budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:



In RF circles, the 'normal' way to do this would be a simple Class C
amplifier with a collector load tuned to the fifth harmonic. In calls C,
conduction only occurs for a small fraction of a cycle which produces a
correspondingly higher proportion of higher harmonics than a square wave.

I've been waiting for someone to post this. I would only add "The drive level,
and the bais point, will vary the amount of fifth (or whichever) you will see."

It's as common as noses in RF, as Ian pointed out. Just look at the average
two-way radio prior to frequency synthesisers. Crystal freqs were multiplied
this way in transmitter chains and for receive injection, although use of fifth
wasn't especially common because you normally had enough design control to use
the more efficient *2, *3 or *4.

'Tune for smoke' isn't an option for most new products, which have to
be manufactured without hands.

Better to pick a suitable duty cycle (or more likely a conduction time
period in a digital circuit), that has an efficient 5th harmonic
component, including delays, at low power levels.

http://www.wenzel.com/pdffiles/choose.pdf

RL