[Elecraft] K3/100 into DX-CC antenna (HI-SWR)

[Brian Alsop]

Jay,

I had one of these in my attic for several months.

I had to tune each band by generally shortening the elements.

Start at 10M.  Find its resonant point via antenna analyzer or by 
"sweeping" frequencies with your SWR meter.  You need to confirm that 
the resonant point is too low before trimming.

If the frequency is only about 100 KHz too low, pull some wire from the 
end insulator out and wrap it about the incomming wire to the insulator. 
  Otherwise you have to cut it.

Proceed to the next higher frequency band and do the same.  Recheck the 
lower band again.  There is some interaction.

When you are done, all bands should present a decent SWR.  I had to take 
a lot of wire off the 40M section beyond the trap.

The difficulty with this is that if you move the antenna to another 
location, it will need to be re-pruned.  The advantage is that you don't 
need a tuner.   While you're at it, remove the spike suppression "pill". 
  It is almost inevitable that it will get shorted sometime in the 
future if your running any higher power level.

73 de Brian/K3KO


On 1/1/2013 03:49, Ron D'Eau Claire wrote:
> Yes. A horizontal, or semi-horizontal, antenna is sensitive to height above
> ground. You want to be about 1/2 wavelength up for optimum DX results. The
> way the radiation interacts with the earth provides additional gain - up to
> 6 dB - at those heights.
>
> Your "inverted V" configuration provides some vertical polarization that has
> a lower radiation angle, but it's not much.
>
> It will be effective for at least short skip down to about 1/4  wavelength
> above ground where the main lobe is straight up and will scatter off of the
> ionosphere. That's what many Hams today call a NVIS (Near Vertical Incidence
> System) antenna. At lower heights the main lobe continues to point straight
> up but with less and less strength as more of the RF is absorbed by the
> earth.
>
> What you've run into with the SWR is exactly why tuners are so popular. It's
> very difficult to get an antenna to show a low SWR, especially on several
> bands, without one.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jay Krishna
> Sent: Monday, December 31, 2012 6:34 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K3/100 into DX-CC antenna (HI-SWR)
>
>
> Hi all,
>
> Just spent the day putting up a multi-band DX-CC (fan dipole, 80-10M) in an
> inverted V configuration. Unfortunately, I could not get the center mast
> extended beyond 20 feet, with one end up ~9 feet from ground, the other, ~5
> feet from ground. I am seeing HI-SWR on all bands. Any suggestions on what
> might be the issue? I was able to get decent SWR with my old 20M monoband
> dipole, 30 feet up.
>
> I have heard that the DX-CC is sensitive to height above ground, and am
> concerned that 20 feet might be too low. On the other hand, I was hoping it
> will at least tune well on 20 M at that height, if not all the bands...
>
> Appreciate any ideas/suggestions. I don't have an ATU in my K3/100, and was
> hoping a multi-band fan-dipole like the DX-CC would work well without need
> for an ATU.
>
> 73,
>
> Jay (KD6AMA) 		 	   		



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