[time-nuts] Z3801A with other GPS receiver

Brooke Clarke brooke at pacific.net
Fri May 18 17:22:26 EDT 2007

Hi Didier:

I seem to remember that one or more of the HP boxes that used the 6/8 channel 
Motorola GPS receivers used a secret method of making use of the sawtooth error 
information.  Some trick was needed because there was a bug that caused the 
sawtooth to be wrong every now and then and it always was wrong in the same 
polarity.  Therefore you could not average using the sawtooth.  Most 
applications just ignored the sawtooth output and averaged.

But if the Z3801 is using the sawtooth, and you replace the receiver with 
another model, then there will be a problem.  A fix would be if someone would 
come clean and tell us how HP got around the sawtooth bug in detail, then you 
could take the output from an M12+T and recreate a data stream that would look 
just like the 6/8 channel unit including the buggy sawtooth byte.

Have Fun,

Brooke Clarke

Didier Juges wrote:
> Here are a few questions about reusing a Z3801A main board.
> Would the Z3801A work with another GPS receiver?
> In other words, does the board talk to the GPS engine via the serial 
> port, other than receiving the 1 PPS?
> If it does talk to the GPS receiver, which GPS receiver other than the 
> original 6 channel Oncore model would work with it (compatible command 
> structure)?
> Thanks in advance
> Didier KO4BB
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