"JAY EMRIE" wrote to "JOE PAULSON" (18 Jul 03  09:48:00)
 --- on the topic of "ANTENNAS"

 JP>I didn't realize that for AM ,you might need a 500 foot antenna.
 JE>
 JE> Antenna length for low frequency AM (and any other frequency) is a
 JE> function of wave length - the lower the frequency the longer the wave
 JE> length - the higher the frequency the shorter the wave length. If I
 JE> remember the physics of it correctly, a full wave length antenna or a
 JE> multiple of the wave length antenna provides a much stronger received
 JE> signal than a 1/2, 1/4 wave length or less antenna.

Indeed the antenna length will influence the received signal strength.
What's more if the antenna can hold several wavelengths then it will
even become directive and thus magnify the signal.

However, don't forget that an antenna works by intercepting the electric
and magnetic fields from the received wavefront. In the typical case the
antenna is equally sensitive to both fields but one can also have an
antenna that is better at intercepting either the magnetic field or the
electric field.

Respectively, in the one case the antenna behaves more like an inductor
and in the other more like a capacitor. An example of the former is the
AM loopstick antenna and an example of the latter is the car whip
antenna. Both can adjusted to give good performance that would only
otherwise be available in a long-wire antenna but much less cumbersome.

 Mike
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