[amsat-bb] Re: Commercial Mode L Antenna sources

w7lrd@comcast.net 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). 
> 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 
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