[time-nuts] Re: Ublox M6T -M8T

[John Ackermann N8UR via time-nuts]

Rich, stand by.  I've been doing a *lot* of testing with higher-speed 
pulserates on the u-blox F9T/M8T/M9N (as high as 20+ MHz) and will be 
ready to report some results in a week or two, I hope.  There are some 
interesting findings.


And that testing underlies a new TAPR project I'm working on; I hope to 
announce that before the end of the summer.


John


On 5/28/22 13:05, R&M Putz via time-nuts wrote:

Has anyone done anything with the Ublox GPS timing receivers? As it appears the
Navman with the 10khz outputs seem to be drying up, I'm wondering about the 
Time Pulse 2 output being set to 10 Khz or 100 Khz. Thoughts anyone?
Rich
W9ENG
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[time-nuts] Re: TICC Question

[John Ackermann N8UR]

On 4/26/22 17:37, Graham / KE9H wrote:

For John A., or anyone comfortable answering.

When using the TICC in the default time stamping mode, is there any minimum
required separation in time required between the channel A and channel B
input events?

Is the TICC capable of handling two events within a few pico seconds of
each other?


Hi Graham --

The two TICC channels are completely independent and there's no minimum 
or maximum offset between them -- you can even have 1 PPS on chA and 10 
PPS on chB, or whatever.


However... if the two inputs are quite close together, there's no 
assurance that the data output will reflect the order of the inputs.  In 
other words, even if chA precedes chB by 10 ns, the serial output might 
be in chB, chA order.


There are a couple of reasons for that, the main one being that the TDCs 
are clocked at 10 MHz (their ps resolution comes from a much higher 
speed internal ring oscillator).  If a timestamp for each channel is 
processed within the same 100 ns tick, both chips will raise their 
measurement complete interrupt at the next tick, and there's no way 
ahead of time to know which channel has the earlier timestamp.


The data for each channel will always be correct, but there's no 
guarantee that the every line of output will have a later timestamp 
output than the one immediately preceding (from the other channel).


John
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[time-nuts] Re: Question about GPS 1PPS ADEV

[John Ackermann N8UR]

On 4/16/22 15:53, Matthias Welwarsky wrote:


John, what constellations did you have enabled during the test? Just GPS, or
also others? I usually run with GPS and Galileo enabled (and I avoid GLONASS,
it messes everything up). Can this make a difference?


I'm afraid I'm not certain.  Normally, I do all my work with GPS only, 
as for timing purposes adding in the other constellations can result in 
clock-jumping and other issues.  But at the beginning of the paper I 
said that all receivers were set to default configuration except for 
setting to 0D timing mode when available.  So I don't know if that means 
I left all the default constellations were enabled.


My gut feeling, though, is that I probably turned everything off but GPS.

John
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[time-nuts] Re: Question about GPS 1PPS ADEV

[John Ackermann N8UR]

On 4/16/22 09:52, Matthias Welwarsky wrote:

Dear list members,

in 2020 John Ackermann published an evaluative survey of current day GPS and
GNSS receivers (URL below). I have a question about figure 26, which shows,
among others, the ADEV of a NEO-M8T against a Cesium reference, with
quantization correction applied. The curve shows a significant "bulge" above
1e-10 between about 10s and 100s tau.

I'm using a LEA-M8T in my DIY GPSDO, which I think is the same chipset in a
slightly different package. I have attached an image worth about 3000 seconds
of data, raw 1PPS phase difference against the LO used in the GPSDO. The GPSDO
is locked, not in hold-over mode.

The bulge between 10s and 100s is not really visible here. There is a slight
bend, but not as pronounced. My explanation is that this is due to the LO
being pulled by the GNSS receiver so that it is no longer fully visible. I
reason that, were the LO more stable, more loosely coupled to the GNSS, I
should see the bulge from figure 26. Would you agree?


My theory of the ADEV flat spot when the M8T is qErr corrected is that 
multiple things contribute to noise on the PPS output, and the qErr is 
only one of them, and it consists of a noise source (clock granularity) 
that is unrelated to any external analog process.


Since Qerr has a fixed limit of ± XX nanoseconds (half the receiver 
clock granularity), its contribution to the PPS noise decreases with 
longer averaging times.  Meanwhile, the other sources of noise such as 
ionosphere, etc., are slower and become more pronounced as tau 
increases.  At around 30 seconds, the external noise factors become 
larger than the qErr.


So at short tau cancelling out the qErr gets rid of a major noise source 
and improves ADEV but as tau increases beyond ~30 seconds the qErr 
contribution is gradually outweighed by the other noise sources and 
disappears, returning the ADEV slope to its normal -1.


Also note that in Fig. 26, at tau below 3 seconds it's possible that 
both the M8T and F9T corrected plots are limited by the TICC resolution, 
which is around 8e-11 @ 1 second on a good day.  That's below these 
traces, but may still be high enough to impact the measurement.


Finally, it looks like you're comparing the raw PPS with an oscillator 
that is steered by that same PPS.  I have to think their correlation 
could lead to possible and unpredictable errors.  It would be better to 
have the OCXO remain unsteered during the measurement.


Best,
John



Best regards,
Matthias

https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/
N8UR_GPS_Evaluation_August2020.pdf


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[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[John Ackermann N8UR]

On 4/7/22 18:46, Lux, Jim wrote:

Wenzel is not some giant WalMart of oscillators, with forklifts going 
hither and yon full of palletized ULNs - there are probably 50-60 people 
there total, so odds are, you'll be talking to someone who actually has 
touched (with gloves) your oscillator.


This is true.  Wenzel is a small shop that really tries to be helpful. 
For example, I've asked them for details on surplus oscillators that 
have a custom part number.  They won't give you data for that exact 
part, but they'll nudge you to something that's very similar.


And while they're by no means cheap, a lot of their 
multiplier/divider/buffer/PLL/etc. modules are not out of the reach of a 
serious experimenter.  They actually have things in their parts list 
that are priced in three figures.


They're just good people.

John
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[time-nuts] Re: Temperature effect on delay of FatPPS :)

[John Ackermann N8UR]

The FatPPS should be pretty stable when you trigger off the leading edge 
of the output, since the delays are in silicon.  But the trailing 
(usually falling) edge of the output is a different matter as the pulse 
width is controlled by a simple RC circuit and is likely to wander all 
over the place.


John


On 3/29/22 05:10, Hal Murray wrote:

I'm putting some data collection toys back together.

I've got a TAPR TICC watching a couple of PPS signals.

The clock for the TICC comes from a HP 5334B with the good crystal option.
It's not right-on in frequency, but there is no control voltage that might be
wiggling around so it should be stable.

This setup is half backwards.  I'm using the PPS to calibrate the frequency of
the TICC reference clock, then assuming the reference clock is short term
stable and using it to examine the short term characteristics of the PPS
signals.

The green line is the PPS signal from a Sure demo board with a SKG16B GPS chip.
   http://www.leapsecond.com/pages/MG1613S/

The wander in the green line is a combination of warmup and temperature.  The
5334B was off for several months.  This graph starts on day 18.  The wiggles
are easy to see on an expanded scale but that blows the FatPPS signal off
scale.  The daily temperature swings are roughly the same size as the daily
drift.  (Another graph for another message...)

The PPS signals are connected via clip leads to handy places.  One of those
was after a FatPPS.  That signal is upside down so the TICC is triggering on
the trailing edge.  No problem, I thought, I can just fix that up when
graphing things.  :)

After I saw the initial results, I put a temperature probe on the FatPPS.  The
spike at 18 hours is the direct morning sun peeking through the houses and
trees across the street.




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[time-nuts] Re: Coupling between oscillators -- an example

[John Ackermann N8UR]

On 3/26/22 13:23, Joseph Gwinn wrote:


It's the ever-present ship-hull vibration (under full steam) that is
being compensated for operational vibration, which falls largely
between ~10 Hz and 200 Hz.  Big gun shocks cause rare noise bursts.
Also, the shock from a naval gun quickly degrades anything as
delicate as this kind of time hardware, and so the time stuff is
never mounted close to a gun.


Thanks!  That's really interesting background.
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[time-nuts] Re: Coupling between oscillators -- an example

[John Ackermann N8UR]

On 3/25/22 19:22, ed breya wrote:

I'm a firm believer in using signal isolation transformers where needed 
and practical. I've had plenty of issues with ground loop interference - 
usually from line frequency harmonics - especially between different 
pieces of equipment, but it can show up internally too.


It seems like isolation transformers are a coin toss between helping, 
doing nothing, and sometimes actually making things worse.  I think the 
problem is there are so many possible ground paths via power wiring, or 
even chassis bolted to racks, that one size very much doesn't fit all.


Another interesting thing is that this situation was easy to spot 
because of the significant frequency differences that made the beat 
period fairly short.  If these guys had all been within 1e-10 of each 
other, the trouble might have been harder to spot.

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[time-nuts] Re: CF cards and the Trimble NetRS

[John Ackermann N8UR]

You can stream data out of the receiver via either TCP or serial port 
without storing to disk, so that's probably the best bet to save CF wear 
and tear.  I'm not sure if it's more difficult to turn the


But for now I'm doing as you suggest -- I have one "T00" format session 
logging to disk in 24 hour files, with the "autodelete" function turned 
on to delete oldest files first when the disk gets nearly full.


However, I've been collecting data now for almost 4 months, and have 
used 68.5 MB, with 770 MB still available, so I won't need to delete 
anything for quite a long while.


John


On 3/21/22 11:22, Skip Withrow wrote:

Hello Time-Nuts,

Seems like there has been a lot of interest in the NetRS lately
because of their availability at reasonable prices (sometimes).

They use a Compact Flash card to store the operating system and logged
data files.  I'm not very knowledgeable about Linux, but I would guess
that there is no wear leveling implemented in this receiver.

So, when considering how best to use the data logging area it would
seem that instead of collecting some data, downloading it, deleting
file(s), and repeating the best strategy would be to collect data and
let the data logging area fill up before deleting (the files could be
read anytime).
This would minimize the number of writes to any one area of the CF
card I believe (except perhaps the directory structure).

However, even if you were deleting data often, you still may not be
able to get to the life of the CF card.  The good news is that even if
a card does go bad you can reconstruct a new one from the image of
version 1.3-2 of the software that is floating around.  I have tried
it and it works.

If there is better insight into the operation of this receiver, or
best practices strategy I'm all ears.

Regards,
Skip Withrow
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[time-nuts] From the Admins: Forged time-nuts messages

[John Ackermann N8UR]

Several time-nuts subscribers have recently reported that they've 
received malicious email messages claiming to be from the time-nuts list 
or from known members of the list.  At first glance, the messages might 
appear legitimate because they include text taken from old time-nuts 
postings.  But their real purpose is to deliver an attachment containing 
malicious code intended to infect your computer.


These messages were not sent through the time-nuts list.  A hacker got 
access to a time-nuts subscriber's personal address book or maybe they 
scanned the public time-nuts archives.  They used that information to 
forge messages to look as though they came from the list.


In these recent messages the forgeries aren't particularly good; while 
the "From" header says "Time nuts" the email address in brackets 
following the name is obviously not from the mailing list (for example 
"From: Time nuts "). Sometimes, though, the forgeries 
are much better, and can be very difficult to spot.


Unfortunately, there's not much that can be done about malicious email 
like this.  The messages don't go through our server so we can't block 
them.  Spam filters are good, but not perfect, and tricks like including 
seemingly real text in the message can fool them into accepting a 
dangerous message.


Our advice is to be vigilant: Never open attachments, or click links, in 
an email that you haven't verified is real.  Look at the headers and 
body of any suspicious message; the clues are often fairly obvious. 
Don't forward suspicious messages as that may spread the malware.


Further discussion is welcome at the time nuts support email address: 
time-nuts-ow...@lists.febo.com; to help keep the main 
time-nuts@lists.febo.com address as on-topic as possible, please don't 
follow-up here.


Thanks,
The Time-Nuts Admins
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[time-nuts] Re: FTP with Trimble NetRS

[John Ackermann N8UR]

Hi Skip --

I have had no trouble FTPing into two NetRSs from a Linux command line 
ftp program.  A couple of config settings might be important if you 
haven't checked them:


Under "Internet/FTP" make sure "Anonymous FTP" is enabled with 
appropriate access rights.


Under "Security" make sure the file access rights are set to 
"Unrestricted", and that it's set to listen on port 21.


John


On 3/13/22 12:23, Skip Withrow wrote:

Hello Time-Nuts,

I would like to download files from a Trimble NetRS via ftp and seem
to be running into a roadblock.

I'm running NetRS firmware 1.3-2 talking to it with a Windows-10
running a DOS command prompt window.

Issuing an 'ftp IP'  (IP = IP address of NetRS) gets a response of
'Connected to IP.' (there is a period after the IP address).  Then,
nothing.  No prompt asking for user name, and no response to any
keyboard input.  Then, after a timeout period, it responds with
'Connection closed by remote host.'

I have tried switching to named versus anonymous ftp on the NetRS.
Have also switched to another computer running Windows-7.  Always
behaves the same.

Any suggestions?  Has anyone connected to the ftp server on the NetRS?
  I have to believe that it works (if you get everything right) as
there are many of these units collecting remote data around the world.

Thanks,
Skip Withrow
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[time-nuts] Re: Measuring oscillators against GPS

[John Ackermann N8UR]

I've been working on frequency/stability measurements using the Trimble 
NetRS and newer Mosaic-T dual-frequency receivers.  Very early data 
indicates that the NetRS does just about as well as the Mosaic, assuming 
you are only interested in GPS and not GLONASS or the other 
constellations the Mosaic-T covers.


I have been sending data to the Natural Resources Canada PPP processing 
system (https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php) and 
am just finishing a set of python scripts to completely automate the 
process from pulling the files from the GPS via FTP to building an 
ever-growing file of phase values that can be fed into TimeLab.


Attached is an ADEV plot for 18 days of post-processed data.  I don't 
know whether the noise floor at around 2e-15 is the measurement system, 
or the reference.


In a few weeks, I hope to have some more complete results to show off, 
and the python scripts uploaded to Github for anyone else who might want 
to try this.


If NetRS's are becoming available as Stewart noted, that's a Very Good 
Thing as they really do work well and are easy to manage.  The only 
downsides are (a) GPS only, and (b) the data files are in a proprietary 
format that needs to be converted to RINEX.  (My script handles the 
conversion process, using a couple of third-party programs.)  And 
remember they require a dual-frequency antenna.  Those have been scarce 
but there seem to be some hockey-puck antennas available now for <$100 
that might do the job.


John


On 3/7/22 4:02 PM, Stewart Cobb wrote:

Skip Withrow's writeup is very interesting. As Skip mentioned, the Trimble
NetRS is a survey-grade dual frequency GPS receiver which accepts a 10 MHz
clock input.

It appears that the US Coast Guard has recently replaced a large number of
these NetRS units, and sent the old ones to surplus. They are now appearing
on eBay for approximately the price of a Thunderbolt (they used to be
several times higher). This situation probably will not last.

It seems possible to use a NetRS, plus an OCXO and an external computer
such as a Raspberry Pi, to build a dual-frequency GPSDO which would be
immune to ionosphere effects.

It seems possible to extend such a system by running RTKLIB on the external
computer, fed with global GPS correction data from ITRS via NTRIP, to build
a GPSDO with PPS precision of a few nanoseconds.

Implementation is left as an exercise for the reader (but see Ole's hints
at https://www.efos3.com).

Cheers!
--Stu
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[time-nuts] Re: Picotest U6200A problem with measuring PPS period very second.

[John Ackermann N8UR]

On 2/27/22 6:56 PM, Bob kb8tq wrote:


These are *all* compare to a reference measurements. The floor will always be
set by that, one way or another.


Bob just stated a great truth that explains why and how we become 
time-nuts -- in order to characterize an oscillator, you need another 
oscillator that's (preferably 10x) better.  Then you need one that's 10x 
better than *that*, and so on until you have a strontium optical lattice 
clock.  And then you need three of those to cross-check each other. :-)


John
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[time-nuts] Re: HP Z3801A project update

[John Ackermann N8UR]

I recently fired up my old Z3801As and ran across a similar problem. 
Art Sepin helpfully reminded me that the old Motorola receivers' 
on-board oscillators drift with time and after a long power off the 
oscillator may drift so far that it can't lock.  The receiver stores 
calibration data in eeprom and after a long power down that data no 
longer works due to crystal aging, etc.


The symptom is that on power up the receiver doesn't seem to get past 
acquiring and periodically losing one or two satellites.  The cure is 
simple -- just leave it running (connected to an antenna) and come back 
a few hours later.  It should be locked, and will have recalibrated and 
stored new constants in eeprom, so you won't see the problem again until 
after another prolonged power-down period.


John

On 2/24/22 12:14 AM, ed breya wrote:
I found a spare Oncore VP GPS RX unit in the parts department last week, 
and tried it out in the Z3801A. It would not track, even after quite 
some time in use. The original would pop right up almost immediately, 
after warm up.This one had some slight differences from the original, 
around the antenna connector area. It was originally rigged up with the 
rechargeable Li cell option - I remember removing it years ago. I added 
a jumper to carry the external battery supply line in, to make it the 
same as the other. After several swap-outs with the good one, with no 
improvement, I did a direct comparison, and deleted a couple of parts 
from the bad one, making it look "exactly" like the good one. I 
suspected the problem was in the memory chip enable/reset circuit, or 
the left over Li cell charging part.


On this last round of checking, it acted just like before, no good. It 
seemed to operate, and all parts showed OK in SatStat, but it just would 
not track any satellites, even though it seemed to recognize and list 
them. I checked the antenna power and such, and all looked OK.


I was even planning to send a message about this to the group, asking 
for ideas, but finally, after quite some time (maybe an hour), it seemed 
to miraculously come alive, and showed satellite tracking. My theory is 
that either the power up reset wasn't working, or the memory was so 
corrupted (yet remembered enough) from all the different trials and part 
changes, that it just took a while to gradually clear enough of it to 
work. During earlier testing, I found responses to queries like 
"invalid/data corrupted," to paraphrase.


So anyway, it seems to be working right now. I'll have to put through 
some power up and down tests and such, to make sure it really is good to 
go. It's comforting to have a spare of this part, since it appears 
replacements are getting hard to find.


Ed
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[time-nuts] Re: Testing GPSDOs

[John Ackermann N8UR]

That's a very good question, Hal.  If you're talking about stability 
testing, GPSDOs are a challenge because they (can) work well over a wide 
range of measurement intervals -- you can have the short term stability 
of a good OXCO, the mid-term stability of a mid-range Rb, and the long 
term stability of a Cesium standard.


When we measure one quantity (the DUT) relative to another (the 
reference), you want the reference to be significantly better than the 
DUT, or you don't know what you're actually measuring.  A rule of thumb 
seems to be that the reference should be 10 dB better than the DUT.  Any 
smaller difference increases the reference's contribution to the noise.


So, ignoring for a minute the resolution/noise of the measuring device 
(I'll come back to that), to measure the short term stability you need 
an OCXO.  Since a good GPSDO doesn't compromise the short term 
performance of its internal OCXO, that means if the GPSDO has a pretty 
good OCXO, to measure it you need a *very* good OCXO as reference, 
ideally with ADEV an order of magnitude better.


For midterm stability, the GPSDO is at its worst because of the "hump" 
where the drift of the OCXO meets the noise of the GPS.  The worst ADEV 
in a typical GPSDO occurs around 1000 seconds, and the ADEV might be in 
the high parts in 1e12.  The telecom Rbs are in the low 12's to high 
13's at 1000 seconds, so they will work reasonably well.  Or a really 
good OCXO may still be good enough at that tau.


Long term stability is actually the easiest measurement because you can 
use a GPS PPS signal and time interval counter, or even oscilloscope, to 
get good results at tau >10K seconds -- it's easy to compare the GPSDO 
PPS with the GPS PPS.


At short and mid term, the capability of the measurement device is a 
factor.  Few time interval and timestamping counters have a 
resolution/noise floor better than high parts in 1e11 at one second, 
improving at one order of magnitude for each order of magnitude tau.  So 
unless the GPSDO is pretty awful, the time interval counter method is 
the limiting factor for tau out to to somewhere between 100 and 1K seconds.


To do better than that, you can buy an expensive test set like the 
TimePod, or build a "dual mixer frequency difference" test set or the 
"tight PLL" measurement system that's been described here.


So the bottom line is that to fully characterize a GPSDO's stability, 
you probably need three references -- OCXO, Rb, Cs -- (unless you have a 
maser) and two measurement systems -- one for short term, the other for 
mid and long term.


Or... if you build two GPSDO that perform very similarly, you can 
measure one against the other and take the square root of two to get the 
average performance between them.  That might or might not be absolutely 
correct, but as long as the two have similar stability, it will get you 
into the ballpark.


What you *can't* do, though, is rely on any internal measurement, like 
plotting the EFC voltage in the correction loop, to get absolute 
results.  How much the EFC wiggles is meaningless if the wiggles keep 
the frequency where it should be.  It's the output that counts and you 
have to measure that against an external source.


And all this is what happens when you become a time-nut. :-)

John

On 2/20/22 3:41 AM, Hal Murray wrote:


Let's change the discussion a bit.  Assuming I have a GPSDO, home built or
eBay, how can I test it with a limited budget?

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[time-nuts] Re: Phase Station 53100A Questions

[John Ackermann N8UR]

Hi Joe --

The TimeLab software that's used with the 53100A is available from John 
Miles at http://www.miles.io/timelab/beta.htm.  There is a pretty 
comprehensive users guide as well as a couple of app notes there, 
although I don't think any of them document the .TIM file format. 
However, he provides the TimeLab source code so it should be discernable 
from there.


John


On 2/9/22 1:43 PM, Joseph Gwinn wrote:

I will be doing some residual phase noise tests in a month or so
using a 53100A Phase Noise Analyzer (not yet in hand), so I've been
studying the users manual and datasheet of the Microchip 52100A Phase
Noise Analyzer.  I do know the history, starting with Sam Stein
developing the Timing Solutions Corp (TSC) model 5120.

Anyway, some questions have arisen:

1.  Where is the ".TIM" file format documented?  Google fails here,
chasing after some other kinds of .TIM file unrelated to the 5120 and
descendants.  The 53100A users manual does not define the .TIM file
format, or say where to find it.

2.  There will be some debugging required in my test setup, and it
would be very useful if I could independently demodulate the
Amplitude Modulation (AM) and Phase Modulation (PM) components of the
phase noise, and present the low-passed waveforms in voltage versus
time form.  Signals leaking in for other places may well be
recognizable by resemblance of the demodulated AM or PM baseband
waveform to other signals known to exist in the system under test.  I
was thinking that the TIM file may be a start.

3.  Where are the fundamental Principles of Operation documented?
The best I've found so far is a pair of patents by Wayne Solbrig,
US7227346 (Two channel digital phase detector) and US7436166 (Direct
digital synthesizer producing a signal representing an amplitude of a
sine wave), both originally assigned to TSC, and now expired.

Thanks,

Joe Gwinn
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[time-nuts] Re: HP Z3801A project update

[John Ackermann N8UR]

The Z3801As that I have seen have the Motorola Oncore VP 6-channel 
receiver which I think predates the UT+, and all have had the rollover 
issue.


The problem with swapping in another unit is that unless it sufficiently 
imitates the VP at startup, the Z3801A will throw an error and never get 
to locked state.


Of course, many of the old units still work fine except for the rollover 
providing a bogus date, and external software can easily correct that.


John


On 2/5/22 6:19 PM, Bill Beam wrote:

I do not know what Z3801 uses for GPS.
I have several Motorola UT+ GPS modules running.
Older ones with V2 firmware suffer 1024 week rollover failure.
My units with V3.2 and V3.1 do 1024 week rollover correctly.
If you are able to communicate with your device using Lady Heather
she will correct any rollover error and display correct date.

On Sat, 5 Feb 2022 16:36:15 -0500, John Ackermann N8UR wrote:


I think the problem with the Z3801 is that it expects to see specific
handshake things at startup, in Motorola binary protocol.  Dropping in a
random GPS will result in a "No GPS" error.



John




On 2/5/22 12:44 PM, Keelan Lightfoot wrote:

Depending on whoG€™s GPS chipset is being used, a fix might be possible. IG€™ve 
poked around inside the firmware of a number of

Trimble receivers (so far three generations of the 4000 series, and the Placer 
series). Because the first week rollover occurred in 1999,
any receiver made close to that date already has logic to handle a week number 
rollover. Finding this in the disassembled code is usually
easy because they simply add 1024 to the week number, which usually appears as 
an add instruction with a 0x400 immediate operand.
changing a 0x400 to 0x800 will extend the receiverG€™s lifetime another 20 
years. The most difficult part of this is figuring out the
processor used on the receiver, and figuring out how to get the patched 
firmware back into the receiver.


- Keelan


On Feb 3, 2022, at 8:50 PM, Bill Beam via time-nuts  
wrote:

The date issue is a 1024 week rollover failure in the GPS receiver.
A fix is to replace the GPS receiver with one that does not have this problem.

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Bill Beam
NL7F




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[time-nuts] Re: HP Z3801A project update

[John Ackermann N8UR]

I think the problem with the Z3801 is that it expects to see specific 
handshake things at startup, in Motorola binary protocol.  Dropping in a 
random GPS will result in a "No GPS" error.


John


On 2/5/22 12:44 PM, Keelan Lightfoot wrote:

Depending on who’s GPS chipset is being used, a fix might be possible. I’ve 
poked around inside the firmware of a number of Trimble receivers (so far three 
generations of the 4000 series, and the Placer series). Because the first week 
rollover occurred in 1999, any receiver made close to that date already has 
logic to handle a week number rollover. Finding this in the disassembled code 
is usually easy because they simply add 1024 to the week number, which usually 
appears as an add instruction with a 0x400 immediate operand. changing a 0x400 
to 0x800 will extend the receiver’s lifetime another 20 years. The most 
difficult part of this is figuring out the processor used on the receiver, and 
figuring out how to get the patched firmware back into the receiver.

- Keelan


On Feb 3, 2022, at 8:50 PM, Bill Beam via time-nuts  
wrote:

The date issue is a 1024 week rollover failure in the GPS receiver.
A fix is to replace the GPS receiver with one that does not have this problem.

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

[John Ackermann N8UR]

One thing I've seen on several OCXO and small Rbs is that the EFC pin is 
internally wired in the middle of a voltage divider using two fairly 
high value (>10K) resistors between Vref and ground.  That ties the 
varactor to the middle of the EFC range when no external tuning is 
required.  For external tuning, put the EFC pin on the wiper of a pot 
between the Vref pin and ground that has a much lower value than the 
internal divider.  That stiffer voltage will override the internal divider.


John


On 12/23/21 12:51 PM, Andy Talbot wrote:

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
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[time-nuts] Z3805 PPS on comm port?

[John Ackermann N8UR]

I'm replacing a dead Z3801 with a less-dead Z3805 (the Samsung labeled, 
2 each 10 MHz and PPS BNCs, two DB25s).


Has anyone looked into whether that version of the 3805 has a PPS signal 
on the DB25, or a mod to put it there?  I've done some Googling and most 
of the discussion of the Z3805 seems to have been tracking down the 
various versions and not much on using it for NTP.  I can use one of the 
BNC PPSs if necessary, but a signal on the serial cable would be more 
convenient.


Thanks!
John
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[time-nuts] Re: Assessing performance of a frequency counter

[John Ackermann N8UR]

Hi Erik --

Unfortunately, your attachment did not make it through the list.  That 
sometimes happens when you put images "in line" or as HTML content. 
Best thing is to send them as a "real" attachment.


Your question breaks into two pieces: (1) what's the resolution or noise 
floor of the counter, and (2) how good is its internal oscillator?  I'm 
not sure which piece you are most interested in.


1.  To characterize the counter itself, the easiest test is to feed the 
same signal into both the counter timebase and its input (e.g., if 
there's a "10 MHz Out" on the rear panel, connect that to the input). 
That will show you what the counter is capable of -- what's its 
resolution, how stable is the gating, etc.


2.  To characterize the internal oscillator, there are two things to 
consider:


(a) is your reference oscillator stability/accuracy better than the 
counter's over the ADEV "tau" range you're considering?  Ideally you'd 
like to *know* that the reference is at least 10x more stable than the 
device under test. Otherwise you may find yourself measuring the 
reference rather then the DUT.


(b) what's the resolution of your measurement system (see point 1)?  For 
short measurement periods, the counter is likely to be the limiting 
factor because it has a fixed resolution and internal jitter that impact 
short measurements more than long ones.  If you think about it in the 
time domain, a "perfect" time interval counter with 2ns resolution will 
have a measurement floor of 2e-9 at 1 second (2ns / 1 second). At 10 
seconds, it's 2e-10 (2ns / 10 seconds), and this slope continues until 
you hit some ultimate noise floor.   In the frequency domain, the number 
of digits per second implies the same thing.  Most test-bench counters 
probably have a resolution of around 1e-8 to 1e-9 in 1 second.  Some of 
the best are in the 11s, but to get better than that at 1 second 
averaging you are getting into esoteric gear.


Based on all that, ADEV measurements of two good oscillators are 
probably going to be counter noise limited at tau (measurement interval) 
of less than 100 seconds.  Your 0.1 and 0.05 seconds measurements are 
almost certainly limited by the resolution of the counter.


I've ignored some subtleties and gotcha's in the above, but hopefully it 
gives you an idea of how to take and interpret measurements.


John



On 11/8/21 10:53 AM, Erik Kaashoek wrote:

Hi all time-nuts.
Hopefully one of you can provide some advice on how to proceed.
The ambition is to assess the short term (less than 1 hour) performance 
of a frequency counter.
As I understood this can be done by plotting the Allan Deviation of a 
repeated measurement of a very stable source.
Below plot shows the Allan deviation of a 1 hour measurement of the 
10MHz output of an OCXO versus the internal reference of the counter 
with a 1 and 0.1 second gate time.
To be able to better see the gate time impact, short measurements with a 
gate time of 0.05s and 5s have been added.
Temperature variations during the measurement have not been recorded but 
there where some more variations during the 1s gate time measurement.



Are there any conclusions to draw from this plot?
Or should I do a different measurement, or use different representation?
A pointer to a web page or document describing how to do this type of 
assessment would be most welcome.

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

[John Ackermann N8UR]

Check Startech (https://www.startech.com).  They have a range of RS-232 
and similar I/O cards and at least the last time I bought one several 
years ago, the chip emulated a 16550 UART and didn't seem to have more 
jitter than any other serial board I'd tried.


John


On 11/6/21 12:32 PM, Chris Caudle wrote:

On Nov 5, 2021 9:14 PM, Rich Wales  wrote:

  > If we could find PCI or PCIe serial cards

The old Exar product line that MaxLinear acquired might still have PCIe
UART.
https://www.maxlinear.com/product/interface/uarts/pcie-uarts/xr17v352
If you could find those on a card they should be good performance.  I
haven't measured the performance of the UARTs in super IO chips.  Those
would share the upstream connection with a lot of other things, so
might vary in latency.
 -- Chris Caudle
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[time-nuts] Re: Death of a Capacitor

[John Ackermann N8UR]

Indeed, Dana.  Texas Instruments has a nice "designer workbench" for 
their switching regulators like the TPS53400 to help select the 
components.  Using that worked much better than trying to follow the 
data sheet circuits.


I also found that high ESR caps, particularly on the output, are 
important.  And also that you don't want to slowly ramp up the input 
voltage for testing, as the thing will start sqealing if fed with 
voltage way below the output.  You want a quick start at the working 
input voltage.


On 9/27/21 9:56 AM, Dana Whitlow wrote:

One other thing to consider with LDOs:  some types can go  unstable and
oscillate with
the wrong (combination of) capacitors on input and output.  So any time you
design in
an LDO, it is important to closely scrutinize the datasheet and application
note(s) and
heed their warnings.  Unless you like rude surprises, that is :-)

Dana


On Mon, Sep 27, 2021 at 3:16 AM n...@lazygranch.com 
wrote:


I've only designed one LDO as a discrete chip (as opposed to a portion
of a chip where performance just has to be good enough), so I have no
guru status. That said, what spikes pass through a LDO if you do it
right is simply a capacitor divider comprised of the capacitance across
the pass device and the filter capacitor. This is a bit more
predictable with a PFET pass than a PNP.

https://www.analog.com/en/products/lt3045.html

You can see the PSRR after a point (200kHz) rolls off and appears to
flatten. I assume the error amp is out of loop gain. It goes flat for a
while. The idea here is the drive on the pass device is constant
and just maintains the DC voltage. The AC rejection is mostly due to
capacitance ratios. This being a bipolar pass device there is some
secondary effect here where after 2MHz the rejection improves then goes
flat again.

The bipolar pass control is harder than MOS since you are trying to
keep the device out of saturation. That is besides the error amp there
is some sort of anti-saturation circuit controlling the drive on the
pass device.

My thinking here is small signal. If you have huge spikes the
performace even in the region where you do have loop gain can be
nonlinear. For example the error amp can be slew rate limited.

This looks like fine performance given the chip only draws 2.2mA.

Just trawling the interwebs I found this on the TI website:
https://training.ti.com/ldo-architecture-review
At about the 18 minute point he goes into the regions of PSRR.  I poked
around so I can't vouch more all of the talk,

.

On Sun, 26 Sep 2021 18:21:36 -0400
John Ackermann N8UR  wrote:


I got some interesting and unintended data today. I was measuring low
phase noise oscillators using a set of power supplies I just finished
putting together.

The configuration is ~24 VDC into a TPS-53400 switching regulator
that outputs 19.2 volts at up to 3 amps.  That output is fed to
separate regulator boards for each oscillator.  Those boards each
have an LT-1086 linear pre-regulator that drops the input to about 17
volts, which then goes into an ultra-low-noise LT3045A outputting 15
volt to drive the oscillator.  So there are two linear regulators and
lots of caps, inductors, and ferrite beads to isolate the oscillators
from the switching supply.

Due to an error by an assembly tech who will remain nameless, the
wrong electrolytic was installed on the output side of the switching
regulator.  It should have been 33uF at 50 volts, but what got
installed was 330 uF at 16 volts, so it was rated below the operating
voltage. (I was building two boards at the same time, one for 5V and
one for 19.2V. Apart from the voltage setting resistor, the only
difference between the two was the output cap.  I managed to swap
them.)

I tested the system on the bench for 24 hours and everything worked
fine, so I buttoned up the enclosure and started a 4 hour data
capture. About 70 minutes in, the electrolytic became very unhappy
and whatever it turned into caused the switcher to start spewing all
sorts of crud. The regulator kept working (sort of) through the end
of the run, but when I came into the lab the next morning it had shut
down completely and troubleshooting showed that the cap had shorted
at some point after the run completed, and the regulator chip went
into shutdown.

Attached are a plot of frequency showing the whole run with the very
obvious change when the cap failed, and another zoomed view of the
critical moment.  The failure was very abrupt with no visible lead-in.

What I find interesting is that all that crud got through not one,
but two linear regulators, one of which is touted for its extremely
high PSRR (and I did my best to follow the recommended PCB layout for
that chip).  That must have been one ugly 19V line when the cap
went...

John

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[time-nuts] Re: Micrel (Microchip) PL-500 Low Phase Noise VCXO

[John Ackermann N8UR]

On 9/18/21 10:50 AM, Lux, Jim wrote:

LT3042 and LT3045 are your friend here.  Excellent PSRR well up past 10 
MHz.


If you need more current, you can just parallel them.

$6 each for the 3045 from Digikey


For best performance, take a look at the layout suggestions in the 
3042/3045 datasheet, and especially the way the evaluation board is laid 
out.  There's quite a difference between their recommendation and what 
my first uneducated attempt looked like.


John
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[time-nuts] Comparison/evaluation of u-blox timing receivers

[John Ackermann N8UR]

In 2020 I did an extensive evaluation of the timing ability of the 
u-blox LEA-M8F, NEO-M8N, NEO-M8T, NEO-M9N, ZED-F9P, and ZED-F9T.  The 
work was made possible by support from the HamSci consortium 
(https://hamsci.org) under NSF grants supporting HamSci activities.


I was sure I'd posted about the paper on time-nuts, but I can't find any 
record that I did, so this is a belated announcement.  It's available 
for download from


https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf

As BobC says, "Lots of fun!"

John

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[time-nuts] Re: LH "No usable sats"

[John Ackermann N8UR]

IIRC Lady Heather comes with a TCP/IP example configuration that 
connects to a couple of remote Thunderbolts, one of which is in Seattle. 
 Are you sure that's not what you're seeing?


John


On 7/8/21 10:00 AM, Admin wrote:

Chris,

Thanks for your comments.

However, how do you explain that having  changed the longitude (ONLY) 
from my position to the Seattle longitude, many satellites  are now 
received several AMU beyond 1.0?


A 2021-07-08 14:10, Chris Caudle escreveu:


On Thu, July 8, 2021 4:30 am, Admin wrote:


Now, I recognize my mistake. I shouldn't invoke LH


Lady Heather is a very full featured GPSDO management program.  Using 
that

for setting up your GPSDO is rarely a mistake, although it has so many
features it is sometimes difficult to find what you need.


It is not enough to change the TZ and location, as I did.


How did you change the location?  Did you run the self-survey?


seems to me that the signal strenght algoritm continues referencing to
Seattle.


That makes no sense.  Signal strength has no location reference, it is
just a value returned directly from the GPS receiver that is displayed 
and

reported by LH.  There is no algorithm involved.

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[time-nuts] Re: Help ID'ing Frequency Standard (John Ackermann N8UR)

[John Ackermann N8UR]

If anyone who has a 5110A system would like this unit as a spare or 
replacement, drop me a note off list.  It's yours for the cost of 
shipping.  (Only those who can use it as intended need not apply... if 
it were to be dissected and played with, I'd be the one doing it :-) )


John


On 6/7/21 5:52 AM, vilgot...@gmail.com wrote:

This is indeed the frequency standard from the 5110A synthesizer driver. A few 
years ago I scanned and posted the manual for it on BAMA from where you can 
download it. I first encountered this marvelous instrument when I was an EE 
student in the late 1960's and was absolutely blown away by it. I wrote my 
final year thesis in 1970 on frequency synthesizers and the direct synthesis 
technology in the 5100A figured prominently. Compared to the other RF signal 
generators if the day it was way ahead!

Years later I am lucky enough to have a 5100A/5110A combo here and it works 
beautifully. I had to replace an immolated  SRD with a varactor as described in 
the prc68 web page which is a story in itself, and it hasn't missed a beat 
since. The synthesizer has provision for computer control of the push button 
functions so the frequency can be switched very rapidly by software. I have the 
connectors and suitable cable but have never got around to building a suitable 
interface. More modern equipment superseded it but I'm very pleased to have one 
still working.

73, Morris Odell VK3DOC
Locked down in Melbourne, Australia
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[time-nuts] Re: Help ID'ing Frequency Standard

[John Ackermann N8UR]

And (thanks to TVB) -- that's the answer.  It's from the 5110A 
synthesizer driver, circa 1965.


On 6/6/21 1:28 PM, Poul-Henning Kamp wrote:


Magne Mæhre writes:

On 6/6/21 4:22 PM, John Ackermann N8UR wrote:

Looking through the junk box I came upon a metal box labeled:

Frequency Standard
05110-6014
Series 330


This eBay listing lists it as a 1 MHz HP frequency standard


HP 5110 was the driver HP's first "cash-register" synthesizer.

According to the HP5110A manual:

 05110-6014 is "A2 Frequency Standard"

And:

 05110-6081 is "A3 Crystal Filter"

https://bama.edebris.com/manuals/hp/5110a/




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[time-nuts] Re: Help ID'ing Frequency Standard

[John Ackermann N8UR]

Thanks for doing that digging, Magne!  The eBay pics exactly match what 
I have.  I wonder what HP product it was used in... the parts list 
doesn't help with that, unfortunately.  I did a quick search for 
05110-6030 which is what it replaces, and that didn't turn up anything 
on Google.


John


On 6/6/21 11:39 AM, Magne Mæhre wrote:

On 6/6/21 4:22 PM, John Ackermann N8UR wrote:

Looking through the junk box I came upon a metal box labeled:

Frequency Standard
05110-6014
Series 330


This eBay listing lists it as a 1 MHz HP frequency standard

https://www.ebay.de/itm/133759143331?mkevt=1&mkcid=1&mkrid=707-53477-19255-0&campid=5338722076&toolid=10001



This list refers to it as a replacement

http://hparchive.com/PARTS/HP-Parts-List-1973-74.pdf

I couldn't get a solid URL for these outdated ebay pics, so I did a
screenshot:
http://ixocarpa.hytra.org/pub/2021-06-06-zSYSQQhalxs/hp05110-6014.png

--Magne / LA1BFA
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[time-nuts] Re: Help ID'ing Frequency Standard

[John Ackermann N8UR]

Bob, that could be -- the R-1051 rings a bell.  Found this page with 
lots of info: http://www.navy-radio.com/rcvrs/r1051.htm


But the part numbers they show for the frequency standard are very 
different than this one, so I'm not sure.


John


On 6/6/21 11:35 AM, Bob kb8tq wrote:

Hi

Sounds a lot like the sort of thing you would see in an R-1051 or similar 
military
gear from the late 1950’s or 1960’s.  The labeling does not sound right for an
assembly out of a piece of HP gear.

Bob


On Jun 6, 2021, at 10:22 AM, John Ackermann N8UR  wrote:

Looking through the junk box I came upon a metal box labeled:

Frequency Standard
05110-6014
Series 330

It's about 4 1/2 x 5 1/2 x 3 inches and has odd voltage inputs -- -16V, +10V, -12.6V 
along with a terminal for "meter switch" and 2 BNC jacks. There are several 
adjustment points accessible through the box.

Google doesn't turn up anything.  Anyone know what this beast is?

Thanks!
John
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[time-nuts] Help ID'ing Frequency Standard

[John Ackermann N8UR]

Looking through the junk box I came upon a metal box labeled:

Frequency Standard
05110-6014
Series 330

It's about 4 1/2 x 5 1/2 x 3 inches and has odd voltage inputs -- -16V, 
+10V, -12.6V along with a terminal for "meter switch" and 2 BNC jacks. 
There are several adjustment points accessible through the box.


Google doesn't turn up anything.  Anyone know what this beast is?

Thanks!
John
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[time-nuts] Re: Looking for gerber files for a timing GPS board

[John Ackermann N8UR]

The RCB-F9T is definitely something *not* to emulate -- it uses an SMB 
connector for the antenna (which no one else does) and it only has a 10 
pin header (on 2mm, not 2.54mm spacing) that provides only one TIMEPULSE 
output and no EXTINT inputs.  Why u-blox decided that was a good form 
factor is beyond me.


You might take a look at the Sparkfun carrier boards.  They seem well 
thought out.


I've also done a ZED-F9T/P carrier board that I'd be happy to share 
designs for; it's the opposite of the RCB in that it makes *everything* 
accessible.  I'll try to get the design files on my github 
(github.orb/n8ur) later today.


Note that the ZED-F9 chips have multiple ground pads under the chip and 
can't be hand soldered; you'd need to use an oven.


John


On 6/3/21 11:09 AM, John Miller via time-nuts wrote:

Hello Everyone!
I am interested in designing a Pi hat PCB to be compatible with a timing GPS 
PCB design that I have seen used in a number of places. I have found an “okay” 
digram, but if anyone has already made gerbers for this thing, I would greatly 
appreciate it.

- Diagram: https://files.millerjs.org/misc/timing_board_PCB.jpg 

- LEA-M8T using this format: https://files.millerjs.org/misc/LEA_M8T.png 

- Trimble Resolution T: https://files.millerjs.org/misc/trimble_resolution_t.png 


Even the relatively new uBlox RCB-F9T uses it, calling it an “industry standard form 
factor” : https://www.u-blox.com/en/product/rcb-f9t-timing-board 


In the RCB-F9T documentation they have a very nice diagram of the module that surely 
came out of something like Altium, but I can’t find any files to replicate it - 
https://files.millerjs.org/misc/RCB_F9T.png 


Any help would be greatly appreciated, I think one of the biggest things 
holding me back here is that I simply don’t know what this form factor is 
called.

Thanks in advance!

John

PS - My plan, once I get a hat design that works, is to make a mess of these 
PCBs and mail them out to everyone on this list that wants one for the cost of 
shipping.
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[time-nuts] Re: 2nd Run of TimeHats

[John Ackermann N8UR]

I'm interested in one, John

John


On 4/26/21 8:32 AM, John Miller via time-nuts wrote:

Hello everyone,

I’ve seen a number of messages lately that reference the TimeHat boards I put 
together a couple of months ago, with lots of positive feedback, which I really 
appreciate. The first run of boards I did sold fairly quickly, and based on a 
number of emails I have gotten lately there seems to be some renewed interest.

As such, I’m going to order up another batch of PCBs and parts, but I’d like to 
get an idea of how many I need to order to satisfy current demand. The GPS 
modules come from China, so there is about a two or three week wait them, so I 
want to make sure I have enough.

For those not familiar, you can learn more about the TimeHat here:
https://millerjs.org/timehat

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

[John Ackermann N8UR]

Hi Chris --

The difference is that the ublox module is outputting a signal that's 
being generated without much concern for its phase noise.  The digital 
process used creates a  lot of jitter in the edges of the output 
waveform.  It simply wasn't intended for the TIMEPULSE output to be used 
in RF (analog) circuits.


The Bodnar GPSDO follows the GPS output with a synthesizer chip that 
also functions as a "jitter attenuator" which in addition to allowing a 
wide range of frequency outputs also cleans up the input signal.   The 
synth chip output has much lower phase noise than the GPS by itself.


But the synth output is still noisier than a simple crystal oscillator 
and might not be sufficiently good to be multiplied up to the 10 GHz 
range.  That's why others have suggested starting the LO chain with a 
higher frequency XO that is locked (in a narrow loop bandwidth) to the 
GPS signal.  That will result in significantly lower phase noise when 
multiplied up to 10 GHz.


73,
John


On 3/31/21 8:09 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.




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[time-nuts] Re: TAPR TIC: TimeLab mode question (John Ackermann N8UR)

[John Ackermann N8UR]

Hi Christophe and Matthias --

The "TimeLab" mode code was broken with the seemingly-minor change in 
the 2020 version of allowing varyiable numbers of decimal places in the 
results (with the default of 11) I had to rework the TimeLab mode code 
and I screwed it up.


I spent some time on this last week and have implemented a hopefully 
much simpler and cleaner routine that will work properly. 
Unfortunately, I had to go out of town and won't be able to test the 
changes until I get back later next week.  I'll post a note to the list 
when I've done that and a new binary version is available.


Sorry for the regression.

John


On 3/18/21 6:11 AM, Christoph Guenther via time-nuts wrote:

Hi John, hi Matthias

I have the same problem with the channel C output of the TICC with the
latest firmware.
John, we already had direct email contact therefore from the end of April
to early May 2020. I had already tested all available versions in
conjunction with Timelab. Here are the data with version 2017, which in my
opinion works hard-free, but without the improvements in recent versions.

# TAPR TICC Timestamping Counter

# Copyright 2017 N8UR, K9TRG, NH6Z, WA8YWQ

#
# TICC Configuration:
# Measurement Mode: TimeLab 3-channel
Debug

# EEPROM Version: 7, Board Version: D

# Software Version: 20170108.1

# Board Serial Number: 1FBD4D12

# Clock Speed: 1000

# Coarse tick (ps): 1

# Cal Periods: 20

# SyncMode: M

# Timeout: 0x04

# Time Dilation: 2500 (chA), 2500 (chB)

# FIXED_TIME2: 1283 (chA), 1256 (chB)

# FUDGE0: 0 (chA), 360 (chB)

#

# Type any character for config menu

# 


# timestamp chA, chB; interval chA->B (seconds)

1.533148076819 chA

1.533148080106 chB

2.3286 chC (B-A)

2.533148076981 chA

2.533148080163 chB

3.3181 chC (B-A)

3.533148077646 chA

3.533148080380 chB

4.2733 chC (B-A)

4.533148078019 chA

4.533148080491 chB

5.2471 chC (B-A)

5.533148077533 chA

5.533148080328 chB

6.2794 chC (B-A)

6.533148077378 chA

6.533148080264 chB

7.2885 chC (B-A)

7.533148077413 chA

7.533148080327 chB

8.2913 chC (B-A)

8.533148077962 chA

8.533148080590 chB

9.2627 chC (B-A)

Did other time-nuts have found this problem and possibly a solution?
It would be great if John would process the problem again.
Many Thanks

Best regards,
Christoph







Message: 4
Date: Sun, 14 Mar 2021 14:51:58 -0400
From: John Ackermann N8UR 
Subject: [time-nuts] Re: TAPR TIC: TimeLab mode question
To: time-nuts@lists.febo.com
Message-ID: 
Content-Type: text/plain; charset=utf-8; format=flowed

Hi Matthias --

I just took a look at the source and the "Debug" is meaningless...
stupid program error (missing a "break" in a case statement) caused that
to be printed when it shouldn't be.  Easy fix.

But why you're seeing the bogus chC results will take a little more
investigation.  I suspect it's something that broke when I made changes
to the print routine in the latest version.  I'll see if I can figure it
out, and if/when I do I'll push changes to the github repository.

Thanks for letting me know about the problems!

John


On 3/14/21 5:29 AM, Matthias Jelen wrote:

Hello Time-Nuts,

after I finally managed to get my TAPR TIC into a case,
together with two 1PPS dividers, I wanted to give the 3
channel measurement a try. I remember that I successfully
used the TimeLab mode some years ago, but this time I can´t
get it to work. I installed the lasted firmware (binary from
github).

Channel A and B work fine, but the (B-A) doens´t seem to be
calculated - see output from TIC below.

Should the line reading "debug" in the TIC Configuration
make me nervous?

Any help highly appreciated...

Thanks & have a nice weekend,

Matthias

# TAPR TICC Timestamping Counter
# Copyright 2016-2020 N8UR, K9TRV, NH6Z, WA8YWQ

#
# TICC Configuration:
# Measurement Mode: TimeLab 3-channel
Debug
# Poll Character: none
# EEPROM Version: 10, Board Version: D
# Software Version: 20200412.1
# Board Serial Number: A92D670B
# Clock Speed: 10.00 MHz
# Coarse tick: 100.00 usec
# Cal Periods: 20
# Timestamp Wrap:  0
# SyncMode: M
# Ch Names: A/B
# PropDelay: 0 (ch0), 0 (ch1)
# Timeout: 0x05
# Trigger Edge: R (ch0), R (ch1)
# Time Dilation: 2500 (ch0), 2500 (ch1)
# FIXED_TIME2: 0 (ch0), 0 (ch1)
# FUDGE0: 0 (ch0), 0 (ch1)
#

# Type any character for config menu
# 

# timestamp chA, chB; interval chA->B (seconds with 11
decimal places)
1.14527049228 A
0.16498914776 B
2.001chC (B-A)
2.14527049186 A
1.16498914789 B
3.001chC (B-A)
3.14527049132 A
2.16498914799 B
4.001chC (B-A)
4.14527049068 A
3.16498914839 B
5.001chC (B-A)
5.14527049019 A
4.16498914834 B
6.001chC (B-A)
6.14527048961 A
5.16498914850 B
7.001chC 

[time-nuts] Re: TAPR TIC: TimeLab mode question

[John Ackermann N8UR]

Hi Matthias --

I just took a look at the source and the "Debug" is meaningless... 
stupid program error (missing a "break" in a case statement) caused that 
to be printed when it shouldn't be.  Easy fix.


But why you're seeing the bogus chC results will take a little more 
investigation.  I suspect it's something that broke when I made changes 
to the print routine in the latest version.  I'll see if I can figure it 
out, and if/when I do I'll push changes to the github repository.


Thanks for letting me know about the problems!

John


On 3/14/21 5:29 AM, Matthias Jelen wrote:

Hello Time-Nuts,

after I finally managed to get my TAPR TIC into a case,
together with two 1PPS dividers, I wanted to give the 3
channel measurement a try. I remember that I successfully
used the TimeLab mode some years ago, but this time I can´t
get it to work. I installed the lasted firmware (binary from
github).

Channel A and B work fine, but the (B-A) doens´t seem to be
calculated - see output from TIC below.

Should the line reading "debug" in the TIC Configuration
make me nervous?

Any help highly appreciated...

Thanks & have a nice weekend,

Matthias

# TAPR TICC Timestamping Counter
# Copyright 2016-2020 N8UR, K9TRV, NH6Z, WA8YWQ

#
# TICC Configuration:
# Measurement Mode: TimeLab 3-channel
Debug
# Poll Character: none
# EEPROM Version: 10, Board Version: D
# Software Version: 20200412.1
# Board Serial Number: A92D670B
# Clock Speed: 10.00 MHz
# Coarse tick: 100.00 usec
# Cal Periods: 20
# Timestamp Wrap:  0
# SyncMode: M
# Ch Names: A/B
# PropDelay: 0 (ch0), 0 (ch1)
# Timeout: 0x05
# Trigger Edge: R (ch0), R (ch1)
# Time Dilation: 2500 (ch0), 2500 (ch1)
# FIXED_TIME2: 0 (ch0), 0 (ch1)
# FUDGE0: 0 (ch0), 0 (ch1)
#

# Type any character for config menu
# 

# timestamp chA, chB; interval chA->B (seconds with 11
decimal places)
1.14527049228 A
0.16498914776 B
2.001chC (B-A)
2.14527049186 A
1.16498914789 B
3.001chC (B-A)
3.14527049132 A
2.16498914799 B
4.001chC (B-A)
4.14527049068 A
3.16498914839 B
5.001chC (B-A)
5.14527049019 A
4.16498914834 B
6.001chC (B-A)
6.14527048961 A
5.16498914850 B
7.001chC (B-A)
7.14527048907 A
6.16498914865 B
8.001chC (B-A)
8.14527048859 A
7.16498914890 B
9.001chC (B-A)
9.14527048800 A
8.16498914895 B
10.001chC (B-A)
10.14527048751 A
9.16498914913 B
11.001chC (B-A)
11.14527048687 A
10.16498914928 B
12.001chC (B-A)
12.14527048644 A
11.16498914941 B
13.001chC (B-A)
13.14527048602 A
12.16498914966 B
14.001chC (B-A

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[time-nuts] Test message

[John Ackermann N8UR]

Sorry about the intrusion.  New systems always bring new challenges, I 
mean opportunities.

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[time-nuts] time-nuts list migration complete

[John Ackermann N8UR]

If you receive this message, that means the lists.febo.com mailing lists 
have transitioned from Mailman 2 to Mailman 3.


The list server was inaccessible for several hours today while the 
migration was taking place.  If you attempted to post a message today 
and got an "undeliverable email" bounce, please resubmit it now.  The 
list address is still time-nuts@lists.febo.com


We'll be posting further information about how the new system functions 
after we are sure that they are working correctly.


Thanks,
John and Tom
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[time-nuts] Upcoming changes to time-nuts and volts-nuts lists

[John Ackermann N8UR]

The ISP that hosts the febo.com mailing lists is migrating to a new 
version of the Mailman mailing list software.  The switch will happen 
some time around March 11.


Day-to-day list operation won't change, and there won't be any action 
required on your part.  The address for posting messages will remain the 
same and the list archives will still be accessible at the same URL 
(though the archives may be down for a short time as some internal 
configuration changes are processed).


The ISP tells us that they have migrated over 600 lists without any 
issues, but of course there may be glitches, and there will be some 
"look and feel" tweaks that we won't be able to make until after the new 
software is running.  Please bear with us.


After the change I'll post further information about new features and 
differences from the old software.  If you have any questions or issues 
you can contact us at time-nuts-ow...@lists.febo.com which continues to 
be the list admin email.


Thanks,
Tom and John



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Re: [time-nuts] U-blox teaser

[John Ackermann N8UR]

A while ago I tried doing a decidedly non-anechoic measurement with a 
VNA exciter going to a 1500 MHz ground plane and the receiver connected 
to the antenna (with a known delay cable) and I got a similar result, 
but there was enough noise that I didn't think I could nail it down to 
within 10 ns.


I've also measured GPS antenna splitters and they tend to have 20-ish ns 
delays, mainly due to the SAW filters.  I did surgery on an HP splitter 
to remove the filters so it could be used for L1 and L2 and that dropped 
the delay down to only 1 or 2 ns.


So there's definitely lots of stuff to calibrate if you want to get 
accurate time transfer.


John


On 2/26/21 8:02 PM, Michael Wouters wrote:

Typical L1 antenna delays range from 20 to 70 ns.
I know of only one antenna for which a delay is given by the vendor and the
technique used was just to measure the electronic delay ie by injecting a
signal into the circuit. To do it properly, you need a setup in a microwave
anechoic chamber with transmitting antenna etc. The practical difference
may be small though, 1 or 2 ns ( sample of one antenna!).

Cheers
Michael

On Sat, 27 Feb 2021 at 11:42 am, John Ackermann N8UR  wrote:


They're claiming "even better than" 5 ns for relative time, which given
the 4 ns jitter seems at least sort-of reasonable.  But until someone
shows me otherwise, I'm still thinking that getting better than 25 ns
absolute accuracy is a pretty good day's work.

John


On 2/26/21 5:26 PM, Bob kb8tq wrote:

Hi

I can’t think of many antennas (multi band or single band) that claim to

know their

delay to < 5 ns. Simply having a *differential* delay spec of < 5 ns is

quite good.

Same thing with delay ripple, you see specs out to around 15 ns on a lot

of antennas.

None of this is getting you to the actual total delay of the antenna.

It’s a pretty good

bet that number is a bit larger than either of these.

Some of the ripple probably comes out in the standard modeling. I’m not

sure that

the differential delay is taken out that way. Total delay, not taken out

in any obvious

fashion ( at least that I can see). If the F9 has a built in antenna

database, that’s not

mentioned in the doc’s. Any benefit from the corrections would have to

be part of

post processing.

No, that’s not the same as talking about the F9 it’s self doing X ns,

but it would be part

of any practical system trying to get close to 5 ns absolute accuracy.

5 ns *relative* accuracy between two F9’s? I probably could buy that if

the appropriate

one sigma / on a clear day / with the wind in the right direction sort

of qualifiers are

attached.

Bob


On Feb 26, 2021, at 4:27 PM, John Ackermann N8UR  wrote:

It's interesting that they talk about the F9 receivers offering 5 ns

absolute time accuracy.  Does anyone know of tests confirming that, and
what sort of care was required in the setup to get there?


John


On 2/26/21 9:34 AM, Robert LaJeunesse wrote:

FWIW. No detailed content, and a rather quick read. "Five key trends

in GPS".

https://www.u-blox.com/en/blogs/insights/five-key-trends-gps
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Re: [time-nuts] U-blox teaser

[John Ackermann N8UR]

You have to be careful comparing the LEA-M8F with other GPS units.  It 
does have low jitter because the "TIMEPULSE" signal is derived from the 
TCXO which is locked to the GPS time mark.


But their claim of "essentially jitter free" depends on your definition 
of "essentially" -- attached is a comparison of LEA-M8F PPS jitter vs. 
NEO-M8T and ZED-F9T raw, and NEO-M8T and ZED-F9T sawtooth corrected PPS. 
 The M8F is definitely better than the raw M8T and even the raw F9T, 
but the corrected M8T and F9T are both much better than the M8F.  And 
the M8F does *not* have sawtooth correction available.


So, it's a neat implementation and has some applications (basically as a 
modest performance 30.72 MHz GPSDO), but TANSTAAFL.


John


On 2/26/21 5:37 PM, ed breya wrote:
John, if you look back at the recent GPSDO discussion initiated by 
"dandober" in hpaligent keysight group, you'll see a post by Leo Bodnar, 
linking a Ublox model here


https://www.u-blox.com/sites/default/files/products/documents/LEA-M8F_DataSheet_%28UBX-14001772%29.pdf 



I looked it up, and I recall the PPS timing spec is +/- 5 nSec. After I 
studied it some, I replied back


"Thanks Leo, that's a great example of what I've been picturing. This is 
from the data sheet, regarding the PPS output:


"After an initial phase of acquisition the time-pulse becomes 
essentially jitter-free, generated coherently from the built-in 
reference oscillator and guaranteeing an exact number of reference 
frequency cycles between each time-pulse."


It looks like this is an implementation of what we've talked about here 
before a few times, for saw-tooth error reduction. BTW I didn't call it 
"1PPS" above, because it can be programmed for different rates - I don't 
recall what they are.


BTW, did dandober ever sign up here?

Ed



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Re: [time-nuts] U-blox teaser

[John Ackermann N8UR]

They're claiming "even better than" 5 ns for relative time, which given 
the 4 ns jitter seems at least sort-of reasonable.  But until someone 
shows me otherwise, I'm still thinking that getting better than 25 ns 
absolute accuracy is a pretty good day's work.


John


On 2/26/21 5:26 PM, Bob kb8tq wrote:

Hi

I can’t think of many antennas (multi band or single band) that claim to know 
their
delay to < 5 ns. Simply having a *differential* delay spec of < 5 ns is quite 
good.
Same thing with delay ripple, you see specs out to around 15 ns on a lot of 
antennas.
None of this is getting you to the actual total delay of the antenna. It’s a 
pretty good
bet that number is a bit larger than either of these.

Some of the ripple probably comes out in the standard modeling. I’m not sure 
that
the differential delay is taken out that way. Total delay, not taken out in any 
obvious
fashion ( at least that I can see). If the F9 has a built in antenna database, 
that’s not
mentioned in the doc’s. Any benefit from the corrections would have to be part 
of
post processing.

No, that’s not the same as talking about the F9 it’s self doing X ns, but it 
would be part
of any practical system trying to get close to 5 ns absolute accuracy.

5 ns *relative* accuracy between two F9’s? I probably could buy that if the 
appropriate
one sigma / on a clear day / with the wind in the right direction sort of 
qualifiers are
attached.

Bob


On Feb 26, 2021, at 4:27 PM, John Ackermann N8UR  wrote:

It's interesting that they talk about the F9 receivers offering 5 ns absolute 
time accuracy.  Does anyone know of tests confirming that, and what sort of 
care was required in the setup to get there?

John


On 2/26/21 9:34 AM, Robert LaJeunesse wrote:

FWIW. No detailed content, and a rather quick read. "Five key trends in GPS".
https://www.u-blox.com/en/blogs/insights/five-key-trends-gps
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Re: [time-nuts] U-blox teaser

[John Ackermann N8UR]

It's interesting that they talk about the F9 receivers offering 5 ns 
absolute time accuracy.  Does anyone know of tests confirming that, and 
what sort of care was required in the setup to get there?


John


On 2/26/21 9:34 AM, Robert LaJeunesse wrote:

FWIW. No detailed content, and a rather quick read. "Five key trends in GPS".

https://www.u-blox.com/en/blogs/insights/five-key-trends-gps

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Re: [time-nuts] An Other Ublox 8

[John Ackermann N8UR]

Hi Bert --

That's very interesting.  Can you explain a bit more about how you are 
generating the 24 MHz and the role of the Si5351?


I took a close look at the M8F a year or so ago, looking at PPS and the 
30.72 MHz output it makes directly available:


1.  PPS jitter is very, very good compared to other single-frequency 
receivers -- it's about the same as the dual frequency ZED-F9.  However, 
there is no sawtooth correction available to deal with the jitter that 
remains.  When you look at the M8F PPS vs. M8T with sawtooth correction, 
the results are about the same.


2.  The internal 30.72 oscillator seems to be adjusted with a sort of 
PWM control -- it does a bang-bang of about +/- 3e-10 around the true 
frequency, getting the average frequency correct by spending more or 
less time above or below nominal.  (See attached.)


3.  It's an interesting question whether you could get better results 
disciplining an external oscillator, but I think that would depend on 
the DAC sensitivity and whether the PLL time constant was appropriately 
set (see point 4).


4.  One considerable disadvantage to using the M8F as a GPSDO is that 
there doesn't seem to be any way to adjust the loop time constant (or 
even to know what it is).  The only adjustable parameter I've been able 
to find is the EFC sensitivity.




On 1/27/21 7:27 AM, ew via time-nuts wrote:

Over the last couple of years I have looked at the LEA M8F, it is a GPSDO with 
1 pps.  not needing Saw Tooth correction. How ever its frequency output is not 
time-nut friendly. 10 MHz is only 5 E-9. An ebay post showed an 8F board with 
intriguing 24 MHz data. Juerg did some tests with an SI 5351 at 24 MHz. Spec is 
25 to 27 MHz but his tests at 24 MHz shows 10 MHz at 1 E-12.  So I bought some, 
one on the way to Switzerland. Also made some of our heavies aware of our work. 
The seller initially was not going to make more boards but changed his mind. I 
suspect the parts a pulls and he has to make boards to make sure the F8's work. 
My goal is to use it for aging tests always use 24 to 48 hour average testing. 
See my attached results exceed my expectations. 2.39 E-13 mean! Will update 
once Juerg has his unit and uses a SI 5131 to generate 10 MHz.  I can use the 
24 MHz it is a true representation of the GPS signal. Can also use other GNS 
signals. Leave that up to others.                                               
                          Bert Kehren


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Re: [time-nuts] Leakage, tinySA

[John Ackermann N8UR]

You can get custom-made decent quality cables with double shielded coax 
(either RG-316D or RG-142) from China (where else?) for pretty low 
prices.  I am sure the cable isn't mil-spec but I cut a piece open and 
the shield coverage, which is the main thing I worry about at HF 
frequencies, is pretty good.  The connector finish is sometimes a bit 
rough (particularly the BNC bayonet part) but they hold up pretty well 
and I haven't seen any damage from mating them.


The place I mainly work with is "RF Bat" or "SuperBat" at rfbat.com. 
Ask for Amy and tell her I sent you. :-) (no commercial relationship, etc.)


John


On 1/16/21 12:40 PM, Brian Lloyd wrote:

On 1/16/21 04:32, Hal Murray wrote:

The 10 MHz is stronger near coax carrying 10 MHz and next to a 
Z3801A.  I'll
have to try some good cables.  Anybody have a favorite source?  Is 
there a

magic word?  Do I have to specify the type of coax?


Yes. RG400 or RG316. Do NOT use RG58 or RG174. Both RG400 and RG316 are 
double-shielded to reduce leakage. The choice is dictated by length of 
run and physical flexibility required. Mostly I use RG316 cables on the 
bench. For more than a meter or so I go with RG400. You can get either 
type of cable terminated with N, BNC, TNC, or SMA connectors.


All kinds of pre-made cable assemblies using RG316 are available from 
Amazon for surprisingly-low prices. I can't buy the coax and connectors 
for what I end up paying Amazon for completed cables. For RG400 I end up 
making my own cable assemblies.


The LMR cables (Times Microwave and knock-offs) are pretty good too. 
LMR195 is pretty good but not nearly as flexible as the aforementioned 
cables. LMR400 is just too big and inflexible for easy use on the bench.




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Re: [time-nuts] Examples of traditional phase noise analyzers

[John Ackermann N8UR]

Hi Attila --

A really good place to start would be the docs for the HP 3048 phase 
noise system and associated app notes -- 
https://www.hpmemoryproject.org/technics/bench/3048/bench_3048_home.htm 
is a good place to start.  There's a *lot* of description there of how 
the system worked.


In a very brief nutshell, the main approach was to lock the DUT in 
quadrature with a reference at the same frequency and send the output of 
the phase detector to a spectrum analyzer measures the

1 Hz normalized power at various offsets.

John


On 12/17/20 6:02 AM, Attila Kinali wrote:

Good afternoon,

In the process of writing my thesis I stumbled over the problem
that the definition of what phase noise is in IEEE 1139 is a bit
confusing, to put it mildly. After a short discussion with
Magnus, it seems clear to me that I need to have a better
understanding of how phase noise measurement was done in the
past to properly understand what the standard means to say.

I think, I have a decent grasp on how modern phase noise analyzer
work, safe for a few details here and there, where they seem to
try to mimic what the old analog analyzers did.

Before I go on a wild goose chace, I thought I ask here for
advice: Could you point me at as detailed as possible descriptions
on how phase noise analyzers used to work in the purely analog
times? Preferably also as many different approaches as possible.
And, if you are aware of anything that I should have a look at
that might not be obvious to a youngster like me, I would very
much appreciate if you would let me know.

Thanks in advance

Attila Kinali



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Re: [time-nuts] WWVB teensy BPSK early experiments

[John Ackermann N8UR]

Just a thought, Paul --

If the teensy can generate an output that is accurate but jittery, you 
could use a simple PLL to lock a crystal to that with a time constant 
that smooths out the jitter.


John

On 10/31/20 1:47 PM, paul swed wrote:

Hello to the group. Wanted to update the everyone thats interested in
what I have learned so far on the Teensy and audio codec. No complete
solution yet. Much of my experimentation and knowledge has come from Frank
and Chris, who built the complete wwvb AM time receiver. In addition
and important is Johns KD2DB BPSK receiver. There is a reason this matters.

The teensy combination is powerful and somewhat easy to use. (Has to be for
me). So over the week or so it's been getting used to the audio libraries
and how pieces are connected in software and then seeing the results. All
of the base experiments worked very quickly. Simple things like signal
generators, multipliers and filters. Things already accomplished by Chris
in the wwvb AM receiver.

But the question really is what to accomplish?
If its the wwvb bpsk timecode. Simply buy an ES100 and be done.

The interest that I have is a locked reference. Minimizing soldering and
construction. This is the point things get interesting.
A NCO can be created in Teensy but it tends to be low frequency and a
multiple of 60 KHz. Stability sort of isn't. But if it could be created
then a complete frequency reference in the teensy could be accomplished.
That makes for a heck of a low power receiver 1 watt, inexpensive, and
little soldering.
The above path literally follows the old Spectracoms and Truetime direct
conversion receivers.
Have to look at their schematics because they do lock a useful reference.
But that means something external has to come into the teensy. Get the
soldering iron hot.

The other approach is essentially Johns KD2BD receiver in software with an
external reference chain delivering 50KHz and 10 KHz to the teensy. Well
this is getting ugly now because that external chain is made up of a
classical divider 10 MHz to 50 KHz etc. But does give a very nicely locked
useful wwvb reference. Its really a hybrid because it significantly reduces
the soldering required in a true KD2BD receiver but isn't the pure in
a chip solution.

All of this is just for fun because the fact is the GPDSOs we use are
better.
If a receiver is built a natural by-product is the time message. Its just
not my focus or interest.
Much more to learn.

Next steps
Start to reuse the wwvb teensy AM receiver.
Chop out all of the display software. Its all very nice but for me at this
stage gets in the way of understanding things.

With respect to I&Q generation several suggestions have been made. But the
teensy supports multiple multipliers. Sort of thinking, use the sine
wave oscillator and add a 90 degree delay to a second path to a second
multiplier. An alternative inject the delay in the wwvb signal also. How
fine a delay is a serious question.
Much to learn and potholes to fall into.
Regards
Paul
WB8TSL
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Re: [time-nuts] Fwd: cheap frequency extension for timepod

[John Ackermann N8UR]

FWIW, I have done PN measurements at 144 MHz with the TimePod and a 
Frankenstein's laboratory lashup of 80 MHz ULN, HP doubler to 160 MHz, 
HP mixer, and several amp and filter blocks.  As far as I can tell, it 
worked pretty well; at least, I could discern the PN difference among 
several sources, some of them quite good.


Not sure why you are doing two oscillators/mixers, though.  I used a 5 
or 10 MHz reference directly into the TimePod, and the DUT fed through 
the mixer.  No need to increase the frequency of the reference to match 
the DUT.  But if you do want to mix both the REF and DUT channels, 
wouldn't it be better to use a single source to drive both mixers?


John


On 10/17/20 8:59 AM, Gerhard Hoffmann wrote:



I'm trying to make a quick frequency extender for a timepod.


MCL PSC2-1 power divider, 2* SRA-1  7 dBm ring mixer, 2 DIL 80 
MHz-oscillators


The oscillators can drive the ring mixers with just a coupling capacitor 
and 50 Ohm


load limiting resistor. It is still a square wave at the LO port, but 
the diodes in the mixer


would square it up on their own.


When there is no 5V-power, the oscillators are off and the LO inputs are 
connected


to SMA connectors via the normally closed contacts of two reed relays.

Then the whole thing is passive and needs two external synthesizers.


Before I continue with the material I had in the junkbox, a quick 
question to those


of you who have done that already:


Are 7 dBm mixers like SRA-1 good enough or is 17 dBm an advantage worth the

driver amplifiers? The usual signal generators max out at 13 dBm.

I have 2 17 dBm SRA1-WH, but it would require slaughtering something 
unimportant.



How close must the oscillators be in frequency?


Have a nice weekend,

Gerhard, DK4XP





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Re: [time-nuts] Experiment in lowering the TAPR TICC noise floor

[John Ackermann N8UR]

Hi Attila --

Just a couple of corrections -- the "coarse clock" in the TICC runs at 
10 kHz (100 us), not 1 kHz, and therefore the TDC never sees a 
measurement interval longer than 100 us, not 1 ms.


More importantly, the chart in Figure 17 of the datasheet is for 
operation in "Mode 1" of the TDC, which is recommended for time 
intervals of 500 nanoseconds or less.  But the TICC uses "Mode 2" which 
doesn't have that limitation, and Figure 17 doesn't apply.


It would be possible to lower the noise slightly by using a 16 MHz clock 
rather than 10 MHz (but if you look at Figure 15, the improvement 
wouldn't be very great).  That would require reprogramming the PIC 
divider chip, and may some Arduino code changes as well.  (I *think* the 
clock speed is set as a constant in the code that could be changed at 
compile time, but I never tested to see if that would work without 
breaking anything.)


John


On 10/7/20 2:29 PM, Attila Kinali wrote:

On Sat, 03 Oct 2020 10:37:59 +0200
Matthias Welwarsky  wrote:


When I started to look more into the software side of the TICC and especially
the ominous "time dilation" parameter, I set up an experiment where I feed the
same event into both channels of the TICC, for evaluating the sensitivity of
the measurements to this parameter (spoiler: there is a measurable influence
but it's not as critical as I originally thought).


That is to be expected. There are two resons for this:

First, the major limit to the measurement is the noise within
the TDC7200. If you want to get lower, then you have to reduce
this noise. If you look at Figure 17 in the TDC7200 manual, you
will see that the noise of the TDC is highly dependent on the
length of the measurement. Shortening the measurement will
decrease the noise. For this you need to use a higher clock
of the stop signal to measure against, than the 1ms that the TICC
does. But that will not work with the Arduino. You can get around
this if you use a faster µC like an STM32F4. See Tobias Pluess GPSDO
design for an example how to do this.

Second, both inputs of the TICC measure against the same divided
1kHz clock with a modified half-Nutt interpolator. I.e. most of
the measurement time will be common to both input signals and thus
most of the noise seen due to the TDC and the reference clock are
common.


On Wed, 07 Oct 2020 18:34:00 +0200
Matthias Welwarsky  wrote:


the noise is likely not white, but it really depends on what is the dominant
noise source in the system. I guess there is some correlation but still enough
entropy to make a difference. I'll try with different cable lengths next to
see if it makes a measureable difference, but ideally you'd use two TICCs and
two non-coherent reference clocks. But they'd need to be somehow frequency
locked.. You'd need some mechanism that causes enough jitter to break the
correlation. A delay line controlled by some noise source?


Adding noise will not break any correlation. It will only mask it.
I.e., the correlation will pop up once again, when you start
using methods to remove the added noise.

Adding noise helps only if your noise is mostly quantization noise,
then it acts as a dithering mechanism which allows you to average
over the quantisation (and added) noise, which wouldn't be possible
otherwise.


Attila Kinali



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Re: [time-nuts] Experiment in lowering the TAPR TICC noise floor

[John Ackermann N8UR]

That's very interesting, Matthias!  The lower noise floor intuitively 
and the sqrt(2) improvement comes to mind, except that would apply only 
if the two measurements were uncorrelated.  Here, you have a common 10 
MHz reference, so there's correlation.


But... the high-speed ring counters inside the two TDC7200 chips are 
free-running and independent, so when looking at picoseconds, maybe the 
non-correlation requirement is met, at least to some extent.


John


On 10/3/20 4:37 AM, Matthias Welwarsky wrote:

Dear all,

When I started to look more into the software side of the TICC and especially
the ominous "time dilation" parameter, I set up an experiment where I feed the
same event into both channels of the TICC, for evaluating the sensitivity of
the measurements to this parameter (spoiler: there is a measurable influence
but it's not as critical as I originally thought).

While looking at the phase measurements the idea evolved to see if the noise
floor could be lowered by combining the measurements of the two channels.

I have attached the resulting ADEV and the raw channel timestamps. The red
trace is one individual channel, the blue trace is the combination of both
channels. I used Octave to evaluate the measurements.

I used the following commands to get from timestamps to phase data:

A=detrend(cumsum(1-diff(load("chan-a.txt";
B=detrend(cumsum(1-diff(load("chan-b.txt";

The combination of both channels is the an element-wise arithmetic mean:

V=(A+B)/2;

As you can see in the ADEV chart, there is indeed a slight improvement of the
noise floor from 7.8e-11 @1s to 6.8e-11@1s.

Of course this combining doesn't work too well if the noise of the two
channels is correlated, and there's plenty opportunity in this setup for this
to happen. For one, both channels are driven by the same clock source, they
share the same power supply, connected to the same Arduino base board and the
cables from the event source to the channel inputs are of the same length. It
would be interesting to repeat the experiment with a more elaborate setup, for
example using two TICCs with individual clock sources (locked to each other
but not coherent), using different lengths of cables to feed the channels etc.

Regards,
Matthias


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Re: [time-nuts] Phase Noise and ADCs

[John Ackermann N8UR]

On 9/26/20 9:33 PM, John Miles wrote:


One consequence of charge retention is that when the input signal is in the 
first Nyquist zone, meaning below fLO/2, no net frequency translation occurs in 
a sampler.  There is no mixing going on, hence no reciprocal mixing either.  
The sampler's zero-order hold characteristic passes the captured input signal 
straight through to the output.  Because your ADC's front end is a sampler, 
this is the condition that applies when you digitize a 10 MHz input signal with 
a 122.88 MHz clock.  About 13 times per input cycle, a sample of the 10 MHz 
signal is captured and transferred to the hold capacitance for eventual readout 
on the data bus.  Any jitter that's present on the 122.88 MHz clock will be 
transferred as well, but it will be attenuated by 20*log10(12.288) dB because 
each clock cycle is responsible for capturing only about 1/13 of each input 
cycle.


That actually makes a lot of sense.  Thanks very much!

John

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[time-nuts] Phase Noise and ADCs

[John Ackermann N8UR]

We know that phase noise scales with frequency, so if you multiply 
frequency by 10 you get a 20 dB increase in noise.


What I don't fully understand is how that relationship works with other 
than simple multiplication/division.


For example (and my real life concern), if I have an analog to digital 
converter that is clocked at 122.88 MHz and know the phase noise of that 
clock signal, what do I know about the effective phase noise when the 
ADC is receiving a signal at, e.g., 12.288 MHz?


In other words, if I were to measure the phase noise at the output of 
the ADC when fed a high-enough quality 12.288 MHz signal, would I see 
something like the 122.88 MHz phase noise, or something better due to 
the scaling by 10?


Thanks!

John



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Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[John Ackermann N8UR]

I've had good luck with Iota brand chargers for 12 and 24 volt... I 
think they are "DCL" series or something similar.  They are available in 
various amperage and include a smart-charger circuit.  I know Amazon 
sells several models and the prices are in the $100-200 range.  One of 
their selling points is that they are electrically quiet, though I 
haven't done any real tests, and are designed to work as a regular power 
supply (ie, they don't flake out if there's no battery load attached.


John


On 9/25/20 1:22 PM, Bob kb8tq wrote:

Hi

Properly charging batteries is a bit complicated. Why does “properly” matter? 
You want them to be fully
charged, but not damage them in the process. That generally involves some sort 
of variable voltage
for the charging source. If you decide to go with Lithium based parts, you can 
get BMS (battery management)
IC’s that can help with the charging and the balancing ( = you want them all at 
equal voltages) of the cells.

If you look at older gear, this sort of thing didn’t get a lot of attention. 
Most of the backup battery setups
worked poorly as a result.

==

One “cute” alternative is to do a battery + boost converter ( = switcher) 
instead. If the device only operates
during a power outage, noise is not a big deal. Everything that is attached to 
the OCXO output is dead anyway ….

The advantage of a switcher is obviously efficiency. A fully charged “12V” 
LiFePo4 stack could easily be at 14.8V.
Fully discharged it might get down to 10.4V. Allowing for that 1.4:1 output 
ratio with a linear regulator means a
lot of (expensive) battery energy goes up in heat ….

Bob


On Sep 25, 2020, at 11:55 AM, Mark Spencer  wrote:

Pondering the backup power issues for my BVA a bit more,  I am thinking a 
dedicated DC battery bank (maybe 5 or 6 nominal 6 volt batteries in series) 
powering a suitable linear regulator circuit is probably the direction I will 
go in.  I suspect there are more elegant and or simpler approaches but I think 
from my perspective as a hobbyist this is probably the best direction for me.

I like the idea of using a diode arrangement to facilitate changing the power 
source for the BVA.   I expect I will also add some form of over voltage 
protection as well.

I need to ponder the likely voltage drops in the voltage regulator and diodes 
along with the voltages the batteries will provide as they discharge under load.

It seems I have another winter project.

Thanks all for the suggestions.


Mark Spencer
m...@alignedsolutions.com
604 762 4099


On Sep 25, 2020, at 7:16 AM, Magnus Danielson  wrote:

Hi,

On 2020-09-24 23:47, Tom Van Baak wrote:

Next time I power down mine is to integrate a new supply and back-up


May I recommend PowerPole connectors and frequent use of diode-OR. For
details see:

http://leapsecond.com/pages/powerpole/diode-or.htm

I got the inspiration when my Dad was in the hospital and I saw how
they did IV tubes with multiple injection points. It seemed so simple,
clever, reliable. Details [1] and graphic photo [2].

So now I use diode-OR "Y" connectors on all my long-term standards. It
allows me to replace either power supply live without interruption at
any time. Come to think of it, they call it an IV in the hospital. And
here in my lab the I is about 0.18 and V is 24 so my IV is 4 watts. ;-)

That's how we do it in Telecom, but on the 48V level. I managed to drive
my company into do it with 48V all the way to the various boards,
because that way the protection switching out there handled multiple
faults. Also, for some reason there is this line of DCDC converters from
48V to about anything. We kept doing that since, even if the diodes now
been replaced with MOSFETs to lower losses.

If you look into say the 5065A that's how it's done there too.

As for power-pole, those are great connectors, but I need to keep 12V,
24V and 48V in the lab, so I need to get the different color codes not
to interchange them. You usually react when you see a yellow-black
trying to mate with a red-black. So, I recommend folks to do the same.
Once one got started with the Anderson PowerPole, it becomes more and
more a solution.

But yeah, thanks for reminding me that I need to progress on the
power-pole and power supply projects. I'll do that after the PiDP-11
project.

Cheers,



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Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[John Ackermann N8UR]

Seconded!  I don't have that set up on all my oscillators, but plan to 
get there.  I *do* have things set up so I can remove the 24V battery 
bank for maintenance and run directly on the AC power.


BTW, I've standardized on using orange-black PowerPoles for 24V 
(red-black for 12/13.8V, green-black for 5V, etc.).  West Mountain Radio 
has 24V distribution panels with over/under voltage monitoring and 
orange-black connectors.


And, if you use PowerPoles, please spring the $30 and get a crimping 
tool.  It makes life so much easier, and connections so much more reliable.


John


On 9/24/20 5:47 PM, Tom Van Baak wrote:

 > Next time I power down mine is to integrate a new supply and back-up

May I recommend PowerPole connectors and frequent use of diode-OR. For 
details see:


http://leapsecond.com/pages/powerpole/diode-or.htm

I got the inspiration when my Dad was in the hospital and I saw how they 
did IV tubes with multiple injection points. It seemed so simple, 
clever, reliable. Details [1] and graphic photo [2].


So now I use diode-OR "Y" connectors on all my long-term standards. It 
allows me to replace either power supply live without interruption at 
any time. Come to think of it, they call it an IV in the hospital. And 
here in my lab the I is about 0.18 and V is 24 so my IV is 4 watts. ;-)


/tvb

[1] https://en.wikipedia.org/wiki/Intravenous_therapy
[2] https://en.wikipedia.org/wiki/File:ICU_IV_1.jpg


On 9/24/2020 12:38 PM, Magnus Danielson wrote:

Hi Tom,

I second this, these oscillators you want to power up and just leave for
them to settle and then keep powered.

Next time I power down mine is to integrate a new supply and back-up
batteries, which can be a recommended little exercise. Currently only
the H-maser is on battery backup.

Cheers,
Magnus

On 2020-09-24 01:25, Tom Van Baak wrote:

James Robbins wrote:


Oscilloquartz BVA has been sold.

To the time nut who ended up with this BVA -- do not worry if it looks
like it is broken when you power it up. These oscillators take their
time to warm up. Here is a test I did last year on a similar BVA
oscillator:

"Oscilloquartz 8600-series OCXO warm-up"
http://leapsecond.com/pages/osa-warm/

/tvb


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Re: [time-nuts] GPSDO "accuracy"

[John Ackermann N8UR]

Hi Donald --

Over a 10 second interval, you're really looking at the short term 
stability of the oscillator in the GPSDO, which could vary be several 
orders of magnitude.  The GPS component will set the nominal frequency, 
but the noise around nominal will be that of the OCXO.


A quite good GPSDO, like a Z3801A or Trimble Thunderbolt, can show short 
term stability in the 12s, but not all will be that good.  An 
inexpensive unit like the Bodnar might be more like 1 PPB.


John


On 9/9/20 7:04 PM, donald collie wrote:

Can any list member please tell me the "accuracy" that can be expected from
a typical GPSDO
over, say, a 10 second interval? I have several measuring instruments
connected to my Trimbal GPSDO, and would like to know what to expect. At
the moment I am guessing about 1 to 2 parts in 10^12.
Thankyou,Donald
Brett Collie


Virus-free.
www.avast.com

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[time-nuts] Fwd: [TangerineSDR] ARRL/TAPR DCC in 10 days

[John Ackermann N8UR]

The annual Digital Communications Conference that TAPR co-sponsors with 
the ARRL is coming up on Sep. 11 and 12 and will be available on the 
Interwebs.


I'm forwarding the announcement here in an act of shameless 
self-promotion because I'll be doing a presentation on the timing 
performance of current generation u-blox GPS modules.  It might be of 
interest to some here.


Conference and registration info is below.
John

 Forwarded Message 
Subject:[TangerineSDR] ARRL/TAPR DCC in 10 days
Date:   Tue, 1 Sep 2020 11:00:28 -0400
From:   Stan Horzepa via TangerineSDR 

The 39th Annual ARRL and TAPR Digital Communications Conference (DCC) 
will be a virtual conference on September 11 and 12, using Zoom video 
communications and YouTube video-sharing platforms.


Registered DCC attendees participating via Zoom will be able to interact 
with presenters and other attendees via a chat room as well as raise a 
virtual hand to ask questions. Click here 
 to register (you 
don’t need a Zoom account to register).


Non-registered DCC attendees can watch the live stream for free on 
YouTube, however, non-registered DCC attendees will not be able to ask 
questions or chat. No registration is required for YouTube access (the 
YouTube URL will be announced and posted on this webpage preceding the DCC).


DCC registration is free for TAPR members and $30 for non-members. 
Members receive a 100% discount at checkout. Click here 
 to register.


Non-members who would like to join TAPR and receive the free DCC pass 
can simply add TAPR membership and DCC registration to their shopping 
carts. After checkout, they will receive the free DCC pass when their 
membership is processed.


-- 
TangerineSDR mailing list
tangerine...@lists.tapr.org
http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org

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Re: [time-nuts] TICC TAPR and TimeLab

[John Ackermann N8UR]

Some answers below.

John

On 7/3/20 10:54 AM, w8ycm--- via time-nuts wrote:

New guy here needs help using the TAPT TICC and Timelab software

  


The TICC documentation, I am sure, is sufficient to those in the community,
but to someone who has only lurked around the edges, there are a few
questions I have.   I suspect some are obvious, and some others of no
consequence, so here goes:

M   Measurement ModeT   default T
S   clock Speed  (MHz) 10.00   default 10
C   Coarse Clock Rate (us)  100.00  default 100
P   calibration Periods   20  default 20
T   Timeout0x05default 0x05
Y   sync:  master / slave   M   default M
E   trigger EdgeR R default R
D   time Dilation2500 2500   default 2500
F   Fixed Time20 0 default 0
G   fudge00 0 default 0

(1) In  M (Measurement mode), what is the use for the “  L TimeLab
interval mode “?  Should it only be used with Timelab? If “Yes” skip  and b:


"TimeLab" mode is a special configuration for doing three-corner hat 
measurements.  Don't use it unless you know what those are, and why they 
may not work. :-)




a.In  M (Measurement mode), the  functions of the T/P/I,
modes are reasonably obvious,

   but with ones should be used with Timelab to compute Allan Deviation.




TimeLab works in "normal" fashion with either time interval, or one or 
two channel timestamp, data.  Of course, you need to configure TimeLab 
to match what's coming out of the TICC.



b.Are any of the Measurement modes of particular use in
other Timelab functions?


You could probably kludge the period data mode to work with TimeLab, but 
that one would not normally be used for a typical stability analysis. 
It shows the period (inverse of frequency) of the input channel.



All of the following questions could be answered with, "Leave them alone 
unless you're doing hardware or software development" but I'll try to 
provide some info.  To make much sense of it, you would need to study 
the TICC schematics and source code, and also spend some quality time 
with the TDC7200 chip data sheet.



(2)  In  M (Measurement mode), what does one do with “ D Debug
mode”?


Nothing, unless you're working on the code.  That mode outputs the raw 
data values used within the system and is for testing purposes.




(3)  What is the rational for selecting a  particular “Coarse Clock
Rate” value?


The Coarse Clock needs to match the hardware configuration.  Unless 
you're changing the TICC hardware (or the PIC divider chip), don't 
change this.




(4)  What is the rational for selecting a particular  “calibration
Periods” value?


Trade-off of measurement speed vs. calibration accuracy.



(5)  What is the rational for selecting a particular  “Timeout” value?


Trade-off of measurement speed vs. proper operation.


(6)  What is the rational for selecting a particular  “time Dilation”
value?


There's a small non-linearity in the TDC7200 chip output and this value 
compensates for that.  It's determined experimentally and seems to be 
about the same in all units.



(7)  What do the “Fixed Time” options do, and why?


It's an experimental configuration option that in theory could provide 
slightly less jitter in the results.  We haven't proven whether or not 
it actually does.



(8) What do the “Fudge” options do, and why?


These allow you to "trim" the results to account for slightly differing 
cable lengths or path delays.  By experimental adjustment, you can use 
there to match the channel A and channel B results to compensate for 
these variations.  It's not normally necessary to mess with them.


John

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Re: [time-nuts] differences among TADD-2, TADD-3, PulsePuppy, TADD-2 mini

[John Ackermann N8UR]

What, the names aren't self-explanatory? :-)

TADD-1 -- broadband (0.1 - >30 MHz) analog distribution amplifier
TADD-2 -- 5/10 MHz 6 channel divider (1k to 1 PPS)
TADD-2 Mini -- 1/2.5/5/10 MHz to PPS single channel divider; very tiny
TADD-3 -- 6 channel PPS distribution amplifier (no divider)

PulsePuppy is an oscillator carrier with divider and, assuming it's
fitted with 10 MHz oscillator, can provide a jumper-selected 10 MHz, 100
PPS, 10 PPS, or 1 PPS output.

All the dividers use versions of TVB's PicDIV code.

John

On 6/2/20 1:39 PM, jimlux wrote:
> 
> I'm trying to distinguish among all these options..
> 
> TADD-2 and TADD-3 are 5/10 in, multi out  - 3 is just a new 2?
> TADD-2 mini is 1,2.5,5,10 in and one out
> PP  has a way to solder a packaged oscillator on the board, lower power,
> and puts out 1, 10, and 100pps.
> 
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Re: [time-nuts] OCXO Support Board

[John Ackermann N8UR]

On 5/14/20 5:07 PM, Bob kb8tq wrote:

> No, the cheap board houses don’t check for this stuff. They just build and 
> send it
> back. If there’s a gotcha, you get it on the board. 

I was pleasantly surprised last week when Seeed Fusion contacted me to
point out a problem where two vias were too close together (by a couple
of thousandths).  They asked if they could reduce the hole diameters
slightly to correct.  I agreed, they made the change, and the boards are
with DHL right now.  So they do have a process to kick at least some
issues to human beings for resolution, rather than just rejecting the job.

BTW, two things I've learned from my current project:

1.  Seeed claims that they can do down to 4mil trace width and spacing,
and down to 0.2mm holes, but those add extra charges.  For their $4.95
for ten boards deal, the minimums are 6mils and 0.5mm holes (why can't
they pick one dimension system for the specs???)  Go smaller and the
price goes up 10x or more.

2.  Where I had the clearance problem was on a USB C connector.
Whatever advantages they have, they are a pain to route and solder.  The
one I used (which seems fairly common) has both through hole and SMT
pads, and the space to get all the signals lines connected and routed is
very, very tight.  The smaller trace and hole sizes would have made the
job easier, but I wasn't willing to jack up the cost for that.

John



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Re: [time-nuts] Alfred Loomis - an early time nut

[John Ackermann N8UR]

Check out "Tuxedo Park" by Jennet Conant -- it's all about Loomis and
his very interesting life.

John


On 5/12/20 7:24 PM, Bob Martin wrote:
> Does anyone know about Alfred Loomis and his
> early precision time measurements?
> 
> According to the article in the link below, he
> was also involved in WWII radar and the creation of Loran.
> 
> http://www.ob-ultrasound.net/loomis.html
> 
> bob
> 
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Re: [time-nuts] GPS antenna splitter recommendation?

[John Ackermann N8UR]

So, being a heartless butcher I opened up one of the HP 8-port GPS
splitters (forget the number) and removed the sawtooth filters so the
unit would pass both L1 and L2.

I found that to bridge the filter pads even the smallest cap I had (I
think 7pf) caused problems.  I ended up making "gimmick" capacitors out
of a couple of inches of #26 magnet wire twisted together.  That has
worked well; there's a little difference in gain between ports, but not
enough to worry about.

John


On 4/30/20 11:39 AM, Bob kb8tq wrote:
> Hi
> 
> At 1.5 GHz something like a 50 to 100 pf NPO is probably the best
> pick for a blocking cap. 
> 
> Why? It does a fine job at the intended frequency. It acts as a high pass
> down lower where lightning energy is a bit higher ….
> 
> Bob
> 
>> On Apr 30, 2020, at 9:25 AM, Ben Hall  wrote:
>>
>> On 4/30/2020 7:33 AM, Bob kb8tq wrote:
>>> Pretty much all the Mini Circuits splitters will pass DC.
>>
>> Hi Bob and all,
>>
>> That's absolutely correct.  Something you might consider is what I did - I 
>> got a pair of Mini-Circuits ZC6PD-1900W's cheap on the e-place. 
>> Frequency-wise and loss-wise, not perfect, but good enough for me. Problem 
>> was, like you note, all the ports are DC-pass, and I wanted only output port 
>> 1 to be supplying DC to the antenna.
>>
>> So I opened mine up, carefully cut the trace going to outputs 2 and up, and 
>> bridged them with, IIRC, a 0.01uF ceramic capacitor to block DC.
>>
>> Before and after plots on the VNA at work showed very little increase in 
>> loss after the mod compared to before the mod.
>>
>> Just some food for thought.  :)
>>
>> thanks much and 73,
>> ben, kd5byb
>>
>>
>>
>>
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Re: [time-nuts] TICC / TimeLab fun

[John Ackermann N8UR]

Hi Chris --

Two possibilities:

1.  Make sure you have TimeLab set for the correct mode (timestamp vs
time interval), for two channels, and for the right scaling factor (for
timestamps, scale by 1).  Any of those can cause 1e0-type results.

2.  If the two channels have timestamps that are within a few
nanoseconds, there can be a crossover where the channel sequence doesn't
maintain strict "ABABABABAB" order.  TimeLab expects that order and if
you get something like "ABBA" apart from bad '80s music you also get bad
readings.

The easiest way to avoid the problem is to split the TICC output stream
into the two channels and then feed them into TimeLab separately.  It is
possible to do that and still get real time readings by using the "Read
Streaming ASCII file" TimeLab acquire option, but it takes a little
finagling to do it.

[ BTW -- this is not really a "bug" in either the TICC or in TimeLab,
it's just the way things work.  I've spent much time thinking about
addressing it in the TICC code, but there's no sure-fire fix that works
across all possible operating scenarios. ]

Hope this helps.

John

On 4/29/20 1:12 PM, Chris Burford wrote:
> I'm trying to characterize a pair of GPSDO units using the TICC / TimeLab.
> The issue I'm having is when both GPSDO units are wired simultaneously to
> the TICC the resulting ADEV plot looks a little strange, beginning at
> 3.74E-1. Both GPSDO units are referenced against my PRS-10 Rb for the clock
> source.
> 
> If the GPSDO units are wired individually to chA then all seems fine and the
> plot begins with a more anticipated value of about 1.4E-8. I'm at a loss as
> to where to proceed from here to get both units characterized
> simultaneously.
> 
> Thanks for the assistance.
> 
> Chris
> 
> 
> 
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Re: [time-nuts] Vaperware Parts and pulse stretching circuits

[John Ackermann N8UR]

I know this is getting off topic, but one more comment from me.

Solder flux is really important.  I use nothing but "no clean" type for
SMT work -- very thin 0.015 no-clean solder (63/37 PbSn while I still
can), and a bottle of liquid no-clean flux with a needle dispenser.  I
make sure the work is wet with flux before I start, and add as needed.

Note that "no clean" isn't strictly that -- it leaves a residue, but it
is supposedly non-conductive and doesn't *need* to be removed.  But for
aesthetics, when I'm finished I dip the board into a bath of isopropyl
alcohol and apply a toothbrush.  Sometimes after that a distilled water
rinse is good if you're a perfectionist.  If nothing else, the cleaning
makes inspection easier.  (But use care... some components, like the
uBlox GPS modules, warn against immersion in any kind of liquid.)

John


On 4/25/20 12:00 PM, Burt I. Weiner wrote:
> John,
> 
> What you and I do for SMT type IC's is pretty much the same.
> 
> Several years ago the wife of a close friend was in the re-work business
> with a home setup.  What she taught me was to first line up one of the
> corner pins and tack solder it down.  Then do the opposite corner,
> center the pin and tack solder it down.  Do that with all four corners,
> taking care that the pins are properly centered before tack soldering
> them.  Once you've got the four corners properly in places, then go and
> center the remaining pins; depending on the size of the chip, this might
> require either a microscope or very pointy eyes.  Once all the pins are
> properly centered, flow solder over all the pins.  At this point
> shorting all the pins together is not a problem.
> 
> Once you've flowed soldered across all of the pins you need to slurp up
> all of the solder with a fine pitch SolderWick.  If done correctly you
> will wind up with all of the pins properly soldered and centered.  The
> next step is to remove and flux using Denatured Alcohol.  Once that's
> completed, inspect for any possible shorts or pins in the wrong place. 
> If all looks good, cover your eyes and power it up.
> 
> I have done the above one time on my own and to my utter amazement it
> worked!
> 
> Burt, K6OQK
> 
> 
> At 04:41 AM 4/25/2020, you wrote:
>> I do have a microscope (cheap Chinese unit, maybe $400 with
>> articulated arm and the works) and it does make things much easier. 
>> But as long as you can see the work, you can do the job. It's not that
>> hard to do small pitch parts.  I usually do the best I can soldering
>> individual pins, knowing their will be bridges, then clean up with
>> solder wick and *lots* of no-clean flux.  You can never have too much
>> flux.  I've found a 1.6 mm chisel tip is a good all around size for
>> SMD work, though I have a 0.8 mm chisel available for when things get
>> tight. The hardest part is getting the first couple of pins tacked
>> down so the part is square on the pads
> 
> Burt I. Weiner Associates
> Broadcast Technical Services
> Glendale, California U.S.A.
> b...@att.net
> K6OQK
> 
> 
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Re: [time-nuts] Vaperware Parts and pulse stretching circuits

[John Ackermann N8UR]

Hi Perry --

The circuit in the FatPPS is really simple and would be easy to duplicate.

Frankly, the reason we had to significantly increase the cost is because
we provide the board fully assembled (it's all surface mount parts), and
with the low volume we've had in the last few years, the per-unit
assembly cost has gone way up.

John


On 4/24/20 7:19 PM, Perry Sandeen via time-nuts wrote:
> Learned Gentlemen,
> Several poster wrote:
> TAPR offers a FatPPS kit to stretch the pulse out, and it looks likethey're 
> back in stock. I have one but haven't assembled it 
> yet.https://tapr.org/product/fatpps-pulse-stretcher/
>  OK no problemo. But it's $55. It's probably a great device, but does this 
> application warrant such expense?
> I looked up *pulse stretcher circuits* and found over a dozen inexpensive 
> circuits.
> 
> 
> DRV8662and is available from Digikey for $3.35. It is a small-pitch 
> device(0.5mm) but not impossible to solder.
> 
> RV-3028 is 3.2x1.5 mm in size, 1.5ppm, additionally trimmable, 45 nAstandby 
> current, under $3 USD in price and in stock at Mouser andDigikey. 
> 
> Aswonderful as the DS3231 is, there is a newer chip from Micro Crystalthat is 
> smaller, more accurate than the DS3231M, much cheaper, anddraws less power
> 
> These three chips fall into the *Vaperware Parts* category. Yes, they are 
> great chips and I don't mind someone posting their advantages.
> I believe It is a bit disingenuous to say: *It is a small-pitch device but 
> not impossible to solder*.
> Really?  If you've dropped $750 to $1K for a stereo microscope and other 
> specialized soldering equipment then you can probably do it without too much 
> difficulty.  Or some may access to such specialized equipment.
> But for us *Po Folks* hobbyist we have to stick with older but larger parts.
> Now if there was a service where you could order the part soldered to a 
> breakout board with .1 inch breakout pins for say, $20 then using many of the 
> latest chips would be feasible.  But until then I believe 99.9 percent of us 
> have to find a commercial product or some other workaround.
> Regards,
> Perrier
> 
> 
> 
> 
> 
> 
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[time-nuts] App Note describing the "multi-TICC" 8 channel timestamping counter

[John Ackermann N8UR]

The TICC hardware design has features that make it possible to
synchronize and run several units from a common clock, allowing creation
of 4, 6, 8 or even larger multi-channel timestamping counters.  The TICC
firmware has sort-of supported this capability as well.  I think a
couple of people may have tried it, but I haven't had any feedback on
their results.

A recent project here led me to build an 8-channel "multi-TICC" and
update the firmware to match, and I've documented how it's put together
and how it works in the first-ever TAPR Appplication Note.  It's a bit
too large for the list, but you can download it from:

https://github.com/TAPR/TICC/blob/master/multi-ticc/multi-TICC_App_Note_2020-01.pdf

and probably other locations later.

As a teaser, attached is a plot showing ADEV of 8 GPS units measured
simultaneously for over 500K seconds vs. a Cesium standard.

The multi-TICC currently is *not* available as a TAPR product. The
material cost is significant, as is the labor required for assembly and
testing. We suspect that this is very much a niche device, and TAPR
can’t justify the financial and human resources required to stock it as
a completed item. However, we know of sources potentially willing to
build units to order. Please contact me if you’re seriously interested
in that.

Enjoy!

John

PS -- the system includes a Python server script running on a Raspberry
Pi.  If someone would like to help me robustify that code, I would
appreciate that very much.
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Re: [time-nuts] Phase measurement of my GPSDO

[John Ackermann N8UR]

It's a feature not a bug. :-)

I was going to address possible out-of-sequence output in this update,
but after lots and lots of thinking and experiments, and discussions
with a few bright folks on this list, I've come to the conclusion that
there is no 100% reliable way to do sample ordering within the TICC,
unless you provide it with additional information about the test
configuration and guarantee the integrity of the incoming signals.

It seems trivial to just sort samples if you make some assumptions: that
both channels are providing data at the same rate, that neither one will
ever glitch, and that both of them will always be present.

But... what if chA is at 1 PPS and chB is at 10 PPS?  What if you're
only measuring one channel?  Those could be solved by telling the TICC
what the configuration is, or doing some sort of signal analysis at the
start of the run, but that adds a lot of complexity to the code (and
operation).

And then, what if chA goes away during the measurement but chB keeps on
ticking?  What if one of the DUTs glitches so there is a missing sample?
 Or an extra one?  Those occurrences will screw up any attempt at
sequencing.

Apart from that, there is a subtle quirk in the TICC architecture
(thanks to TVB for spotting this) -- because of the way the TDC7200 chip
works, if a sample arrives on each input nearly simultaneously, you
cannot tell which one occurred first until *after* both samples are
processed.  Because there are non-deterministic latencies in the
processing loop, there can be a situation where, for example, chB has a
slightly earlier timestamp but is processed after chA. So you can get an
output file where the timestamps are not always in ascending order.

I was originally going to say that addressing this particular problem in
the firmware would be sensitive to all the gotchas mentioned in the
previous paragraphs.  But as I was typing I realized that there might be
a fairly simple way to guarantee that the output is at least in
increasing-timestamp order. That doesn't guarantee chA/chB sequencing,
though.  I'll play with this idea when I get a chance.

But taken all together, it is *much* easier to sequence the data outside
the TICC than within it.  Something like:

tail -f /dev/ttyUSB0 | tee >(grep "chA" > chA.dat) >(grep "chB" > chB.dat)

should do it. (Check the syntax; I didn't actually try this out but have
used the idea in the past.)

John
(whose hair, at least what's left of it, is more gray after having
wrestled with this for the last several months)


On 4/14/20 1:10 PM, Bob kb8tq wrote:
> Hi
> 
> Have you tried it with the latest firmware update?
> 
> I’ve never seen the problem here.
> 
> Bob
> 
>> On Apr 14, 2020, at 1:05 PM, Taka Kamiya via time-nuts 
>>  wrote:
>>
>> Bob, Tobias, et al
>>
>> TICC (TAPR) isn't problem free either.  It has a tendency to get TimeLab 
>> confused on data from port A and port B.  The data stream has identifier on 
>> them but TimeLab discards it.  Then it expects A and B comes alternately.  I 
>> communicated with both developers but for time being, the solution is to 
>> record the data and inspect. 
>>
>> --- 
>> (Mr.) Taka Kamiya
>> KB4EMF / ex JF2DKG
>>
>>
>>On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq  
>> wrote:  
>>
>> Hi
>>
>> If the phase slips are “well behaved” they can be handled. The problem 
>> with a dual channel setup is that they are often not well behaved.  The
>> period is 100 ns so a frequency drift of 1 ppb will put you in trouble in 
>> under 2 minutes. 
>>
>> The only real answer is to do it properly and time tag the two outputs. 
>> Any other approach will get you yelling and screaming at the test set. 
>> Playing with two counters and not time tagging is in the “yelling and 
>> screaming” category as well. 
>>
>> Get a TAPPR TICC if you really want to do a DMTD. 
>>
>> Of course you *could* just use a single mixer. That works fine with the 
>> counter you already have. It will give you an A to B test just like a 
>> DMTD. The only limitation is the need to tune at least one of the 
>> oscillators 
>> in each pair. 
>>
>> There is no requirement that you tune only one. If both are tunable, 
>> you could tune one to the high end of its range and the other to the low 
>> end. 
>> With most OCXO’s, there is plenty of tune range. 
>>
>> Bob
>>
>>> On Apr 14, 2020, at 2:23 AM, Tobias Pluess  wrote:
>>>
>>> Hey Bob
>>>
>>> ok now I see your point! you talk about the phase spillovers. Timelab and
>>> also Stable32 can correct for them, so it shouldn't be a problem, right?
>>>
>>> But I agree, if you cannot correct for the spillovers it becomes even more
>>> difficult.
>>>
>>>
>>> Tobias
>>>
>>> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq,  wrote:
>>>
 Hi

 The gotcha with using a conventional counter (as opposed to a time tagger)
 is that you never know when things are going to “slip” past each other.
 When they
 do you get a major burp in

[time-nuts] Announcement: New TICC firmware available

[John Ackermann N8UR]

I've just released an update to the Arduino firmware for the TICC; the
new version is 20200412.1.  It, along with all the TICC source code and
documentation, is available at:

https://github.com/TAPR/TICC.

In addition to a few bug fixes and cleanups, there are a couple of more
noticeable changes that are discussed in the LATEST_CHANGES.txt file.

One item changes current behavior: data is now output with 11 decimal
places (10 ps resolution) instead of the previous 12 (1 ps resolution).
The last digit was simply noise, and it contributes to an esoteric issue
I don't need to go into here.  So you'll see one less decimal place in
the output, but the useful resolution hasn't changed.

To install the new firmware you can use the Arduino IDE, but that's a
lot of download and hassle if you're not interested in actually working
with the source code.  As an alternative,

https://github.com/TAPR/TICC/tree/master/binaries

has hex files of the new version (TICC.ino-20200412.1.hex) that can be
uploaded directly into the TICC via USB, as well as install tools for
doing so under Windows and Linux.  These don't require installing the
Arduino IDE.

NOTE: TICC units currently shipped by TAPR still have the prior firmware
version installed; unfortunately it's not feasible for us to update the
firmware before shipping.

Enjoy!
John


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Re: [time-nuts] Phase measurement of my GPSDO

[John Ackermann N8UR]

Hi Tobias --

Several years ago, with a bunch of help from Bruce and John Miles, I did
a very high isolation, very low phase noise buffer amp design that TAPR
sold for a limited run.  It's built with surface mount parts but they
are user-friendly sized.

Details and schematic are at https://www.febo.com/pages/TNS-BUF.  The
TAPR product page and link to manual are at
https://tapr.org/product/tns-buf-isolation-amplifier/

It is possible we might still have some bare boards available; I need to
check on that.  It's also possible that if there's enough interest, we
could do another small production run (we'd need at least 25 orders to
make it economically feasible).

John


On 4/3/20 8:09 PM, Tobias Pluess wrote:
> Hi Bruce
> 
> the NIST design you mentioned - do you mean that publication where they
> used 2N's for a diode ring mixer? if so I can perhaps build this as
> well because I think I even have some 2Ns in my home lab :-)
> Concerning the RPD vs. TUF mixers - what is the actual property which makes
> the RPD "better" than the TUF?
> 
> Thanks,
> Tobias
> 
> On Sat., 4 Apr. 2020, 02:01 Bruce Griffiths, 
> wrote:
> 
>> Tobias
>>
>> That would certainly work for a start and have a better performance that a
>> counter front end.
>> The performance can be estimated using the tools at the link Bob provided.
>> Lower noise opamps will improve the performance somewhat.
>> A wider bandwidth opamp with a higher slew rate may be useful for the
>> final stage of a Collins style zero crossing  detector.
>> The RPD series of phase detectors will have better performance than the
>> TUF-1.
>> For the ultimate performance at low offset frequencies one can build a
>> mixer using diode connected BJTs as NIST have done.
>>
>> Bruce
>>> On 04 April 2020 at 12:38 Tobias Pluess  wrote:
>>>
>>>
>>> Hi Bruce
>>>
>>> I have some TUF-1 mixers in my junk box as well as some JFET OpAmps
>> AD8626.
>>> So, if I connect the OpAmps appropriately with some diode limiters as you
>>> suggest, would you say this would give an acceptable DMTD system?
>>> If so it sounds like something that can easily be built on a breadbord or
>>> in manhattan style, as Bob already mentioned. That would be really cool.
>>> I think a while ago I asked a question which goes in a similar direction
>> -
>>> which mixers are better as phase detectors (to build a PLL for phase
>> noise
>>> measurement) and which ones should be used as actual mixers (like in this
>>> case).
>>>
>>>
>>> Tobias
>>> HB9FSX
>>>
>>> On Fri., 3 Apr. 2020, 23:09 Bruce Griffiths, >>
>>> wrote:
>>>
 One can merely add diodes to the opamp feedback network form a feedback
 limiter and maintain the opamp outputs within the range for which the
>> opamp
 is well behaved whilst maintaining the increase in slew rate for the
>> output.

 Bruce
> On 04 April 2020 at 04:26 Tobias Pluess  wrote:
>
>
> Jup, some of them even have phase reversal when they are overloaded,
>> so
 it
> is perhaps not a good idea in general, but I think there are opamps
>> which
> are specified for this.
>
> Tobias
>
>
> On Fri, Apr 3, 2020 at 3:30 PM Dana Whitlow 
 wrote:
>
>> Caution: opamps make terrible limiters- their overload behavior is
>> generally ugly
>> and unpredictable.  It's much better to use a genuine level
 comparator, and
>> wire it
>> up so that it has a modest amount of hysteresis.
>>
>> Dana
>>
>>
>> On Fri, Apr 3, 2020 at 6:45 AM Bob kb8tq  wrote:
>>
>>> Hi
>>>
>>> The quick way to do this is with a single mixer. Take something
>> like
 an
>> old
>>> 10811 and use the coarse tune to set it high in frequency by 5
>> to 10
 Hz.
>>>
>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
>> audio
 tone.
>>> That tone is the *difference* between the 10811 and your device
>> under
>>> test.
>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>>
>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
 small
>>> shift
>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
 change
>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
 increase ).
>>>
>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
>> it’s
 not
>>> that
>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>> second.
>>>
>>> The reason its not quite that simple is that the input circuit
>> on the
>>> counter
>>> really does not handle a 10 Hz audio tone as well as it handles
>> a 10
 MHz
>>> RF signal. Instead of getting 9 digits a second, you probably
>> will
 get
>>> three
>>> *good* digits a second and another 6 digits of noise.
>>>
>>> The good news is that an op amp used as a preamp ( to get you up
>> to
 maybe
>>> 32 V p-p rather than a volt or so) and 

Re: [time-nuts] Phase measurement of my GPSDO

[John Ackermann N8UR]

Your counter can measure 1e-9 *at 1 Hz*  but you are feeding it with 10
MHz's worth of noise, so divide the reading by the factor of the down
mixing (1e7) so the result is 1e-16 -- you are multiplying the effective
noise.

Though as Bob says, you don't get close to 7 digits of improvement
without paying attention to a lot of other details.

John


On 4/3/20 11:59 AM, Tobias Pluess wrote:
> Hi John
> 
> Yes, I totally agree with you and I also understand the difference.
> But what I still don't understand is the following:
> Obviously, my 5335A is not accurate/precise enough to measure below 1e-9
> for short tau. Currently I am comparing the 1PPS signals, but when I change
> that and use the DMTD method, I will still compare some 1Hz signals, and
> the counter is still not able to resolve stuff that is lower than 1e-9. So
> why would the DMTD work better?
> I totally see that the error is somehow multiplied, but if my GPSDO is good
> (which I hope it is :-)) the error will still be very small - perhaps in
> the 1e-9 or 1e-10 region, so too low for my 5335A. Not?
> 
> 
> Tobias
> 
> On Fri, Apr 3, 2020 at 5:34 PM John Ackermann N8UR  wrote:
> 
>> I think the difference is between *mixing* or *dividing* down to a low
>> frequency.
>>
>> When you divide, you divide the noise along with the carrier frequency.
>>
>> When you mix, you "translate" the noise.  If the signal bounces around
>> 0.1 Hz at 10 MHz (awful, I know), when you divide to 1 PPS the noise is
>> also divided by 1e7 so the ratio remains the same.
>>
>> But if you mix via a 9.999 999 MHz local oscillator, now your output at
>> 1 Hz still has 0.1 Hz of noise on it.  i.e., it's the same absolute
>> value of noise as you started with.  So you measure that absolute value
>> but don't compare it to the mixed down 1 Hz frequency, compare it to the
>> original 10 MHz frequency.  It's basically an error multiplier.
>>
>> John
>> 
>>
>> On 4/3/20 11:25 AM, Tobias Pluess wrote:
>>> Hi again Bob,
>>>
>>> yes you describe a simple DMTD measurement. But could you tell me what
>> the
>>> difference is between that and comparing the 1PPS pulses?
>>> I mean, I could set the 10811 high in frequency by just 1Hz, and then it
>>> would result in two 1Hz signals which are then compared.
>>> Which is essentially the same as comparing two 1PPS signals, isn't it?
>>> Ok there is a minor difference: since the 1PPS signals are divided down
>>> from 10MHz, their noise is also divided down, which is not the case for
>> the
>>> DMTD.
>>> However, in the end I am comparing signals in the 1Hz to 5Hz or 10Hz
>>> region, and apparently, the 5335A is not suitable for those, at least not
>>> with the desired stability, is it?
>>>
>>>
>>> Tobias
>>>
>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
>>>
>>>> Hi
>>>>
>>>> The quick way to do this is with a single mixer. Take something like an
>> old
>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 Hz.
>>>>
>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio tone.
>>>> That tone is the *difference* between the 10811 and your device under
>>>> test.
>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>>>
>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
>>>> shift
>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the change
>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X increase
>> ).
>>>>
>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s not
>>>> that
>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>>> second.
>>>>
>>>> The reason its not quite that simple is that the input circuit on the
>>>> counter
>>>> really does not handle a 10 Hz audio tone as well as it handles a 10 MHz
>>>> RF signal. Instead of getting 9 digits a second, you probably will get
>>>> three
>>>> *good* digits a second and another 6 digits of noise.
>>>>
>>>> The good news is that an op amp used as a preamp ( to get you up to
>> maybe
>>>> 32 V p-p rather than a volt or so) and another op amp or three as
>> limiters
>>>> will
>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high
>> 

Re: [time-nuts] Phase measurement of my GPSDO

[John Ackermann N8UR]

I think the difference is between *mixing* or *dividing* down to a low
frequency.

When you divide, you divide the noise along with the carrier frequency.

When you mix, you "translate" the noise.  If the signal bounces around
0.1 Hz at 10 MHz (awful, I know), when you divide to 1 PPS the noise is
also divided by 1e7 so the ratio remains the same.

But if you mix via a 9.999 999 MHz local oscillator, now your output at
1 Hz still has 0.1 Hz of noise on it.  i.e., it's the same absolute
value of noise as you started with.  So you measure that absolute value
but don't compare it to the mixed down 1 Hz frequency, compare it to the
original 10 MHz frequency.  It's basically an error multiplier.

John


On 4/3/20 11:25 AM, Tobias Pluess wrote:
> Hi again Bob,
> 
> yes you describe a simple DMTD measurement. But could you tell me what the
> difference is between that and comparing the 1PPS pulses?
> I mean, I could set the 10811 high in frequency by just 1Hz, and then it
> would result in two 1Hz signals which are then compared.
> Which is essentially the same as comparing two 1PPS signals, isn't it?
> Ok there is a minor difference: since the 1PPS signals are divided down
> from 10MHz, their noise is also divided down, which is not the case for the
> DMTD.
> However, in the end I am comparing signals in the 1Hz to 5Hz or 10Hz
> region, and apparently, the 5335A is not suitable for those, at least not
> with the desired stability, is it?
> 
> 
> Tobias
> 
> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq  wrote:
> 
>> Hi
>>
>> The quick way to do this is with a single mixer. Take something like an old
>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 Hz.
>>
>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio tone.
>> That tone is the *difference* between the 10811 and your device under
>> test.
>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>
>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very small
>> shift
>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the change
>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X increase ).
>>
>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s not
>> that
>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>> second.
>>
>> The reason its not quite that simple is that the input circuit on the
>> counter
>> really does not handle a 10 Hz audio tone as well as it handles a 10 MHz
>> RF signal. Instead of getting 9 digits a second, you probably will get
>> three
>> *good* digits a second and another 6 digits of noise.
>>
>> The good news is that an op amp used as a preamp ( to get you up to maybe
>> 32 V p-p rather than a volt or so) and another op amp or three as limiters
>> will
>> get you up around 6 or 7 good digits. Toss in a cap or two as a high pass
>> and low pass filter ( DC offsets can be a problem ….) and you have a
>> working
>> device that gets into the parts in 10^-13 with your 5335.
>>
>> It all can be done with point to point wiring. No need for a PCB layout.
>> Be
>> careful that the +/- 18V supplies to the op amp *both* go on and off at
>> the
>> same time ….
>>
>> Bob
>>
>>> On Apr 3, 2020, at 5:13 AM, Tobias Pluess  wrote:
>>>
>>> hi John
>>>
>>> yes I know the DMTD method, and indeed I am planing to build my own DMTD
>>> system, something similar to the "Small DMTD system" published by Riley (
>>> https://www.wriley.com/A Small DMTD System.pdf).
>>> However I am unsure whether that will help much in this case, because all
>>> what the DMTD does is to mix the 10MHz signals down to some 1Hz Signal or
>>> so which can be measured more easily, and I already have 1Hz signals (the
>>> 1PPS) which I am comparing.
>>> Or do you suggest to use the DMTD and use a higher frequency at its
>>> outputs, say 10Hz or so, and then average for 10 samples  to increase the
>>> resolution?
>>>
>>> Thanks
>>> Tobias
>>> HB9FSX
>>>
>>>
>>> On Fri, Apr 3, 2020 at 12:53 AM John Miles  wrote:
>>>
> b) if I want to measure 1e-11 or even 1e-12 at 1sec - what resolution
 does
> my counter need? If the above was true, I would expect that a 1ps
> resolution (and an even better stability!) was required to measure ADEV
 of
> 1e-12, The fact that the (as far as I know) world's most recent,
> rocket-science grade counter (some Keysight stuff) has "only" 20ps of
> resolution, but people are still able to measure even 1e-14 shows that
>> my
> assumption is wrong. So how are the measurement resolution and the ADEV
> related to each other? I plan to build my own TIC based on a TDC7200,
 which
> would offer some 55ps of resolution, but how low could I go with that?

 That sounds like a simple question but it's not.  There are a few
 different approaches to look into:

 1) Use averaging with your existing counter.  Some counters can yield
 readings in the 1E-12 region at t=1s even though their si

Re: [time-nuts] Crystal filters in test equipment

[John Ackermann N8UR]

One of my Sulzers on an oddball frequency seems, from the phase noise
plot, to have a crystal filter about 1 kHz wide -- see attached.

John


On 3/26/20 8:04 PM, Richard (Rick) Karlquist wrote:
> On 3/26/2020 3:03 PM, Perry Sandeen via time-nuts wrote:
>> Learned Gentlemen,
>> Both the HP 106 and 107 have a post oscillator crystal filter.  There
>> is also a 10 MHz crystal filter used in my Tracor 527E FDM.
>> So the question I have is there anything to be gained by adding 10 MHz
>> crystal filters to the 10811 and similar OCXO's?  They are very
>> inexpensive to purchase.
>> Regards,
>> Perrier
>> ___
> 
> I never knew those oscillators had filters, even though
> I worked for HP.  My understanding is that the flicker
> noise of a crystal oscillator is established by the
> crystal, as opposed to the electronics.  A crystal
> filter using a similar crystal could not clean up
> flicker noise.  However, it could follow the buffer
> amplifier and clean up far out phase noise.  I am
> thinking that is why those models have filters.
> 
> The 10811 has an improved buffer that has very low
> far out phase noise, so I am thinking that there
> is no need for a post filter.  In all my time at HP,
> no one ever suggested a 10811 post filter.
> 
> "inexpensive to purchase" filters would probably not
> have good enough flicker noise and would degrade the
> close in noise.
> 
> The 8662 sig gen multiplies 10 MHz to 80 MHz and then
> has an 80 MHz crystal filter to clean up far out
> phase noise.  That makes more sense than a filter at
> the oscillator frequency.
> 
> If you really need lower far out phase noise than
> the 10811 offers, you can redesign the 2nd and 3rd
> buffer amplifier stages.  The 10811 designers knowingly
> degraded the phase noise in those stages because of
> requirements to be backward compatible with 10544
> sockets.  They made a one-off demonstration oscillator
> coded named "Barnabus" with ultra low noise.  It always
> seemed to be the proverbial "solution in search of a problem."
> 
> When I was designing the E1938A oscillator, I remember
> reading some papers about crystal oscillators that
> had a 2nd crystal that was installed in a Wheatstone
> bridge and used to servo the frequency of the oscillator
> to reduce temperature drift.  The breakthrough in the
> E19838A was to put the crystal in a bridge while
> simultaneously using it to make an oscillator.
> 
> Rick N6RK
> 
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Re: [time-nuts] time-nuts no longer carried by GMane.io

[John Ackermann N8UR]

To answer Achim's recent question (that's also been posed by others,
neither Tom nor I are fans of "list scraping" sites like gmane.org.
They offer convenience, but they also divert searches from the canonical
archive at lists.febo.com to their own archives, which may not be
complete.  Their archives also make it less likely that search engines
will return results from lists.febo.com.

And they add advertisements to the non-commercial time-nuts list content.

Additionally, gmane.org (and perhaps others) allows posting through its
site, which breaks our list management tools, and makes problems harder
to track.

It's pretty hard to stop these sites from subscribing and capturing our
content, and we're not inclined to try to prevent them.  But we don't
favor list-scrapers and prefer that people interact with the list directly.

Thanks,
Tom and John

On 3/3/20 12:50 PM, ASSI wrote:
> Hi John,
> 
> It seems that the time-nuts mailing list has lapsed from gmane.io (if indeed 
> it got re-subscribed under the new domain, changed from formerly gmane.org) 
> somewhere in January (there is one later mail from February, but I think 
> that's courtesy of a cross-posting).  Could you check what's going on and if 
> maybe you can do something about it?  I've already contacted the Gmane folks, 
> but haven't heard back yet.  Thanks.
> 
> 
> Regards,
> Achim.
> 


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Re: [time-nuts] PCB layout question for GPSDO

[John Ackermann N8UR]

On 2/29/20 7:40 AM, Matthias Welwarsk wrote:

> For example, there's the TDC7200 itself. When I tested my design first, the 
> measurements had a distinct relation to temperature, in the order of maybe 
> 300ps/°C, but there's other stuff as well, for example, the 74ALVC74 in 
> yours, 
> the whole analog output section etc.

The TDC7200 should compensate for temperature changes, though in
practice I'm not sure how quickly.

Because the ring oscillator in the chip that provides the
picosecond-level clock is free running and violently temperature
sensitive, it needs to be calibrated and the TDC7200 does that
automatically after each measurement.

After the STOP pulse is received, the chip measures the time interval of
several cycles of the external 10 MHz clock, and works that result
backward to determine the actual frequency of the ring oscillator.  The
TI calculation uses that measured frequency as an input and thus should
take into account any tempco.

Now, I've tried sticking my finger on the chip and that causes a wild
tempco for at least some seconds, so there is some inertia in the
correction, but the calibration process should take care of more typical
slowly changing temperatures.  Isolating the chip from moving air should
be helpful.

John


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[time-nuts] Administrivia: time-nuts message headers

[John Ackermann N8UR via time-nuts]

Hi All --

I just had a report from a member that they were getting strange DMARC
errors on messages they posted.  DMARC is a spam prevention tool that
really and truly messes up mailing list operation; I'll spare you the
details but it makes things very complicated for list traffic.

I just changed one of the list settings to hopefully better cope with
this.  You'll see in future messages that the "From:" line will look
different, and this may impact how the reply, reply to list, etc.
options work in your email programs.  I hope this change both solves the
reported problem and doesn't cause any new ones.  It sets time-nuts to
work consistent with current configuration recommendations.

John



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[time-nuts] List Archives

[John Ackermann N8UR]

If you've been missing the time-nuts list archives for the last week or
so, they have been turned back on.

The archives were hit with a denial-of-service attack and our hosting
company had to disable them because the traffic was crashing their
servers.  Things have settled back down, so the archives have been
enabled again.

Messages posted during the down time were added to the archives as
normal; the only thing that was affected was public access to the
archive pages.

Sorry for the inconvenience.

John


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[time-nuts] Looking for HP GPS splitter board

[John Ackermann N8UR]

This is a long shot, but...

A long while ago TAPR obtained and then sold some printed circuit boards
that were intended to go into HP GPS antenna splitters.

The boards were about 1.5 by 3.5 inches and had all the parts mounted
for a 4 port splitter, but with no connectors attached.  The part number
on the board was 58516-60001, Rev. G.

I would dearly like to find one or two of these boards to use in a
project.  If anyone has any they are willing to sell, please contact me
off list.

Thanks!
John
jra at febo dot com


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Re: [time-nuts] tracking position & orientation

[John Ackermann N8UR]

On 11/22/19 12:21 PM, Tim Lister wrote:

> You probably don't need to wait that many days for the Final GPS
> satellite orbits; the IGS products page
> (https://www.igs.org/products)shows that even the real-time
> ultra-rapid products are a factor of 20x better in the orbit (but
> interestingly not the satellite clocks) than the broadcast ephemeris.
> But if you are trying to find small drifts over a year, rather than
> say doing real-time RTK corrections, you have the luxury of time to
> wait for the absolute best orbits before doing the processing.

My (limited) experience with sending L1/L2 data to both NRCan and OPUS
is that there is a noticeable improvement from the "ultra-rapid" to the
"rapid" results a day or so later.  The difference from "rapid" to
"final" is barely noticeable (but is real).


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Re: [time-nuts] Difference in antennas

[John Ackermann N8UR]

Thanks to Bob, Achim, Greg and others for their input on this.

It seems the real challenge is that the outputs available from most GPS
don't provide the kind of info that would let you know if IMD or
overload are occurring.  In most cases we can only infer from
positioning performance, which is hard to quantify or correlate.

I like the idea of inserting attenuation until the SNR or Cn values
start to go down.  That may be the most practical solution.

John


On 11/21/19 4:05 PM, Greg Troxel wrote:
> John Ackermann N8UR  writes:
> 
>> One related question, especially with mixed systems -- how do you tell
>> if you have optimum signal level at the receiver?
>>
>> Most show some sort of SNR or Cn value.  What should we look for?  What
>> are the indication of *too much* signal?  One issue in particular is how
>> to handle a modern GPS that expects modest antenna gain when it's
>> plugged into a system with a 50dB gain antenna at the top.
> 
> Too much gain can manifest in at least two different ways:
> 
>   1) intermodulation distortion in the preamp
> 
>   2) distortion/overload in the GPS receiver
> 
> Adding an attenuator or cable as someone suggested can help you
> determine if the preamp gain is excessive *given your cabling and GPSr
> frontend*.  If you add 10 dB of loss, and the C/N0 doesn't change,
> arguably you have gain you didn't need, and which therefore has elevated
> risk of IMD.  If it goes up, you (mostly) know you are overdriving your
> receiver (which would be surprising to me).  If it drops, then you
> probably need most of the gain.
> 
> This is tricky, because a system with too much preamp gain will be prone
> to IMD if other signals appear but may operate just fine when they
> don't.
> 
> That said, I am unclear on:
> 
>   typical filtering before the antenna preamp (very little in a
>   dual-frequency antenna?)
> 
>   3rd-order IMD dynamic range in these preamps
> 
>   strength of non-GNSS signals that appear in the filter passband
> 


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Re: [time-nuts] Difference in antennas

[John Ackermann. N8UR]

I believe that's to avoid errors from phase center offset -- when the antenna 
calibrations are done, the measurements are taken with the antenna aligned that 
way so aiming it in the fields ensures releatability.

On Nov 22, 2019, 12:01 PM, at 12:01 PM, Bill Dailey  wrote:
>I would like to tag on to this.  I have a large Leica L1 choke ring
>antenna.  It has an indicator for “N”.  Not sure why.  I placed it on
>the roof without respect to directionality.  I will rotate it with “N”
>facing north in a month or so to see if there is any effect.
>
>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 21, 2019, at 6:00 PM, Dana Whitlow 
>wrote:
>> 
>> Most modern GPS receivers are very quiet even barefoot.  So, one
>could
>> argue that one should
>> not have much more LNA gain in the antenna than required to make up
>for
>> feedline loss, which
>> should be easily calculable.  While excess gain  in the antenna can
>improve
>> overall system noise
>> figure a small amount, it will degrade intermod performance, which is
>> likely to be a worse problem
>> than simple weak signals.  It's likely that the cure is worse than
>the
>> disease, as my doctor likes to
>> say.
>> 
>> Dana
>> 
>> 
>> 
>>> On Thu, Nov 21, 2019 at 4:00 PM Taka Kamiya via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>> 
>>> So concensus is, 50dB gain antenna is too much gain, unless feed
>line
>>> is too long, reception is poor, or there are other circumstances
>extra gain
>>> is desired?
>>> 
>>> ---
>>> (Mr.) Taka Kamiya
>>> KB4EMF / ex JF2DKG
>>> 
>>> 
>>>On Thursday, November 21, 2019, 3:00:14 PM EST, Bob kb8tq <
>>> kb...@n1k.org> wrote:
>>> 
>>> Hi
>>> 
>>> That is indeed the gotcha. Once you get past a certain amount of
>gain in
>>> the
>>> preamp, the C/N levels don’t change enough to notice. Looking today
>vs
>>> looking
>>> tomorrow is unlikely to be of any help if you are after a fraction
>of a
>>> db.
>>> 
>>> About the only way to check would be to fast switch an attenuator in
>and
>>> out of
>>> the signal path. Watch things for a minute at one setting and then
>do the
>>> same at
>>> another setting. Run for a while and log all the deltas. If you see
>a
>>> degradation of
>>> more than a few tenths of a db, you are getting towards the minimum
>gain
>>> point.
>>> 
>>> Indeed there are some receivers that have an AGC built in. *IF* your
>>> receiver has one
>>> and *IF* you can get at it, that would be a great way to work this
>out.
>>> Indeed anybody
>>> who makes it past both of those constraints has a pretty unique
>device.
>>> 
>>> 
>>> 
>>> Simple answer for a 50 db antenna is to put an attenuator in after
>the DC
>>> has
>>> been eliminated from the circuit. It’s not idea, but it’s the best
>you can
>>> do. Running
>>> a great big splitter is one great way to come up with attenuation
>…..
>>> 
>>> Bob
>>> 
>>> 
>>>>> On Nov 21, 2019, at 10:29 AM, John Ackermann N8UR 
>wrote:
>>>> 
>>>> Bob, this is a great summary, thanks!
>>>> 
>>>> One related question, especially with mixed systems -- how do you
>tell
>>>> if you have optimum signal level at the receiver?
>>>> 
>>>> Most show some sort of SNR or Cn value.  What should we look for? 
>What
>>>> are the indication of *too much* signal?  One issue in particular
>is how
>>>> to handle a modern GPS that expects modest antenna gain when it's
>>>> plugged into a system with a 50dB gain antenna at the top.
>>>> 
>>>> Thanks!
>>>> John
>>>> 
>>>> 
>>>> On 11/21/19 8:00 AM, Bob kb8tq wrote:
>>>>> Hi
>>>>> 
>>>>> Way back in time, the first gear out there to use what we now look
>at
>>> as “normal” antennas
>>>>> was survey gear. For various reasons they decided on a 12V power
>supply
>>> and 40 to 50 db
>>>>> of gain in the preamp mounted in the antenna. They also got into
>L1 /
>>> L

Re: [time-nuts] Difference in antennas

[John Ackermann N8UR]

Bob, this is a great summary, thanks!

One related question, especially with mixed systems -- how do you tell
if you have optimum signal level at the receiver?

Most show some sort of SNR or Cn value.  What should we look for?  What
are the indication of *too much* signal?  One issue in particular is how
to handle a modern GPS that expects modest antenna gain when it's
plugged into a system with a 50dB gain antenna at the top.

Thanks!
John


On 11/21/19 8:00 AM, Bob kb8tq wrote:
> Hi
> 
> Way back in time, the first gear out there to use what we now look at as 
> “normal” antennas 
> was survey gear. For various reasons they decided on a 12V power supply and 
> 40 to 50 db
> of gain in the preamp mounted in the antenna. They also got into L1 / L2 
> pretty quickly. 
> 
> A bit later the cell phone (and later broadcast) guys got into this. In a 
> location with a lot of 
> RF (like a cell site) having a lot of gain at the antenna didn’t work all 
> that well. IMD issues 
> got into the act pretty quickly. In addition, front end filtering was 
> required to reduce overload
> issues. The focus was on L1 only so filtering was relatively easy.
> 
> There is a whole separate set of antennas that put a big chunk of the RF 
> portion of the radio
> in the antenna. Those still survive here and there. I have one of them and 
> probably a couple
> of dozen of the more “normal” antennas. 
> 
> As time marched on, supplying 12V to antennas became a bit less popular. Most 
> of the cell 
> guys went over to a 5V antenna supply. The net result was 12V 50 db survey 
> antennas that did 
> L1/L2 and much smaller 5V 25 db antennas for “timing”. The timing antennas 
> didn’t do L1/L2 so
> not going to work for survey. The survey antennas had way to much gain and no 
> filtering so 
> not going to work for a cell site. 
> 
> Indeed things did and do get crossed up in various pro and basement systems. 
> With care and
> the right set of circumstances things may work. In other cases the result can 
> be an ongoing set
> of systems issues over an entire network of stations. 
> 
> Prices for a good new survey antenna are up in the many thousands of dollars 
> range. They have
> very stable phase centers and (usually) test results to allow correction of 
> any residual phase 
> issues. This is part of what lets you get into the “couple of mm” range on a 
> survey. 
> 
> For timing, you have to dig a bit and answer a few questions. Is your concern 
> how close you
> are to BIH? If so you will need to know all the delays in your system. This 
> includes the delays
> in the antenna filters and the preamp. Is your concern (or measure) the ADEV 
> at 1 second?
> If so the delays are not a concern. Your antenna choice may be a bit 
> different depending on
> this focus.
> 
> Bob
> 
> 
> 
>> On Nov 21, 2019, at 1:25 AM, Taka Kamiya via time-nuts 
>>  wrote:
>>
>> I have been looking antennas.  Prices seem to range less than 30 dollars to 
>> more than 500 dollars.  Some are 20db gain and some are 40 db gain.  Some 
>> are specified as marine use only.  Some are specified as timing use.  Some 
>> doesn't say anything at all.  Power supplies are different.
>> Other than obvious, antenna is an antenna, isn't it?  It captures L1 signal, 
>> amplify it and send it down the coax.  What makes one more costly than 
>> others?  What makes one timing antenna and one navigation antenna?  It 
>> doesn't make sense to me.  
>>
>> I did some simple experiment with 26db, 40db, and magnetic stick on type.  I 
>> didn't really see significant difference.  Signal level itself even wasn't 
>> all that different.  I have nearly a clear sky view 360 degrees above 30 
>> degrees above horizon.  In some directions, clear view to horizon.  My feed 
>> is Timewave type.  So It may not be the best but nearly ideal.  
>>
>> Can someone shed light on this topic?  (of course, I know some antenna has 
>> integrated receiver.  I am not talking about those)
>>
>> --- 
>> (Mr.) Taka Kamiya
>> KB4EMF / ex JF2DKG
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Re: [time-nuts] Mounting thread on TopGNSS GN-GGB0710

[John Ackermann. N8UR]

The limited knowledge I've obtained about survey antenna is that almost all use 
a straight 5/8-11 thread.  There are various 5/8 adapters available.  I use one 
to 1/4-20 to mount the antenna on a camera tripod.

On Oct 30, 2019, 3:17 AM, at 3:17 AM, Hal Murray  
wrote:
>
>> I have two of these. They are both 5/8-11, however they were both
>tapered.
>> The taper can be removed with a hand tap.  
>
>Are tapered threads used for something other than pipes?
>
>
>> The ones I���ve seen all thread fine onto the standard survey poles.
>I believe
>> that is a 5/8-11 thread. 
>
>Do survey poles have a tapered thread, or are the threads short enough
>not to 
>encounter the tapered part of the hole?  Google found lots of adapters.
> None 
>of the threads looked tapered.
>
>I'm not a machinist (but my dad was).  Wiki says it's common to start
>with a 
>tapered tap because they are easier to get started, then follow up with
>a 
>bottoming tap if necessary.  Did they just forget that step for a batch
>of 
>antennas?
>
>
>-- 
>These are my opinions.  I hate spam.
>
>
>
>
>
>
>
>
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Re: [time-nuts] HP 5065A owners, a question!

[John Ackermann N8UR]

 IIRC, there's a description in the 5065A manual about how to restore
the lamp if this happens, but I think the mechanism tends to occur
during long periods of storage, not during operation.

The small telco Rb's certainly have the flooding problem and there the
restoral methods are a bit more ad hoc.

John


On 10/24/19 5:27 PM, Charles Steinmetz wrote:
> John wrote:
> 
>> The 5065A is a Rubidium standard and unlike Cesium units it doesn't
>> have a "wear out" mechanism.  With a little TLC they can run
>> indefinitely.
> 
> We have heard a lot about vaporized Rb plating (condensing) out on the
> cooler spots of the envelope, and the need to refurbish tubes by heating
> the envelope to encourage the Rb to condense back to its original
> position to keep the physics package running.
> 
> All of the discussion I recall pertained to the small-cell telecom Rb
> units, but I may have missed posts about refurbishing 5065A Rb cells. Is
> the 5065A free from this mode of deterioration, and/or is there a
> similar fix for them?  (I could easily imagine that it takes a much
> longer time for a large Rb cell to show degradation from this cause.)
> 
> Best regards,
> 
> Charles
> 
> 
> 
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Re: [time-nuts] HP 5065A owners, a question!

[John Ackermann. N8UR]

Hi Greg --

The 5065A is a Rubidium standard and unlike Cesium units it doesn't have a 
"wear out" mechanism.  With a little TLC they can run indefinitely.  While they 
drift (very slowly), they have much better short term stability than a Cs and 
so in some ways are more useful.

John

On Oct 23, 2019, 11:00 PM, at 11:00 PM, "Gregory P. Ennis"  
wrote:
>Hi Corby,
>
>I very new to this list and have been monitoring it for the last 6
>months.  I was
>interested in doing some time dilation experiments with some Cs, but
>had to become a little
>hesitant when I discovered the price of them.
>
>My initial review of the Cs caused me to conclude there were not many
>around and used parts
>were not available.  
>
>If you have had yours running for 5 years without a blink, I have to be
>impressed.  
>
>Where did you get yours?
>
>Greg Ennis
>
>Hi,
>
>How many of you leave your 5065A on all the time?
>
>Approximately how many years have you had it running without major
>maintenance?
>
>My current "gold standard" 5065A has been running for over 5 years.
>
>Cheers!
>
>Corby
>
>
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>
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Re: [time-nuts] 10MHz dist amps

[John Ackermann N8UR]

Thanks, Bruce.  That's pretty much it -- while the layout/lack of
shielded enclosure might have a bit to do with it, the opamps used
(MAX477) aren't super-duper low noise at the floor.  The AD8055 we've
used in the lasts few batches since the MAX477 went unobtainium seems to
be a little quieter.

Re the frequency range, the opamps are rated to I think something like
275 MHz but there is some roll-off built into the design to reduce a
tendency toward oscillation; no real attempt was made to keep it flat
across frequency.

There's some difference in frequency response depending on the input
level and gain setting, but in general the gain is around unity at 5 and
10 MHz, then rises about 5 dB to peak at about 40 MHz, then it falls off
to abotu -9 dB at 100 MHz.

At the time I designed the unit, I was young and foolish* and thought a
5 or 10 MHz bandpass filter might be a good idea.  I soon learned and
now strongly discourage including the filter unless you have a very good
reason.

73,
John

* I just looked at the original design files and good Lord, they date
back to August, 2005.  That thing is going on 15 years old without a
significant change, other than the opamp substitution (which was a
direct drop-in replacement).


On 10/23/19 7:38 PM, Bruce Griffiths wrote:
> Its measured noise floor is consistent with that expected from the noise 
> specifications for the opamps employed.
> 
> Bruce
> 
>> On 24 October 2019 at 08:46 Tom Knox  wrote:
>>
>>
>> Hi John;
>> Amazing product, I did not realize you could use the TADD-1 for 100MHz 
>> distribution.
>> I do have a question, as someone who has tested most of the commercially 
>> available distribution amps on the market TADD-1's -140dB @ 1Hz is among the 
>> very very best best in the industry, (nothing is close for the price) but 
>> compared to the very best the noise floor is a bit higher. Is this simply a 
>> result of a raw board instead of a shielded enclosure?
>> Thanks;
>>
>> Tom Knox
>>
>> 303-554-0307
>>
>> act...@hotmail.com
>>
>> "Peace is not the absence of violence, but the presence of Justice" Both MLK 
>> and Albert Einstein
>>
>> 
>> From: time-nuts  on behalf of John 
>> Ackermann. N8UR 
>> Sent: Wednesday, October 23, 2019 11:54 AM
>> To: ew via time-nuts 
>> Subject: Re: [time-nuts] 10MHz dist amps
>>
>> FWIW, I designed the TADD-1 to have equal length signal paths for all six 
>> channels.
>>
>> 73,
>> John
>>
>> On Oct 23, 2019, 1:01 PM, at 1:01 PM, "Bill Dailey, MD, MSEng, MSMI" 
>>  wrote:
>>> I am working in a project that requires me to have very similarly
>>> phased
>>> 10mhz references (beamforming).
>>>
>>> Previously I just used splitters for 10MHz but now I am graduating to a
>>> distribution amplifier.  Looking for suggestions/recommendations and
>>> what I
>>> should consider.  Distributing a Fury or a manually set a (May have
>>> the
>>> numbers wrong on this) oscillator.
>>>
>>> 1. TADD-1 x 2
>>> 2. 5087A
>>> 3. 58502A
>>>
>>> 2&3 are from the usual auction site and may have problems now or in the
>>> future.
>>> --
>>> Doc
>>>
>>> Bill Dailey
>>> KXØO
>>> ___
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Re: [time-nuts] HP 5065A owners, a question!

[John Ackermann N8UR]

Hi Corby --

I normally keep the 5065A running all the time -- it's usually set up as
the "house standard" and I tweak the frequency against Cs every few
months.  You know more about its service history than I do. :-)

When it was working, I usually kept the 5061A running full time as local
time standard.  One or the other of the two Cs with high-perf tube
usually get turned on for a couple of weeks at a time when I'm doing a
measurement campaign; otherwise they are powered up but in "oven off"
standby.

John


On 10/23/19 11:34 AM, cdel...@juno.com wrote:
> Hi,
> 
> How many of you leave your 5065A on all the time?
> 
> Approximately how many years have you had it running without major
> maintenance?
> 
> My current "gold standard" 5065A has been running for over 5 years.
> 
> Cheers!
> 
> Corby
> 
> 
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Re: [time-nuts] 10MHz dist amps

[John Ackermann. N8UR]

FWIW, I designed the TADD-1 to have equal length signal paths for all six 
channels.

73,
John 

On Oct 23, 2019, 1:01 PM, at 1:01 PM, "Bill Dailey, MD, MSEng, MSMI" 
 wrote:
>I am working in a project that requires me to have very similarly
>phased
>10mhz references (beamforming).
>
>Previously I just used splitters for 10MHz but now I am graduating to a
>distribution amplifier.  Looking for suggestions/recommendations and
>what I
>should consider.  Distributing a Fury or a manually set a (May have
>the
>numbers wrong on this) oscillator.
>
>1. TADD-1 x 2
>2. 5087A
>3. 58502A
>
>2&3 are from the usual auction site and may have problems now or in the
>future.
>-- 
>Doc
>
>Bill Dailey
>KXØO
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Re: [time-nuts] DC distribution

[John Ackermann N8UR]

One thing the PowerPole tool does is provide a little cavity for the
blade to go, so it keeps the depth of the crimp and also the angle where
they should be.

On 10/5/19 7:24 AM, Adrian Godwin wrote:
> I used powerpoles on a project and tried to use a crimping tool I had to
> hand. Amphenol, I think. It appeared to be the right size but ended up
> bending the terminal badly where it changes from circular to flat. The
> results were unreliable and I ended up soldering (though adding sleeving,
> which together with the natural bend-restriction on the shell has mostly
> avoided stiffening the wire where it's most vulnerable).
> 
> I know some crimp terminal are very fussy about the tool used but it's
> usually the miniature ones like JST. Does the powerpole terminal need a
> powerpole-specific crimp tool ? I note that the West Mountain tool seems to
> be branded by themselves rather than Anderson, but I can't tell if it's
> generic or made to their specs.
> 
> On Sat, Oct 5, 2019 at 2:00 AM John Ackermann N8UR  wrote:
> 
>> Not a perfect solution, but for semi-permanent connections you can run a
>> small tie-wrap lengthwise so the ends pass through the space between where
>> the wires on each end split and the body.  Cinch it tight and the
>> connectors won't come apart without cutting the tie wrap.
>>
>> On Oct 4, 2019, 7:04 PM, at 7:04 PM, Taka Kamiya via time-nuts <
>> time-nuts@lists.febo.com> wrote:
>>> I used to use power pole, too but they don't lock firmly enough for my
>>> liking.  So I don't use them anymore.  It would be perfect if there is
>>> an option to add positive locking mechanism of some kind.
>>>
>>> ---
>>> (Mr.) Taka Kamiya
>>> KB4EMF / ex JF2DKG
>>>
>>>
>>> On Friday, October 4, 2019, 4:06:50 PM EDT, Didier Juges
>>>  wrote:
>>>
>>> That's what I do too. I do use Power Pole for my ham stuff that draws
>>> high
>>> current but for all the <2A 12V stuff the 5.1mm barrel connector with
>>> positive center is hard to beat because I have so many power sources
>>> and
>>> equipment already wired for it. I am not ready to rewire all the off
>>> the
>>> shelf equipment that came with one of those.
>>>
>>> Power Pole are convenient for batteries though because you can use the
>>> connector to charge the battery or use it as a source.
>>>
>>> Didier KO4BB
>>>
>>> On Fri, Oct 4, 2019, 2:01 PM Taka Kamiya via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>>
>>>> Mine is very simple
>>>> USB connector for 5VBarrel connector 5.5/2.1mm for 12VTerminal strip
>>> for
>>>> 24V
>>>> None of them are high power devices.
>>>>
>>>> ---
>>>> (Mr.) Taka Kamiya
>>>> KB4EMF / ex JF2DKG
>>>>
>>>>
>>>>On Friday, October 4, 2019, 2:03:55 AM EDT, Bill Dailey <
>>>> docdai...@gmail.com> wrote:
>>>>
>>>>  Setting up a new workbench and am wondering what wisdom people can
>>>> offer.  I am powering numerous synthesizers (5v), small receivers
>>> (5v),
>>>> Upconverters (5v), larger receivers (12v), fury Gpsdo’s.. etc.
>>> anyone use
>>>> something neat and not real expensive for distributing 5v and 12v.  I
>>> am
>>>> hoping for a long COTS pcb with fusing and maybe holes for plugs.
>>>>
>>>> Any insights?
>>>>
>>>> Bill
>>>>
>>>> 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
>>>> ___
>>>> 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.
>>>>
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>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>> and follow the instructions there.
>>>>
>>> 

Re: [time-nuts] DC distribution

[John Ackermann N8UR]

Not a perfect solution, but for semi-permanent connections you can run a small 
tie-wrap lengthwise so the ends pass through the space between where the wires 
on each end split and the body.  Cinch it tight and the connectors won't come 
apart without cutting the tie wrap.

On Oct 4, 2019, 7:04 PM, at 7:04 PM, Taka Kamiya via time-nuts 
 wrote:
>I used to use power pole, too but they don't lock firmly enough for my
>liking.  So I don't use them anymore.  It would be perfect if there is
>an option to add positive locking mechanism of some kind.
>
>--- 
>(Mr.) Taka Kamiya
>KB4EMF / ex JF2DKG
> 
>
>On Friday, October 4, 2019, 4:06:50 PM EDT, Didier Juges
> wrote:  
> 
>That's what I do too. I do use Power Pole for my ham stuff that draws
>high
>current but for all the <2A 12V stuff the 5.1mm barrel connector with
>positive center is hard to beat because I have so many power sources
>and
>equipment already wired for it. I am not ready to rewire all the off
>the
>shelf equipment that came with one of those.
>
>Power Pole are convenient for batteries though because you can use the
>connector to charge the battery or use it as a source.
>
>Didier KO4BB
>
>On Fri, Oct 4, 2019, 2:01 PM Taka Kamiya via time-nuts <
>time-nuts@lists.febo.com> wrote:
>
>> Mine is very simple
>> USB connector for 5VBarrel connector 5.5/2.1mm for 12VTerminal strip
>for
>> 24V
>> None of them are high power devices.
>>
>> ---
>> (Mr.) Taka Kamiya
>> KB4EMF / ex JF2DKG
>>
>>
>>    On Friday, October 4, 2019, 2:03:55 AM EDT, Bill Dailey <
>> docdai...@gmail.com> wrote:
>>
>>  Setting up a new workbench and am wondering what wisdom people can
>> offer.  I am powering numerous synthesizers (5v), small receivers
>(5v),
>> Upconverters (5v), larger receivers (12v), fury Gpsdo’s.. etc. 
>anyone use
>> something neat and not real expensive for distributing 5v and 12v.  I
>am
>> hoping for a long COTS pcb with fusing and maybe holes for plugs.
>>
>> Any insights?
>>
>> Bill
>>
>> 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
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
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>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
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>>
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Re: [time-nuts] DC distribution

[John Ackermann N8UR]

The idea of using a short piece of thicker wire is a good one.  Thanks
for that!

On 10/4/19 3:17 PM, MLewis wrote:
> With audio signals, a soldered crimp is one of the worst possible
> connections. I wouldn't think it would be different for anything else,
> but may go undetected until failure. If you've used the correct size of
> crimp and used a proper crimping tool, then you've got the proper
> pressure for a solid reliable connection. If you then solder, the heat
> expands the crimp lessening the crimp pressure, and when it cools it's
> no longer at the correct crimp pressure (often the wire will pull right
> out), and with iffy wicking of solder. The worst of both methods
> combined in one.
> 
> Where the wire is too thin for the crimp I have available, I've cut a
> piece of a correct thickness wire/cable, inserted that into the crimp
> along with the signal wire/cable, so it's crimped between them. I don't
> know if that is the best way of handling that, but it's worked for me.
> 
> On 04/10/2019 11:41 AM, John Ackermann. N8UR wrote:
>> West Mountain is a good source for all things PowerPole, but there are
>> a bunch of other vendors as well.  And do youself a favor -- spend $30
>> on the three size 15/30/45 amp crimping tool.  It saves much
>> aggravation.  But if you're using thin wire, soldering after crimping
>> is a good precaution.
>>
> 
> 
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Re: [time-nuts] DC distribution

[John Ackermann. N8UR]

West Mountain is a good source for all things PowerPole, but there are a bunch 
of other vendors as well.  And do youself a favor -- spend $30 on the three 
size 15/30/45 amp crimping tool.  It saves much aggravation.  But if you're 
using thin wire, soldering after crimping is a good precaution.

On Oct 4, 2019, 10:03 AM, at 10:03 AM, Bill Dailey  wrote:
>Yes.  I am using 12v agm.  Good wmr for the connectors also?
>
>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 Oct 4, 2019, at 7:17 AM, John Ackermann. N8UR 
>wrote:
>> 
>> I use lots and lots of Anderson PowerPoles and (mostly) West
>Mountain Radio distribution units.  I have different color codes for
>different voltages -- red/black for 12v, orange/black for 24v,
>green/black for 5v, etc.  Primary 12 and 24 volt sources are big AGM
>batteries across float chargers.
>> 
>>> On Oct 4, 2019, 2:03 AM, at 2:03 AM, Bill Dailey
> wrote:
>>> Setting up a new workbench and am wondering what wisdom people can
>>> offer.  I am powering numerous synthesizers (5v), small receivers
>(5v),
>>> Upconverters (5v), larger receivers (12v), fury Gpsdo’s.. etc.  
>anyone
>>> use something neat and not real expensive for distributing 5v and
>12v. 
>>> I am hoping for a long COTS pcb with fusing and maybe holes for
>plugs. 
>>> 
>>> 
>>> Any insights?
>>> 
>>> Bill
>>> 
>>> 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
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com
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>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
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Re: [time-nuts] DC distribution

[John Ackermann. N8UR]

I use lots and lots of Anderson PowerPoles and (mostly) West Mountain Radio 
distribution units.  I have different color codes for different voltages -- 
red/black for 12v, orange/black for 24v, green/black for 5v, etc.  Primary 12 
and 24 volt sources are big AGM batteries across float chargers.

On Oct 4, 2019, 2:03 AM, at 2:03 AM, Bill Dailey  wrote:
>Setting up a new workbench and am wondering what wisdom people can
>offer.  I am powering numerous synthesizers (5v), small receivers (5v),
>Upconverters (5v), larger receivers (12v), fury Gpsdo’s.. etc.   anyone
>use something neat and not real expensive for distributing 5v and 12v. 
>I am hoping for a long COTS pcb with fusing and maybe holes for plugs. 
>
>
>Any insights?
>
>Bill
>
>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
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Re: [time-nuts] Beginner's Atomic Clock

[John Ackermann N8UR]

On 9/17/19 3:33 AM, Dr. David Kirkby wrote:
> On Tue, 17 Sep 2019 at 04:00, Dana Whitlow  wrote:
> 
>> The nice thing about a Rb is that its short term stability (seconds to
>> minutes and perhaps
>> even longer) is much better than that of a GPS timing receiver.  The bad
>> news is that Rb
>> standards exhibit long term frequency drift in the neighborhood of a few
>> parts in 10^11
>> per month.  A pretty fair compromise is to use an Rb standard that is
>> disciplined by GPS
>> PPS pulses with a loop time constant on the order of a day or so.
>>
>> Dana   (K8YUM)
> 
> 
> Is  there any advantage in using a GPS Rb disciplined oscillator vs a GPS
> disciplined high quality OCXO like the HP 10811A? I can’t understand why
> there should be, as a Rb source would use an OCCO in its output stage
> Therefore in each case
> 
> * Short term stability depends upon the quality of the OCXO
> * Long term stability depends upon GPS.
> 
> Perhaps there’s is period over which the the overall stability can be
> improved by adding a rubidium oscillator. I would be interested to know if
> that is the case or not.

There are a bunch of interesting tradeoffs in choosing a frequency
reference.

Any Rb (except the HP 5065A which is in a different class as a lab
instrument vs. the small telecom units) will be worse at short tau than
a good OCXO, and is also likely to have much worse phase noise.  A
typical telecom Rb will be around 1e-11 at 1 second while a good OCXO
can be one or even two orders of magnitude better.

At medium tau (say a few thousand seconds) the Rb will likely be in the
mid to upper 13s, which is better than any but a very good OCXO.

At long tau, the Rb should show at least an order of magnitude less
drift than even a very good OCXO.

A Cesium at short tau will typically be worse than either an OCXO or an
Rb.  The Cs only wins (a) at long tau since there is zero drift; and (b)
for absolute accuracy.  But at anything shorter than around 10K seconds,
it's not the best choice.

A good GPSDO is really the overall performance winner -- short term
stability and phase noise limited only by the quality of the OCXO, and
very good long term stability and accuracy due to the GPS lock.  It's
only in the mid range of a few hundred to to a couple of thousand
seconds, where the OCXO drift kicks in before the GPS discipline takes
over, that a GPSDO will underperform a telecom Rb.

In short, the GPSDO takes much of the fun out of time-nuttery. :-\

John


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Re: [time-nuts] TAPR TIC Upgrade?

[John Ackermann N8UR]

In theory, making a new TICC that ran on an RPi could provide
significantly more measurements per second, and more convenient I/O, but
wouldn't affect the quality of the results.

I've thought a bit about an RPi-based TICC, but it's a significant
redesign effort for limited gains.

John


On 8/14/19 3:18 PM, Forrest Christian (List Account) wrote:
> The TICC uses an Arduino mega clone, not a Raspberry Pi.
> 
> My understanding is that most of the magic happens on the shield board not
> in the processor - the processor is just there to capture the data from the
> shield and format and report it via the serial port.
> 
> On Wed, Aug 14, 2019 at 12:10 PM Perry Sandeen via time-nuts <
> time-nuts@lists.febo.com> wrote:
> 
>> Yo Bubba Dudes!,
>> I've just purchased a TAPR TIC module.  Now the new Raspberry Pi Model B
>> has just been released.
>> So my question is would there be any worthwhile advantage to replacing the
>> TAPR unit with the new Model 4B?
>> Regards,
>> Perrier
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> 


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Re: [time-nuts] TAPR TIC Upgrade?

[John Ackermann N8UR]

The TICC uses an Arduino, not a Raspberry Pi.  It would require both
major hardware and software changes to utilize an RPi.

On 8/14/19 1:28 PM, Perry Sandeen via time-nuts wrote:
> Yo Bubba Dudes!,
> I've just purchased a TAPR TIC module.  Now the new Raspberry Pi Model B has 
> just been released.
> So my question is would there be any worthwhile advantage to replacing the 
> TAPR unit with the new Model 4B?
> Regards,
> Perrier
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Re: [time-nuts] Galileo service currently degraded

[John Ackermann. N8UR]

Having just been through the endian issue with a similar parser, I'll mention 
that in Python the struct.unpack() function can handle endian swaps at tne same 
time as it pulls binary data out of the message.  It makes it pretty painless.

On Jul 13, 2019, 11:08 PM, at 11:08 PM, Mark Sims  wrote:
>Lady Heather is open source and has parsers/decoders for just about any
>receiver you are likely to see... and a few that your aren't.One
>big issue with binary protocols is handling big/little endian (byte
>order) issues when reading messages or sending them to the device.  You
>need to be aware of what the system CPU uses and what the receiver
>uses.
>
>
>
>>  One alternative, if you only need two lines is to write a parser
>just for them. 
>There’s not a whole lot to the protocol and the uBlox doc’s are pretty
>good at
>describing it. Yes, it’s a binary protocol so there will be a bit of
>this and that
>involved. 
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Re: [time-nuts] AN/URQ-10A standard docs

[John Ackermann N8UR]

I have several pages of schematics at:

https://www.febo.com/pages/hardware/AN_URQ_10/

but unfortunately not the full manual.

John


On 7/10/19 12:43 PM, Walter Shawlee 2 wrote:
> Does anybody have the manual for this old standard?  mine works, but is
> a bit high, and needs internal adjustment, and a new battery pack. 
> pretty good condition for this old unit, and the 5MHz output is only
> 4.8Hz off after heaven only knows how many years in a dark corner. it's
> only been running for 12 hours, so it might drift in after 30 days at
> the oven temperature, but my offset adjustment is maxed out.
> 
> I have had good luck converting the older 5Mhz standards to 10Mhz using
> a cheap chinese doubler board off ebay and a 10Mhz bandpass filter. the
> results were great (although about 6dB down from the original level),
> and made them a bit more useful around the shop as an external reference.
> 
> Any PDF would be appreciated.  All my web searches were total dead ends
> so far.
> all the best,
> walter
> 


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[time-nuts] interesting book -- Einstein's Shadow -- mentions masers

[John Ackermann N8UR]

I just finished reading Einstein's Shadow by Seth Fletcher
(https://www.amazon.com/dp/B075WSLWFX/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1).

It's a pop-science story about the development of the Event Horizon
Telescope and the quest to image a black hole.  It was published just
before the recent announcement that they've done it.

I'm mentioning it here only because it makes several references to
masers (installed at all the radio telescope sites) and even mentions
the Microsemi MHM-2010 by name.  But even without that, it's a pretty
good read.

John


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Re: [time-nuts] Logging and correlating NMEA messages with TICC timestamp

[John Ackermann. N8UR]

Just a note about possible spurious pulses with the TICC.  The input circuit is 
a 3.3v logic gate that's 5v-safe.  Some PPS signals have much greater peak 
amplitude than that (e.g., the HP atomic clocks).

Experience has shown that these pulses don't know have enough energy to damage 
the input, but the voltage can cause ringing that results in occasional double 
pulses.  So use a scope to look at the pulse and if its peak is more than about 
5v, use an attenuator to knock it down.  Also, make sure the pulse is 
terminated in a 50 ohm load at the TICC input.

John

On Jun 24, 2019, 2:00 AM, at 2:00 AM, "Forrest Christian (List Account)" 
 wrote:
>I have a couple of GPS receivers I'm experimenting with that I've been
>using a TICC to gather timestamps of the 1PPS output to ascertain
>their relative quality.
>
>In the process of doing this, I've discovered that some of the 1PPS
>outputs are not as stable as I'd like them to be.  For instance, the
>one currently on my bench emits stuff like this every once in a while:
>
>330364.902989667231 chA
>330365.582893064933 chA
>330365.584094826326 chA
>330365.902989679840 chA
>
>Note the 2 inserted pulses between the two correct ones.
>
>I'd like to be able to look at a log of the GPS NMEA output at the
>appropriate time for this and other events to determine if they
>correspond to some sort of GPS event.In addition, I'd like to
>gather the phase correction data (aka quantization error) from the GPS
>(and which is spit out in a NMEA sentence as well) in a way that is
>correlated to the TICC timestamp it goes with.
>
>I know I can hack together something in python or similar to open both
>ports and log them together using a common timestamp.  But this also
>seems like something which is probably being done regularly in time
>labs around the globe so there's likely some tool to do this that I'm
>unaware of.
>
>So I guess I'm asking what everyone else is using to gather both
>timestamp data and NMEA data in a correlated way
>
>Thanks for any input.
>
>-- 
>- Forrest
>
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Re: [time-nuts] Excellent equipment rack

[John Ackermann. N8UR]

Star Case (https:www.starcase.com) is  U.S. company (in Indiana)  that sells 
similar open-frame rack kits for very reasonable prices.  I have several and 
have been very pleased.  They are available whatever height you want, with 
depths of 20 to 30 inches.  They have lots of accessories to trick out your 
rack.

As Perry ssid, they are quite wobbly but they have various cross braces 
available that will stiffen them up.  I have hundreds of pounds in a 6 foot one 
and it's rock-stable.

They ship broken down in a flat box plus tall cardboard tube for the vertical.  
Assembly is bssically like an Erector Set.

On Jun 11, 2019, 7:00 AM, at 7:00 AM, Perry Sandeen via time-nuts 
 wrote:
>Yo Bubba Dudes!,
>Needing to go vertical with my test equipment I went bottom feeding for
>an equipment cabinet on ebay.
>To make a long search story short: they were way too expensive, too
>heavy to ship and too far away for pickup.
>So I kept searching and finally came across what was listed as *42U
>Four Post Open Frame Server Data Rack 19 inches.  Adjustable depth 23
>to 32 inches.ebay number 152319524877.Sold by Raising Electronics for
>US $188 and free shipping.
>I was unsure what a *U* height meant put it seemed tall enough so I
>bought one.
>I was a little apprehensive about this being a Chinese metal product. 
>I was very pleasantly proven very wrong.
>Although it only comes with a picture of an assembled unit it has been
>engine ed so there is no way you can assemble improperly. The four
>posts are all equal and can be installed with any end up or down and
>the top and bottom brackets will fit.  It comes with the exact 50 M6-20
>head bolts and nuts needed for assembly.  The nearest SAE equivalent
>bolt size is 1/4 20 x 1/2L which I purchased to hold L shelf brackets
>to the frame.
>I set the depth of mine to 26 inches so my 5370's fit well and I had
>space for both power and BNC cables to be inside the frame.
>
>This rack is designed to be bolted to the floor.  Wanting to be able to
>move it, I cut a piece of 3/4 inch plywood a little longer and wider
>then the base footprint and installed 4 inch tall Harbor Freight swivel
>casters on the four corners for ease of movement in any direction, even
>on floor carpeting.  After assembly it was 6 ft 9 inches tall. 
>
>Now this being a bolted together *skeleton frame* it is prone to
>twisting and or becoming a parallelogram sideways.  To prevent
>twisting, I fitted a plywood board on the top bolted to the top front
>and rear angle pieces.  To prevent a side-to-side movement required an
>8 inch wide piece of scrap aluminum plate bolted to the rear vertical
>posts.  This is easy to do as there are a plethora of precision spaced
>holes available.
>There was some very serious thought given to the vertical post design. 
>It has six 90 degree folds done in such a way that the inner edge on
>each outer side gives a 19 inch opening.
> However behind it is as inner fold where one can install recessed L
>shaped brackets. Now the inner fold is about and inch narrower than the
>outside edge.This allows making a wider shelf that can *float* on top
>the brackets but can't slide out either end.
>This was very useful when configuring the instrument arrangement.
>I also found that with the bottom shelf being just 6 inches above the
>floor I was able to install more equipment in the same vertical space
>than in my previous normal sized equipment cabinet.
>Another bonus with this type of configuration is that it's easier to
>keep the equipment cool and it's much lighter.
>Regards,
>Perrier
>
> 
>
>
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Re: [time-nuts] Bombe clock

[John Ackermann. N8UR]

Other than the fact that his description of how the bombe worked is totally 
wrong... 

On May 21, 2019, 5:00 PM, at 5:00 PM, Mark Sims  wrote:
>Everbody needs one of these...
>
>https://www.ebay.co.uk/itm/The-Covert-Bombe-Clock-from-Bad-Dog-Designs-Codebreaking-in-Secret/123775434764
>
>https://www.youtube.com/watch?v=O4ctUqgj7aY
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