[time-nuts] Good GPSDO on eBay?

Mark Sims holrum at hotmail.com
Sat Jul 9 22:07:26 EDT 2016


You are confusing these units with those made by that ham in China (can't remember his callsign, begins with a "B").   The guts of these boxes is a telco GPDDO board made by either Trimble or Symmetricom (you can tell because of the 6.0V power requirement).    And that reference to a Thunderbolt in his Ebay listing seems to refer to him comparing the output of these  to his Thunderbolt,  not that the oscillator in them came out of a Thunderbolt.

> It is very hard to say exactly what you will get, because the seller 
(who uses a dozen or more different ebay IDs) seems to change the design 
every time the wind shifts.  But typically they are FLLs (frequency 
locked loops), not genuine PLLs (phase locked loops), and have a small 
frequency offset because the design does not address some systemic 
issues of FLL design.  It is unlikely to deliver better than 10e-11 
performance with any certainty.

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