Oddly enough, I am also building a portable loop antenna. Yes, it performs
worse than beverages or
other receive antennas. But a portable loop (~1.5m diameter) is very helpful
for DFing RFI
problems... and I have a fat S7 noise across 160m!
So far I have the loop itself done: two turns of RG-6 with the shields opened
up at a point opposite
from the feedline attachment. It has deep (about 7 S-units) and very narrow
(<10° in azimuth) nulls
where it should. But it's pretty deaf! I can't hear the noise yet... only the
very strongest signals.
Next steps are a resonating variable capacitor and a preamp. Maybe I'll need a
3rd turn... but the
books recommend keeping the overall length <0.1 wavelength. I'd like to use
this on other bands
when chasing down RFI sources, so I put a switch in to choose the number of
turns.
I've never done this before. I'm just following the details in the current
edition of "The ARRL
Antenna Book". Any hints will be appreciated from those with practical
experience!
-- Eric K3NA
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