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Old August 31st 06, 10:28 PM posted to rec.radio.amateur.antenna
Wimpie Wimpie is offline
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First recorded activity by RadioBanter: Aug 2006
Posts: 106
Default the Inside of the loop antenna..........?

Hello,

I'm not sure whether I have a good picture of your situation but there
are some general rules.

In general, magnetic field lines generated by the loop that are
parallel with the wire from the inverted V, do not induce voltage into
the wire. On the other hand when the E-field lines are perpendicular to
the V's wire, there will be no induced voltage in the wire.

Imagine a plane that cuts your loop (inclusive the tuning capacitor)
into half. The loop is perpendicular to the plane. Every wire that
passes along or inside the loop and stays in that symmetry plane obeys
the above statement, and interaction will be negligible. The above is
valid when you loop is fed fully balanced (no common mode current on
feed line).

When you use the V, the loop will introduce some capacitance to the V.
It is best to keep the wire away from the high voltage ends (where the
tuning capacitor may be present), because a slight deviation from the
symmetry plane will cause interaction between the loop and the wire.

Besides this general rule, also wires running close or through the
loop, but off the symmetry plane may be acceptable, but prediction is
difficult. You are able to measure the effect. When you make a kind of
common mode (current) transformer with a diode detector (with a
suitable ferrite the you can place around the feed line), you are able
to detect the common mode current (when transmitting).

If you run the questionable wire of your V through or along the loop
and the output of your transformer does increase significantly, there
is (undesirable) interaction.

I hope this will help you.

Best Regards,

Wim
PA3DJS