[time-nuts] HP Z3817A Reverse Engineering

[David Hooke]

Hi Ed,

My E1938 also came from a very battered STLN4096A from the same source, 
and I might also try to get the other boards functional. Could you share 
the details of the GPS connections, and which GPS receiver you used?

Cheers,

david

> I recently purchased a Motorola STLN4096A with the HP E1938A 
> oscillator.  I bought it for the oscillator only.
>
> Then I got intrigued by the HP Z3817A GPSDO that's included.  I've 
> reverse engineered most of it and I've got it running.  The 1 PPS is 
> really good ( 1000 measurements, Std. Dev. of <200 ps, min to max 
> range of <1.5 ns) and the HUP is very slowly dropping (currently at 13 
> us after ~1.5 days) as the oscillator works out the kinks after it's 
> long sleep.  It's dropping much slower than my Z3801A did when I first 
> turned it on.
>
> There's one input that I haven't been able to figure out.  I've got 
> data in and 1 PPS in from the GPS receiver.  Everything seems to be 
> working so I'm at a loss what that the other input could be for.  
> There are no clues to it's function because it appears to go into one 
> of the Xilinx chips.
>
> Does anyone have any more info on the unit?  Has anyone figured out 
> the other input?
>
> I have searched the net and the archives.  There's very little info or 
> discussion on this unit.
>
> Ed
>
>