UTC-GPS is based on UTC-USNO, and therefore there will be a small offset between other establishments like NIST, NPL who contribute to the UTC.
As you say, the offset will vary with time, so post-processing is the answer in critical applications (which is the way UTC is determined anyway). Rob K -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Ackermann N8UR Sent: 12 March 2007 16:51 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- an answer, and a question In short, yes. If you want true traceability to NIST, you need to take into account UTC(GPS) versus UTC(NIST). I don't think you would do this by adjusting the cable delay, because that offset will change over time. Instead, you post-process by getting the offset for the time during which you made the measurement, and adding it to your solution. John ---- Jason Rabel wrote: > Since we are on the subject... I came across this page the other day > and am curious about what other's thoughts are about it. > > http://tf.nist.gov/service/gpstrace.htm > > If I understand correctly looking at the graphs, they are saying the > time from GPS is currently off about 24-30ns from the NIST frequency > standard. So does that mean that a person wanting every last ns should > adjust their delay according to the data on that page (and of course > things like cable delay and other circuitry)? > > Jason > >> But we're time-nuts... we DO worry about those things. :-) >> >> While we were at it with the network analyzer, we did FDR (frequency >> domain reflectometry) to measure the cable delay to the antenna, and >> I spent yesterday making up six matched cables to go from the >> splitter to the receivers -- they all test within about 1 nanosecond of each other. >> >> Obsessive compulsive? Me? >> >> John > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
