[Antennas] Using the AH-4 tuner on 80 meters

[Robert Lay]

Dear David,

In my original reply to your original posting, I assumed that the output
interface of the tuner was for coax - bad assumption. I have many tuners, but
not an AH-4. Most of my tuners provide output for coax, for balanced line and
also to long wires.

I guess I should have asked you what you meant by a "resonant 80 m antenna as if
it were a whip".

If the wire that you want to use presents a moderate impedance to the tuner,
then it will tune it. Generally speaking, a moderate impedance will be presented
to the tuner when the end fed long wire (fed against ground) is an odd number of
quarter wavelengths. So, for 80 meters, that means your antenna should be 20
meters in length (nominal quarter wave) or 60 meters in length (nominal 3/4
wavelength) or 100 meters in length, etc.

Any time the length of the antenna becomes an even number of multiples of a
quarter wavelength, such as 40 meters in length (nominal half wavelength, or 80
meters in length (nominal full wavelength), etc., then the impedance presented
to the tuner will be extremely high and the tuner cannot transform it down to 50
ohms as needed by the rig.

Bob Lay (W9DMK), Dahlgren, VA
w9dmk at crosslink.net
http://www.qsl.net/w9dmk