On 6/13/2012 5:11 PM, garyr wrote:
This site http://www.frontiernet.net/~jadale/Loop.htm states that: "A
properly designed Loop primarily responds to the magnetic component of the
radio wave. Note that noise resides primarily in the electrical
component..."

Whereas this site shows that that is not the case:
http://vk1od.net/antenna/shieldedloop.

So what is the advantage, if any, of a shielded loop antanna?

None. The only purpose is to ensure balance, which helps give
deeper nulls.

But that is not the only way to ensure balance. A shield is
not required for that function.
None of my AM-BC loops are shielded. I have tried shielded
loops though, just to see for myself if any difference.
There no difference, assuming all of the loops were balanced
and fed properly.
The mythology of loops is a lot like the various myths you
see pertaining to grounds, and grounding. :|
Some claim a shielded loop is "quieter" than an unshielded loop.
I know from testing, that is pure hogwash.
Both are quite capable of picking up noise. After all, noise is
RF just like any other signal, and follows all the same rules.
The true test of a small loop is how deep the nulls are.
If you can make daytime AM ground wave signals disappear by
turning the loop, you are in pretty good shape.
And *any* small loop is capable of that if all is well in the
world.