In addition to what John L. posted about adding in 4th and 6th
harmonics and making it harder to filter, if you have a 40% or 60% (or
20% or 80%) duty cycle, there will be NO fifth harmonic. From what
you've posted, that likely is the crux of your problem.

Cheers,
Tom

Paul Burridge wrote in message . ..
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it will
drop fairly quickly as the sides of the input square wave deviate from vertical.

Does the 3.44MHz have a 50% duty cycle?

Not quite, no. Why would that make any difference? I'd have thought
any decent 'squarish wave' of the correct frequency with sharp
rise/fall edges ought to do the trick? It's spewing out the 3rd quite
nicely after all.
How about I post a pic of the sig trace into the multiplier? I'll see
if I can do that a bit later 2day...