[Elecraft] Questions for KAT100 Gurus

[Vic Rosenthal]

Lee Buller wrote:

> What types of matches will it not match?  For instance, I have a
> Inverted-L that sags with 16 radials under it.  Matches as a 1/4 wave
> on 160 very nicely, but on 80 meters as a 1/2 wave it comes up to
> about 1.7 to 2.0-1.

I don't know the precise answer, because a load's impedance can be 
composed of various combinations of resistance and either inductive or 
capacitive reactance.  So a '500-ohm' impedance can be harder or easier 
for a particular tuner to match depending on its composition.

Obviously, extremes are where you have problems.  We know that an 
end-fed halfwave antenna when resonant has a very high purely resistive 
impedance at its  feedpoint (several thousand ohms).  A short whip (like 
an 8-foot mobile antenna being loaded on 80 meters) will have a very low 
resistive component and a lot of capacitive reactance.

When you connect a feedline to an antenna and the system has an SWR 
greater than 1:1, the impedance that is seen at the end of the feedline 
varies cyclicly with the length of the feedline.  So if you have a 
1/4-wavelength feedline connected to the end of a half-wave radiator, 
the impedance that is seen at the end of the feedline will be very LOW. 
  You can therefore make the tuner's job easier by choosing a feedline 
length that will present an impedance that is away from the extreme high 
or low points.

Of course, this will not affect the SWR on the line, the line losses, or 
the efficiency of the antenna system at all.  It will affect the 
efficiency of the TUNER, however, and its ability to find a match.

I'll let someone who understands the firmware answer your other questions!

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco