[time-nuts] Jupiter GPS receiver

Johan Swenker Johan.Swenker at xs4all.nl
Tue Jan 3 18:34:29 EST 2006


>>Hello Didier,
>>The Jupiter GPS receiver (if used in NMEA and not binary mode) has a known
>>fault, that it can be 1 or 2 seconds delta to UTC, this is independent of
>>the "leap-second" situation.

I use my Jupiter GPS to synchronize my ntp-server. When I ran it in 
NMEA-mode, I had to fudge it 1.135 sec. A few days later I had to 
fudge it 2.135 sec to give a time similar to public ntp-servers.

The NTP newsgroup tells me that most consumer grade GPS-devices are 
meant for navigation; giving an accurate time to the outside world is 
not of primary importance. Thus I attributed the bad NMEA quality to 
the unimportance of time to NMEA-engineers.

I currently run my Jupiter in binary mode. According to ntpd the 
offset is generally a few microseconds. I have no independant way to 
check that claim.

Regards, Johan Swenker

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