[time-nuts] GPS Timing Antenna Failure - Long

Bob kb8tq kb8tq at n1k.org
Sun May 13 18:44:33 EDT 2018


The shape of the radome on your typical timing antenna is all because of birds. If the antenna is 60 feet up
a cell tower you do *not* want to have to pay a crew to go up there and knock the nest off of the  antenna. 

Even in the flatlands, you can get multipath. All it has to do is bounce off the ground and back to your antenna.
A wide open flat area actually is “ideal” for that particular type of problem ….


> On May 13, 2018, at 4:53 PM, Larry McDavid <lmcdavid at lmceng.com> wrote:
> 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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