Ken K3VV wrote; ...one of the best pieces of advice was Don's suggestion to make the antenna a bit longer than the ~66 ft required for a resonant half-wave dipole on 40 meters. As Don mentioned making the antenna longer will make it easier to tune on 20 and 10 meters where a 66-ft antenna has an extremely high feedpoint impedance.
---------------------------------------- Avoiding a close encounter with 1/2 wavelength is important, Ken, but cutting the antenna to a length other than 66 feet won't necessarily help and might make it worse. That's because the feed line acts like an impedance transformer. The impedance at the feedpoint at the antenna will appear at the terminals of the feed line *only* if the feed line happens to be exactly 1/2 wavelength long, electrically. It can be rather difficult to predict the actual feedpoint impedance without some careful measurements and calculations. Usually it's easier to see if the ATU doesn't have enough range, then adjust either the feed line length or the antenna length a bit until it works on all the bands. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
