[time-nuts] Thunderbolt vs Z3801A

SAIDJACK at aol.com SAIDJACK at aol.com
Mon Jul 21 14:17:41 EDT 2008

Hi Didier,
the drawback of this approach is that everything is connected together as  
one big circuit, and thus processor noise can get into the GPS front end and  
reduce the sensitivity and cause other errors..
For RF performance, it's probably better to have the GPS receiver sit all  by 
itself in a shielded enclosure with it's own TCXO.
Trimble seems to have done a pretty good job at the layout to handle these  
types of issues though.
In a message dated 7/20/2008 18:01:11 Pacific Daylight Time, didier at cox.net  

Because  Trimble integrated the GPS receiver and the OCXO, they use the OCXO
as a  clock to run the processor, therefore that source of error is  not

The ultimate performance is not better than a perfectly  optimized
"conventional" GPSDO + OCXO, but excellent performance can be  achieved at
lower cost, and without having to deal with certain  tradeoffs.

Now, I am sure there are other, more subtle details that  explain why the
Z3801A is generally superior to the Thunderbolt, but that I  cannot


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