Hi Guys,
I have had a 80m loop antenna,up at 30ft.;in my backyard for over 4
years. It works great.
Tunable on many bands except 160. I suppose I could short the leads
together to get 160m but I don't do that. Which brings me to this
question: I have a COBRA ultra-lite senior which
is an inverted "V". The feedpoint is at 55ft.,and the ends are at say
15ft. above ground. NOW,
I was wondering about the end of that inverted "V".......it goes right
into and near that 80m loop ! I believe that the inside the 80m loop
is where the "action" is. It doesn't matter if the
loop is delta,or square,or even totally round! IS MY inverted "V" leg
of the dipole interacting
with the loop ?? I have plans to RAISE my 80m loop up another 15ft.
higher....will I get problems when I do ?? One leg of my 160m antenna
goes right in the middle of my 80m loop. IF the LOOP goes higher will
it intereact? So far,at how I got things set now....no major
issues. I never use both antennas at the same time.

Great Place
to "air" antenna ideas......HERE.


Thanks, RayN kb1-ghh

Paladin wrote:
I have had a 80m loop antenna,up at 30ft.;in my backyard for over 4
years. It works great.
Tunable on many bands except 160. I suppose I could short the leads
together to get 160m but I don't do that.

There's another way to put your 80m loop on 160m for
NVIS operation. Cut the 80m loop directly across from
the feedpoint and install a good insulator. Use that
configuration for 160m and short out the insulator for
all higher bands. I'll let you come up with a cute
shorting arrangement because whatever switch you use
has to withstand thousands of volts on 160m.
--
73, Cecil http://www.qsl.net/w5dxp

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