Re: lOOP cONSTRUCTION
The problem with a lot of "improved" loop designs like the shielded and Mobius designs is that they don't work as you would expect at first glance.
The "shielded" loop actually works as two halves of a short dipole transformer coupled to the inner wire.
The Mobius design is similar. It's original purpose was to protect an RF measuring instrument from the EMP spike of a nearby nuclear explosion. It is similar in operation to the shielded loop.
I think it may be a bit harsh to describe them as snake oil. More a case of enthusiasts looking for something better than a simple loop without thinking it through.
Chris, if you want to try a different design try the cardioid loop designs on this web page:
Rather than having two sharp nulls the cardioid loop has a wide (120 degree) null off the back. If you can mount it so that it faces the area you want to cover and null noise off the back then it works really well.