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: [email protected]
[mailto:[email protected]] On Behalf Of Jay Krishna
Sent: Monday, December 31, 2012 6:34 PM
To: [email protected]
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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