On Jan 17, 2012, at 12:32 AM, Hank Garretson wrote:
> 100 feet will give essentially the same performance as 135, 130, or 125
> feet, just squirt the RF in different directions. By "same performance," I
> mean the same total amount of RF energy will be radiated.
I see it differently. When going significantly below a half wave, you are
eliminating a significant portion of the high current portion of the radiator.
The highest radiation currents flow in the center of a half wave dipole.
Removing 30' of a 130' antenna (just using a 100' antenna) is halfway to going
to a 70' antenna (40m dipole) and 40m dipoles significantly underperform an 80m
dipole (on 80m).
Of course, all antennas are compromises of one sort or another. If your tuner
won't tune a full wave dipole, then shortening (or lengthening) the antenna is
an option. Changing the feedline length is another option but that can
sometimes be more difficult with open wire or ladderline feedlines, you can't
coil them up or lay them on the ground like you can coax.
TowerTalk mailing list