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 Seattle
-- "if this were easy, everyone would be doing it"
-------------- Original message -------------- From: Wayne Estes [email protected]
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). http://www.plumdragon.com/teksharp/hr_AO-40_products.htm 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: http://s238.photobucket.com/albums/ff239/Wayne_Estes/Ham%20Radio/
Wayne Estes W9AE Oakland, Oregon, USA, CN83ik _______________________________________________ Sent via [email protected] Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb