[time-nuts] HP Z3817A Reverse Engineering
dhooke at gmail.com
Mon Oct 28 18:53:33 EDT 2013
Thanks Ed (and Skip),
I've bolted the PCBs back together, and have it connected both via
SatStat and Ulrich's Z38XX. I'll let the oscillator cook for another
week and check the PN and ADEV, and if the E1938 looks good, figure out
the UT+ configuration.
> Hi David,
> Skip Withrow and I were able to figure out the connections and the
> basic operational features. I've attached a document that describes
> our findings.
> I wouldn't mind picking up another E1938 oscillator, but I'm reluctant
> to buy one that might have mismatched oscillator and circuit board
> (i.e. the serial numbers don't match). I've asked a couple of vendors
> if the serial numbers matched, but they won't respond. Does anyone
> have any experience with a mismatched combination? How's their
> On 10/27/2013 1:26 PM, David Hooke wrote:
>> 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?
>>> 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.
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