Mark Keith wrote:
I don't know what a Select-A-Tenna is, but a loop is a loop is a loop.
There is no magical quality that any one loop would have over another
besides voltage. The larger the loop, the higher the voltage out. But
the directional qualities are the same. Several hundred bucks for a MW
loop is ridiculous. I'd have to be on some kind of drugs to pay that
much. My loops are all free. And they work as well as any other loop,
not counting extra tricks like phasing, etc. The size of the loop, IE:
bigger, is only important if you actually have a low enough noise
floor to take advantage of it.
You have to be out in the country in most cases. Here in the big
breast bearing city of Houston, my smaller loops work as well as the
bigger ones. If the station listened to is strong, a ferrite stick is
about as good as anything. Even my fairly small 16 inch round loop
gives me enough voltage to be well over the city noise floor, with no
preamp used. Only a coupling loop. It covers 500-2000 kc. Lower into
LW, if I tack on extra fixed caps in parallel with the variable. To
see an improvement over a normal bi-directional loop, a K9AY
terminated loop, or something along those lines can be used. That IS
an improvement over the average loop as it's unidirectional. Most run
a pair, switched to change in 4 directions. Looks kinda like an
eggbeater of sorts. MK

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

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.

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.

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.
--
Ron Hardin


On the internet, nobody knows you're a jerk.