On 12/16/2012 8:31 AM, Tom W8JI wrote:
You likely had an antenna with 1/2 wave of wire spooled up on a short
fiberglass rod, which would never behave like a half-wave.
You are exactly right. Unfortunately, this myth dies hard.
Below is a link to a page on this topic from "ANTENNAS," 3rd edition, by
John Kraus.
Kraus states in the middle of that page that the radiation resistance of
such an antenna is the same as a linear conductor of the same overall
height/length.
http://i62.photobucket.com/albums/h85/rfry-100/Helically-woundVertical.gif
RF
Everyone should know, by now, that radiation resistance in a simple single
element is tied directly to ampere-feet of linear spatial area.
If we remember this, the E-H antennas, folded monpoles and dipoles, spirals,
fractals, CFA's, isotrons, and all the other magically folded, curved, or
bent antenna would all become the antennas they actually are.
_______________________________________________
Topband reflector - topband@contesting.com
|
