Hi
It’s *lots* easier to apply it in software than to do the fun and games with
the delay line.
One of the biggest issues with the delay line approach is finding one that is
good enough
( stable, 0.1 ns resolution, wide enough range, low noise ….) to do the job.
Bob
> On Nov 10, 2020, at
Joe,
I mentioned those spikes in an earlier, private email as well, I think Bob is
correct, there's something going on with the sawtooth correction.
Since you're already reading the quantization error correction data from the
Ublox TIM_TP message, you might want to try "digitally" applying it.
Bob, Thanks for that. I am going to dig!
Joe
On Tue, Nov 10, 2020 at 7:56 PM Bob kb8tq wrote:
> Hi
>
> If you are handling the sawtooth correctly, you should see no hanging
> bridges
> at all. My guess is that the spikes are coming from a problem in the
> sawtooth
> correction “stuff”. With no
Rather than using the hardware delay line, I suggest you add or subtract
(as appropriate) the sawtooth correction data directly to/from your time to
digital converter data. In the Ublox devices, the sawtooth should be
applied to the following pps pulse.
Also you might consider using the TI
Hi
If you are handling the sawtooth correctly, you should see no hanging bridges
at all. My guess is that the spikes are coming from a problem in the sawtooth
correction “stuff”. With no correction, you *will* see a spike as is rolls
over. With
a correction error, you would also see a spike.
Hi Bob,
Yes, I am - I use a Dallus digital delay line in series with the GPS 1pps
and program the delay line each second with the GPS delay estimate in the
GPS NAV message.
It works really well, jitter on the 1pps pulse is hugely reduced, but one
side effect is that those 'hanging bridges' can
Hi
Are you using sawtooth correction?
Bob
> On Nov 10, 2020, at 8:55 AM, Joe & Gisela Noci wrote:
>
> Hi everyone,
> Still playing with my GPSDO..The Rubidium source I was hoping to have the
> loan off did not work out, so still in the dark. I have sort of convinced
> myself to procure a
Hi everyone,
Still playing with my GPSDO..The Rubidium source I was hoping to have the
loan off did not work out, so still in the dark. I have sort of convinced
myself to procure a reasonable 'proven' source, Rubidium or whatever, but
that
seems to be more easily decided than done..Or at least so
On 2020-10-28 2:29, jimlux wrote:
I'm still agitating for alien deviation - Microsoft offers it as a
suggestion, but not Allan, so it must be true.
:-):-):-)
Thanks Tom and Jim for the explanations. All clear now.
73 Alberto I2PHD
___
Hi
I’m pretty sure you can find multiple posts from me spelling it any of a half
dozen ways ….. :)
Bob
> On Oct 27, 2020, at 9:29 PM, jimlux wrote:
>
> On 10/27/20 6:16 PM, Tom Van Baak wrote:
>> Alberto,
>> Thanks for asking. The correct spelling is Allan variance or Allan
>> deviation,
On 10/27/20 6:16 PM, Tom Van Baak wrote:
Alberto,
Thanks for asking. The correct spelling is Allan variance or Allan
deviation, named after David Allan, of NBS (NIST). Yes, on rare
occasions it is misspelled Allen, as in the hex key wrench. Note it's
spelled correctly in the Subject line of
Alberto,
Thanks for asking. The correct spelling is Allan variance or Allan
deviation, named after David Allan, of NBS (NIST). Yes, on rare
occasions it is misspelled Allen, as in the hex key wrench. Note it's
spelled correctly in the Subject line of this thread. I'm not aware of
national
On 10/27/20 11:00 AM, Alberto di Bene wrote:
On 2020-10-27 17:38, Andy Talbot wrote:
They use Allen variance, TDEV and MTIE plots.
Is "Allen variance" just the British way of spelling "Allan variance",
or are they two different things ?
73 Alberto I2PHD
It's David Allan's name, and
On 2020-10-27 17:38, Andy Talbot wrote:
They use Allen variance, TDEV and MTIE plots.
Is "Allen variance" just the British way of spelling "Allan variance", or are
they two different things ?
73 Alberto I2PHD
___
time-nuts mailing list --
On another thread, G3YSX described this technique :
Taken in conjunction with the Wikipedia entry it begins to make sense here.
...
"A note on this thread: plotting phase against time will tell you a lot
about the effect of propagation on phase, but it is not the
Hi
Indeed this *is* a very fundamental problem in doing this sort of work.
The test setups and references generally are way harder to set up (and
more costly) than the design and construction of this or that device.
Indeed, as part of a normal design process on a GPSDO, the testing /
tweaking
Hi,
I'd like to add a comment.
What is ADEV?
It is the replacement for standard deviation as we attempt to measure
the frequency of a source using a frequency estimation based on two
phase-samples with some time distant tau between them. Thus, it shows
the frequency stability for a 2-point
Thanks Bob. Slowly it penetrates..
The 1PPS source is as you say far from being a good reference, so I will
cease that route!
I think I have to accept what I have - I believe it is good enough for my
Ham Radio work as a reference for my radios, at least into the low GHz
region.
If I manage less
Hi
What are we trying to measure with ADEV?
On a frequency source, it’s used to measure the noise of that source. Mostly we
put up plots of ADEV to show how quiet our source is. (Yes, we might also
measure
noise floor or amplifier contributions ….).
That’s the statistics part. Now for the
Bob and Tom,
Thanks again for your time on this. I understand a lot better, and have
just one issue I would like to 'harp' on a little, if you would allow..
In the simplistic example of a freq counter measuring its own reference, It
it easy to grasp and understand the incestous nature of the
Joe,
> I log the output of the TIC, in nanoseconds, and use that file to
generate an ADEV plot.
Good. That's what you need. During normal operation those readings are
bounded by the PLL. So it's essentially a measurement of how well the
PLL is working, how aggressive the OCXO is steered,
Hi
To be really clear:
ADEV can be used to measure anything and done any way you wish.
To have an ADEV that is a valid measure of a device, you need to do a
comparison to another *totally independent* device. That independent
device needs to have a better ADEV over the range of Tau that you
Hi
> On Oct 26, 2020, at 3:36 PM, Joe & Gisela Noci wrote:
>
> Bob, thanks for the very detailed explanation. It starts to make much more
> sense.
>
> To answer your question, yes, the 10MHz OCXO I am measuring is part of the
> GPSDO and is steered to GPS 1PPS.
> The process I explained ( the
Bob, thanks for the very detailed explanation. It starts to make much more
sense.
To answer your question, yes, the 10MHz OCXO I am measuring is part of the
GPSDO and is steered to GPS 1PPS.
The process I explained ( the 1PPS and the 1MHz clock from the OCXO / 10
into the flip flop, etc) and the
Hi
> On Oct 26, 2020, at 10:53 AM, Joe & Gisela Noci wrote:
>
> Hi again Bob - Seems I am destined to hog your time!
>
> If my understanding and my questions appear foolish, sorry - I do have a
> lot to learn to just understand the basics.
>
> Maybe my setup is in fact comparing itself with
On 2020-10-26 15:17, Bob kb8tq wrote:
> Hi
>
> Any practical measure you feed into an ADEV computation will be a look at
> “device A” versus “device B”. In this case one of them is your GPSDO. What
> is the other device? ( = your TIC has a DUT input and a REF IN, it compares
> one to the other
Hi again Bob - Seems I am destined to hog your time!
If my understanding and my questions appear foolish, sorry - I do have a
lot to learn to just understand the basics.
Maybe my setup is in fact comparing itself with itself?..!
I'll try to explain my hardware concisely -
The GPS 1PPS (with
Hi
Any practical measure you feed into an ADEV computation will be a look at
“device A” versus “device B”. In this case one of them is your GPSDO. What
is the other device? ( = your TIC has a DUT input and a REF IN, it compares
one to the other ….).
If you feed your measurement system with the
Hi to all,
Very new and green at this ..
I am trying to understand more about Allen Deviation, a subject about which
I , for practical purposes know 'nothing'.. I have spent a lot of time
digging on internet and have read many articles , inc W.J Wriley
publications, the Stable32 files and user
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