[time-nuts] Advice Z3816A jumping to Holdover: 1PPS TI exceeds hold threshold, then Recovery: phase alignment for 3-4 hours.

[Azelio Boriani]

OK, interesting but putting an attenuator on the antenna input seems
not a good idea when there are 5V present...

On Sat, Jul 20, 2013 at 6:01 PM, Mark C. Stephens <marks at non-stop.com.au> wrote:
> Azelio, I had an interesting experience with the same symptoms tonight.
> I inserted a 6 dB pad on the antenna input and it appears to alleviated the problem.
> Perhaps the GPS module is being overloaded with too much signal?
>
> --marki
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Azelio Boriani
> Sent: Tuesday, 16 July 2013 5:57 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Advice Z3816A jumping to Holdover: 1PPS TI exceeds hold threshold, then Recovery: phase alignment for 3-4 hours.
>
> I have a 58503 that occasionally is not able to track satellites.
> Usually I wait until the holdover expires but then the only fix seems to restart the 58503 (SYST:PRESET) better than power cycle. It seems there is a command to reset only the GPS receiver but it is not in the
> 58503 manual.
>
> On Tue, Jul 16, 2013 at 6:33 AM, Mark C. Stephens <marks at non-stop.com.au> wrote:
>> I have a Z3816A and it periodically jumps into holdover with error message:
>> Holdover: 1PPS TI exceeds hold threshold Then for the next 3-4 hours
>> it gradually adjusts the phase alignment.
>> The error message is Recovery: phase alignment [TI +435.5 us] (when I
>> noticed it had changed, they figure was likely to have been much
>> higher) The TI then gradually decreases, currently it is sitting on:
>> Recovery: phase alignment [TI +129.9 us]
>>
>> I am hoping that I won't have to power cycle the GPSDO to get it locked again.
>>
>> I emailed the seller (Yixun HK) and they are trying to tell me power cycle is only fix.
>> They also claim the cause is due to weather?
>>
>> I explained to Yixun I have a lot of smart clocks here and none have exhibited the same problem ever.
>> This is the 3rd defective Z3816A I have got off Yixun and it is costing me a small fortune to send these back.
>> The first was reporting the 12v Supply was out of tolerance, a quick jump into pForth confirmed the A, B and C 12v supplies were over 12.5v.
>> I ended up sending it back to Yixun.
>> The second I was able to fix myself, apparently someone had changed the OCXO but left the insulating-spacing washers out from the pins of the OCXO.
>> This was causing a short on the EFC.
>> That Z3816A unit and now appears to be running normally except the PU is terrible, I'll run Cal for 24 hours and see if it improves.
>>
>> However, Now the 3rd unit is getting this TI exceeded error.
>> I think I have had enough of shipping things back to these guys - they won't replace anything, including parts, unless you ship back to them first.
>>
>>
>> I would just like to get some informed opinions, could the issue be with:
>>
>> a)      Antenna
>>
>> b)      GPS Module
>>
>> c)       OCXO
>>
>> d)      PLL circuit on main board.
>>
>> Many thanks,
>> --marki
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