[time-nuts] Z3801A holdover

Artek Manuals Manuals at ArtekManuals.com
Thu Feb 25 18:18:09 EST 2016


Joe

Getting the antenna outside for a decent signal even if not in the clear 
  would be advisable before you spend money on other possible solutions 
...Certainly explains the only tracking 4 problem

As a minimum I would go portable on a card table in the yard or parking 
lot for several hours to see if that explains things...

The splitter is by definition not a loss-less device either... going 
direct to the Z3801 with the antenna is a worthy exercise as well to see 
how things behave....still the unusual EFC plot has me wondering 
ultimately if the 10811 or the power supply are being funky.

Try a better antenna location with no splitter first before you open the 
box and start flailing at the power supply and receiver.


Dave
NR1dx



On 2/25/2016 4:52 PM, Joseph Gray wrote:
> 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
>>


-- 
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com

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