[Elecraft] Magnetic Loop Antenna Question
Fred Jensen
k6dgw at foothill.net
Sun Nov 13 16:36:39 EST 2016
I've built several of those ... most before I understood how they worked
... or didn't. [:-) The #1 requirement, if you are building an antenna
and not a dummy load, is resonance. Since most loops are used fairly
close to the TX with short transmission lines, SWR doesn't matter much,
except to keep the TX happy.
It the loop is resonant, you can match the impedance at the input end of
the line with a tuner if you have to. But, the problem is folks new to
mag loops tend to get the loop close to resonance [usually because the
exact point tends to be fairly sharp on the capacitor rotation], and
then "let the ATU do the rest."
Loops will get you attention, sometimes more than you want:
A couple years ago, I set up for the FOBB at a local park on top of a
little knoll with my Alexloop. I sit under mine and can reach up to
tune it easily. Several people inquired what I was doing. Finally, one
older guy who had been walking past me several times at a bit of a
distance finally came up and said, "You're the CIA and you're spying on
me aren't you?"
73,
Fred K6DGW
- Sparks NV DM09dn
- Northern California Contest Club
- CU in the Cal QSO Party 7-8 Oct 2017
- www.cqp.org
On 11/13/2016 12:30 PM, stan levandowski wrote:
> Yeah, if I remember my experience, it was rather "mono frequency" for a
> few kHz. Then I had to adjust the coupling for better SWR. It wasn't
> all that user-friendly! However, it was a great and cheap way to play
> with a mag loop. I remember sitting on my front porch with a K1 and
> working DX with it. The loop was just tie-wrapped to a broomstick stuck
> into a patio umbrella stand and sitting on my driveway. It was enough to
> get me interested in reading and experimenting so it accomplished the
> authors' objective.
> 73, Stan WB2LQF
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