RH,

Well my simply (No Theory Required) Empirical Evidence using several
small commercial AM/MW Loop Antennas: RadioShack AM Loop Antenna;
Terk AM Advantage Loop Antenna, and Select-A-Tenna Model #541-M.
That there were differences in the Peaks and Nulls of each Antenna
when used with a variety of small 'portable' radios.

Even the Kiwa MW Air Core Loop Antenna and the Quantum "QX" Loop
Antenna have different Peak and Null characteristics when I have
used them with my Kenwood R-5000 and Icom IC-R75 (R-75).

When I compared the Justice AM Antenna (JAMA) to the Select-A-Tenna
(SAT) Model 541-M the Peaks and Nulls were different.

The SAT had a relatively Sharp Peak and Normal Null.
- If you move the SAT 'off' Peak by 30* you could see the Peak fall-off.
- From 30* to 80* the Signal would taper-off uniformly.
- From 80* to 90* the Signal would decline further to the Null.

The JAMA had a Wide Peak with a Sharp Null.
- If you move the JAMA 'off' Peak by 30* you would not see the
Peak fall-off as much.
- From 30* to 80* the Signal would not change greatly.
- From 80* to 90* the Signal would dramatically fall to the Null.

This Is Why I Say: The Justice AM Antenna (JAMA) is a Good Signal
Magnet for weak AM/MW Signal Locations.


iane ~ RHF
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= = = Ron Hardin
= = = wrote in message ...
RHF wrote:
* The Justice AM Antenna is directional but not as directional
as a Select-A-Tenna Model 541-M; or a home made Box Loop Antenna
of about 15" or bigger.


All small antennas have the same nulls, the problem being that they
all have two patterns: a magnetic field pattern (with infinitely
deep nulls), and an electric field pattern (with infinitely deep
nulls) that doesn't null anywhere near the same place.

So in the nulls of the magnetic field pattern, you hear the
electric field signal instead of silence.

Careful balance and symmetry can eliminate most of the electric
field response, and that's how you get deep magnetic nulls.

If it's on the end of a long cable, it starts picking up electric
field again.

You can make it less important by having the first amplifier at
the antenna itself.

The passive MW loops work not by gathering signal (signal magnet)
but by matching impedance. Active ones work by having a lower
internal noise level than the receiver they front for.

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