[time-nuts] 58503A date code problem

[GandalfG8 at aol.com]

Date: Sat, 21 Jun 2014 13:06:19 -0400
From: Daniel Burch  <daniel.burch at ieee.org>
To: time-nuts at febo.com
Subject: [time-nuts]  58503A date code problem
Message-ID:
<CAMyugJy7c6LyX7q26zwUM40iEzMFY5ZShrCQ_YGDa5T4VC3sTA at mail.gmail.com>
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Hi All,

I have a HP/Symm 58530A that has  the correct time, but date keeps
defaulting to 1994, Nov, 4 after GPS  Lock.  The pre-lock is 1996, so I do
see a change when it locks, just to  the wrong date.....time is exactly
correct and tracks.

Any  ideas?

Thanks!

db
--------------------------
 
It would seem likely that this could become an ongoing  problem.
 
I don't know what GPS module is used in the 58503A, but last August  it was 
the turn of the Z3815 thanks to the onboard Furuno  GT74.
A pair of 1999 Time and Frequency Solutions GPS8 units I own use the  same 
Furuno GPS module and suffered the same fate, and some versions of the  
Rapco 1804 of similar vintage have also been similarly afflicted. Although in  
the case of the 1804 it seems to be a Rapco firmware issue rather than 
anything  to do with their Trimble SVeeSix GPS modules as it hasn't so far  struck 
all versions of the same product.
 
The "problem" is the well known and well documented 1024 week  rollover 
issue, exacerbated it would seem by some manufacturers, or  individual 
designers, choosing an arbitrary date for the start of  their own 1024 week period, 
perhaps either an  initial production date or firmware compilation date, and 
then not  seeing any need to update that as time went by, probably because 
they  weren't anticipating a near 20 year product life.
With the date chosen unlikely to be public knowledge and perhaps  just lost 
in time anyway, the "failure" can come as a surprise to all and  sundry, 
manufacturer included
 
However, if any such manufacturers did have ongoing production of the same  
module over an extended period, and had the foresight to update the start 
of  their 1024 week period at either regular or irregular intervals as  
production continued, then we also face the interesting possibilty  of 
successively failing batches of the same product rather than all showing  up in one go.
 
Regards
 
Nigel
GM8PZR