[time-nuts] Trimble "UCCM" GPSDO adevs

[Mark Sims]

I just added the capability of Heather to monitor and control a GPS device while simultaneously calculating ADEVs from an external time interval counter like the TAPR TICC  (it can also work with the time interval analyzer only).  This mode lets Heather calculate true adevs instead of "bogo-adevs" derived from the GPSDO self-reported control loop statistics.

As a test.  I connected Heather to a Trimble "UUCM" GPSDO and a TICC.  The TICC channel A is the UCCM and channel B is a Oscilloquartz Star-4 GPSDO.  The TICC reference is a ERC-130 rubidium (uses an LPRO-101.  Attached is a screen dump of a 12 hour run.  The UUCM beats the Star-4 at tau<20 seconds.

There are a few variants of the UCCM receivers out there... one by Symmetricom and at least two (UCCM and UCCM-P) by Trimble.  They run off of 6VDC.   Performance is not too shabby for a small $70-$120 GPSDO.   Search Ebay for "Trimble 65256",  "Trimble GPSDO", or "Symmetricom GPSDO".   Be aware that there are sellers sending units that were damaged in salvage.   I'd probably go with a "tested" unit.
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