[Elecraft] Algorithm for Tuner

[Don]

Bill,

It's worse than that.  Even with my reed relays (very fast compared to 
conventional relays) I have to allow 10 mS for them to settle and the A/D 
requires a millisecond or so to read the forward and reflected power.

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
>