Ask Paul WD7S. He has bult several amplifiers this way. But he uses air
variable caps, not vacuum caps. See
http://home.earthlink.net/~wd7s/gallery_index.htm
Also see: http://www.wv7u.com/yc156amp/pictures/yc156.html
I have used both vacuum and air variables in my amp projects. If I was building
another amp, I would use air variables.
See my amps at: http://s900.photobucket.com/home/w7ry/allalbums
73
Jim W7RY
> -----Original Message-----
> From: rezycle.bin@gmail.com
> Sent: Sat, 11 Sep 2010 17:08:08 +0200
> To: amps@contesting.com
> Subject: [Amps] Autotune amplifier. How to implement actuator / system
> for tank switching?
>
> 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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