[Elecraft] Alpha Antenna/KX3

[Gwen Patton]

I built a loop a few months ago, using flexible plastic pipe strap and 1/2"
copper foil tape with conductive adhesive. I used a junkbox air-gap
capacitor and a 10x vernier knob to tune it. I ran 100w through it on FT8
and ran an infrared thermometer all around it and it barely warmed past
room temperature. From inside my house in the Philly burbs, I got FT8
contacts in northern Wisconsin and Fargo, North Dakota on 30 meters, so I
think it was getting out pretty well. I was running 30 watts or so on it at
the time, as I recall. Not bad from indoors on the first floor with a steel
workbench a foot away and resting on a wire rack. Someday I'll take it on a
park run and see how well it works out in the open. I'm considering making
a better loop first though, as this one is pretty flimsy and probably won't
stand up to any significant wind. I need to redesign it for more rigidity
and probably a somewhat larger loop to get at least SOME efficiency on 40
meters and perhaps even a little on 75/80, though that's asking a lot of a
small loop.

73,
Gwen, NG3P

On Thu, Jun 6, 2019 at 12:11 PM Edward R Cole <kl7uw at acsalaska.net> wrote:

> Interesting reviews on some of the loop antennas.  I've seen W4OP
> adv's for several years.
>
> I plan to make a receive-only 630m loop (4 to 6 foot diam) out of
> some surplus 1/2-inch hardline that is too old for coax use.  The
> copper shield should do well in a loop.  I will use a preamp with it
> (pcb in hand waiting for some spare time to build).  Plan using a
> small TV rotator and tripod mount.  Advantage of the loop is being
> able to null out noise sources. I transmit using 43x122 foot inverted-L.
>
> The loop might also work for 160m if I ever try that band.
>
> 73, Ed - KL7UW
>    http://www.kl7uw.com
> Dubus-NA Business mail:
>    dubususa at gmail.com
>
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