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

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.

Roy Lewallen, W7EL


Yea, if you put them in the metal jar and measure number of electrons (or
whatever trons), including with dummy load, they will "radiate equal amounts "
..

Loops - delta, quad or circular have some advantage (gain) over folded dipole
or dummy load, due to some stacking effect and pattern forming properties. This
is what we are interested in and what was the point of asking the question.
Just stick the folded dipole and quad or other loop in the EZNEC and you will
see if there is any advantage or gain from particular configuration. Just like
two phased verticals produce more radiation in particular direction, the same
applies to loop vs. dipole. If one wants to nit pick, you could find that most
signal (radiation) in particular direction would be coming from circular loop,
followed by square, triangular, folded dipole, dummy load, in that order.

Making a large loop round -- or increasing its
enclosed area -- won't make it "radiate better" or be "more effective".

Stick it in EZNEC and see what you get in favorite direction.

73 + MX Yuri, K3BU.us

On 17 Dec 2004 22:26:56 GMT, oUsama (Yuri Blanarovich)
wrote:
[snip]

|Stick it in EZNEC and see what you get in favorite direction.

Prehaps a return to the original question is in order. Ed asked:

" I would like to put up a 160 meter loop, fed with 450ohm ladderline.
Although I have enought room, the existing trees would only provide
three supports, pretty much in the shaped of a equalaterral triangle.
How well would a three sided loop work? Should I feed it in the
center of one side?"

The man asked a simple question about what I believe is a horizontal
loop and you bozos started telling him it would work better (be more
efficient) if it was round.

Roy is too nice a guy to put it this way, but I'm not; It won't make a
rat's ass difference whether it's a triangle, a square, a circle or
anything in between. Unless it's 100'+ above ground, it's pretty much
going to radiate straight up; which in this case is its "favorite
direction."