[amsat-bb] Re: Commercial Mode L Antenna sources
Gary "Joe" Mayfield
gary_mayfield at hotmail.com
Thu Jul 3 04:49:49 PDT 2008
Wimo got some use in the old days as well.
I have a 23-2 which was okay (not great) with AO-40 with 10 Watts until the
AGC started getting pumped. It is too much for AO-51, so I reduce the
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Wayne Estes
Sent: Wednesday, July 02, 2008 12:34 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: Commercial Mode L Antenna sources
I'm surprised how few people have mentioned parabolic dishes during this
discussion about commercial Mode L antennas. L-band uplinks are mostly
used in combination with a S-band downlink. Most people build L/S
equipment with HEO satellites in mind. A single yagi or helix doesn't
usually provide sufficient gain for L/S band use with a HEO satellite.
You need the gain of a dish for satisfactory S-band reception of a HEO
satellite. So one practical solution is an oversized dish with a L/S
dual-band feed (helix or patch). A 4-foot dish was proven to work well
for this on AO40. In my opinion a single 4-foot dish is more practical
than, for example, cobbling together multiple yagi/helix antennas for
S-band downlink and multiple yagi/helix antennas for L-band uplink.
My 4-foot dish and dual-band patch feed were purchased commercially from
Teksharp (Rick Fletcher KG6IAL).
The dual-band patch feed is sold fully assembled and tested, but the
dish was a kit. I had to locally purchase 1/4 inch hardware cloth, cut
it into 8 "petals", and use 200 zip ties to attach the petals to the
frame of the dish. A mesh dish has somewhat less wind loading than a
solid dish. That's important because a solid 4-foot dish has a maximum
wind load of more than 12 square feet, exceeding the wind load rating of
my G-5500 rotor. A picture of my satellite antennas can be seen here:
Wayne Estes W9AE
Oakland, Oregon, USA, CN83ik
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