> Well I made my first loop antenna:
>
> http://www.hard-core-dx.com/nordicdx/antenna/loop/coaxloop.html
Bob,
Did you remember to gap the shield at the top? Did you tune
the loop with an analyzer?
Sometimes things that should not work or do not work
according to plan wind up working through pure dumb luck.
Multiple mistakes sometimes wind up correcting each other.
There are two flaws I see in that design.
1.) There are two independent parallel resonant circuits
(each loop) in parallel. That's a very bad thing to do,
because if it is done with short leads you wind up with ONE
resonant frequency between the two independent resonant
frequencies. Normally two independent parallel tuned
circuits are SERIES connected. Series resonant circuits can
be paralleled, not parallel circuits.
2.) There is no ground or return path on the side of the
coax. You have a tuned center loop but one side simply
floats!!
I think what is happening or what could happen is the two
mistakes correct each other, if you are lucky. I'm just
guessing, it could be it was originally intended you ground
the center conductor on the left side of the loop and left
that out of the drawing.
The stray capacitance from the center conductor to shield on
the left side of the loop (looking at the diagram) could,
through luck in values, make the loop a combination series
and parallel resonant system. This unplanned path (through
center to shield capacitance) on the left might supply the
ground path to deed the feedline shield. However, this is a
badly unbalanced feed arrangement.
It also could be the author intended you ground the center
conductor entering the box on the left side of the drawing,
and simply left that out.
You can see a walk-through of feed arrangements at this
link:
http://www.w8ji.com/magnetic_receiving_loops.htm
73 Tom
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