Topband: small rx loops and ferrite

[Rick Karlquist]

Sam Morgan wrote:
> Since the topic of ferrite seems to be at the top of the lists focus
> I'd like to ask about what ferrite mix to use at the feed of a small rx
> loop I
> have built
>

You might want to look at the feed technique described here:

http://www.n6rk.com/loopantennas/NCJ_loop_antenna_N6RK.pdf

Although this article talks about a shielded loop, it will work
equally well on your unshielded loop.  The article recommends
Fair-Rite 67 material because it is very low loss at 160 meters.
This gives maximum antenna sensitivity.

If you want to broadband a loop, the thing to do is to
reduce the turns ratio on the transformer so that you
reduce the *loaded* Q.  This will result in better sensitivity
than simply adding loss to the system (ie reducing the *unloaded
Q*) by using a lossy ferrite core like 31.  That sort of "broadbanding"
reduces sensitivity at all frequencies, but reduces it
more at the center.

Rick N6RK