A few months ago I maintained a brief correspondence with some on this list
with an interest in a homebrew balanced autotuner. The project is nearing
the point where I will be installing it into a K2 case. At the moment,
though, I am having trouble coming up with a software algorithm that finds
minimum swr and this message is a request for suggestions.
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.
I have used complex algorithms that vary step size, vary C and L values
intelligently with either positive or negative changes in value. I have
used simple algorithms that stupidly go through an entire range of
possibilities of all values of L for every C and so forth (ugh!) ... and
have to believe there is someone out there in Elecraft-land a lot more
clever than I who can suggest ways to intelligently find best combinations
of L and C quickly using measured swr as the criteria.
It really does not matter a great deal if I never perfect the autotuning
feature of the tuner. It is easy to manually tune the tuner, store L and C
for every band segment in nonvolatile memory, and then let the tuner
automatically switch to the proper values when it senses the frequency at
the input. But I can't call it an autotuner if it doesn't tune well
automatically can I? Perfectionist that I am I would like to make it
autotune like it is supposed to.
Any ideas?
Don K7FJ
http://www.qsl.net/k7fj/
