On 9/29/2012 5:40 AM, Barry, Stephen wrote: > Does Elecraft have a balun solution for balanced feeders for the KAT500 at > 500 watts?
See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the discussion in the preceding pages, for an excellent common mode choke that will satisfy this need. Use one of the chokes that is bifilar wound with #12 THHN, connected as a parallel wire transmission line between your parallel wire line and the tuner. http://audiosystemsgroup.com/RFI-Ham.pdf BTW -- the words "balanced feeders" and "balanced feedline" are pure fiction. You will note that I used the words "parallel wire" to describe the feedline. The balance of any system, including an antenna system, is defined equal impedances to the reference plane. For antenna systems not on aircraft, that reference plane is the earth, and the transmission line is only part of that system. Most wire antennas that hams are able to erect are unbalanced by their surroundings, which in turn causes the feedline to be unbalanced. Imbalance in an antenna is caused by off-center feed, ground slope, sloping wires, trees, buildings, even the varying ground conductivity around the antenna. This imbalance will cause current on the feedline to become unbalanced, which makes it part of the antenna. The feedline picks up noise and couples it to the antenna (because it's part of the antenna). For this reason alone, smart hams have learned to use a common mode choke at the feedpoint of an antenna This decouples the feedline from the antenna, preventing noise pickup (and keeping RF out of the shack). 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
