Jim's another OT like me when all the HF Ham bands were harmonically-related. Paralleled dipoles worked quite well in that setup although there was a fair bit of interaction, especially from an 80 meter dipole on a paralleled 10 meter dipole. I still recall one summer day running my antenna up and down countless times trying to find the right balance. (I think that may have driven me back to open wire feedline at that QTH <G>).
As he pointed out, the lower-frequency antenna tends to offer a very high impedance at the center. For example, on 40 meters, a 120 foot 80 meter dipole in parallel would a two half waves, presenting a voltage loop at the feed point. That means it'd not take (or deliver to the feedline) significant power. Such combinations were used on 80/40/20/10 meters with paralleled 132 foot, 66 foot, 33 foot and 16 foot wires. And 15 meters worked well as a bonus using the 40 meter dipole. On 15 a 66 foot wire is 3/2 waves long, presenting a current loop at the center feedpoint. So one 66 foot long wire did duty as both a 40 meter and 20 meter antenna, presenting a usably-low SWR to a 50 ohm coaxial feedline. It gets a lot more complicated when one tries to use the non-harmonically-related bands. Indeed, I can't imagine how one would pull it off <G>. So your idea is a sound, tried-and-true one for coverage of the bands you listed. And you get 15 meters as a bonus if you want <G>. Ron AC7AC -----Original Message----- In a message dated 2/19/07 4:45:23 PM Eastern Standard Time, [EMAIL PROTECTED] writes: > have been told > lately that the unused antennas on the setup would pick up additional > noise. If so, it will also pick up additional signal. > Has anyone ever done any testing with multiple antennas on one > feedline to see if they really do pick up extra noise? I haven't done any scientific testing, but in actual operation (FD), I have not found any difference from a regular dipole. The principle of multiple parallel dipoles is that the nonresonant dipoles present a high impedance, so almost all of the power goes to the resonant dipole. That principle works the other way, too, when receiving. > I'm thinking about putting up new inverted V antennas on 160, 80, and > 40 meters and feeding them with one coax. Sure beats antenna switching > and it always seem to me that the signal would go to the resonate > antenna. I always used a coaxial balun in the feedline. > Works for me! How high of a center support do you have? 73 de Jim, N2EY _______________________________________________ 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
