[Elecraft] Re: Algorithm for Tuner (Don)

[Don]

Charles,

I have tried that method ... ditto setting L and searching for best C.  It 
works but is no better than the one I am using now which is to begin with 
both L and C at 0 and then search for the best C for every L as L increases 
from 0 to max.  The searching is done in large steps (coarse granularity, to 
use Waynes  term) so it doesn't take very long to cover the range.   When a 
best solution is found the steps are then decreased in size while searching 
a limited range around that  solution.  Typical solutions take from 5 to 10 
seconds and I know it could be much quicker using a more clever algorithm. 
I am happy with what I have because once a solution is found and stored the 
tuner tunes from memory anyway, switching in milliseconds.

I keep pursuing this because of the challenge,   the same reason I do 
crosswords and computer games.

Don  K7FJ

>
> Why not take an approach normal to the manual tuner.  That is capacitance 
> to
> mid scale and adjust L to best.  Then adjust C up or down from midscale 
> for
> min. ? Doing this with a possible repeat  for missing the L value by +/- 1
> has always yielded me good fast manual results on my old mfj tuners and
> doesn't require a tremendous number of iterations or complex programming.
>
> best regards,
>
> Charles
> wb5izd
>
>
>
> A reiterative  multilevel slope-sensing algorithm using decreasing
> granularity*  is the answer.  I have been slowely creeping up on a
> satisfactory solution and, depending on distractions, hope to have a 
> fairly
> fast autotuner in a week or so.  Suggestions from the list have been very
> helpful.
>
> * my term ... don't try to look it up!  ;)
>
> Don  K7FJ
>
>>
>> On Sep 15, 2005, at 11:22 AM, Craig Rairdin wrote:
>>
>>> In this particular case, if you were to iterate over all possible
>>> combinations of L and C it's only necessary to store the best  result so
>>> far
>>> and compare the current result to the best result. If the current 
>>> result
>>> is
>>> better, it becomes the new best. Now you have no sorting at all and 
>>> your
>>> time is order N instead of order N^2.
>>
>> The problem with the exhaustive search is there are 2^17 = 131,072
>> combinations to try. (256 cap and inductor values, plus reversing the
>> whole L network)
>>
>> It takes a few ms for each relay to physically switch. If you can try 
>> 100
>> combinations a second (10 ms), that's still about 20 minutes to  try them
>> all. Even with 1 ms switching time, you're still looking at  2 minutes to
>> find a match.
>>
>> A tough problem.
>>
>> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
>> Quote: "Not within a thousand years will man ever fly!"
>>             -- Wilbur Wright, 1901
>>
>
>
>
>
>
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