Richard Fry wrote:
"Cecil Moore":
Jimmie D wrote:
One such mistake is calling a 4 ft long antenna that has a coil to
make it resonate on the 10M band a "10M loaded 1/4 wavelength antenna".
They should be more careful and specify that they are
talking about electrical lengths, not physical lengths.
They also should point out that, although a radiator
physically/electrically shorter than needed for first self-resonance can
be "loaded" to resonance, this does not mean that loaded and
self-resonant radiators perform equally well in an installed system. In
some applications there can be as much as a 100:1 difference in their
radiated powers, for a given power at the transmitter output connector.
Good point, Richard. An antenna's ability to "load"
is proportional to its electrical length. An antenna's
ability to radiate seems to be proportional to the
physical length of the antenna that is carrying the
highest current. In 75m shootouts, the mobile antennas
with the loading coil furtherest away from the feedpoint
(closest to top-loaded) generally won the shootout.
--
73, Cecil
http://www.w5dxp.com