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

Mark C. Stephens marks at non-stop.com.au
Sat Jul 20 16:01:01 UTC 2013


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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