Here’s an interesting idea for a portable 20m antenna from Ed K9EW via the Elecraft mailing list:
As long as you mentioned the inverted vee, I thought I’d offer this to think about. I have been using a 20m center-fed inverted vee with very good results. And here’s the great thing about it… it’s a coil of TV twinlead.
One end of the twinlead is split to form the two arms of the vee (each approximately 17 feet long), and then the remainder of the twinlead becomes the feedline which you can connect directly to your rig. The only constraint is that the feedline portion of the twinlead *must be* an electrical half-wavelength long (about 29 feet, depending on the velocity factor of the twinlead you use) in order to present a 72-ohm impedance to your rig.
It’s small (rolled up), lightweight, and requires one branch about 30 feet off the ground for the vertex. At this height, it’s approaching a half-wavelength above the ground which is great for the radiation pattern. The ends are tied off with small ropes to stakes (or rocks) 30 feet from where the feedline would touch the ground. This will give you a 90 degree angle at the vertex. It’s balanced, so no counterpoise. And it works just like a “home” antenna.
72/73, ed – k9ew
I just knew I’d find a use for that 300-ohm twinlead I bought at the dollar store a couple years ago. :)