[time-nuts] GPSDO uncertainties

Tom Van Baak tvb at LeapSecond.com
Tue Oct 9 08:49:51 EDT 2018


Hi Don,

Thanks for the additional information. Ok, your GPSDO is clearly not a TBolt.

Can you confirm that your board is like this one: https://xdevs.com/fix/rb_lpfrs/#gpsdo

You might want to try using Heather on this GPSDO. That will assist you in seeing if it has good reception, and other parameters. It's an alternative to typing raw hp scpi commands (as seen in that web page).

As far as your 10 s gate time frequency accuracy question -- that's hard to answer without seeing Trimble specs for this board, or without doing actual measurement. There are many variables. Not all GPSDO are alike, not even close. But your 1e-10 guess is a good one. Still, we prefer to measure rather than to guess, when possible.

Has anyone on the list used a GPSDO like Don's? Are there specs? Has anyone done performance measurements?

Thanks,
/tvb

----- Original Message ----- 
From: donald collie 
To: tvb at leapsecond.com 
Sent: Monday, October 08, 2018 6:07 PM
Subject: Re: Fw: GPSDO uncertainties


Thankyou to those who have replied so far.  So it depends on the GPSDO itself. I didn`t know this. Mine is ex China, and has a Trimble PCB, with the receiver module, and Double [?] oven There`s another PCB, which is fabricated in China, and well made too, which has PSU`s and buffers for the sinusoidal output. I`ll go open it up now and make some notes... standby... The USA designed PCB is designated  "TRIMBLE 57963-D". The oven is serial number : 468010-0114, and the date code is 0950 - presumably Jan 1995. The Trimble PCB has dimensions : 4 1/2''  x  2 3/4". I`m not sure how many satellites I can aquire this far south [I am below 45 degrees latitude here], but after 20 minutes or so, the data LED goes into high gear, so I reason I`ve aquired at least one. ;-). This little unit seems to outperform the OCXO`s in my 5245L, and 8566B, which are accurate to something like 1 part in 10E9, on a 10 second count, but I`m not sure how much it is outperforming this. Thankyou Bob, Bert, and Tom, for your replies.................................................................................................................................................................................................Donald Brett Collie ZL4GX


On Tue, Oct 9, 2018 at 10:12 AM Tom Van Baak <tvb at leapsecond.com> wrote:

Hi Donald,

Do you have the make/model of that GPSDO? Or some part numbers or a quick photo? Or anything more than just "Trimble receiver and Trimble OCXO". Otherwise I think people will post guesses instead of answers. Trimble only makes a few receivers so even the dimensions of the PCB might be enough that we can ID the part.

Thanks,
/tvb

----- Original Message ----- 
From: "donald collie" <donaldbcollie at gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at lists.febo.com>
Sent: Sunday, October 07, 2018 6:59 PM
Subject: [time-nuts] GPSDO uncertainties


> I have a GPSDO which has a Trimble receiver, and Trimble OCXO inside.[I
> think it runs Lady Heather] What I would like to know is what uncertainty
> the 10MHz output will be with a 10 second count.This presumes that the
> GPSDO is receiving satellite signals, and the OCXO is being suitably
> diciplined. Should I expect 1 part in 10E12?, 1 part in 10E10?. This device
> gives superior performance to an OCXO barefoot - but how much better? Would
> somebody in the group who knows the answer, please wax elequently.
> Thankyou,.................................................................................................Donald
> B. COLLIE
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