[time-nuts] Good GPSDO on eBay?

Mark Sims holrum at hotmail.com
Sat Jul 9 20:39:12 EDT 2016

They are based upon a telco surplus "UCCM" GPSDO board.   Both Symmetricom and Trimble made (mostly) compatible units.  I prefer the Trimble units...  they store their settings in EEPROM.  The Symmetricom units don't... and have to do a long re-survey every time you power them up.   Plus the firmware in the Symmetricom units has a couple of minor glitches (occasionally drops a time stamp output message and can send the time stamp message in the middle of other message outputs).   That said,  the Symmetricom is rumored to have a slightly better oscillator)... but it is driven by a 6V to 12V DC-DC converter that is known to be somewhat unreliable.  I have not measured the output ADEVs, etc.

A little shopping on Ebay (search Trimble GPSDO) will turn up some units for less money.   I bought one of these and it arrived quickly and safely in good condition (BTW, you used to be able to get them for $50):
There are unscrupulous sellers shipping damaged units.

This thread on EEVBLOG covers the units pretty well:

I now have Lady Heather working with both models.


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