[time-nuts] Substitute GPS in a Z3801A

Mike S mikes at flatsurface.com
Thu Jun 24 13:01:49 UTC 2010

At 10:48 PM 6/23/2010, Robert Benward wrote...
>Has anyone ever put another GPS in a Z3801A?  Will the software 
>another GPS that tracks say, 12 channels?

Possibly 8 channels. You must use a Motorola Oncore VP. A 6 channel one 
was what HP used. There are mixed reports on using an 8 channel VP - 
some say it works fine, others say you must configure it in 6 channel 
mode (but you do pick up improved reception). Whether the different 
reports are due to changes in configuration or firmware of the z3801a, 
the Oncore, or both - I have no idea.

The commands/responses used by the z3801a prevent it from working 
directly with newer GPS modules, like the GTs, UTs or M12s (even if you 
adapted them physically).

If you want to try and get better performance with a newer GPS 
receiver, you should be able to leave the existing board in place, and 
bypass the 1PPS input with the signal from the newer receiver. You'd 
only get in trouble in exceptional conditions (new receiver loses sync, 
but existing one is reporting good satellite lock, etc.). Of course, 
the z3801a satellite reporting wouldn't be worth much. 

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