[time-nuts] Z3801A holdover

Artek Manuals Manuals at ArtekManuals.com
Thu Feb 25 10:52:02 EST 2016

Joe, Joe and Bob

I am still not ready to condemn the receiver until we have more data..

Do you have any history on how many satellites you were tracking in the 
past, i.e are the number of sats being tracked and the sat strengths 
typical for your setup or are they noticeably lower now than in the 
past? Describe the antenna and its installation. While not ideal at just 
tracking 4 sats the unit will still track and lock with that few, what 
is more likely to suffer than anything is the holdover performance than 
the power up GPSDO accuracy

I have a dead on Oncore here on the bench and there are as far as I know 
no schematics available and even if there were troubleshooting it could 
be a REAL challenge, certainly there no "adjustments".

If anyone REALLY wants to see one I can post some up close and personal 
photos of the receiver board ...only helpful  in discouraging thoughts 
of repairing it as near as I can tell especially since replacement 
receivers abound from a list member and on Evil-Bay at reasonable prices


On 2/25/2016 9:15 AM, J. L. Trantham wrote:
> Joe,
> I recently had a problem with my Z3816A where it reported an erroneous date, 2035 IIRC.  However, the time was accurate.
> It was only tracking 4 sats and the signal strengths were low.  My TBolt was tracking 8 sats with good signal strength.  My antenna feeds a Symmetricom 58536A 4 way splitter and that feeds the receivers.
> I 'rebooted' the unit by turning off power, leaving it overnight then turned it on.  Same thing.
> I then removed and replaced the 'battery backup batteries' (they tested good) that I had installed and restarted it.  It never found itself.  I then gave it the Lat/Long and it found itself, with the correct time but with only 4 sats and with low signal strength.
> I then replaced the GPS receiver and now all is well.  It found itself, 8 sats, good signal strength, correct date and time, as compared to the TBolt.
> So, the GPS receiver might be on the list for your problem.
> Does anyone know anything about how to repair these receivers?
> Thanks.
> Joe
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Joseph Gray
> Sent: Wednesday, February 24, 2016 10:37 PM
> To: Discussion of precise time and frequency measurement
> Subject: [Bulk] [time-nuts] Z3801A holdover
> I just took a look at my Z3801A that has been in holdover for some time. I have been too busy to do anything about it until now.
> Before looking at the receiver stats just now, my first guess was that the Oncore GPS board went bad. However, I see that it is currently tracking 4 sats. I also see that the 1pps is invalid. Does this still point to a failed Oncore board?
> Attached is a screenshot showing the receiver stats.
> I will open this thing up over the weekend to check voltages and such.
> Until then, any tips on where to look are appreciated.
> Joe Gray
> W5JG
> _______________________________________________

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