MOTM

> I wonder how much a big knob will move if you blow on it?
>
> Mike
>

Ok, I read the jokey responses.  But was anyone here ever a ham radio
operator?  Now *there* is a need for coarse/fine frequency tuning.  Mike's
comment reminded me of a knob I became intimate with, many years ago.  No
one mentioned the big tuning knobs used on some of the old radio receivers.
I actually owned one of these:

http://www.qsl.net/ab0cw/nc303.htm

Now there's a big knob!  Next to that huge wheel, low, and to the side
perches a fine tuning knob about 3/8 inch in diameter.  This little machined
knob had a flange for your fingertips, and was merely a gear that engaged
the big wheel to give fine, smooth movement with plenty of control.  A
mechanical engineer's handiwork!  The little knob snapped in for traction
when in use (as well as to keep the big one from moving when you blew on it
;-), and snapped out when you wanted to sweep.  You got the best of both
worlds: a big wheel for smooth, large sweeps, plus the ability to do really
fine tuning.  Admittedly the application is different.  Sweeping a radio
knob is usually to get to another spot quickly, whereas when sweeping a VCO
or frequency shifter, it's the journey that's more important.  (The radio
knob was hooked to a variable capacitor.  How many of you even know what one
of those looked like?  Three-ganged monsters.  That sort of capacitor no
doubt has a finer resolution than an ordinary potentiometer.  The resolution
of a pot attached to such a knob would have to be considered.  Most
fine-resolution pots are multi-turn, which would seem to defeat the sweeping
ablility.)

Such a specialized knob would be expensive or hard to get, I expect.  But it
might find application to synthesizers.

Ok, resume the debate.  This was sort of a side comment.

-Richard Brewster