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Signal Engineering - The Evolution of High Performance CB Antennas!
SE use to make a dual polarity voltage fed quad using a 1/4 wire stub working against the boom, or when the boom was too short, like with the two element version, they used another wire in parallel with the feeder. You will see that at the Website noted below. They are out of business now, but another firm bought them out and you can find them at:
ttp://www.lightningantennas.com/Quads/
I have pictures of their feeder from a copy of a copy of a copy out of one of their very poor manuals, but I'm not sure how readable it would be. Click here:
View attachment 7129 It is their feeder that makes this dual polarity quad unique.
sandman you are wrong regarding the PDL2. It is a full wave quad, the size is very close to the same as any other quad using a side length that is a 1/4 wavelength or about 9'> for CB. According to the Avanti instruction manual for the PDLII, the wire for the driven element is 458.4" /4= 114.6/12" = 9.55' feet. Where did you get this CB BS about it being a 1/2 wave. All quads work as a 1/2 wave, is that what you meant? Is 9.55' feet larger than you thought? Or, do you just look at the pictures.
The PDL2 just uses a folded feeder setup that uses a gamma device to match, and this allows for current feeding a dual polarity quad. It is a very complicated setup, however, and it might be hard to do homebuilt and from scratch...unless you have a lot of antenna building experience and beams in particular or you have some good parts from a production model.
The SE idea I noted above uses a 1/4 wire stub attached at two adjacent corners, and each one then feeds at a voltage node, instead of at a current node where you will have an insulator separating the driven element wire.
Feeding at a voltage node forces the polarity factor for the antenna to be the opposite of what we tend to find when feeding at a current node. The wires don't radiate like you think they do either.
Get you a good book on quads, you need to read up and try and understand the differences. Don't get me wrong here, it is fine to have ideas, but try and check stuff out a little first. And don't just look at the pictures.
I think you'll find very few dual polarity quads that are current fed. If you do find one, I would like to see pictures of it, so don't just tell me about one that you know about.
