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

[Mark C. Stephens]

Bob Camp bought up an interesting point, 
using a PAD will cut the voltage going up the spout to the antenna amplifier. 
I am using a distribution amp that separately powers the GPS antenna so did not take this into consideration. 
If you try the PAD, measure the voltage output of the pad to make sure that enough voltage is getting through to power your antenna's preamp, please?


--marki

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Mark C. Stephens
Sent: Sunday, 21 July 2013 2:01 AM
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.

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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