Richard Harrison wrote:
Roy, W7EL wrote:
'Ok, let`s start with a triangular loop with negligible loss."

"Negligible loss" eliminates the differences between loops of most
shapes with the same enclosed areas. . .

That's almost correct, but not quite. Except for loss, a triangular
loop, square loop, folded dipole, or round loop radiate equal amounts
*regardless of their enclosed areas* -- the amount of power that's
applied to them. The round loop doesn't radiate any more than any of the
others. None is one more "effective" than another, except that the
patterns will be different, so one might be more effective than another
at communicating in a particular direction -- but the round loop won't
necessarily always be the winner.

The statements you made earlier about a round loop radiating more, and
the continuing hangup about enclosed area, are based on the assumption
that the loop is small and is driven by a constant current source. For a
given amount of wire, the round loop has the highest radiation
resistance, and therefore if fed with a constant current, it consumes
and therefore radiates the most power of any loop made with the same
length of wire. This is a set of conditions often used by textbook
authors to illustrate some basic principles, but it isn't representative
of amateur (or commercial, for that matter) antenna use. It's necessary
to read and understand the qualifications given by the authors before
quoting their conclusions.

For a given length of wire, you'll get the most efficiency from a round
loop for a given length of wire. But unless the loop is electrically
very small, the efficiency will be high enough that this won't make any
noticeable difference. Making a large loop round -- or increasing its
enclosed area -- won't make it "radiate better" or be "more effective".

Roy Lewallen, W7EL