Re: Algorithm for Tuner (Don)

[charles allison-2]

Date: Fri, 16 Sep 2005 08:51:33 -0700
From: "Don" <[hidden email]>
Subject: Re: [Elecraft] Algorithm for Tuner
To: "Bill Coleman" <[hidden email]>
Cc: [hidden email]
Message-ID: <003701c5bad6$8373f6f0$4346433f@den>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response

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.


Don,

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: [hidden email]
> Quote: "Not within a thousand years will man ever fly!"
>             -- Wilbur Wright, 1901
>

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[Don Ehrlich-2]

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: [hidden email]
>> Quote: "Not within a thousand years will man ever fly!"
>>             -- Wilbur Wright, 1901
>>
>
>
>
>
>
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