[Elecraft] KAT500 Tuning issue

[Mark Bayern]

Just to make sure we're all on the same page ...

When the tuner (at the radio) gets an acceptable match, that just
means the transmitter will _think_ there is a good antenna system out
there. The feedline between the antenna and the tuner will know
otherwise and can have points of very high voltage that could cause
insulation breakdown, and points of very high current that can cause
overheating and will be a source of power loss. This isn't really a
problem in QRP operations, but when you head into the QRO world it can
make a difference. The antenna also has issues. In an earlier post
K3KO had the calculated feedpoint impedance, and it was very far from
the 'nominal' 50 ohms of your feedline or the ~75 ohms of a dipole at
altitude. W6GF also gave this info in terms of SWR to show how bad it
was. All in all a resonant 40M dipole makes an unhappy antenna system
on 20 meters.

I understand that if that is all you have you're stuck with it, but it
is really time to consider something else. Maybe a fan dipole, or trap
dipole?

Mark AD5SS



On Sat, Dec 8, 2012 at 3:30 PM, Jerry Weisskohl <jweisskohl at gmail.com> wrote:
> Right now, I have the coax from the antenna directly connected to the
> KAT500. I could try using my Delta-4 switch, have the coax go to that and
> then a small run to the KAT500 to see if that makes a difference. The high
> swr is an issue on 40 and 10 meters, however, ten is manageable, it's about
> 1.9 - 1 and I am working around the issue but using my 80 meter vertical on
> 20 meters. So this is not a "show-stopper" but just wanted to understand
>  why it was happening.
>
> Jerry - AC4BT
>