Hi At least back a while ago, GDOP and TDOP values as reported didn't have quite as strong a correlation as I would have expected them to have. I haven't done that in a while so things may be better with more modern receivers.
Bob On Mar 24, 2010, at 7:11 PM, Tom Van Baak wrote: > Hal, > > That's a really good question and if anyone can point me > to carefully performed measurements already done, I'd > appreciate it. It could be antenna A vs. antenna B, or it > could be antenna A with vs. w/o ground plane, or choke > ring, or radome, or temperature stabilization, etc. > > For short-term effects looking for an improved RMS value > of the internal GPSDO "TI" numbers would confirm that > the antenna is better. An hour of data should suffice. Or > forget GPSDO locking and just look at 2D or 3D position > scatter in survey mode. Mark has done nice work here. > > For long-term effects you'd look for an improved 1 hour > or 1 day RMS value (or ADEV) in a comparison between > the GPSDO output and suitably stable house reference. > A couple of days of data would is probably be enough to > detect A vs. B differences. > > I'm not sure signal strength by itself is the key. I would > think quality of the signal (multi-path) is more important. > Maybe there are other factors. But the bottom line is how > much, if any, better the output 1 PPS or 10 MHz is. > > If you had a set of many days of data with and without > (pie pan, ground plane, choke ring), then you could > correlate the 10 MHz output deviations (vs. house ref) with > any number of parameters and confirm or deny if signal > strength, Az-El, time of day, or temperature had anything > to do with measurable performance. > > /tvb > > ----- Original Message ----- From: "Hal Murray" <[email protected]> > To: <[email protected]> > Sent: Wednesday, March 24, 2010 10:59 AM > Subject: [time-nuts] GPS antenna setup: how good? > > >> How do I tell which of two setups is better? For example, how much does >> adding a pie pan help? >> Is there some simple parameter I can look at that tells me an antenna >> goodness value? If not, what's a reasonable recipe to come up with a number >> or compare two antennas? >> What's the appropriate time scale to use when thinking about that problem? >> I haven't (yet?) looked at any of the satellite position and signal strength >> data. >> Can I do something like wait until a satellite is about to go directly >> overhead and plot the signal strength while occasionally swapping the >> antennas? Are the signal strength readings reasonably noise free and/or >> repeatable from run to run which may be a few days apart? >> Assuming it goes high overhead, how long is a satellite within view? >> (ballpark) > > > > _______________________________________________ > 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. > _______________________________________________ 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.
