[time-nuts] GPSDO three cornered comparisons

Tom Knox actast at hotmail.com
Sun Oct 21 18:00:59 EDT 2012


It would be interesting to switch the A and B oscillators. The 10811 spec can vary widely.


Thomas Knox



> Date: Mon, 22 Oct 2012 07:21:08 +1000
> From: dhooke at gmail.com
> To: time-nuts at febo.com
> Subject: [time-nuts] GPSDO three cornered comparisons
> 
> Hi All,
> 
> I have an HP 58503A and a Symmetricom 58503B which are behaving quite 
> differently to one another using a common antenna. Using Z38xx, there's 
> almost an order of magnitude difference between the reported ADEVs at 
> 40k seconds (HP:7e-13, Sym:5e-12). Both have 10811 oscillators and are 
> reporting similar ADEVs up to about 1000 seconds. The Symmetricom is 
> also showing large daily temperature variations, while the HP is stable, 
> noting that ambient is varying 5-10dC over a day (I'll measure this from 
> now on).
> 
> I connected my modified Tbolt (new/good oscillator removed from PCB, old 
> temperature sensor chip removed from PCB and bonded to oscillator can), 
> which is showing performance between the two 58503s, although it's only 
> been connected for a day (but has been powered for weeks).
> 
> So is my HP 58503A telling me fibs, or is the Symmetricom crook?
> 
> I'd like to do a three cornered hat comparison between them. I'll 
> collect PPS TI data (A-B, A-T, B-T) using Timelab and a PM6681 (the only 
> TIC I have), but need help on how to post-process the data sets to 
> isolate the individual units' performances.
> 
> Any tools out there to help (without purchasing Stable32)? I can use 
> Perl to manipulate the raw data, but don't have the maths skills to do 
> the analysis myself.
> 
> Thanks,
> 
> david (still an apprentice TN, but probably addicted already).
> 
> 
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