[time-nuts] GPS week wrap in HP Z3801A

mike cook michael.cook at sfr.fr
Mon Dec 26 16:40:31 EST 2011

Le 26/12/2011 21:31, Hal Murray a écrit :
> I turned on a Z3801 that had been idle for a while.  The status screen said:
>    UTC      20:03:44 [?] 11 May 1992
> That looks like 1024 weeks (19.7 years) ago.
> When I first turned it on, before finding any satellites, it said:
>    UTC      12:05:00 [?] 01 Jan 1992
> Has anybody else noticed troubles like this?
> I've got another one that still works.  It's got a bigger serial number so I
> assume it's more recent.
> Does anybody know how to read the firmware date or version?  There is a
> command to get info from the GPS unit, but I haven't found a way to get any
> info for the main firmware.
> After a while, the "[?]" goes away.
IIRC the GPSs in the Z3801As are Oncore VPs. They don't suffer from the 
GPS week rollover, but If the RTC in the receiver is not set or its 
battery has failed, and the reference year stored in EEPROM is also 
wrong, the receiver may select the wrong 20-year window. This may be 
fixed by entering a date command when the receiver is not tracking 

send the receiver


and you will get the revision data.

hope that helps


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