On Apr 25, 1:28*am, The Eternal Squire
wrote:
All,

I'm currently considering a design for making a steampunk radio. *I
just
had an idea for the VFO that I want to run by those who have a far
better grasp of the abstract mathematics of harmonics than I do.

Suppose I have a DC motor running steady at 1000 RPM. *Through a
X100 set of planetary gears I create a shaft spinning at 20,000 RPM,
which is pretty much the upper limit for small drills anyway. * *On
the
shaft is a disk that is an etched circuit board with a star pattern,
that is,
500 conductors etched radiating from the center to the edge of the
disk.

Now I have a wiper that is laid across the edge of the disk to make or
break contact with the outside of the star pattern, with 12 Volts DC
potential on the wiper. * Assuming the shaft was conductive and made
firm contact with the center of the star pattern, should I see a 10
Mhz
square wave, suitable for say a switching mixer?

Question: *How bad are the phase noise and harmonics likely to be?

Thanks in advance,

The Eternal Squire

Instead of mechanical contacts I would try an optical sensor but this
may not be very Steampunk. I have a friend who built a small steam
engine, for demo purposes he would run it on compressed air at 40K
RPM.

Jimmie

Jimmie