Ron Hardin wrote in message

1. The depth of the null is different between loops (and loop
arrangements)

True, but this is a design issue, not money..:/

2. And then there's the matter of pointing it.

There are two patterns for small antennas, a magentic field pattern
and an electic field pattern. The radio hears both, and _they don't
null at the same place_. A _loop_ responds mostly to magnetic field,
but there is an electric field response some number of dB down.
That number of dB down limits the depth of the null you can get.
The fields can't be used to cancel each other because they're in
quadrature.

1. Kiwa builds an electric-field balanced loop that has the lowest
possible response to electric fields, and so the magnetic field null is
then very deep.

Some of mine are too, but I don't find the difference between one of
those to say my round 16 inch "normal" loop to be that great. "12
turns and a 2 turn coupling loop" It's mainly an issue of good
balance, and reducing common mode currents, etc I think. I get very
good nulls with mine. I've never actually tested using a step
attenuator or anything, but it's common to knock a loud local BC
station down 20-30db or more going by the s meter. I've seen 40 db a
few times. In the day, most all out of town groundwave signals are
totally gone if I rotate against them. As far as balance, I found
better balance using the coupling loop, than directly feeding the
loop. I noticed a slight skew off true direction when directly fed. I
notice many people complain about a lack of nulls or directivity at
night, but mine does fairly well. Maybe not as "dead air gone" as in
the daytime nulls, but still very effective. Thats where adjusting the
tilt can help a bit.

2. Kiwa's is on an azimuth-elevation mount. Every time you get twice
as close to the true null, you get 6dB more null. Soon you're dealing
with fractions of a degree. The ability to adjust to fractions of a
degree limits the null depth, the finer the better. The Kiwa is about
the best you'll find.

Mine is also. I can turn it around on it's stand, and I can also
adjust the tilt. I usually end up with mine pointing downwards just a
tad for the best nulls. My nulls are very sharp. Just a fraction of an
inch in rotation as I turn it can mean quite a few db in the null
depth.

It's an active loop, so you can feed the radio a high level of signal,
which makes the radio's native loop response less important if you
air-couple it.

That can be handy, but again preamps, etc can be built fairly cheap. I
don't need one on mine. Plenty of signal, and I can kick the radio's
preamp on if I want more. But I prefer not to use it, as it just pumps
up the noise.
I guess to each his own, but I'll never spend several hundred bucks
for a small loop when they can be built for a fraction of that. It
certainly doesn't require near that kind of money to copy what they
are doing. MK