Steve McDonald wrote:

> I have had good results with an ordinary (unbalanced) air-core loop of 10'
> diameter.
> [...]
>
>

Just to add my experience to this debate. when I had an Rx loop, before
the wind decided to take it away with itself, it was of the floating type.
The loop itself had 8 turns, 2-meter each side, connected only to a primary
winding of three turns on a toroid. No ground connection whatsoever.
The secondary had 16 turns, whose inductance needed about 1800 pF to be
resonated on 137 kHz, and was directly connected to the coax cable.
The coax into the shack provided 1200 of those 1800, the rest was
obtained with a variable capacitor in the shack, without any need for
remote tuning. The preamp, also in the shack, was just an FET source
follower to step down the high impedance of the parallel-tuned LC circuit
to the 50 ohm of the Rx.

I did not perform any formal tests, but sensitivity was very good, and
the local noise pick up very low.
My next loop will be similar to this, may be just two turns in the loop,
made with thicker wire.
Just my 2 cents.

73  Alberto  I2PHD