Hi Paul,

Thanks again for the suggestions; I need to do a few simulations to see how
viable some of the approaches are.

However, I think that the OP should also study of making a shortened
1/4 (stripline or microstrip) resonator, with very wide resonators
(and thus low impedance levels) and do the impedance transformation at
the input and output coupling.

The problem with this approach is that I've yet to see a
stripline/microstrip resonator design that -- by design -- doesn't have
re-entrant modes well before covering a 16.7:1 range (30-500MHz, in my
case). Otherwise I'd be all for it!

If the tuning speed is not very large

It's not, 'some low number of seconds' to re-tune is fine.

I don't suppose anyone makes motorized piston trimmer caps? Sure would be
nice...

---Joel