[Elecraft] Automatic tuner implementation

[Walter J. Legowski]

My XYL (Sue, N2LBR) was also interested to try this.  She was watching 
closely as I was doing alpha testing for the KPA1500 firmware, and was 
wondering if using the network solution would provide guidance for an 
iteration scheme.

Her solution works even if the complex load impedance is not available. 
Based on the measured SWR straight through, the minimum and maximum real 
parts (load resistance) can be calculated, along with the corresponding 
(plus and minus) imaginary parts (load reactance).  This defines the 
"space" in which the solution exists.  A binary search proceeds by first 
solving the "exact" solution for the given real part (and the 
corresponding plus and minus imaginary parts), and then using those 
tuner settings (for L and C) to get a SWR with the actual load (which is 
modeled in her solution).  The algorithm proceeds by zeroing in on the 
iterated settings that have the lowest SWR.  It usually converges in 
less than 5 iterations to get a SWR less than 1.1:1, even for very large 
values of (initial, unmatched) SWR.

Walt, WA1KKM


On 4/8/19 1:20 AM, Andy Durbin wrote:
> "It's all about "pruning the search tree," to borrow a term from game theory."
> 
> That always struck me as being a bit like trying to whack a pinata while blindfolded.     Why is it not possible to measure the complex impedance and compute the solution?  That should be a lot faster than any iterative method.  Sure, it needs a better detector but isn't Elecraft about elegant solutions?
> 
> I'll probably find the answer for myself in a while as it's on the list of things to try with my Kenwood/Elecraft interface (I have LP-100A complex load impedance available).
> 
> Pointers to any failed or successful attempts to do this would be appreciated.
> 
> 73,
> Andy, k3wyc
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