Mike,
Models of quad loops show 1 wavelength radiation is normal to the
plane of the loop. (i.e. UP, if the loop is horizontal), while
2 wavelength loops radiate IN the plane of the loop.
Multiband Quads with parallel feeds suffer pattern distortion on
10 meters, because the 20m loop radiates everywhere but where you
want it to. (The only thing that saves the operation of this antenna
is that the driving point impedance of the two loops is such that
the 10 meter loop gets most of the power.)
So the short answer is ONE wavelength, for local work. A dipole at 60 or
70 feet...or even 100...would achieve pretty much the same thing, though.
Might be easier to erect.
Jim/n2ea
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