[amsat-bb] Re: Commercial Mode L Antenna sources
w7lrd at comcast.net
Wed Jul 2 16:43:54 PDT 2008
Hi Wayne and all
I agree a four footer would be good for L/S. I used a four foot primestar for AO-40 (sobsob) on S band. I now have as yet untried dual feed for L/S for the same dish. I'm waiting fo the energy to connect everything up and give it try. I need another downconverter and a bird 43 L band slug, for tweeking. The feed is two concentric helix feeds on the same form for L/S. Should I not get desense to to proximity of the feeds it will be my future L/S antenna. Yes the primestar is solid and heavy, being off center feed it will lend itself to helix as opposed to a patch feed. I have heard the 3731AA downconverters from K5GNA have a good front end. I also have a UEK 3000 downconverter. Which will be be better, I don't know as yet. If anyone has tread here before I would appreciate your input.
73 Bob W7LRD
"if this were easy, everyone would be doing it"
-------------- Original message --------------
From: Wayne Estes <w9ae at charter.net>
> 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
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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