Re: [time-nuts] Accuracy results with Trimble Thunderbolt?

[Taka Kamiya via time-nuts]

Antenna mask of zero degrees is actually NOT good.  You get satellites going in 
and out of your antenna's view too often (because satellite can pop in and out 
of horizon, and other obstructions), cause switches in satellite used, and that 
contribute to fluctuations.  10 to 20 degree, in most cases, will give you 
better results.  I'd suggest seeing what it is set to and adjust accordingly.  
"Auto" anything will assume a lot of things, and what it arrives isn't always 
the best.

Also, what T-bolt outputs and LH displays isn't an actual measurement of the 
output.  It's a computed figure.  I don't actually look at it...  as long as 
it's locked, I'm pretty happy.
By the way...  I have a lot of GPSDO in my lab.  Short term fluctuation of 
output vary quiet a bit.  That is quite normal.  It is designed to give you a 
good average over time.  (hours to days)

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Friday, March 20, 2020, 5:51:27 PM EDT, Frank O'Donnell 
 wrote:  
 
 I hope you all don't mind a novice-level question, but I'd be interested 
in any feedback on what I'm seeing with the accuracy of the 10 MHz 
signal out on my Trimble Thunderbolt.

I bought the Thunderbolt last year used on eBay, and it appears to be of 
about 2001 vintage. Most recently it's been running continuously for 
about 2 1/2 months, attached to a roof-mounted Lucent PCTEL 26db twist 
antenna with a clear view of the sky, with the receiver located in a 
room with a relatively stable temperature. Lady Heather and Thunderbolt 
Monitor both appear to report it to be well settled-in. My main use of 
the Thunderbolt is to supply a 10 MHz reference signal to an HP3586B and 
HP3336B for frequency measurement purposes.

At the beginning of this month I remember typically seeing about 20 ppt 
accuracy for the 10 MHz reference as reported in Heather. I then used 
Heather commands to initiate an autoset of oscillator parameters (set 
antenna elevation mask angle to 0 with FE keyboard command and set 
signal level mask to 1 with FL command in order to allow collection of 
signal level data across full sky; clear signal level history with CM 
keyboard command; let run at least 6-12 hours to build up new satellite 
signal level map; issue “” autotune command, allow time to complete). 
Now I seem to be seeing about 60 ppt accuracy on average.

For my purposes, these differences are probably academic -- if I'm doing 
my math right, 60 ppt in a 10 MHz signal is 0.0006 Hz, far down in the 
noise of frequency variation due to Doppler etc. Still, I guess I've 
drunk enough of the Koolaid to wonder about the accuracy level and any 
ways to improve it.

So, some questions. Is it possible that the increase in the error seen 
could be due to the oscillator parameter autoset sequence that I ran? If 
so, is there a way to remedy this? What would be typical accuracy for 
the 10 MHz reference on a Thunderbolt? Is there anything else I can do 
with the Thunderbolt itself to increase the accuracy?

If I want to consider an alternative to the Thunderbolt that might offer 
better accuracy, is there a logical next step?

Thanks for any suggestions,

Frank


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Re: [time-nuts] HP 106B on Ebay

[Jeff Kruth via time-nuts]

I bet he doesnt know to push the little black buttons to get the dividers going 
for the 1 MHz and 100 KHz!I have one in my lab
Jeff kruth
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Re: [time-nuts] HP 106B on Ebay

[Jeremy Nichols]

I would be concerned the xtal has drifted so far it can’t be adjusted to 5
MHz any more. My 103AR has such a problem.

On Fri, Mar 20, 2020 at 12:17 PM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> I saw this one.
> What scares me is that the seller appears to be competent in testing his
> frequency counter, oscilloscope plugin, and other equipment, but on this
> one he says, "not sure how to operate".  My alarm went off and I didn't bid.
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Friday, March 20, 2020, 2:49:34 PM EDT, Bob kb8tq 
> wrote:
>
>  Hi
>
> I’m guessing that it is a dewar based OCXO. If so, the *big* question is:
> Can the boys at UPS / Fed Ex / DHL / USPS (your pick) get it to you
> without cracking the glass bottle? I’ve had reasonable success at shipping
> them ( = dewar based OCXO’s not HP106’s)  in, but not 100%
> success. Replacing dewars is generally not an easy task.
>
> Bob
>
> > On Mar 20, 2020, at 12:49 PM, Perry Sandeen via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > Gents,
> > This is the only one I've ever seen on ebay in 15+ years.  Sold as parts
> only but it has a clean 5Mhz output.  No bids so far at $499. Auction ends
> Sat 1:52 PDST.  (I'd buy it if my discretionary financial situation was
> better).
> > Regards,
> > Perrier
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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>
>
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>
-- 
Jeremy Nichols
Sent from my iPad 6.
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[time-nuts] Accuracy results with Trimble Thunderbolt?

[Frank O'Donnell]

I hope you all don't mind a novice-level question, but I'd be interested 
in any feedback on what I'm seeing with the accuracy of the 10 MHz 
signal out on my Trimble Thunderbolt.


I bought the Thunderbolt last year used on eBay, and it appears to be of 
about 2001 vintage. Most recently it's been running continuously for 
about 2 1/2 months, attached to a roof-mounted Lucent PCTEL 26db twist 
antenna with a clear view of the sky, with the receiver located in a 
room with a relatively stable temperature. Lady Heather and Thunderbolt 
Monitor both appear to report it to be well settled-in. My main use of 
the Thunderbolt is to supply a 10 MHz reference signal to an HP3586B and 
HP3336B for frequency measurement purposes.


At the beginning of this month I remember typically seeing about 20 ppt 
accuracy for the 10 MHz reference as reported in Heather. I then used 
Heather commands to initiate an autoset of oscillator parameters (set 
antenna elevation mask angle to 0 with FE keyboard command and set 
signal level mask to 1 with FL command in order to allow collection of 
signal level data across full sky; clear signal level history with CM 
keyboard command; let run at least 6-12 hours to build up new satellite 
signal level map; issue “” autotune command, allow time to complete). 
Now I seem to be seeing about 60 ppt accuracy on average.


For my purposes, these differences are probably academic -- if I'm doing 
my math right, 60 ppt in a 10 MHz signal is 0.0006 Hz, far down in the 
noise of frequency variation due to Doppler etc. Still, I guess I've 
drunk enough of the Koolaid to wonder about the accuracy level and any 
ways to improve it.


So, some questions. Is it possible that the increase in the error seen 
could be due to the oscillator parameter autoset sequence that I ran? If 
so, is there a way to remedy this? What would be typical accuracy for 
the 10 MHz reference on a Thunderbolt? Is there anything else I can do 
with the Thunderbolt itself to increase the accuracy?


If I want to consider an alternative to the Thunderbolt that might offer 
better accuracy, is there a logical next step?


Thanks for any suggestions,

Frank


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[time-nuts] HP5061A video on youtube

[Matthias Welwarsky]

Some here may find this interesting.

https://youtu.be/eOti3kKWX-c

BR,
Matthias




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Re: [time-nuts] HP 106B on Ebay

[Taka Kamiya via time-nuts]

I saw this one.
What scares me is that the seller appears to be competent in testing his 
frequency counter, oscilloscope plugin, and other equipment, but on this one he 
says, "not sure how to operate".  My alarm went off and I didn't bid.

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Friday, March 20, 2020, 2:49:34 PM EDT, Bob kb8tq  wrote: 
 
 
 Hi

I’m guessing that it is a dewar based OCXO. If so, the *big* question is: Can 
the boys at UPS / Fed Ex / DHL / USPS (your pick) get it to you
without cracking the glass bottle? I’ve had reasonable success at shipping them 
( = dewar based OCXO’s not HP106’s)  in, but not 100%
success. Replacing dewars is generally not an easy task.

Bob

> On Mar 20, 2020, at 12:49 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Gents,
> This is the only one I've ever seen on ebay in 15+ years.  Sold as parts only 
> but it has a clean 5Mhz output.  No bids so far at $499. Auction ends Sat 
> 1:52 PDST.  (I'd buy it if my discretionary financial situation was better).
> Regards,
> Perrier
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[time-nuts] of possible interest

[djl]

https://www.sv1afn.com/en/products/vhf-uhf-triplexer-1.html

10 mhz and uhf/vhf on same cable.
--
Dr. Don Latham  AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304


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Re: [time-nuts] HP 106B on Ebay

[Bob kb8tq]

Hi

I’m guessing that it is a dewar based OCXO. If so, the *big* question is: Can 
the boys at UPS / Fed Ex / DHL / USPS (your pick) get it to you
without cracking the glass bottle? I’ve had reasonable success at shipping them 
( = dewar based OCXO’s not HP106’s)  in, but not 100%
success. Replacing dewars is generally not an easy task.

Bob

> On Mar 20, 2020, at 12:49 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Gents,
> This is the only one I've ever seen on ebay in 15+ years.  Sold as parts only 
> but it has a clean 5Mhz output.  No bids so far at $499. Auction ends Sat 
> 1:52 PDST.  (I'd buy it if my discretionary financial situation was better).
> Regards,
> Perrier
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> and follow the instructions there.


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Re: [time-nuts] HP 106B on Ebay

[ziggy9+time-nuts]

https://www.ebay.com/itm/HP-Agilent-106B-Quartz-Oscillator-Frequency-Standard/303514587258
 



> On Mar 20, 2020, at 1:20 PM, Tim Lister  wrote:
> 
> On Fri, Mar 20, 2020 at 9:59 AM Perry Sandeen via time-nuts
>  wrote:
>> 
>> Gents,
>> This is the only one I've ever seen on ebay in 15+ years.  Sold as parts 
>> only but it has a clean 5Mhz output.  No bids so far at $499. Auction ends 
>> Sat 1:52 PDST.  (I'd buy it if my discretionary financial situation was 
>> better).
> 
> Do you have a link to the auction ? All I am getting are timing belts
> and printer cartridges... Are the 106 models as loud as the 105 models
> that IIRC other have commented on in the past?
> 
>> Regards,
>> Perrier
> 
> Cheers,
> Tim
> 
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Re: [time-nuts] HP 106B on Ebay

[Tim Lister]

On Fri, Mar 20, 2020 at 9:59 AM Perry Sandeen via time-nuts
 wrote:
>
> Gents,
> This is the only one I've ever seen on ebay in 15+ years.  Sold as parts only 
> but it has a clean 5Mhz output.  No bids so far at $499. Auction ends Sat 
> 1:52 PDST.  (I'd buy it if my discretionary financial situation was better).

Do you have a link to the auction ? All I am getting are timing belts
and printer cartridges... Are the 106 models as loud as the 105 models
that IIRC other have commented on in the past?

> Regards,
> Perrier

Cheers,
Tim

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[time-nuts] HP 106B on Ebay

[Perry Sandeen via time-nuts]

Gents,
This is the only one I've ever seen on ebay in 15+ years.  Sold as parts only 
but it has a clean 5Mhz output.  No bids so far at $499. Auction ends Sat 1:52 
PDST.  (I'd buy it if my discretionary financial situation was better).
Regards,
Perrier
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[time-nuts] Phase measurement of my GPSDO

[Bob Q]

I have seen differences between both UCT and Oscilloquartz 8663 ocxo’s. The 
attached plot shows an example. Both boxes use Ublox LEA-6T receiver, surveyed 
in, AD5680 DAC 18 bit DAC, same level shift circuit and same control circuit. 
The reference is an LPRO-101. The Oscilloquartz ocxo was purchased used. Both 
UCT ocxo’s (only the better one is shown) were purchased new and have 100’s of 
operating hours. I have also seen differences with constant EFC control 
voltage. The differences limit what  performance you can achieve.___
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Re: [time-nuts] Phase measurement of my GPSDO

[Attila Kinali]

On Thu, 19 Mar 2020 20:32:30 +0100
Tobias Pluess  wrote:

> The GPS phase detection happens on page 3. I use the TDC7200 as
> interpolator.
> Inside the STM32 microcontroller, I let a timer run with the 10MHz clock.
> The timer overflows to 0 when it reaches the value 999.
> Further, the 1PPS pulse from my GPS module triggers the interpolator, and
> is delayed by max. 2 clock cycles. The delayed signal stops the
> interpolator and is used as a capture event of the timer.
> So, when the OCXO has the right frequency, the captured value would always
> be the same. To determine the phase, I use the following code:
> 
> if(captured value >= 500)
> phase = 1000 - captured value;
> else
> phase = -captured value;
> 
> with the aid of this bit of code, my phase value is always perfectly in the
> interval -500 to +500. My test today was to let the OCXO run with a
> fixed voltage at its EFC input, while I recorded the resulting phase data.
> My recorded data is here:
> 
> https://hb9fsx.ch/files/gpsdo/phase.txt


I guess the units here are cycles of 10MHz/100ns?

BTW: keep in mind that you might run into metastability effects.
Depending on what the exact phase relation between your 10MHz
signal and the internal clock of the STM32 is, you might or might
not get a +/-1 cycle uncertainty due to metastability.

> 
> Now I made two plots (here: https://hb9fsx.ch/files/gpsdo/phase.png). The
> upper is the raw phase data, and I also fitted a linear function to it
> (i.e. if the OCXO has a constant frequency but has some offset from 10 MHz,
> the phase would drift linear into one direction - at least I expect it to
> do so).
> The lower plot is what results when I subtract my linear fitted function
> from the measured phase. I am wondering whether this makes some sense? One
> can see some wiggles and ripple, especially between sampel 0 and 3000. Is
> this the GPS jitter I see there?

Yes, it makes sense. I would have done a quadratic fit, as your OCXO
is just starting up and thus will have a "large" linear frequency drift,
which results in a quadratic phase drift.

The wiggles in the beginning could be uncorrected saw-tooth as Bob mentioned.
That would aproximately fit the quantization that the u-blox modules have
from their 24MHz clock. The change in the wiggles could be hanging bridges,
but it's hard to see. 

With your antenna position you will also get quite high jitter on the PPS
due to not many satellites being visible. Make sure you are running on
a well surveyed position hold to mitigate this. Or get your antenna outside.
See also the measurements that Said Jackson did a few years ago:

http://lists.febo.com/pipermail/time-nuts_lists.febo.com/2012-December/055731.html
http://lists.febo.com/pipermail/time-nuts_lists.febo.com/2012-December/055774.html

BTW: there were some quite interesting discussions about GPSDOs in
late 2012 and early 2013. Might be worth a read.


> Further, I also imported this phase data into Timelab and determined the
> ADEV. Here is my plot:
> 
> https://hb9fsx.ch/files/gpsdo/timelab.png
> 
> This trace is kind of what I expect, but since I use a OSA/UCT 8663 double
> oven OCXO, I would have expected it to be much lower. Something in the
> 1e-12 regime perhaps? is that realistic?

You are measuring your OCXO against GPS. At short tau, GPS is going
to dominate your ADEV. See http://www.leapsecond.com/pages/m12-adev/
for reference.
BTW: You can tell the difference in MDEV. At taus >1s the OCXO
will be clearly in the flicker phase regime, while GPS will still
be in the white phase regime up to 1000-10ks.

The Timing Appnote of u-blox GPS.G6-X-11007 might give you additional
information on the expected behaviour of the u-blox modules:
https://www.u-blox.com/sites/default/files/products/documents/Timing_AppNote_(GPS.G6-X-11007).pdf

To see the actual performance of the system, you need to measure it
against a stable reference. If you have I would recommend using
a combination of 2 or more references: one stable, free running
OCXO (e.g. OSA 8607 or FE-405), an Rb standard (LRPO or PRS-10).
This way you have something that is more stable than your GPSDO
at (almost) all taus. Of course, to be sure that what you are
measuring is actually the performance of the GPSDO and not your
reference, you need to have at least 2 of each type and then
do an n-cornered hat. And yes, beyond one day, this will not
help you as the instability of the Rb standard will be the
limiting factor. That's when take out your Cs beam standard
and start measuring for real ;-)

And yes, characterizing your GPSDO is the biggest problem
of building one. Soon you will be building lots of
measurment equipment to characterize your GPSDO, get more
gadgets and gear until your garage is full of atomic clocks :-)

> As one can see at tau=800s, the
> ADEV is around 5e-11, so is this really all I can expect from this very
> sophisticated OCXO? (However I should maybe add that the OCXO is brand-new
> and has never