[Elecraft] Remote Antenna Tuner

[Vic Rosenthal]

W B Reese wrote:
> Yes BUT!
> 
> Will the KAT100 match 20-50 to 1?  If you are feeding your 40-meter 
> dipole on 20 meters it may not match, and even if it does, do you want 
> to put that kind of stress on the tuner?

The difficulty of matching an antenna is determined by the impedance 
that tuner sees, not the SWR.  Although the SWR is (almost) exactly the 
same regardless of the line length (measured SWR drops a bit as lines 
get longer because of losses), the impedance varies cyclically as you 
change the length of the line.  So if the impedance at the antenna 
feedpoint is 2000 ohms, the impedance seen by the tuner will be 2000 
ohms only when the feedline is a multiple of exactly 1/2 wavelength. 
The tuner may have trouble with very high or low impedances, but you can 
easily avoid problems by changing the length of the line slightly.  So 
the answer is that it is quite easy to feed an antenna through a line 
with a 50:1 SWR as long as you avoid some problematic lengths.

If there were a remote KAT100, however, you would probably not want to 
put it EXACTLY at the feedpoint of the 40-meter dipole that you are 
using on 20.  It would be best to put it a few feet away from the 
feedpoint to avoid the impedance maximum.

Vic K2VCO