Hi

They very much did not “just go away”. About the only way to get data is to measure a bunch of parts.
Since they typically increase in “time between events”, testing brand new parts likely would give you
the best data.

The main “issue” in terms of a lack of papers seems to be that the tie between cause and effect still
is in the “maybe” category. Over the years, the magnitude of the jumps has dropped. Folks are fixing
something. Most likely they are fixing a number of things that each can create a jump. Tying each change
to this or that maybe 5 or 10%  improvement …. good luck.

Bob

Some time-nuts readers may remember me from 25+ years ago circa 1997
with respect to the E1938A OCXO which used crystals that were basically
the same as the 10811 crystals except for (1) a low profile package and
(2) 10 MHz occurred at series resonance vs parallel resonance.  A small
group of technologists led by Jack Kusters had gradually improved HP
crystal processes over decades of time; by then the 10811 was 20 years
old.  Most of the work focused on aging, rather than jumps.  The method
used to "improve" aging consisted of burning in crystals on an "ager"
system and shipping oscillators (containing crystals) when they achieved
the aging spec they needed.  Certain HP divisions needed tighter specs.
(There were also phase noise specs to worry about).  They didn't
actually materially improve the average aging, but rather the same
division sold frequency counters that could be used to get rid of the
"junk" from the production line.  Jack told me that any sort of process
correlated aging that was discovered would be studied to find the root
cause and then eliminated.  I remember when I first got involved in
crystal oscillators around 1973, before I worked for HP, I was
introduced to crystals from "Colorado Crystal" that were packaged in
glass packages.  Their frequency aging was mostly or completely in the
positive direction (higher frequency as time passed).  Conventional
metal packages mostly were negative aging.  This was explained to be me
by the fact that glass didn't outgass anything that would land on the
resonator and lower its frequency.  Jack's philosophy was to figure out
how to prevent copper packages from outgassing in the first place, and
he was largely successful.  By the late 1990's, the low hanging fruit
had largely been picked, and there were no more papers to be written.
Also, Jack was busy giving private training classes to numerous crystal
fabricators so that we could establish alternative crystal oscillator
sources.  Once this was accomplished, the captive crystal fab at HP was
closed, more or less coinciding with the HP to Agilent spin off and the
retirement of Jack.  They later spun off the legendary 5071A, which I am
proud to say lives on 30+ years later as the 5071B.  Len Cutler would be
proud too.

I built up a lot of E1938A prototypes, and recorded aging data of many
of them.  While it was true that brand new crystals might age much
faster than 5 parts in 10^10 per day (the spec), they mostly improved
over time so that most got down to the spec.  However, they rarely
continued to get better than that with any consistency.  Crystals might
look promising for while, and then for no reason would change and often
go in the opposite direction for a while.  I also looked for jumps,
hoping to find crystals with less than normal jumps, either in size or
how often they occurred.  However, no "jump free" crystals were ever
observed.  The only advice Jack would offer was to say that both effects
were due to slow (or instantaneous) relaxation of stress in the crystal.
Of course, he had already applied any known remedy to this effect.  The
BVA crystal might have been a remedy, but we never attempted that at HP.
You can now buy an atomic standard for the price of a BVA oscillatorl

Meanwhile, mini Rb and mini Cs gas cell standards were getting better
and cheaper and smaller, so they became the defacto replacement for
crystals where jumps mattered (such as when locked to GPS).  Aging
didn't matter as much when GPS locking was in place due to the "smart
clock" concept that was at least named at HP AFAIK.  The smart clock
didn't really work that well in practice.  Len Cutler tried to construct
an ensemble of ten 10811's and operate them as a smart clock.  That
would have made a great paper at FCS, if only it could be made to work.
That is another discussion...

Hope that at least partially answered your question.  I think I can rule
out your theory that "they" figured out how to eliminate jumps and
simply kept it to themselves.  It's more likely they stopped trying due
to lack of a viable value proposition.

Rick Karlquist
N6RK

On 2025-03-12 09:34, Attila Kinali via time-nuts wrote:

Attila Kinali via time-nuts writes:

GPS disciplining ?

Almost nothing is free-wheeling any more.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

Out of curiosity, how much do swept quartz blanks help?

How about ion beam milling or other processes to remove defects from surfaces?

Plasma cleaning surfaces before sealing packages?

From: Bob Camp via time-nuts time-nuts@lists.febo.com
Sent: Wednesday, March 12, 2025 3:21:33 PM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Attila Kinali attila@kinali.ch; Bob Camp kb8tq@n1k.org
Subject: [time-nuts] Re: Quartz crystal frequency jumps

Hi

They very much did not “just go away”. About the only way to get data is to measure a bunch of parts.
Since they typically increase in “time between events”, testing brand new parts likely would give you
the best data.

The main “issue” in terms of a lack of papers seems to be that the tie between cause and effect still
is in the “maybe” category. Over the years, the magnitude of the jumps has dropped. Folks are fixing
something. Most likely they are fixing a number of things that each can create a jump. Tying each change
to this or that maybe 5 or 10%  improvement …. good luck.

Bob

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To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hello,

We will probably regret that one day.

That's why I'm interested (as a mere amateur) by self contained
oscillators (with manual periodical recalibration while the possibility
lasts, and not just via gnss).

Sebastien

On 13/03/2025 08:07, Poul-Henning Kamp via time-nuts wrote:

Ultimately, it's all driven by economics.  GNSS disciplining got so good for most applications, and inexpensive atomic references also fill in the gap. 
A Rb in a box is a few thousand $. The PRS10 is $2k. A CSAC is about the same from digikey. Syrlinks has the MMAC (I don't know what they cost) which appears to be CSAC like

It's hard to justify a big physics research project to dive deeper, unless you've got a customer willing to fund it.  After all, one of the reasons DARPA funded the CSAC development was to avoid having to invest in that physics research project on crystals.  (FWIW, DARPA is quite proud of the CSAC, they've got pictures of it in their lobby wall displays).

I suspect that most development dollars are going towards atomic sources or non-quartz-crystal resonators. 

There is a need for good clocks without GNSS - Timekeeping and time distribution at the Moon, for instance. If you're in low orbit, you're going to lose visibility back to Earth, so you need to have good holdover. Or, at Mars.  

If you want 1 ns timing (to pick a round number), over a 1,000 second gap (~15-20 minutes), you need 1E-12 kinds of adev.  That's a few orders of magnitude better than a CSAC (at least from the datasheet numbers, in reality, they do somewhat better, but not that much better).

CAPSTONE is flying a CSAC connected to a Iris X-band transponder to experiment with this in a cis-lunar environment and it's been flying for about 2 years. One of the claimed benefits of the NRHO orbit is that maintains Earth visibility most of the time (at the cost of having enormous ranges (>100k km) at apolune, which makes it less suitable for time/nav)

On Thu, 13 Mar 2025 10:24:18 +0100, Sebastien F4GRX via time-nuts time-nuts@lists.febo.com wrote:

Hello,

We will probably regret that one day.

That's why I'm interested (as a mere amateur) by self contained
oscillators (with manual periodical recalibration while the possibility
lasts, and not just via gnss).

Sebastien

On 13/03/2025 08:07, Poul-Henning Kamp via time-nuts wrote:

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To unsubscribe send an email to time-nuts-leave@lists.febo.com
 

Strange frequency jumps, I had much fun with it  ......

We manufactured DSL modems which were kicked out of sync with a
temperature change, namely in the exhaust of vacuum cleaners :) . The
test in the climate chamber showed a frequency jump  at a specific
temperature for each crystal.  It was a jump, way beyond the the
specified deltaf/deltaT . We solved it with a smarter PLL and we
substituted the crystal supplier. The root cause was of no further interest

Cheers Detlef

Am 13.03.2025 um 18:05 schrieb Jim Lux via time-nuts:

--
Diese E-Mail wurde von Avast-Antivirussoftware auf Viren geprüft.
www.avast.com

On 3/13/25 08:07, Poul-Henning Kamp via time-nuts wrote:

There is just immense amount of oscillators which will never be steered
or resynthesized (just different frequency adjustment method).

A frequency jump will upset any PLL and depending on the order and
bandwidth, the jump may be within tolerance or not. If not within
tolerance, the lock will be lost and you need to recapture it, or that
happens automatically but you may choose potentially better ways.

Regardless, frequency jumps remains an issue that needs to be handled,
even if this is to ensure that most likely jumps is within PLL tolerance.

Cheers,
Magnus

Hi

Typically that sort of thing would be called a perturbation. They are very common and the reasons behind most of them are pretty well understood.

Bob

A wonderful good Sunday everyone,

Thanks for all the intersting answers.

I'm going to pick a few of the points made and add some comments.
I'll do this in one mail, as not to clutter the mailinglist too much.

On Wed, 12 Mar 2025 16:21:33 -0400
Bob Camp via time-nuts time-nuts@lists.febo.com wrote:

So, we still have this issue, but as people run out of ideas how to fix it,
they just chose to live with it as well as they can?

On Wed, 12 Mar 2025 14:45:57 -0700
Richard Karlquist via time-nuts time-nuts@lists.febo.com wrote:

How did this ager look like? Was it just the bare crystal package in a
bread-board like oscillator, attached to some frequency counter to measure
it's long term behavior?

I have looked at data from ultra high vacuum (UHV) systems and I am pretty sure
that this theory is not fully correct. While it is true that metal surfaces
are full of water and hydrocarbons and that they require proper cleaning
and out-gasing procedure prior to use in UHV systems, glass is even more
porous and contains quite a bit of content that can outgas (technical
glasses used in UHV have about the same outgasing performance as metals).
I think that the biggest difference is, that glass is more "sticky" for the
larger molecules (i.e. hydrocarbons) than quartz, thus the equilibrium
point of these molecules sticking to surfaces shifts towards them sticking more
to glass than the crystal, thus making the crystal surface lighter.

I have also been told (by either by John Vig or Gregory Weaver), that glass
packages in space perform much better than metal packages in space, while
on earth the difference is not significant (probably after applying all types
of cleaning before sealing). This suggests, that glass is porous enough that
smaller contaminants (single atomic and di-atomic gasses, water,..) can get
through the glass and outgas into space. But I have not seen any data that
would support this, nor have I been told about any real measuruement that
would support this hypothesis.

I have been told a few times about this quest of Jack Kusters', but I could
not find any documentation thereof. Do you know whether some form of written
document from these training sessions are left and maybe even where to find them?

Do you remember what the usual rate and size of these jumps were

That would be a discussion I would be very much interested to hear, as I have
been playing with the same idea on and off as well.

On Thu, 13 Mar 2025 07:15:42 +0000
Ed Marciniak via time-nuts time-nuts@lists.febo.com wrote:

I don't know about swept quarzes but surface defect removal is a big part of
frequency jump prevention. From what I have read, there are three general
method groups: surface defect prevention/removal, stress removal and contaminant
removal. But I do not have any numbers, how much each of those help. This wasn't
published, as far as I am aware.

Thanks again, and have a nice evening

		Attila Kinali

--
Science is made up of so many things that appear obvious
after they are explained. -- Pardot Kynes

Hi Attila,

I recall one paper on the BVA where they built a rather large "chimney"
with large cross-area for the bake-out at high temperature and vacuum
pump. The large area helps for ultrahigh vacuum pumping. I think I
recall 200 degrees C and long baking time to evaporate out as much
contaminants as possible. At the end of the bake-out they use the
chimney as a pinch-off.

Cheers,
Magnus

On 2025-03-16 22:06, Attila Kinali via time-nuts wrote:

Hi

Ok, a few more details.

No folks have not stopped working on this stuff. It simply is not very exciting. Like a lot of crystal
processing “stuff”, it’s part of the IP of the company. Those two things combine to make it not
very paper worthy.

====

As the whole HP “crystal empire” changed, Jack Kusters moved from HP and got involved
with the EMXO. The EMXO eventually moved over to Vectron. A lot of discussions went on as part
of those moves. That was on top of the work to outsource crystal production.

====

There is very little data that suggests the crystal package impacts phase jumps. Pretty much
everything points towards the blank structure / supports being the source of the problem. Like
any other “never say never’ situation, there will always be those one in a hundred issues. Still
the big deal is not the package.

Bob

Some other responses, interspersed (and snipped out of)

On Sun, 16 Mar 2025 22:06:34 +0100, Attila Kinali via time-nuts time-nuts@lists.febo.com wrote:

On Wed, 12 Mar 2025 16:21:33 -0400
Bob Camp via time-nuts  wrote:

So, we still have this issue, but as people run out of ideas how to fix it,
they just chose to live with it as well as they can?

On Wed, 12 Mar 2025 14:45:57 -0700
Richard Karlquist via time-nuts  wrote:

How did this ager look like? Was it just the bare crystal package in a
bread-board like oscillator, attached to some frequency counter to measure
it's long term behavior?

I have also been told (by either by John Vig or Gregory Weaver), that glass
packages in space perform much better than metal packages in space, while
on earth the difference is not significant (probably after applying all types
of cleaning before sealing). This suggests, that glass is porous enough that
smaller contaminants (single atomic and di-atomic gasses, water,..) can get
through the glass and outgas into space. But I have not seen any data that
would support this, nor have I been told about any real measuruement that
would support this hypothesis.

That would be a discussion I would be very much interested to hear, as I have
been playing with the same idea on and off as well.

Hi

Hysteresis tends to be rate dependent. Do a full sweep over the entire temperature range in an
hour, you get one result. Run over the same range in ten hours and the result is different. There
are a lot of applications out there. Some cycle at a “once a day over part of the range”  sort of rate.
Others cycle much faster.

Post soldering drift might be called retrace. (Yes, that term gets used for several similar things ….).
It’s one of the reasons you may see folks talking about  “aging after X days” in their specifications.
They want the install and power up sort of effects to damp down before the aging spec applies.
There are a whole lot of IC specs that are worded that way for pretty much the same reasons.
Since install is a one time sort of thing it’s impact may or may not be a big deal. Thermocycle after
install often helps reduce it.

Bob

Hi Sebastien,

I share a similar philosophy, and would also like to work on
self-contained options.

Unfortunately, I have far too many ideas and far too little time/energy
to do them!

My current wish is to make a VCOCXO and be able to discipline it in
different ways.  Various options here are broadcast AM, WWV, or possibly
even picking up JJY.  WWV will be problematic because of ionospheric
height changes and intermittent propagation. JJY is apparently possible
from Australia but no idea of what reliability would be like.  It would
be fun to observe these signals with some confidence.  Before GNSS there
used to be off-air frequency standards that would synchronise to LF
services.

I also started daydreaming about truly human-independent sources like
tracking pulsars but it rapidly becomes unachievable within reasonable
time and energy/motivation constraints.

Once I have a 10MHz reference I'd use that to run a hardware digital
clock with 7-segment displays maybe down to the millisecond, just for
fun (you'd need a high speed camera to see what time it is, but the act
of reading the time that way totally defeats the purpose which I find
amusing).  Synchronising such a clock beyond NTP or GNSS becomes a whole
exercise in itself. Realistically, GNSS is the best way to get accurate
time.  But buying a cheap GPSDO and plugging it in isn't very rewarding,
nor do I learn anything useful.

I was impressed by the ability of WSJT-x to run a frequency calibration
using various sources.  Using it, I found out that some of the local AM
stations are well-disciplined and others are free-running (a couple were
considerably off-frequency, 2.5ppm or so while my FT-897D's TCXO ended
up being around 1ppm off).

Cheers

Geoff VK2WA

On 13/3/25 20:24, Sebastien F4GRX via time-nuts wrote:

Hello Geoff,

Very happy to share some ideas. Yes, I also happen to have too many
ideas for normal 24 hour days.

In france I have the option to sync on the Allouis transmitter (formerly
France Inter AM radio), which is directly traceable to UTC and was
retained for time signals even if the audio broadcast was shut down.

That sync will happen at some point.

I also have wishes and components to build that 7-segment time display
and a plausible design for a 10 MHz PPS divider, with an option to
adjust it to UTC. The idea came after looking at Curious Marc's video
about his HP clocks.

Meanwhile I will receive tomorrow components to build a small portable
clock based on a DS1321 and a little box I found in my scrap box.

So many projects. So many distractions. haha.

At least I am happy to say that I have completed a coaxial to SFP
breakout board that can transmit a 10 MHz signal over any optical fiber.
that one was inspired by Benjojo's presentation at the CCC. At least
that project is complete and working (this is quite rare for me)

https://assets.chaos.social/media_attachments/files/114/070/817/099/369/933/original/9506286b89dda0cb.jpg
(this link may rot after sometime)

Sebastien

On 26/03/2025 01:56, Geoff Van der Wagen via time-nuts wrote:

Geoff, I'm not sure where you are located but in Europe there is of course the DCF77 signal from Mainflingen at 77.5 kHz and the MSF signal at 60 kHz from Anthorn (UK).  I am fairly certain that there are still products around that use these to derive a stable frequency and time source, and there have been a number of amateur projects published.  With the growing concerns over GNSS jamming and spoofing there's increasing interest in e-LORAN at 100 kHz for PNT, there is a station at Anthorn transmitting, possibly a network being set up over the UK, some I believe in Europe and (ironically) in Russia.  With all these VLF standards working in similar frequency ranges a multi-standard receiver ought to be possible  which could apply diversity.

Cellular base stations are extremely stable and GNSS locked, though fixed PNT networks are being deployed to remove this reliance.  A standard frequency receiver based on cellular base station transmissions would be challenging but ought to be possible.  After all, handsets have to lock on to the network frequency!

Digital TV broadcasts must also be very stable I would guess.  These should be much easier to demod and decode as the transmissions are continuous.  Receivable through cheap USB SDR sticks.

A few years back at Bristol University we had a PhD group project looking at using pulsars as a frequency source, inspired by work in Poland that actually resulted in a Pulsar Clock in a museum.  Not such a mad idea, except that you have to keep switching to another pulsar as the earth rotates.  Also not very portable!

-----Original Message-----
From: Geoff Van der Wagen via time-nuts time-nuts@lists.febo.com
Sent: 26 March 2025 00:57
To: Sebastien F4GRX via time-nuts time-nuts@lists.febo.com
Cc: Geoff Van der Wagen vk2wa@thenack.com
Subject: [time-nuts] Re: Quartz crystal frequency jumps

Hi Sebastien,

I share a similar philosophy, and would also like to work on self-contained options.

Unfortunately, I have far too many ideas and far too little time/energy to do them!

My current wish is to make a VCOCXO and be able to discipline it in different ways.  Various options here are broadcast AM, WWV, or possibly even picking up JJY.  WWV will be problematic because of ionospheric height changes and intermittent propagation. JJY is apparently possible from Australia but no idea of what reliability would be like.  It would be fun to observe these signals with some confidence.  Before GNSS there used to be off-air frequency standards that would synchronise to LF services.

I also started daydreaming about truly human-independent sources like tracking pulsars but it rapidly becomes unachievable within reasonable time and energy/motivation constraints.

Once I have a 10MHz reference I'd use that to run a hardware digital clock with 7-segment displays maybe down to the millisecond, just for fun (you'd need a high speed camera to see what time it is, but the act of reading the time that way totally defeats the purpose which I find amusing).  Synchronising such a clock beyond NTP or GNSS becomes a whole exercise in itself. Realistically, GNSS is the best way to get accurate time.  But buying a cheap GPSDO and plugging it in isn't very rewarding, nor do I learn anything useful.

I was impressed by the ability of WSJT-x to run a frequency calibration using various sources.  Using it, I found out that some of the local AM stations are well-disciplined and others are free-running (a couple were considerably off-frequency, 2.5ppm or so while my FT-897D's TCXO ended up being around 1ppm off).

Cheers

Geoff VK2WA

On 13/3/25 20:24, Sebastien F4GRX via time-nuts wrote:

time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi

Be careful with cellular networks. Some networks in some countries may not be a good source of time. Yes, that’s weird. There are all sorts of very strange stories behind each twist and turn that created that situation.

Bob

Speaking of 7-segment clock displays and such:
As it happens, I am in the process of making yet another time-of-day clock,
and it involves a 7-segment display. The inspiration is:
In the last couple of years I've become very interested in "aerospace
telemetry" equipment and history. Somehow, my collection of vintage
telemetry receivers has now grown to seven receivers, plus some related HW.
Details are here: https://spyradios.com/intercept.html .
Then I realized that I need a "countdown clock", like what might have used
in the 1960's in a launch control room.

SO, I'm working on a 3D-print design for a clock display, in the
"+HH:MM:SS" format. The digits are about 2" high in a 3" background, with
two 3mm LEDs per segment.
I haven't decided on what the firmware will do, other than displaying
time-of-day. I'm thinking that periodically (hourly??) it will switch to a
'countdown' mode with "T minus zero" being the top of the hour. With that,
maybe I should also build a light/sound effect for a rocket launch... :-) .
I may use the old Sulzer 5A as the time base.

I'll be happy to share all the details after I've finalized things, in case
anyone wants to leverage it for their own project.

Pete

On Wed, Mar 26, 2025 at 6:00 AM Sebastien F4GRX via time-nuts <
time-nuts@lists.febo.com> wrote:

 
While the SDR sticks (e.g. RTL-SDR) can receive the signal, their clocks aren't so wonderful. One could generate a 28.8 MHz clock with high quality.  There's also not a direct path from ADC to USB - it goes through some sort of digital FIR filter and is potentially resampled. Whatever that transformation winds up being, at least it's deterministic, so once you figure it out, it should be the same every time. 

On Wed, 26 Mar 2025 08:50:59 -0000, "john.haine--- via time-nuts" time-nuts@lists.febo.com wrote:

Geoff, I'm not sure where you are located but in Europe there is of course the DCF77 signal from Mainflingen at 77.5 kHz and the MSF signal at 60 kHz from Anthorn (UK). I am fairly certain that there are still products around that use these to derive a stable frequency and time source, and there have been a number of amateur projects published. With the growing concerns over GNSS jamming and spoofing there's increasing interest in e-LORAN at 100 kHz for PNT, there is a station at Anthorn transmitting, possibly a network being set up over the UK, some I believe in Europe and (ironically) in Russia. With all these VLF standards working in similar frequency ranges a multi-standard receiver ought to be possible which could apply diversity.

Cellular base stations are extremely stable and GNSS locked, though fixed PNT networks are being deployed to remove this reliance. A standard frequency receiver based on cellular base station transmissions would be challenging but ought to be possible. After all, handsets have to lock on to the network frequency!

Digital TV broadcasts must also be very stable I would guess. These should be much easier to demod and decode as the transmissions are continuous. Receivable through cheap USB SDR sticks.

A few years back at Bristol University we had a PhD group project looking at using pulsars as a frequency source, inspired by work in Poland that actually resulted in a Pulsar Clock in a museum. Not such a mad idea, except that you have to keep switching to another pulsar as the earth rotates. Also not very portable!

-----Original Message-----
From: Geoff Van der Wagen via time-nuts
Sent: 26 March 2025 00:57
To: Sebastien F4GRX via time-nuts
Cc: Geoff Van der Wagen
Subject: [time-nuts] Re: Quartz crystal frequency jumps

Hi Sebastien,

I share a similar philosophy, and would also like to work on self-contained options.

Unfortunately, I have far too many ideas and far too little time/energy to do them!

My current wish is to make a VCOCXO and be able to discipline it in different ways. Various options here are broadcast AM, WWV, or possibly even picking up JJY. WWV will be problematic because of ionospheric height changes and intermittent propagation. JJY is apparently possible from Australia but no idea of what reliability would be like. It would be fun to observe these signals with some confidence. Before GNSS there used to be off-air frequency standards that would synchronise to LF services.

I also started daydreaming about truly human-independent sources like tracking pulsars but it rapidly becomes unachievable within reasonable time and energy/motivation constraints.

Once I have a 10MHz reference I'd use that to run a hardware digital clock with 7-segment displays maybe down to the millisecond, just for fun (you'd need a high speed camera to see what time it is, but the act of reading the time that way totally defeats the purpose which I find amusing). Synchronising such a clock beyond NTP or GNSS becomes a whole exercise in itself. Realistically, GNSS is the best way to get accurate time. But buying a cheap GPSDO and plugging it in isn't very rewarding, nor do I learn anything useful.

I was impressed by the ability of WSJT-x to run a frequency calibration using various sources. Using it, I found out that some of the local AM stations are well-disciplined and others are free-running (a couple were considerably off-frequency, 2.5ppm or so while my FT-897D's TCXO ended up being around 1ppm off).

Cheers

Geoff VK2WA

On 13/3/25 20:24, Sebastien F4GRX via time-nuts wrote:

time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
 

In the 1980's when I worked for HP Santa Clara Division, they had three
dedicated 5061A high performance option cesiums that were steered by
Loran C signals.  My boss would brag that this was the most accurate
clock on the West Coast.  This was called the "House Standard" and was
distributed throughout the plant.  They had a setup to measure the
chroma carrier of various local TV stations, and they could tell them by
how much their Rb clock was in error.  (I believe the TV stations moved
on from that paradigm many years ago, so you can't use your TV for a
frequency reference any more).

Rick Karlquist
N6RK

On 2025-03-26 01:50, john.haine--- via time-nuts wrote:

If for no other reason than broadcast TV is now all digital, so there's no color burst or subcarrier to measure.
The transmitted frequency might be fairly accurate (so they can do multiple transmitters on the same frequency - to a receiver, it just looks like multipath, and it uses a RAKE receiver to deal with it).
But that probably wouldn't give you "time".
 

On Wed, 26 Mar 2025 11:17:32 -0700, Richard Karlquist via time-nuts time-nuts@lists.febo.com wrote:

In the 1980's when I worked for HP Santa Clara Division, they had three
dedicated 5061A high performance option cesiums that were steered by
Loran C signals. My boss would brag that this was the most accurate
clock on the West Coast. This was called the "House Standard" and was
distributed throughout the plant. They had a setup to measure the
chroma carrier of various local TV stations, and they could tell them by
how much their Rb clock was in error. (I believe the TV stations moved
on from that paradigm many years ago, so you can't use your TV for a
frequency reference any more).

Rick Karlquist
N6RK

On 2025-03-26 01:50, john.haine--- via time-nuts wrote:

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Correction to Jim's statement that DTV signals do not
have subcarriers:

ATSC 1.0:  There is a continuous pilot carrier near the
bottom end of the overall spectrum.

ATSC 3.0:  There are pilot tones all over the place.
While most would be very difficult to use,
two of them (one at the bottom and one
at the top) are easy to use.  Each is
interrupted very briefly at a rate of 4X per
second, and a clean uninterrupted tone
can be obtained by merely selecting that
clean carrier with a BPF narrow enough to
block the sidebands.  Caveat: these tones
track variations in the transmitting station's
RF frequency.  For the two stations within
indoor dipole receiving range of my home,
I see frequency variations in the neighborhood
of 50 mHz (that's milli-Hz) P-P.  Both stations
(KMYS & KPXL) operate at roughly 500 MHz
regime, and had roughly comparable stability,
although their detailed waveforms differed.  I
think this could offer insight into the nature of
their frequency references.

Dana
Kerrville, TX

                variations of

On Thu, Mar 27, 2025 at 11:59 AM Jim Lux via time-nuts <
time-nuts@lists.febo.com> wrote:

The Tx frequency (at least for the DVB-T2 standard) is specified to be within 1e-9 for single frequency networks.  I think that it's highly likely that most DVB transmitters will use GNSS to provide a local frequency reference just like cellular does, so this requirement is probably easily met.  The modulation is COFDM so multipath handling doesn't require a RAKE.  The receiver will need to accurately recover a reference clock locked to the incoming signal for the COFDM demod to work, so I think that it would be possible to get "frequency" from the modem.  "Time" signals are at least included in the data multiplex in a standardised way I believe.

Digital audio broadcasting should also be a potential source for time and frequency.  It also uses (in Europe) OFDM and single frequency networks are more common I think.

-----Original Message-----
From: Jim Lux via time-nuts time-nuts@lists.febo.com
Sent: 27 March 2025 16:36
To: time-nuts@lists.febo.com
Cc: Jim Lux jim@luxfamily.com
Subject: [time-nuts] Re: Quartz crystal frequency jumps

If for no other reason than broadcast TV is now all digital, so there's no color burst or subcarrier to measure.
The transmitted frequency might be fairly accurate (so they can do multiple transmitters on the same frequency - to a receiver, it just looks like multipath, and it uses a RAKE receiver to deal with it).
But that probably wouldn't give you "time".

On Wed, 26 Mar 2025 11:17:32 -0700, Richard Karlquist via time-nuts time-nuts@lists.febo.com wrote:

In the 1980's when I worked for HP Santa Clara Division, they had three dedicated 5061A high performance option cesiums that were steered by Loran C signals. My boss would brag that this was the most accurate clock on the West Coast. This was called the "House Standard" and was distributed throughout the plant. They had a setup to measure the chroma carrier of various local TV stations, and they could tell them by how much their Rb clock was in error. (I believe the TV stations moved on from that paradigm many years ago, so you can't use your TV for a frequency reference any more).

Rick Karlquist
N6RK

On 2025-03-26 01:50, john.haine--- via time-nuts wrote:

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On the DVB

In the case of local 'translators' or 'gap fillers' as we used to call
them... Those transmitters may well be a local OCXO, and not tied to
anything, although, where phase noise is not the strictest
consideration, but more so frequency accuracy , I have found that its
cheaper to put in a $20 XO and and $12 GPS receiver chip .... rather
than a $200 XO or Rb.

-glen

On 28/03/2025 05:29, john.haine--- via time-nuts wrote:

There is a proposal to distribute time over ATSC 3.0 with some
modifications in the signal.

Measurements have been done by NIST and it's gives ns stability. You
need to compensate for offset delay, but you can do that through several
methods.

It will solve some, but not all needs.

Cheers,
Magnus

On 2025-03-27 18:28, Dana Whitlow via time-nuts wrote:

Hi,

This is a topic right up my alley, as I've worked with time-transfer to
DVB-T and DAB SFN networks.

The 1E-9 specification is more technical than anything else, it needs to
be that stable at the least for proper signal quality. This does not
reflect in any way the accuracy you will get, as it will in practice be
much better. The original design assumed GPS receivers (they had not
taken the shift over to denote it GNSS), but in practice many countries
operating SFN mode made their network GNSS-independent, because they
treat TV signals as a critical infrastructure that needs to function.

Similar goes for DAB, which when run in SFN also goes to COFDM from the
usual OFDM. You have the same background timing network typically. Some
DAB transmitters may operate independent of national resources thought,
so it may be not as robust.

Both these is typically operated with 1-5 us allowance of transmitter
time error. In practice within 1 us is often achieved.

Cheers,
Magnus

On 2025-03-27 19:29, john.haine--- via time-nuts wrote:

However, when the "gap filler" is in an SFN region, it is not a
translator and needs to obey SFN rules. This can be done either through
a simplified retransmission or a full SFN DVB-T modulator. Then the gap
filler locally improves the signal without using frequency space, which
is a very compelling reason to do SFN as gap fillers can be used more
generously as needed.

Cheers,
Magnus

On 2025-03-28 02:07, glen english LIST via time-nuts wrote: