View Single Post
  #24   Report Post  
Old February 20th 08, 09:40 AM posted to rec.radio.amateur.antenna
Richard Harrison Richard Harrison is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 588
Default Horizontal loop antenna

Roy Lewallen wrote:
"I don`t see anywhere in the response which explains how "radiation is a
function of loop area" and why increasing the loop circumference would
be advantageous."

Didn`t want to bore with details. Terman knows all and tells all. His
loop antenna story begins on page 907 of his 1955 opus:
"The radiation resistance of a loop antenna is less the smaller the loop
area. For the radiation resistance to be large enough to give good
antenna efficiency, it is necessary that the loop perimeter be of the
order of a wavelength. This introduces a difficulty, since when the
perimeter approaches or exceeds a half wavelength, then the loop current
in Fig. 23-40 will not be constant, nor will its phase nnecessarily be
the same in different parts of the loop. The prectical solution is to
build up the loop in such a way that the perimeter consists of resonant
antennas so arranged that the current everywhere in the loop perimeter
flows in the same direction around the loop. A variety of practical
physical arrangements for achieving this result have been devised, three
examples of which are illustrated in Fig. 23-41."

Yet another elegant phase inverter from Kraus as applied to a colinear
dipole appears on Cecil`s webpages.

Best regards, Richard Harrison, KB5WZI