Originally posted by abcd567
View Post
In order to answer a simple question—why an antenna made of a cable would radiate at
all—we first realize that it consists, in fact, of two antennas, one within the other (the
inner and outer coaxial-line conductors), connected to the same feed point and source.
The currents in the two antennas are in oppositedirections. Transposition of the coaxialline conductors at certain intervals does not change the propagation along the line, and is
intended to produce proper voltages across the gaps between adjacent line segments. It is
a simple matter to conclude that if the characteristic impedance of the coaxial-line
sections were made to approach zero (i.e., the radius of the inner conductor to approach
that of the outer conductor), the CoCo antennawould not radiate any more. This indicates
that the CoCo antenna radiates because the two parallel antennas which make it have
different current magnitudes at the feed, i.e., the feed-port currents are unbalanced.
Comment