This was the wrong group for this kind of request.
It should have been in an electronics group.

Actually, this group has fielded ferrite, air core, active and passive loop
designs hundreds of times over the years. Do an archive search under loops, or
loop construction. Or, do the same kind of search on an engine somewhere. But
this group is a VERY good place for such info, the usual idiots
notwithstanding. In fact you'll get a better answer here than a lot of places,
even if you do have to put up with a few things in the meantime, if only
because the serious and helpful replies you DO get are coming from people with
real-world experience over many years in antenna experimentation.
I've been in this group off and on for many years, and while I've also had my
share of flame wars and idiot posts, a GREAT deal of the antenna experience I
have gained has come directly (and in some cases *exclusively*) from this
group.
Linus