Radio scan controller?

[terry michaels]

Message text written by "Chris (the Hex)"
>Bear with me folks, this is probably going to sound a little wacked, but
I'm
open to honest opinions/debate.  A friend of mine and I were discussing the
prospect of using MIDI to control radio frequency scanning -- that is, to
produce the sort of "scratch" sound effect you get by rapidly rotating the
FM radio dial from 88.1 to 107.9 and back again as if it were a DJ
turntable.  (If you have to ask why anyone would want to do that, just
remind yourself that I warned you I was wacked.)  Anyhoo...in a fit of
brainstorming, I came up with the following thoughts:

>Well...a standard radio tuner is controlled by a knob, which means it's 
>connected to a potentiometer (aka a "dial pot").  It should be possible to

>simply hack around the circuit that connects to the tuner knob and replace

>it with a CV (control voltage) jack.  After that's done...well, there are 
>lots of gadgets on the market already that convert MIDI streams to control

>voltages (including the Paia Fatman).  There might need to be some voltage

>scaling involved or something -- still a tad out of my league but
shouldn't 
>be too difficult for anyone with a strong EE background.

Anyone care to comment?  More improbably, has anyone ever attempted
anything
like this in a "musical" context?  I'm an amateur (as indicated above), so
go easy on me please.

Thanks,
Chris (the Hex)

<

Chris:

Until recently, the knob on a radio was attached to a multi section, ganged
variable capacitor, which controls the local oscillator, and the RF
pre-selector.  This could be replaced by varicap diodes which are voltage
controlled, although making them track together like the ganged variable
cap did won't be easy.

Modern, digitally controlled radios use a microprocessor to send commands
to a PLL to select the frequency.  This type of PLL is usually not designed
to make fast frequency changes.  Probably be a major hack to get it to do
what you want.

Terry