On Wed, 28 Apr 2010, Mike.WE0H wrote:
Most people thought a TX loop would not radiate out of a backyard.
a few years ago i've tested some very modest setups (no kilowatts and
kilometers of wire).
in a country area 1 km is certainly possible with a 4x14m loop made of
pieces of 4mm2 and 1.5mm2 wire (if i remember correctly). the power was
abt 40W and the matching was done via a capacitive divider.
btw. 1km is more than my backyard :)
you can also get 500m easily with a 1.5x2.5m 3-turn loop in a city area.
The calculations say a TX loop is a terrible antenna, but it does
radiate very well.
yes and no. the calculations are correct in free space, however it has a
very strong near-field, which will couple into anything that will conduct
(powerlines, underground streams etc). thus if you're not in the cosmos,
then in a realistic setting the antenna size is much greater.
actually someone on this list called it "cheating" :) it's interesting
that this cheating by law of recipriocity should increase the receive
antenna size too.
as mentioned above, with a very small loop i can do 500m in the city. this
is probably because of all of the underground conductors here (powerlines,
phone lines, catv etc).
VY 73
Jacek / SQ5BPF
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