[RFI] LF noise

[Missouri Guy]

> I've seen blogs that shielding a loop really doesn't do much.

Rick, that's because the "shield" is part of the antenna.
You can prove that to yourself by grasping a resonant loop, say,
on it's side (assuming it's gap is at the top) and noticing that
the resonance has changed frequency.
 
> With high local line noise, is a TUNED LOOP or non-resonant receiving
loop antenna a >better option? 
 
For line noise or local signals, either loop should have the same
directivity.  A tuned
(resonant) loop will have a higher "Q" and attenuate both signals and
noise that
are away from its resonant frequency....useful when you want to
reduce strong out-of-band signals or noise.  A non-resonant loop
will be quite broad-banded and have less output....useful when you
want to receive signals and noise over a broad frequency range without
having to re-tune the loop.
 
73,
Charlie, N0TT