Keith, KB3ILS wrote: It sounds like the 22 feet per side is a common length that works for people. I will start with that. It also sounds like I should test different feedline lengths as well to get the best setup.
------------------------------------------ Another approach many use to get around an out-of-range impedance on some bands is to put an Elecraft BL2 balun at the rig end of the feeder and switch it between 1:1 and 4:1 impedance ratios as needed. That has the same effect as changing the length of the feedline. I've used that antenna with excellent results on 40-10 meters. It was between 25 and 30 above the ground. At that height it's a FB short-skip antenna (NVIS) on 40 that gave me excellent signals out to 1,000 miles or so with the occasional contact well beyond that when cdx were just right. On 20 meters, where it was almost 1/2 wave up (the optimum height for a half wave horizontal antenna), and above I "worked the world" without hesitation whenever the bands were open/ 44 feet (22 each side of the feed point) is a good compromise length for a doublet 7MHz and above. You don't start to see significant loss of radiated signal until the radiator gets shorter than 1/4 wavelength, or about 33 feet on 40 meters, as long as you "make up" the missing radiator length in the feedline (keep in mind that the feeder has two wires, so 15 feet of feeder equals 30 feet of radiator). So 22 feet gets you a fairly short doublet for easier installation that is still virtually as good as a full half wave on the lowest band, and is as good or better than a dipole on the higher frequencies. I think that length became popular, in part, due to the work by Cebik in an article he wrote about his "ideal" multiband dipole (see http://www.cebik.com/radio.html). L.B. Cebik's (W4RNL) web site is a treasure trove of excellent data and observations about antennas for anyone tinkering with them! Cebik observed that is the ideal length that provides the must useful radiation pattern up through 10 meters. Longer antennas start breaking up their pattern in ways that aren't always helpful on the higher frequencies where they are well over one wavelength long. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
