[amsat-bb] Cheap LEO antennas
Fri Aug 18 07:27:41 PDT 2006
I would also stongly recommend the "Cheap Yagi" design, especially for 435 mc. band.
I used a 3/4 square wood boom and a full length 435 mc. "AMSAT" cheap yagi design. I built one for my AO-40 uplink and another for LEO's both worked great. Sand the wood so it is nice and smooth. If you can find a drill press you will have nicely squared elements. To paint it I use a white "exterior wood primer" from the hardware store which is for priming the wood surfaces on the outside of your house. If you get the good kind, it takes 2-3 days to dry completely. Then I painted it with aluminum colored enamel ("rustoleum" or similar). I picked up some Coaxial cables at a flea market with BNC connectors, cut one in half and used that 2 antenna drive cables. From the ground it looks just like a "store bought" antenna and more important it really lasts. My LEO antenna has been up for about three years and still looks like new.
The other thing is to be really careful about letting water get into the coax. Just use some caulking and be sure to loop your coax near the driven element to form a "drip loop". Gravity will keep things dry. Don't crush the wood while tightening the mounting bracket.
It is easy to clip the driven element to tune the SWR. If you have time use a file to trim it when you get close to the best SWR.
This is a GREAT antenna, just use exterior primer and enamel paint to protect it. I prefer wood to PVC (and I have used PVC for other projects).
I used it today to work EB1FG on FO-29 on an east coast pass which peaked at less than 1 degree elevation here!
Grant Zehr AA9LC
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