[Elecraft] [K2] wire antenna lengths for portable operations

[Ron D'Eau Claire]

Tom, that’s true if you have one radial, but making it 1/4 wavelength long
minimizes RF on the rig and, in most situations, only a small part of the RF
flows in it. It’s a function of the ratio of the impedances of the "radial"
and the radiator. 

Consider the "ideal" case. A radiator close to 1/2 wavelength may present a
feed point impedance of 2000 ohms while a carefully trimmed 1/4 wavelength
radial may show something near 35 ohms. In that case, well over 95% of the
RF power is delivered to the 2000 ohm impedance of the antenna and less than
5% is delivered to the radial. 

Real life is usually not that good. Most compact ATU's can't handle the very
high impedances near 1/2 wavelength so the antenna must be longer or shorter
than ideal, and the "radial" usually doesn't provide anything less than a
few hundred ohms impedance. Even so, most of the RF is delivered to the
radiator. 

73, 

Ron AC7AC



Just to restate the obvious:  Do not make the radials resonant on any of the
operating frequencies.  Doing so causes high current in the radials and you
end up with a very low horizontally polarized radiator.

73,
Tom (K7ZZ)