On Sat, 13 Mar 2004 16:51:48 +0000, Paul Burridge wrote:

On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa)
wrote:

Fifth harmonic frequency multipliers do exist, but it's usually much
easier to double and triple your way to the final frequency if possible.
(You just discovered this, I think!)

Yeah, but trying to get the 5th is hardly asking for the moon...

The lack of even harmonics is typical of push-pull stages ... if you
are messing around with CMOS gates, you might try using a TTL gate
(which pulls low much stronger than it pulls high) or an open collector
TTL gate, both with smmallish (100-200 ohm) pull-up resistors for
doubling.

I've a reasonably fast Schmitt I'm going to stick in there in place of
the 74HC04 before I resort to anything fancy (same pin-out).

Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz?

Because I don't have a rock lying about for that fundamental!

Hopefully some supreme being here will spot a problem with the traces
I've now posted...

Just a rough guess, since your calling on supreme beings...

That input cap... I take it the input source is a reasonable
estimate of your square wave... if the time constant of that input
RC net isn't right, it'll be a differentiator, and turn your square
wave into pulses coincident with the rising and falling edges. Your
scope trace suggested otherwise, but IIRC, at that tin=me you were
using the filter at the input to the mult., xo things have changed.

It doesn't look like you're biased in Class C. All the mults I've
seen are Class C biased with the tuned circuit on the collector. And
remember, when you're doing this later for some other purpose, in
Class C, the transistors Vceo - reverse breakdown - must be at least
twice the supply voltage.

--
Best Regards,
Mike