https://www.ngs.noaa.gov/ANTCAL/#
Look at say an old Ashtech ASH700936D_M which you can find calibrations for both SCIS and “Snow” radomes and without radome for the same antenna. I have seen more recent radomes that are hemisphere-shaped. However these are more prone to be favored bird view points. Radomes, like the Aeroantenna SPKE with a plastic “spike” to discourage birds are less ideal for super high accuracy applications due to its non uniform signal delay impact. See also clear acrylic domes OSOD/OSOS http://www.euref.eu/symposia/2015Leipzig/p-02-01-Ohlsson.pdf https://kb.unavco.org/kb/article/unavco-resources-radomes-520.html /Björn Sent from my iPhone > On 7 Sep 2019, at 02:54, Bob kb8tq <[email protected]> wrote: > > Hi > > Based on the papers I have seen, there is no “magic” shape that can be > ignored. > Part of the issue is that the cover is going to be in the near field of the > antenna. > As noted in another post, the impact is more complex than a simple delay. ( > consider > that signals bounce off the cover material …. ). > > Also consider that if I’m going to 3D print the device, I have a limited > number of > materials available. Teflon isn’t going to run through a 3D printer. Unless > you paint > the gizmo it will not be water tight so humidity will get into the act as > well. > > ===== > > A “good” GPS antenna should have roughly the same phase center regardless of > the angle to the sat it’s receiving. Indeed GPS antennas in general get this > right. > There is a modest variation with angle, but it’s not all that great. Units of > mm are not > uncommon. It will be greater on a multi band design. The impact of your cover > also > will be greater on a multi band device. All the various delay /. loss / > reflection parameters > are frequency dependent….. > > Bob > >> On Sep 6, 2019, at 5:57 PM, Hal Murray <[email protected]> wrote: >> >> >> [email protected] said: >>> The gotcha with putting anything on top of a GPS antenna is that it impacts >>> the phase shift from the sat’s. How important that is gets quickly into >>> just >>> how picky you happen to be. >> >> How picky do I have to be before that is significant? How geeky would I >> have >> to be to measure it? >> >> Would a hemispherical cover provide equal delays at all elevations? I think >> the solidly mounted USGS fault/volcano monitoring setups have a round top. >> https://www.usgs.gov/media/images/gps-tracks-ground-deformation >> >> Do any antenna manufacturers advertise uniform phase delay? >> Do any software vendors advertise that their software works better with >> specific antennas? >> >> >> >> -- >> These are my opinions. I hate spam. >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
