[time-nuts] Good GPSDO on eBay?

Charles Steinmetz csteinmetz at yandex.com
Sat Jul 9 20:58:37 EDT 2016

Richard wrote:

> This looks like a good beginner's GPSDO on eBay: 172148560746
> "This is GPS Disciplined Clock made with trimble GPSDO Board.Full tested
> by Agilent 53132A with US-012 option and Ex-ref from trimble thunderbolt
>       The seller says it has a sine wave output and is accurate from
>       10e-11 to 10e-12.
> Any thoughts?

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.

In addition to that, if  "Ex-ref from trimble thunderbolt GPSDO" is 
supposed to make a buyer think it will have the best Trimble OCXO (P/N 
37265), the one that was in the Trimble Thunderbolts of list legend, 
that is almost certainly false.  It may have a Trimble-branded OCXO, but 
even if it does it will be one of the many lesser part numbers.

To me, the attempts to mislead buyers is enough, by itself,  to rule out 
dealing with that seller, under any of his ebay IDs.

Best regards,


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