Hi Nick. You write: >To answer Keith's question, I think the delta-C for >the larger multi-disc unit might have been like 100 pF >or so. A decidedly non-sinusoidal 100pF I might add.
Yes, it's a challenge to make rotary capacitive systems with high enough values of delta-C to make a useful parametric resonator at audio frequencies. One ends up with a field mill type circuit. I agree that the field mill does fit into the spectrum, as you say, but perhaps closer to the class D modulator end rather than the parametric oscillator end. You would do far better to return to your original design and drive the compression and expansion of the large capacitor with a motor rather than your hand. I haven't done the calcs but it looks far more promising than the rotating plate design. By the way, if you still have that rotary system set up, try biasing the plates with a few millivolts DC and see what sort of gain you're getting. It will make interpretation of your results much more meaningful. I'll bet you'll be amazed at how little bias voltage is required to see huge outputs ( like the several volts you're seeing ). K. --- Jones Beene <[EMAIL PROTECTED]> wrote: > Hey Nick, > > Nice experiment. > > One wonders why you did not try to get the spacing > down to a > very minimum, since the ouptut is directly related? > Couldn't > the contacts be rearranged somehow such as on the > circumference to get below the 3mm? > > Jones > > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
