[time-nuts] Good GPSDO on eBay?

Charles Steinmetz csteinmetz at yandex.com
Sat Jul 9 23:12:56 EDT 2016

Mark wrote:

> Charles,
> 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.

Thanks, Mark, I stand corrected.  That also means it will have a PLL, 
not an FLL.

How good is the OCXO? Can you adjust the loop tuning parameters for best 
stability with the individual OCXO?  If not, does the loop cross over 
from the OCXO to the GPS at an appropriate tau, or does it exhibit the 
notorious "crossed over too early" hump in the xDEV plots?  Does it 
store its surveyed location or does it need to do a new survey every 
time it is powered up?

Finally, is there a good reason to pay $160 for one the seller has put 
in a box, or can you buy the board for much less and do that yourself?

Best regards,


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