[Amps] Autotune amplifier. How to implement actuator / system for tank switching?

Marius Hauki rezycle.bin at gmail.com
Sat Sep 11 08:08:08 PDT 2010


I am thinking about making my GS35B amp project autotune. A
microprosessor circuit will remember the correct tune settings for
each band (C1, L, C2) and when I switch bands the amp will tune
itselves to presets that had been previously programmed. I have got
hold of two nice big vacuum variable capacitors,  that will be
actuated with stepper motors via pulleys (some gearing / reduction) or
via motors that have a gearbox.

The question is how to implement the PI or PI-L coil switching.
Several of the rugged swithces that are in use on manual tune amps are
quite hard to rotate and needs to "snap" into contact engagement. I
suspect those are not easy to actuate properly via a motor / gear
system.

I have been thinking about different options:

-Several vacuum relays that are electronically controlled from a
control board (will the added capacitance of the body / wiring be a
problem?). Has a solution like this been attempted before by anyone on
this list?

-Normal relays that are electronically controlled from a control board
(will the added capacitance of the body / wiring be a problem?) Has a
solution like this been attempted before by anyone on this list?

-A special switch that is designed for "motor actuation" (Where do I
get hold of that and is the cost prohibitive?) Has a solution like
this been attempted before by anyone on this list?

Are there other ways that has been tested in practice to implement
this? (Apart from a roller coil with a motor / gearbox on it of
course).

73
LB3HC


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