"Andrey" wrote in message
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How do I design an automatic antenna tuner with no moving parts?

This is a good question.

How to do it - without relays, motor driven capacitors and inductor
cotacts?

I'm not so sure that is really all that off the wall.

Most autotuners are pretty mindless ... you only need to get down to a
"reasonable" SWR, so you can use a finite number of LC circuits. Most
tuners count frequency (easy) and use that to look up where they were the
last time they were near that frequency, so they randomly try everything at
first, but then use their experience to get there quicker the next time. A
few actually look at the phase angle to figure out which way to go, but they
are in a minority and it isn't all that clear that they do much better than
just guessing.

Typically, relays are used in commercial autotuners. Latching relays are
simple, cheap, and require very little power. But I can see no reason why
one couldn't use PIN diodes if the "no moving parts" was a requirement. It
would ratchet up the price a bit, and probably also the power consumption,
so I can see why it wouldn't be a common commercial approach, but if the no
moving parts limitation is a hard requirement I can't see why it wouldn't
work.

I would also think about the "why" on the no moving parts. Something like
PIN diodes is going to mean constant power consumption, which in turn means
constant generated heat. It isn't obvious to me that this will result in
better reliability than latching relays, which are pretty darned good these
days as far as reliability is concerned. It will also end up (I think)
increasing the parts count quite a bit, which again will hurt the
reliability, to say nothing of the cost.

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