Hi Tom - how about the Trimble NTPX26AB-06 made for Nortel Z3801 clone - where does this rank compared to the T-Bolt? It seems to run the same software.
Regards, John, K1AE, Bolton, MA, USA, newbie time-nut. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Tom Van Baak Sent: Thursday, August 13, 2009 10:23 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt precise positions needed > With a good (geodetic/survey) quality antenna I get my location to > within a few inches. With a conical timing antenna, I get around > 8 inches of error. With a cheap patch antenna, around a foot. HI Mark, A couple more thoughts. I still question the value of all this for a cheap receiver such as a Thunderbolt. Before you get too far measuring your sub-meter position, or putting code into LH, it would be helpful to know what effect, if any, this has on the actual performance of the GPSDO. The plot I'm looking for is how the time/frequency output degrades as a function of error in fixed position. I'm not convinced an error of a couple of cm, or even a couple of meters is going to make a real difference in the stability of the 1 PPS or the 10 MHz output. The question is how far off does the surveyed position have to be before the effects of position error rise above the sum of all the other normal sources of bias and noise in the GPSDO? True, these issues are important for high-end, dual-band GPS receivers, with choke-ring antennas, clear views of the skies, and post-processing, etc. But I question where the line is for your average GPS timing receiver, such as a TBolt. Have you or anyone measured the short- or long-term output accuracy (1 PPS) and stability (10 MHz) as a function of the position error (say, from 10 cm 10 m)? For a TBolt, or M12 or any other time-nut class of GPSDO? This might also shed light on why the TBolt defaults to (only) a 2,000 second survey. And why the TSIP LLA initial position is single- not double-precision. /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
