Re: KX3 & Loop Antennas

Posted by k6dgw on May 31, 2016; 12:13am
URL: http://elecraft.85.s1.nabble.com/KX3-Loop-Antennas-tp7618249p7618253.html

I replaced my Buddipole with an Alex and use it a lot in the field ...
understand that as I accumulate birthdays, "field" more and more means a
drive-to a park or friendly hill.  It works better than the BP ever did,
I can set it up in 5 min, it is fairly insensitive to ground and
surrounding objects, including me.  I sit under it so I can reach the knob.

It's a resonant transformer.  To be effective, it must be EXACTLY
resonant.  That's a bit touchy on 30 and 40.  You MUST bypass the ATU.
"Getting close" with the knob and then letting the ATU do it's matching
job yields a fairly pricey dummy load.  On 40, the BW of the Alex isn't
much more than a SSB signal.

Beware:  Small mag loops can involve some huge circulating currents and
RF voltages.  The Alex is OK to 10W.  Google "magnetic loop calculator"
for a very cool little calculator.  Try it with 1 KW, it will really
surprise you.  And sadly, I don't think a Reynolds Wrap hat will protect
you if you're close.

Small mag loops are bi-directional in the plane of the loop but it is
very broad.  Orthogonal to the loop plane, there are two very sharp,
deep nulls, sometimes useful to eliminate noise from a point source or QRM.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 5/30/2016 4:38 PM, TFJM via Elecraft wrote:
> Has anyone had much success using either an Alex Loop or Chameleon P Loop
> antenna with their KX3? I have few antenna options in an apartment situation
> and throwing a 25 foot long wire into a nearby tree has not worked for me.
> Even tried loading up a 33 foot long aluminum balcony railing with no luck.
>
> Thanks,
> Tom W1PDI

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