root@petro.UUCP (Petty System God) (12/28/90)
There have been several programs posted recently to allow one to have his system call the Naval Observatory clock and have the time set all without human intervention. Having decided that this is a good idea I coerced some code into working only to discover that there appears to be a discrepancy between the time reported by WWV and that reported by the dial up number at the Naval Observatory. The difference is about 12 seconds which I consider significant since both these guys are supposed to be time standards and should do better than my Timex. I noticed, after spending a couple of hours hacking code to call the Naval Observatory and set the clock, that the time reported by the Naval Observatory was not the time I expected. I was expecting something close to the drumming that WWV was producing in the corner but to my surprise the Naval Observatory was reporting time about 12 seconds behind WWV. To confirm the observation I called back the Naval Observatory with cu and let it report while WWV was reporting over the shortwave -- sure enough when WWV hit 124900 the Naval Observatory was reporting about 124848. OK, I give up, who's right ? ---- Gilbert B. Andreen - bruce@petro.UUCP cs.utexas.edu!swrinde!petro!bruce
bob@rel.mi.org (Bob Leffler) (12/29/90)
In article <63354@petro.UUCP> root@petro.UUCP (Petty System God) writes: >the Naval Observatory was reporting time about 12 seconds behind WWV. >To confirm the observation I called back the Naval Observatory with cu and >let it report while WWV was reporting over the shortwave -- sure enough when >WWV hit 124900 the Naval Observatory was reporting about 124848. My first guess for the difference is the delay intransmitting the data via the different transports. i.e. How long does it for the data to transmit through the numberous switches, land lines, satelites, etc to reach your modem? I'm sure that it is different than shortwave. bob -- Bob Leffler, (bob@rel.mi.org), (313) 696-2479 Opinions expressed Electronic Data Systems, GMC Truck SBU may not be those Box 7019, 5555 New King Street, Troy MI. 48007 of my employer.
wht@n4hgf.Mt-Park.GA.US (Warren Tucker) (12/29/90)
In article <63354@petro.UUCP> root@petro.UUCP (Petty System God) writes: > >... the Naval Observatory was reporting time about 12 seconds behind WWV. >OK, I give up, who's right ? Most assuredly it is WWV. Certainly propagation through the phone network is no 12 seconds, so the Naval Observatory time must be just plain wrong. The WWV time over radio is absolutely correct (some will disagree, but really, what's a few femtoseconds among time freaks?). The propagation delay is a factor, but my clock ticks are 60HZ :-). ---------------------------------------------------------------------------- Warren Tucker emory!n4hgf!wht or wht@n4hgf.Mt-Park.GA.US "I was 35 years old before I knew a pie was meant to be eaten." - Moe Howard
swh@hpcupt1.cup.hp.com (Steve Harrold) (01/03/91)
Re: Naval Observatory time To add a data point: I called the Naval Observatory with my PC (1-202-653-0351) on New Year's Eve around 23:50 PST, and received a time value that matched exactly what US network television was displaying as the approach of (local) 1991 was being counted down. The program that did the dialup reported a 0.07 second delay for the round-trip signal propogation, so I have difficulty believing that a delay of 12 seconds is due to networking/routing behaviour.
bernhold@qtp.ufl.edu (David E. Bernholdt) (01/06/91)
In article <-286639992@hpcupt1.cup.hp.com> swh@hpcupt1.cup.hp.com (Steve Harrold) writes: >Re: Naval Observatory time > >The program that did the dialup reported a 0.07 second delay for the >round-trip signal propogation, so I have difficulty believing that a delay >of 12 seconds is due to networking/routing behaviour. Has anyone considered the possibility that they may be reporting _different_ times -- for example sidereal versus solar? -- David Bernholdt bernhold@qtp.ufl.edu Quantum Theory Project bernhold@ufpine.bitnet University of Florida Gainesville, FL 32611 904/392 6365