[Elecraft] K2 + ATU + Loop antenna in the attic

[Ron D'Eau Claire]

I played with a fan dipole back in the 1960's, and played and played and
played trying to get a decent (less than 3:1) match to 50 ohm coax. Never
was happy. 

That experiment taught me the efficiency, ease and simplicity of a doublet*
fed with open wire line. Working out the process of getting the open wire
line into the shack wasn't nearly as difficult as trying to get the antenna
to present a decent match to the coax, and it was a wonderfully efficient
and effective all band antenna mounted at an "inverted V" with the apex at
50 feet.

BTW, my doublet was 100 feet end-to-end and worked beautifully on 160
through 10 meters. Granted, at so close to the ground the radiation was
mostly straight up on 160 but on that band I was mostly interested in
working locals out to 100 miles or so. We had a lot of mobiles active on 160
back then as well as fixed stations. And none of the rude nonsense so often
found on 75.  

Ron AC7AC

*Wire fed at the center but not necessarily a "dipole" - i.e. 1/2 wavelength
long - on any band.

-----Original Message-----
Subject: Re: [Elecraft] K2 + ATU + Loop antenna in the attic

  Alan,

Sorry to hear about your lack of success with the fan dipoles.  I have 
three of them - one for 80 and 40, another for 30, 17 and 12m, and yet 
another for 20, 15, and 10.  They work very well.

My "secrets" - space the wires for each band away from one another - my 
80 and 40 antennas are at right angles to each other, so there is little 
of any interaction.  The other two have the wires spaced about 1 foot 
apart using CPVC pipe with holes drilled in them (wires through the 
holes) to maintain the spacing.  PVC would work too, but is heavier).

The antennas do interact, so plan ahead, you will have to do some "cut 
and try" pruning.  Tune the lowest band or resonance first, and then the 
next band higher in frequency.  Trying it the other "way 'round" is an 
exercise in futility (been there, done that, and have the scars).

I usually consider 3 bands on one feedline the limit of my patience, but 
this last weekend I helped a friend construct an antenna with 4 wires - 
80, 40, 20, and 10 meters.  It was a bit of a pain to tune, but it 
worked out well.  Cut the wires at least 10% long and prune as required.

One other point - do not use separate wires for bands that are close to 
the 3rd harmonic of another band - in other words, for HF, do not put a 
30 meter radiator on a feedline that contains an 80 meter wire, and do 
not put a 15 meter wire on a feedline that also has a 40 meter wire.  
The lower band antenna may be usable on the 3rd harmonic (likely with a 
tuner), but trying to combine those two wires will result in even more 
frustration.

73,
Don W3FPR

On 4/15/2011 6:15 PM, Alan D. Wilcox wrote:
> FWIW, see my fan antenna at
> http://wilcoxengineering.com/projects/amateur-projects/39-fan-dipole
> A bright idea that didn't work out so well!
>
> Cheers, Alan
>
> Alan D. Wilcox, W3DVX (K2-5373, K3-40)
>
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