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MMDS Antenna feeds



G'day people, Just watching the msgs on amsat-bb I noticed people talking
about weak / poor reception using the dipole type feed on their MMDS dish. I
have no equipment to do any measurments but my first antenna was an ex MMDS
dish with a dipole feed. I could hear the sat but poorly, I changed the feed
to a 2 1/4 turn helix and the sig improved greatly, I then lined the dish
with foil to make a solid surface and sig's again improved, I then went to a
solid prime focus dish a touch bigger and there was a small inprovement. The
biggest improvement was changing the feed from a dipole to a helix. With the
dipole I could decode telemetry maybe 5-10% of the time and that went to
70-80% with the helix feed. Just something for people to think about when
playing considering the cost was minimal (~$10) for a big improvement. All
the playing was done ages ago when the sat had just returned to S band and
sigs are better now than they were then due to sat orientation.


Cheers Geoff VK3JDG

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