As far as an "optimum" height, it seems that a loop oriented such that
it lies in a vertical plane, such as the one you have and Reg is
describing is not going to perform better as you change the height,
once you're far up enough to eliminate ground return losses. In fact,
my little toy EZNEC model at 14Mhz with a 4' loop shows the development
of high angle lobes if you increase the height of a vertical-plane
magloop.

Seems though that if you oriented the loop such that it was in a
horizontal plane and put it at a good "DX height", up where a dipole
would start to give good low angle radiation, you would get an
omnidirectional azimuth pattern but the elevation pattern more like a
dipole at that height. This could be advantageous if you have a high
support.

So if you're down at 3.5MHz or something, loop in the vertical plane
near the ground is the way to go, as you'd not likely be able to get
the loop up high in terms of wavelengths.

Seems, though, if you had a 20m (1 wavelength @ 14MHz) high tower with
low windload capability and wanted to put up a horizontal-plane loop
for 14MHz, you'd get more gain at low angles than a near-ground-mounted
vertical-plane loop.

It's analogous to the situation with a ground mounted vertical vs. a
high dipole. The ground mounted vertical has better low angle
radiation than a low dipole, but not better than that of a high dipole,
and leads to the usual situation of verticals for the low bands and
horizontal antennas for the high bands.

this comment over normal soil, if you've got sal****er, pse
disregard :-)

73,
Dan
N3OX