[time-nuts] Z3815A date problem fixed?

[Morris Odell]

Thanks for the reply Magnus. I know the frequency control function is
unaffected by the date problem but I'm far too obsessional to ignore it :-)

I contemplated the AVR solution to correct the code but once I looked at the
output of the receiver with a MAX232 as suggested here, I found there were
quite a few different and varying NMEA and proprietary sentences being sent
each second and most of them contained the time & date in one form or
another. Not knowing which ones the Z39815 relies on means they all have to
be identified and corrected. Programming an AVR to fix this would not be
beyond me but it would be complex and time consuming compared to the
receiver transplant and I'd still have to make the hardware for the AVR. It
would also mean finding a bit of room inside the Z3815 to fit an AVR board .
It's also sort of kludgy, like wearing gloves because your pen leaks. 

Better, I think, to transplant the receiver. The GT-8031 will suffer a
similar fate according to the spec, at midnight on December 31, 2079 but
I'll be 130 years old then so probably won't need to replace it again....

Morris
 

From: Magnus Danielson <magnus at rubidium.dyndns.org>

On 24/01/14 11:59, Morris Odell wrote:
> Hi all,
>
> There was some consternation here 5 months ago when Z3815A GPSDOs began
> reporting a date 1024 weeks in the past. This was due to a storage
overflow
> condition in the Furuno GPS receiver in the Z3915A. The designers probably
> never anticipated that they would still be in use 20 years later....
> Oscillator discipline was unaffected as the 1 pps was still good.

It's kind of expected that the oscillator discipline works, because all 
what has happen is that the conversion from GPS time to normal time 
(being GPS or UTC) has been unable to unwrap the GPS week number 
properly. It's really a problem with the system than with the receiver.

> Obsessional types like me looked for a solution. There didn't seem to be
any
> knowledge out there about reprogramming the receivers so it had to be a
> transplant.

Interesting approach. There is two things one can do: Toss in a small 
PIC/AVR/whatever that modifies the time, or update to a receiver which 
does not have the issue. You can also just completely ignore the fact :)

Cheers,
Magnus



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End of time-nuts Digest, Vol 114, Issue 96
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