kb8tq@n1k.org 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.

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 <hmurray@megapathdsl.net> wrote: > > > kb8tq@n1k.org 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 -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

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 <kb8tq@n1k.org> 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 <hmurray@megapathdsl.net> wrote: >> >> >> kb8tq@n1k.org 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 -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

To the OP, Dan, Just curious - do you use something like this: https://endruntechnologies.com/products/antennas-accessories/lightning-arrestor Good luck with the new antenna. 73's, John AJ6BC On Sat, Sep 7, 2019 at 3:17 AM Björn <bg@lysator.liu.se> wrote: > 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 <kb8tq@n1k.org> 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 <hmurray@megapathdsl.net> wrote: > >> > >> > >> kb8tq@n1k.org 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 -- time-nuts@lists.febo.com > >> To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. >