So there are 3D quadrifiliar GPS antennas; I am gratified to hear that
as I surely remember promotions for GPS antennas that showed a
quadrifiliar design.
Regarding GPS multipath, I agree that is a problem. But, here on the
flatlands of Anaheim, I can stand on the roof of my 2-storey home (where
the GPS antennas are located) and be the tallest thing around for many
miles. Yes, there are surrounding LA area mountains, but those are miles
and miles away. Trees? This is Southern California! There are no tall
trees anywhere near me. There is little nearby to produce GPS multipath.
GPS receivers, at least in my GPSDO units, have an Elevation Mask option
to inhibit processing data from satellites near the horizon. I believe I
set those to 10 or 15 degrees.
The Symmetricom 58532A antenna does use a patch element and does not
need the cone-shaped radome to provide space for a quadrifiliar element.
That cone shape must be entirely for environmental reasons for it surely
adds cost to the antenna. Snow release? Beats me! There is snow atop
Matterhorn Mountain in nearby Disneyland but non falls here...
Larry
On 5/13/2018 5:20 AM, Azelio Boriani wrote:
Usually GPS antennas are patch antennas. The PROCOM GPS4 (I have 2 of
them) should be a real QFH (I haven't opened it to verify), the
Vaisala radiosonde RS92 has a real QFH. The Sarantel SL series seem is
a double helix not a classic QFH with the two different-size loops.
They name their series GeoHelix.
<https://www.datamatik.no/media/produkt/gps-4.pdf>
<https://www.wmo.int/pages/prog/www/IMOP/meetings/Upper-Air/Systems-Intercomp/Doc3-4(1)Vaisala.pdf>
<http://www.wless.ru/files/Accessaries/Antenna/sl1200%20product%20spec%20v7_1210.pdf>
...
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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