Dan,
I hate to speculate but it's really odd that more than one person is
reporting EFC issues with the Z3801A this week. I wonder if it's a bug
in the Motorola Oncore; the OEM GPS receiver used in the Z3801A (and
other early hp GPSDO). Two events have happened recently:
1) There was a GPS WNRO in April 2019, so Oncore dates will be wrong.
But, like the rollover in August 1999, this shouldn't cause a GPSDO to
go crazy.
2) More interesting, as of June 16, it's been 128 weeks since the
previous leap second. There were reports of some aircraft GPS receivers
losing lock from June 9 to June 16 due to an obscure bug in certain GPS
receivers. It's related to leap seconds and 8-bit week numbers (127 + 1
is -1 not 128).
In theory this shouldn't cause a GPSDO any trouble, but I know that a
vaguely similar 8-bit problem occurred with the Oncore VP back in 2003. See:
http://leapsecond.com/notes/leapsec256.htm
If anyone happens to have a binary log from an Oncore VP or UT for the
past week or two, please let me know.
Thanks,
/tvb
On 6/20/2019 10:05 AM, Dan Rae via time-nuts wrote:
I have an elderly 3801A with some 182,000 hours on the clock, which if
my arithmetic is correct means over twenty years of operation. Since
it has a well aged and remarkably stable OCXO I would like to keep it
going if possible. Recently it has been going into Holdover and
staying there for no reason that I can see, it is fed from the same
antenna / splitter amp combination with a good sky view as eight other
GPSDOs here. LH reports as good a signal strength on it as any of the
others. A Cold Reset gets it going again.
Does anyone know if a more modern receiver can be fitted in place of
the existing VP6? Is it likely to be a Rx problem anyway?
I'm running LH at the moment and will try to capture a screen when it
next goes into Holdover to see if that gives me any clues.
Thanks for any advice!
Dan
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