[Elecraft] Homebrew Autotuner

[John Magliacane]

--- Don <ehrlich at olypen.com> wrote:

> At the moment, though, I am having trouble coming up with a software
> algorithm that finds minimum swr and this message is a request for
> suggestions.
> ....
> Any ideas?

Hi Don.

Most tuners contain directional couplers to indicate VSWR, but they
are often sandwiched between the transmitter and the tuning network.
The tuning network is then adjusted for zero reflected power using
a trial-and-error approach.

If the directional coupler were instead placed between your tuning
network and the antenna jack (the OUTPUT of the tuner), you could
use the amplitude and phase information returned from the coupler
to determine the complex impedance of the load (antenna) you wish
to match to 50 ohms.

Next, you could calculate what conjugate impedance the tuner needs
to place in series with antenna jack to produce the 50 ohm resistive
output impedance you desire, and then select the appropriate L and C
values in your tuner network to produce that impedance.

Done!


73, de John, KD2BD


Visit John on the Web at:

	http://kd2bd.ham.org/
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