JP>I came across an excellent 2 page article on antennas in
JP>Scientific American,May,2003  P.89-89
 
JP>Describes AM,FM,TV antennas and horizontal,vertical and 
JP>corkscrew polarizations.
JP>I didn't realize that for AM ,you might need a 500 foot antenna.
 
Antenna length for low frequency AM (and any other frequency) is a
function of wave length - the lower the frequency the longer the wave
length - the higher the frequency the shorter the wave length. If I
remember the physics of it correctly, a full wave length antenna or a
multiple of the wave length antenna provides a much stronger received
signal than a 1/2, 1/4 wave length or less antenna.

In the 20s and 30s is wasn't too uncommon to see rural residential
antennas several hundred feet long. My grandfather put one up that way.
He lived out in the country and ws one of the first in the area to have
a radio in his house. This was in the early 1900s.

Thus for UHF for example the antenna can be quite short
- just look at some of the "all band" roof top long range TV antennas.
That's why the antenna elements vary from maybe 6" long for UHF
(called "bow ties"> to several feet for channels 3--12.

Jay

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