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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