[time-nuts] GPS clock error.

Max Robinson max at maxsmusicplace.com
Thu Apr 14 04:15:34 UTC 2011


Hi Hal.

The manufacturers logo consists of the lower case letters ila next to an 
hour glass.  The instruction book calls it a talking atomic alarm clock.  It 
is somewhat of a battery hog.  They have to be replaced every 2 or 3 months.

Regards.

Max.  K 4 O D S.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: "Hal Murray" <hmurray at megapathdsl.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Wednesday, April 13, 2011 3:29 PM
Subject: Re: [time-nuts] GPS clock error.


>
>> This morning at 10 AM CDT my GPS clock read 8 PM July 5th.  My wife 
>> reported
>>  that the time had been 2 hours off at 6 AM local time.  She didn't 
>> notice
>> if it was AM or PM.  The parabolic dish icon was missing from the 
>> display.
>> I manually set the time and date but when compared to my two WWVB clocks 
>> it
>>  was clear it was in holdover mode.  I waited about 3 hours then removed 
>> the
>>  batteries and reinstalled them.  ...
>
> Could you say more about this clock?
>
> How long do the batteries last? ...
>
> I'm familiar with battery operated "atomic" clocks that listen to WWVB.  I
> didn't know about GPS versions.
>
> I'd expect a WWVB receiver to use much less power but maybe modern GPS
> receivers are good enough so they would have reasonable battery life.
>
> My best guess is that your receiver got tricked by noise that looked good
> enough.  I've seen GPS receivers report that their info was valid when it 
> was
> miles from the reported location.  Usually, that's right after recovering
> from not-enough-satellites.
>
>
> albertson.chris at gmail.com said:
>> There are also endless ways that logic inside th GPS can fail in a "soft"
>> way.  Memory can become pattern sensitive or a tiny sense amp in a RAM 
>> chip
>> can get noisy and cause one in a billion type soft errors.   I don't 
>> bother
>> to fix things until I can make it repeat on demand
>
> Memory doesn't usually "become" pattern sensitive.  It might be designed 
> that
> way.
>
> Cosmic rays or alpha particles are the usual ways that DRAM gets soft 
> errors.
> You can also have noise/crosstalk at the board level (or on chip) or power
> supply problems.
>
> If you want to build a reliable system, you have to pay attention to rare
> bugs.  If nothing else, you want to collect data on them so you know if 
> you
> have a problem and/or how bad it is.
>
>
>
> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
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