[time-nuts] Good GPSDO on eBay?

Michael Wouters michaeljwouters at gmail.com
Sat Jul 9 21:44:13 EDT 2016

"Full tested by Agilent 53132A with US-012 option and Ex-ref from
trimble thunderbolt

I think what the seller saying is that the counter was externally
referenced to the Thunderbolt for the frequency measurements that they


On Sun, Jul 10, 2016 at 10:58 AM, Charles Steinmetz
<csteinmetz at yandex.com> wrote:
> 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
>> GPSDO."
>>       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,
> Charles
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