I've been using a EFHWA vertical for a couple years now as a portable antenna for 20, 30 and 40 meters. It is 33 ft tall and supported by the MFJ fiberglass pole. It uses a small, tapped inductor located about 6 feet from each end to provide electrical half wave length on 30 and 40 meters. The coils are shorted for 20 meters. The only downside is you have to pull the antenna down to change bands. The matching network is a tuned tank using a toroid wound coil and air variable. The tank circuit is matched to 50 ohm coax using a secondary winding with several taps. Full credit goes to N0LX for the design and construction details ( http://www.n0lx.com/efhwa.html ).
I usually use it with a short (10 ft) counterpoise wire and about 10-15 ft of coax to the rig. I suppose a bead style choke balun could be used on the coax but I've never noticed problems with RF at the tranceiver I typically run 5 - 15 watts into the antenna. YMMV Brian K0DTJ ______________________________________________________________ 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
