[time-nuts] Z3801A holdover

[Joseph Gray]

Dave,

I haven't monitored the Z3801A in quite some time, but I do remember
that it used to track more satellites. For probably a year, the unit
would go into holdover often. Then a few months ago, it stayed in
holdover. Last night was the first time that I have looked at the
stats and information recently.

The antenna is a Symmetricom timing antenna. It used to sit on top of
my service monitor, but has recently been raised up several feet, in
the clear. I can't easily get it outside because I'm renting
(single-story frame house). When the Z3801A used to track more sats,
the antenna was in the old location.

I am using a 4-port Symmetricom GPS splitter. My Lucent 2-box GPSDO is
on one of the ports. I moved the Z3801A to another port, to make sure
that wasn't the problem.

What I will do tonight when I get home is to see how many sats the
Lucent is tracking.

Joe Gray
W5JG


On Thu, Feb 25, 2016 at 8:52 AM, Artek Manuals <Manuals at artekmanuals.com> wrote:
> 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
>
> Dave
> NR1DX
>
>
>
>
> 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
>> WB4BPP
>>
>>
>>
>> -----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
>>
>> _______________________________________________
>
>
> --
> Dave
> Manuals at ArtekManuals.com
> www.ArtekManuals.com
>
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