[Elecraft] Homebrew Autotuner

[Vic K2VCO]

Don wrote:

> I have found that it is not as easy as I had imagined.  I have been 
> using several methods to automatically find minimum swr and some work 
> pretty well most of the time but none work well *all* of the time.  The 
> problem is that on some bands minimum swr occurs over a very narrow 
> range of C and L.  With either C or L are set only a little off of these 
> optimum values any change in C or L will have  *no* effect on measured swr.

Some tuner algorithms use a phase detector as well as measuring VSWR. 
If you compare the phase of the current and voltage, the error signal 
from the phase detector will go through zero and change sign when you 
pass resonance.  This tells you to reduce the step size and back up.

I bet Wayne knows a good algorithm!  Looking at the schematic of the 
KAT100 I only see a sensitive SWR detector.

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