[time-nuts] HP Z3805A with 100+ns PPS Jumps

Jim Sanford wb4gcs at wb4gcs.org
Sun Mar 23 17:33:21 EDT 2014

I will be eager to see responses to this.  It is similar to the behavior 
I was seeing on my "tested" nortel unit that I purchased from the 
e-place.  Tried a bunch of things, new antenna, higher antenna (even 
though my Z3801 worked fine on the old, before the Z3801 died) and 
different power supplies.

Finally gave up & shut it off.  Another time.

Hoping to see some ideas . . . . .

wb4gcs at amsat.org
On 3/23/2014 3:45 PM, John Stuart wrote:
> I just bought my second HP Z3805 (this one has a 12 ch. receiver) and have
> been monitoring it with Ulrich Bangert's Z38XX software tool.
> Last week, and again today, the PPS output has had several sudden excursions
> of +- 100 ns or more.  It appears that each jump is followed by a  jump in
> the opposite direction a few hours later.
> I have inserted the following Z38XX graphs below:
> 1. Several PPS jumps from last night and early this morning.
> 2. Similar jumps from last week.
> 3. Oscilloscope measurement confirming PPS offset. Yellow trace =
> ThunderBolt PPS,  Blue = HP Z3805A PPS
> Might I have a faulty HP Z3805A, or an erratic 10811-60165 DOCXO waking up
> from a long nap in China?
> John Stuart, KM6QX
> Lafayette, CA
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