%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C34fd0d2e9a8748b929c308d8aa797df9%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637446786072625838%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000sdata=r8oYhRkOXFHfKDTdTxlt6y7uaLhSs2IOJAKybbH8Xsk%3Dreserved=0
> >
> >
> >
> > On Sun, 27 Dec 2020 at 14:02, Peter Vince 
> wrote:
> >
> >> Hello Andy,
> >>
> >>   I have an old Maplin digital LCD clock for MSF, and that is always
> >> about a second slow, but the Coopers analogue clocks are MUCH closer,
> as is
> >> the Junghens DCF digital LCD clock.  But the Junghens DCF clock always
> >> misses one or other of the DST changes!
> >>
> >>   Peter
> >>
> >>
> >> On Sun, 27 Dec 2020 at 12:11, Andy Talbot  wrote:
> >>> With this talk of Radio Controlled clocks...
> >>> I have three domestic RC clocks here, receiving the UK 60kHz signal,
> MSF.
> >>>However, I notice that when compared against a GPS clock, timed from
> >> the
> >>> 1 PPS signal & NMEA output, they all are a few hundred milliseconds
> fast,
> >>> ie the display changes just before the GPS derived time.
> >> ...
> >> ...
> >>> I only ever have digital display clocks, so wouldn't know if the same
> >>> happens with round ones with hands.Anyone else using domestic MSF
> or
> >>> DCF77 clocks who have observed this?
> >>>
> >>> Andy
> >>>
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.g4jnt.com%2Fdata=04%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C34fd0d2e9a8748b929c308d8aa797df9%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637446786072625838%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000sdata=r8oYhRkOXFHfKDTdTxlt6y7uaLhSs2IOJAKybbH8Xsk%3Dreserved=0
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >>
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.febo.com%2Fmailman%2Flistinfo%2Ftime-nuts_lists.febo.comdata=04%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C34fd0d2e9a8748b929c308d8aa797df9%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637446786072625838%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000sdata=wzkD9rJQh3N0lDangtmH6sNwvGhf39xOJrq163myhvw%3Dreserved=0
> >> and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.feb

Re: [time-nuts] Radio Controlled Clocks

[Andy Talbot]

Update.
The Junghans Mega is approx 100ms late updating its display.  And it's
pretty cold, sitting in the outside shed so the LCD is a bit sluggish. It
looks like the designers of that tried to do the job properly.

Andy
www.g4jnt.com



On Sun, 27 Dec 2020 at 14:54, Andy Talbot  wrote:

> I've just had a look around the house, and actually have four MSF clocks
> and an old wristwatch minus its strap (antenna is a small ferrite rod
> inside).  Forgot I had an old Junghans one as well - that is sitting out in
> the shed as it requires a stronger signal than the more modern ones, and
> seems to get better reception out there.   It's the only one that shows MSF
> outages as it updates every hour - and the battery seems to last forever!
>  I never checked to see how close that is to GPS;  if they implement proper
> timing or just a simple delay bodge.
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 27 Dec 2020 at 14:02, Peter Vince 
> wrote:
>
>> Hello Andy,
>>
>>  I have an old Maplin digital LCD clock for MSF, and that is always
>> about a second slow, but the Coopers analogue clocks are MUCH closer, as
>> is
>> the Junghens DCF digital LCD clock.  But the Junghens DCF clock always
>> misses one or other of the DST changes!
>>
>>  Peter
>>
>>
>> On Sun, 27 Dec 2020 at 12:11, Andy Talbot  wrote:
>> >
>> > With this talk of Radio Controlled clocks...
>> > I have three domestic RC clocks here, receiving the UK 60kHz signal,
>> MSF.
>> >   However, I notice that when compared against a GPS clock, timed from
>> the
>> > 1 PPS signal & NMEA output, they all are a few hundred milliseconds
>> fast,
>> > ie the display changes just before the GPS derived time.
>> ...
>> ...
>> > I only ever have digital display clocks, so wouldn't know if the same
>> > happens with round ones with hands.Anyone else using domestic MSF or
>> > DCF77 clocks who have observed this?
>> >
>> > Andy
>> > www.g4jnt.com
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Radio Controlled Clocks

[Andy Talbot]

I've just had a look around the house, and actually have four MSF clocks
and an old wristwatch minus its strap (antenna is a small ferrite rod
inside).  Forgot I had an old Junghans one as well - that is sitting out in
the shed as it requires a stronger signal than the more modern ones, and
seems to get better reception out there.   It's the only one that shows MSF
outages as it updates every hour - and the battery seems to last forever!
 I never checked to see how close that is to GPS;  if they implement proper
timing or just a simple delay bodge.

Andy
www.g4jnt.com



On Sun, 27 Dec 2020 at 14:02, Peter Vince  wrote:

> Hello Andy,
>
>  I have an old Maplin digital LCD clock for MSF, and that is always
> about a second slow, but the Coopers analogue clocks are MUCH closer, as is
> the Junghens DCF digital LCD clock.  But the Junghens DCF clock always
> misses one or other of the DST changes!
>
>  Peter
>
>
> On Sun, 27 Dec 2020 at 12:11, Andy Talbot  wrote:
> >
> > With this talk of Radio Controlled clocks...
> > I have three domestic RC clocks here, receiving the UK 60kHz signal, MSF.
> >   However, I notice that when compared against a GPS clock, timed from
> the
> > 1 PPS signal & NMEA output, they all are a few hundred milliseconds fast,
> > ie the display changes just before the GPS derived time.
> ...
> ...
> > I only ever have digital display clocks, so wouldn't know if the same
> > happens with round ones with hands.Anyone else using domestic MSF or
> > DCF77 clocks who have observed this?
> >
> > Andy
> > www.g4jnt.com
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] HP5061 Cesium ion pump question

[Andy Talbot]

When I found my HP5061A lingering in a skip, soaked in rainwater some 20
plus years ago, I thought I'd be lucky if it was only good for the OCXO,
and never even contemplated it might be fully working.  I first left it in
a warm room for a week to dry out then, without having a clue about how to
get it going, tentatively plugged it in with the switch set to 'Caesium
off', and just left it alone to stabilise.   With no instructions that
seemed instinctively the right thing to do.   To my delight 5MHz appeared,
so I borrowed a Rb standard from work to check, and the OCXO was clearly
working well - very well - at first sight, just looking at traces on a
scope, the OCXO seemed as stable  and accurate as the Rb was supposed to
be.   I already had an MSF reference at that time, so comparisons were made
against that too.

Over a period of a couple of weeks I just left teh 5061A running and put
out an appeal on the LF chat group on the  (still quite new then) Internet
for anyone who could help me with a manual.   SOme kind person trusted me
enough to actually post me their hard copy on loan, which I copied,
returned the original and studied thoroughly.  And discovered

THE FIRST THING TO DO when powering up from cold is to leave it in standby
for several days / weeks to pump out the ions.   EXACTLY what I'd already
done! Without thinking.  So as soon as I'd read that paragraph, following
the instructions, tentatively switched to 'open-loop' and watched the meter
showing beam current rise.  After an hour or so when it appeared to have
settled,  (I was too excited to wait the recommended three) switched to
'OPER' and pressed the reset button.   The joy when the green light came on
!   A working Cs standard, recovered as scrap from a skip.   The light went
off after an hour, but pressing the button made it come back on, and it
stayed on from then on.

Further studying the manual, and vaguely knowing that unit's history and
politics surrounding the original owning organisation, (don't ask, I won't
say)  suggested there could actually  be a fair bit of life left in the
tube - beam current certainly suggested so.The internal NiCd batteries
were completely dead and had a few green crystals on them, so I removed the
whole battery and its charging circuitry, substituted an LM317 regulator
set for 27.2V and used a pair of (old second hand) lead acid gel cells as
backup instead.   And there it sits to this day, on standby
continuously for over 20 years with the Cs switched on when wanted.
 Typically it only needs 35 - 45 minutes warm up, so I allow 1.5 - 2 hours
before any serious tests that need full accuracy.   Ironically, it's been
running for so long the only things to have failed have been my backup gel
cells - floated in series at 27.2V, one set bulged alarmingly after some 13
years, and another pair died such that it couldn't hold-up even standby for
more than about 15 minutes when mains went off.   I replaced those only two
weeks ago.

The only thing I've never tried is calibrating out local magnetic field
using Zeeman lines.   Not having the Cs running continuously, I suspect
this would be a pointless exercise  anyway, and the loss of a few parts in
10^-13 don't over-worry me.


Andy
www.g4jnt.com



On Wed, 2 Dec 2020 at 14:43, paul swed  wrote:

> Morris
> I do see that of the 3 HP5061s the results are different and do know each
> tube leaks or internally emits stuff. But as you say maybe the metering is
> off. It definitely trips out at 40ua.
> I have my units that pulse like that and then settle down as the tube
> clears.
> But its hard to explain that if a unit is pumped down how quickly it
> pollutes again.
> Wondering if as an example the getter just releases its captured crud when
> the power is removed. That way you are always pumping down mostly the same
> stuff.
> Just very curious.
> Regards
> Paul
> WB8TSL
>
>
> On Wed, Dec 2, 2020 at 6:23 AM  wrote:
>
> > I think there's quite a bit of variation in leakage rates between
> > individual
> > physics packages, and there's also variation in the accuracy of the
> > metering. I recently started up my spare 5061A after over a year in
> > storage.
> > The Ion current meter showed zero with the Cs off but about 40 in the
> Open
> > Loop position. I tried connecting an external +3500V supply through a
> > microammeter as described in the manual and that showed less than 10 uA.
> > The
> > unit kept trying to start and pulsed for about 12 hours at a peak reading
> > of
> > 40 and then settled down nicely to a zero reading and hasn't missed  a
> beat
> > since.
> >
> > I have a spare tube sitting here that hasn't been powered up for several
> > years. It was removed from a junked 5061A that wouldn't start at all but
> > after the unit was parted out some failed caps were found in one of the
> > modules that could have explained the fault. I plan to try it on the
> bench
> > with the +3500 V supply and microammeter but I don't know whether I can
> > trust 

Re: [time-nuts] OCXO housings - Why copper and not iron/steel?

[Andy Talbot]

Actually, diamond has five times better thermal conductivity than silver,
so is the most conductive element, although graphene is suspected to be
better still.


Andy
www.g4jnt.com




Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Fri, 30 Oct 2020 at 22:17, Luiz Alberto Saba  wrote:

> My bad... copper is the second, losing only to silver, as a thermal
> conductor.
>
> Enviado do meu iPhone
>
> > Em 30 de out. de 2020, à(s) 19:06, Luiz Alberto Saba <
> l...@intercat.com.br> escreveu:
> >
> > If my memory serves me, copper has the better conductivity of all the
> periodic table...
> >
> > Enviado do meu iPhone
> >
> >> Em 30 de out. de 2020, à(s) 18:56, Attila Kinali 
> escreveu:
> >>
> >> Moin,
> >>
> >> I have been looking at heat capacities of different materials
> >> lately. One thing that struk me odd is, that the volumetric
> >> heat capacity of copper, which is the thing that most people
> >> use when building something that needs to have high heat capacity
> >> to get stable temperature, has only a volumetric heat capacity
> >> of 3.45 J/(cm^3·K). Meanwhile, the much cheaper iron has
> >> a volumetric heat capacity of 3.53 J/(cm^3·K) and steel
> >> even 3.75 J/(cm^3·K).
> >>
> >> In an OCXO, which is generally size limited, getting the most
> >> heat capacity in the limited volume would be the main goal,
> >> wouldn't it? Also optimizing for price would be a major thing.
> >> I can understand that iron is probably not the right choice
> >> due to its tendency to oxidize. But using a soft (annealed) steel
> >> would be easy to machine, cheaper per piece and give almost 10%
> >> higher heat capacity in the same volume.
> >>
> >> So why do people choose copper instead of steel?
> >>
> >>
> >>   Attila Kinali
> >>
> >> PS: Fun fact: Water has a volumetric heat capacity of 4.18 J/(cm^3·K)
> >> at 25°C. We should fill OCXOs with water! :-D
> >>
> >> --
> >> The bad part of Zurich is where the degenerates
> >>   throw DARK chocolate at you.
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Mentorship needed in learning about Allan Deviation and variation.

[Andy Talbot]

On another thread,  G3YSX described this technique :
Taken in conjunction with the Wikipedia entry it begins to make sense here.

...
"A note on this thread:  plotting phase against time will tell you a lot
about the effect of propagation on phase, but it is not the technique used
in the synchronisation world to understand the behaviour of oscillators.

They use Allen variance, TDEV and MTIE plots.

Fundamentally what these measurements do is to look at the error every
second, and then cumulatively work out what the error is every second,
every two seconds, every four seconds etc until the limit of the
measurement, but they do it using a sliding window system so in a one
hundred second time (say) they have one hundred one second measurements to
average, 99 two second measurements, 98 three second measurements…. 49 50
sec measurements etc. Then they plot this on a log scale.

This tells you a lot more about what is going on than the phase error vs
time measurements and revolutionised understanding of oscillator and hence
time measurement characteristics. In particular with the more sophisticated
plots developed after Allen initial work, the slope of the curve at various
places along the plot tells you the cause of the error in the system."


Andy
www.g4jnt.com




Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Tue, 27 Oct 2020 at 15:59, Bob kb8tq  wrote:

> Hi
>
> Indeed this *is* a very fundamental problem in doing this sort of work.
> The test setups and references generally are way harder to set up (and
> more costly) than the design and construction of this or that device.
>
> Indeed, as part of a normal design process on a GPSDO, the testing /
> tweaking phase is much longer and much more expensive than the
> work leading to the first “working” batch of units.
>
> Fun !!!
>
> Bob
>
> > On Oct 27, 2020, at 9:46 AM, Joe & Gisela Noci  wrote:
> >
> > Thanks Bob.   Slowly it penetrates..
> > The 1PPS source is as you say far from being a good reference, so I will
> > cease that route!
> >
> > I think I have to accept what I have - I believe it is good enough for my
> > Ham Radio work as a reference for my radios, at least into the low GHz
> > region.
> > If I manage less than 100Hz error in the 2.4GHz band, I am OK..
> >
> > As I mentioned before, its very difficult for me to obtain or have
> > access to Reference Grade solutions, or for me to buy a handful of
> suitable
> > surplus sources, etc...
> > The usual Ebay sources don't work well to our part of the world, very
> > difficult, very costly, and most Ebay vendors won't even ship toNamibia!
> >
> > Having learned a lot from you chaps, for which I am grateful, I think I
> now
> > at least know the size of the cliff above of me!
> >
> >
> > Thanks to all..
> > regards
> > Joe
> >
> > On Tue, Oct 27, 2020 at 3:29 PM Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> What are we trying to measure with ADEV?
> >>
> >> On a frequency source, it’s used to measure the noise of that source.
> >> Mostly we
> >> put up plots of ADEV to show how quiet our source is. (Yes, we might
> also
> >> measure
> >> noise floor or amplifier contributions ….).
> >>
> >> That’s the statistics part. Now for the instrumentation:
> >>
> >> There is no device that will directly measure frequency / time / phase
> to
> >> the accuracy
> >> levels we are after. The closest we can get is to measure A against B
> and
> >> look at the
> >> delta. We also could look at A vs B vs C and do some fancy math, that
> >> takes a bit
> >> of setup and has some pretty significant limits. You still are doing a
> >> comparison.
> >>
> >> With an A to B comparison, you need to know that one or the other device
> >> is much
> >> lower noise than the other. Then the plot will (essentially) be the
> noise
> >> of the not so
> >> quiet source. If that’s not true, you have a real tangle. It’s even
> worse
> >> if both our
> >> sources have the *same* noise in them.
> >>
> >> So how does this apply in your case?
> >>
> >> The 1 pps out of your GPS module is *far* from a low noise source close
> >> in. Further
> >> out it will wander more than a little due to ionosphere issues.
> Depending
> >> on how the
> >> OCXO is locked, there  will be a cross over between “free run” and
> >> “follows GPS”.
> >>
> >> The real ADEV of any GPSDO starts out with the free run OCXO noise +
> loop
> >> noise +
> >> GPS noise. Hopefully (but not always) the OCXO noise is the big item
> close
> >> in. As you
> >> get further out, GPS noise becomes the dominant contributor to the
> output
> >> noise. Again
> >> this is a “hopefully” sort of thing. We test our designs because that’s
> >> what shows us
> >> where improvement is needed …..
> >>
> >> What to do?
> >>
> >> You need an 

Re: [time-nuts] WWVB Dephaser Question

[Andy Talbot]

That doesn't appear to give you 1/4 the base sampling rate as you suggest
with "... to sample at 4 times the desired rate..."
I do something similar on a 1kHz tone, generating I/Q at 1kHz sampling rate
on a bandwidth up to 500Hz, ie 750 - 1250Hz
Samples at 4kHz are S1, S2, S3, S4
Then  I = S1 + S2 - S3 - S4
 Q = S1 - S2 - S3 + S4   at 1kHz sampling, centred on 1kHz tone


See http://g4jnt.com/Coherent_LF_Receiver.pdf where the technique is used
in a coherent LF receiver.

Andy
www.g4jnt.com



On Sun, 25 Oct 2020 at 02:17, jimlux  wrote:

> On 10/24/20 3:53 PM, paul swed wrote:
>
>
> The classic way to get I/Q is to sample at 4 times the desired rate,
> then, given that your input samples are x(1),x(2),x(3),x(4), etc. the
> I/Q streams are
>
> I(1) = X(1)
> Q(1) = X(2)
> I(2) = -X(3)
> Q(2) = -X(4)
> I(3) = X(5)
> Q(3) = X(6)
> I(4) = -X(7)
> Q(4) = -X(8)
>
> and so forth.
>
> This will put your signal right in the middle of the sampling bandwidth.
>
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>


Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Frequency Counter Choice

[Andy Talbot]

In days of yore + DOS, I implemented a GPIB control by bit-banging a
parallel printer port.
Those were the days

Andy
www.g4jnt.com




Virus-free.
www.avg.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Thu, 22 Oct 2020 at 17:59, jimlux  wrote:

> On 10/22/20 8:29 AM, Tom Van Baak wrote:
>
> >
> > 3) Instead of replacing the front panel readout, instead do all your
> > comms over SCPI, to the point where you have created a virtual
> > instrument, not unlike some of the logic analyzer or 'scope PC apps.
> > This solution would be very welcome by lots time-nuts. It means we could
> > fully operate our 53131/53132 counters with the VFD disabled. The
> > downsize is that it requires a GPIB (Prologix) adapter.
> >
> > /tvb
> >
> >
> While I love my Prologix adapters, I wonder if one could implement the
> protocol using GPIO pins on something like a Beagleboard or Arduino clone?
>
> (yes, as a product, with the right connector and line driver/receivers,
> etc. - it would cost the same as a Prologix... but as a hack...)
>
> After all GPIB is a very old standard, and was developed back in the day
> of 1 MHz logic. I think you could do the handshaking in software - punch
> the bits one by one, assert DAV, etc.
> Listener reads bits one by one, then asserts the ACK or NAK
>
>
>
> (Aieee.. Wikipedia says it was supported by the Commodore PET... there's
> a challenge for you)
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] GPSDO Short Term tests

[Andy Talbot]

While my next plot of Droitwich is being generated at this moment, for the
meantime here's an analysis of the short term stability of the Leo-Bodnar
GPSDO made a couple of years ago.   It was done by multiplying the
output up to 10GHz and comparing with a caesium derived reference
multiplied up.

The results, which show the performance over the tens of seconds to minutes
time frame can be seen here .
http://www.g4jnt.com/ShortTermStabilityLeoBodnarGPSDO.pdf

Compare this with a test done a few days ago, comparing the 10MHz outputs
over a 30 minute period.
http://www.g4jnt.com/DropF/gpsdo_cs_10mhz_30min.bmp

This sort of short term stability reflects on how 'good' a GPSDO is when
used as a reference for a synthesizer for microwave Tx/Rx.   The artefacts
are just about audible at 5.76GHz when listening to a steady tone (they are
to me anyway, although it may be only a few Hz wobble) and very definitely
so at 24GHz and higher.

Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] Droitwich Frequency Error

[Andy Talbot]

Hi Folks
I've just joined this list, but have had an interest in accurate frequency
measurement for decades, ever since finding a fully operational HP5061A in
skip with what appears to be plenty of Cs life left in the tube.   It only
gets turned on when needed here.Anyway :

This morning, mainly to prove something it to myself I made a plot of the
off-air UK Droitwich LF transmitter whose carrier is supposed to be a
national standard - although I believe it uses a Rb source that is
periodically updated with a Cs one - manually.

I have a Leo-Bodnar GPSDO had been turned on only some 20 minutes before
the plot was started, as teh reference into a custom own-design LF receiver
that gives a digitised baseband I/Q output to a PC.  Its LO is tuned using
an  AD9852  48 bit DDS clocked at 10MHz and set by an algorithm that allows
a micro-Hz but completely deterministic tuning error - it was this error I
was trying to show by doing a plot of Droitwich off air using the GPSDO as
a reference.

The plot at http://www.g4jnt.com/DropF/clipboard_202010181333.png shows the
result - the phase is the red line.My calculated tuning error at this
frequency is 3uHz, but there is a slope to the line showing around 20
degrees of phase shift in a little under 2 hours.   This corresponds to
about 7.8uHz error. If my tuning error contributes 3uHz of this, that's
still 4.8uHz on 198kHz , or 0.024 PPB.   It was well after sun rise, and
the transmitter is only 100km away from me, so oughtn't to expect
propagation anomalies

My question,  does anyone know if a GPSDO, has any inherent drift over its
first hour or so?   I wouldn't have thought there was any mechanism for
that, but who knows.

Finally, I guess 2.4E-11 isn't really outrageous for a rubidium source,
even one that is 'supposed' to be corrected from 'time-to-'time' Or  Is it?


Andy
www.g4jnt.com
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.