[time-nuts] GPSDO three cornered comparisons

David Hooke dhooke at gmail.com
Sun Oct 21 17:21:08 EDT 2012

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.


david (still an apprentice TN, but probably addicted already).

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