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

[Mark C. Stephens]

Bob - Pad is connected between Distribution amp that powers antenna from separate supply. Good idea.

I haven't bothered measuring the voltage at the output of the pad, perhaps a simple calculation for you?


--marki

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Camp
Sent: Sunday, 21 July 2013 12:06 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.

Hi

Pad = resistor in series with the dc. That will drop the voltage on the amp in the antenna. Not a good idea. 

Bob

Sent from my iPhone

On Jul 20, 2013, at 9:26 PM, "Mark C. Stephens" <marks at non-stop.com.au> wrote:

> I did a quick check of the antenna current on a normal (un-attenuated) vs. the attenuated receiver:
> 
> Normal:
> Antenna current: 26.470589
> 
> Attenuated:
> Antenna current: 32.352940
> 
> Slightly higher, but well within range.
> 
> 
> --marki
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 
> On Behalf Of Azelio Boriani
> Sent: Sunday, 21 July 2013 8:24 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.
> 
> 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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