[Elecraft] KX2 Antenna Curiosity

[David Gilbert]

Your field antenna is essentially a very low off-center fed sloped 
dipole slightly longer than a half wavelength.  I'm not surprised you 
can tune it with the KX2, but it certainly isn't any kind of ideal 
antenna configuration that Elecraft would design for.  They just made a 
very well performing tuner for the KX2 that will work with almost 
anything.  I have a KX2 ... it's amazing what it can tune.

You didn't say how long your feedline is, but with a feed that far off 
center the shield of your coax is probably doing some of the radiating 
anyway.

Yes, a center fed normal dipole with the middle (high current portion) 
higher off the ground (say 50 feet for 40m) and a common mode choke at 
the feedpoint would almost assuredly perform better. If you can't get it 
that high, a vertical (even a 30 foot wire oriented mostly straight up) 
fed against a decent radial system might be a better choice if you don't 
have a lot of surrounding buildings/trees/telephone poles.

For the record, I also have on rare occasions used low sloped wires fed 
near one end against some sort of ground or counterpoise when camping or 
for a hurried Field Day setup.  They are easy to set up and sort of 
work, but they always performed very poorly compared to even the most 
basic dipole if I could get the dipole off the ground approaching a half 
wavelength in height.  Over the years I have operated roughly 20 Field 
Day contests (almost always 5 watts CW for the extra QRP points) and one 
year I used only a low sloped wire similar to what you described.  It 
was memorable for being the worst Field Day result I have ever had, and 
that's in spite of the fact that I've placed top 3 nationwide in my 
category on more than one occasion using only wire antennas strung from 
tall trees.

73,
Dave   AB7E



On 10/10/2019 9:01 AM, Joseph Shuman via Elecraft wrote:
> I have had my KX2 with the ATU for about 10 months and operate on 40m QRP SSB from various locations.  Experimenting with different antennas I have experienced best results with a 58.5’ wire tossed about 25’ up a tree with a 16.5’ counterpoise.  I ran the same length wire from my house to the workshop, grounded the shield side of the cable, and have seen similar results to the field setup.
>
> Is there some engineering/design factor of the KX2 for this type of antenna setup?  I am planning to setup a Dipole at home, but as a newbie am wondering if the “ideal” Ham Dipole can be expected to improve performance.
>
> Keeping Watch-
> shu
>
> Joe Shuman