I'm missing something here. 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.

Richard Harrison wrote:
Roy Lewallen, W7EL wrote:
"Can you please explain that a little more? (Radiation is a function of
loop area.)"

Not being a typist, I`ll refer you to "TV And Other Receiving Antennas"
by Arnold Bailey. On pages 407 and 408 Bailey gives two formulas for
computing the antenna resistance for a loop antenna.

On page 408, Bailey has Fig. 8-14 which plots radiation resistance (the
stuff we build antennas for) versus the loop perimeter in wavelengths.
For a square closed loop of one wavelength perimeter, the graph
indicates about 50 ohms.

Perhaps you build antennas for radiation resistance, but I think most
people build them to maximize radiation in some direction. In any case,
please exclude me from the "we" in your statement about what "we" build
antennas for. You said "radiation is a function of loop area" and
recommended a larger circumference. Equations are useless unless you
understand how to apply them. So can you use those equations to show us
how much more a loop of 800 foot circumference will radiate than one
with a 400 foot circumference? You can assume 100 watts applied to each,
and either zero wire resistance or any reasonable value.

Bill Orr, W6SAI in "All About Cubical Quad Antennas" gives the full-wave
vertical loop antenna an impedance of 125 ohms on page 15.

On page 14, Orr writes:
"For purposes of illustration, the two wire folded dipole may be "pulled
open" to a diamond-shaped loop fed at the bottom point. If this
distortion of the loop is continued the antenna will become a shorted
transmission line."

A perfect circle is the geometric shape enclosing the most area for a
given perimeter. The more corners a closed figure has, the more closely
it usually approximates a circle. That is why I commented on an octagon
versus a square.

Which brings me back to the question I asked,

Is the radiation pattern the same for a long skinny loop as for a round
one, as long as the enclosed area is the same?

Roy Lewallen, W7EL