I’m still amazed at the success I’m having with my random wire antenna on 80m. Yesterday, I worked a guy who said he was running 500W. He was, of course, 599 here, but he gave me a 589. There’s now no doubt in my mind that a random wire can be an effective antenna.
On the HamRadioHelpGroup mailing list, there was a related discussion about the “almost random” wire antenna. The idea is that some lengths just won’t work well on one or more bands. In general, you want to avoid choosing a length that is a half wavelength, or multiple of a half wavelength of a band that you want to operate.
Tim, N9PUZ notes:
I have used the 49.2 ft (15 Meter) length of wire on vacation with both automatic tuners and an MFJ Model 16010 tuner with good results for 40, 20, 17, and 15 Meter operation. This is not as good an antenna as a dipole or doublet in my opinion but it’s a workable antenna.
Moe, AB8XA, added:
With all the bands we have at our disposal, finding an end-fed antenna length that’s not near 1/2 wavelength on some bands is tough, impossible for me so far. As far as dodging 1/2 wavelengths, 86.9′ may be the best compromise for most bands. Using 95% velocity factor, I find 86.9′ roughly 1/3 λ on 80 m, 2/3 λ on 40 m, 4/3 λ on 20 m, 5/3 λ on 17 m, 7/3 λ on 12 m, and 8/3 λ on 10 m (2.60 – 2.73 λ). But it is exactly 1/2 λ on 60 m, and 0.94 λ, almost 3/3 or 2 half λ, across 30 m, and 1.95 – 2.00 λ, or 6/3 and 4 half λ, on 15 m.
My IC-718 doesn’t have 60m, so slightly shortening the 86.9′ may make it possible to tune 30 m and the lower, CW end of 15 m. But that might bring the lower end of 10 m too close to 2.5 λ.
It appears to me, with an integrated tuner in the radio, which may not have the tuning range necessary for some bands, or even with a wide-range tuner in the shack, the end-fed brings the antenna inside and close to the operator. A remote automatic wide-range tuner, such as the Icom AH-4 or SGC SC-230, between the end of the antenna and lengths of coax and control cable to the shack, appears to me might resolve that problem.
One of these tuners mounted well away from the shack, and close to the ground to feed the required radials, also offers the opportunity to turn an almost all horizontal wire into an inverted-L. From what I’ve seen playing with some modeling software, adding some vertical portion to the antenna can slightly ease the cloud-burning effect of a relatively low horizontal run on lower frequencies, as well as significantly reduce the depth of the nulls of a long horizontal wire on higher frequencies. But I’m sure no antenna expert. It’s always been my toughest subject.
My antenna is 85-ft. long, so I bet I can get mine to load on nearly any band. My next project is to connect it so an SGC-239 automatic antenna tuner that I have and just see what I can do on bands other than 80m.