WA3LTJ wrote:

I recently built a 100W HF amplifier by modifying existing designs.
Now I'd like to build an automatic antenna tuner. Where can I find
some good articles / web sites on theory, practical design, and tuning
algorithms for the switching circuit. Has anyone published all the
details including source code.

Thanks for all the suggestions. I found the QST article on the switched
automatic tuner at LDG sold (AT-11). The source code was not published
and I think the ARRL has a new policy requiring source code (in most
cases). The article does hint at the algorithm. It was written in
assembler on a Motorola 'HC11.

I am interested in building a similar design and playing with the
tuning algorithms. I need a suggestion for a
microprocessor/microcontroller. I am most experienced with the Motorola
'HC08, PIC, and Rabbit Semi 2000 series. I think I would rather code in
C. So here are the basic specs for the processor:
1) low cost C compiler/IDE
2) at least 28 available general I/O bits
3) built in 8 or 10 bit A/D (2 channels are enough)
4) low cost development board or easily constructed one.
5) 16 bit or larger counter

What is the easiest way to have the tuner measure the frequency? Should
I just put a pre-scaler in front of a digital port and sum pulses over
time?

What do you think of this idea? Have the tuner control the
transmitter. Use the combination to completely characterize the antenna
across each band of interest. Then select the tuning "instantly" based
on a large frequency-based lookup table. With enough table space, you
could create a table for each antenna and each band. This assumes that
none of the programmed antennas changes much over time.

Andy WA3LTJ

(remove the b's for address)