John Larkin ) writes:
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell 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.

But if you want to filter the 5th, it's mighty handy not to have nuch
4th or 6th around.

But one of the problems Paul seems to be having, on an ongoing basis,
is the lack of a historical perspective.

He's going the digital route because that's where he comes from, and
therefore he extends the idea. But anyone of us who have been around for
a while, or even has just spent time with older books and magazines, knows
that RF multipliers was done all the time before digital circuits had
made much inroad.

WItness the thread about VXOs a while back. He started with a digital
oscillator, again because that's all he knows, and then sets out to
pull it as much as possible. But this too has been done before, and
doing some research in older ham magazines would have shown the problems
and solutions.

Maybe "oldtimers" are biased towards what they grew up with. But I see
time after time in the sci.electronics.* hierarchy people wanting to do
RF and see it as simply extending audio or digital concepts they already know.
So they suddenly need a 5MHz oscillator, and wonder why they aren't having
success with a function generator type IC, where the needed frequency is
at it's upper limit. "How can I make an active filter at 10MHz" is not
usually someone who has a specific need for an active filter at that
frequency, but from someone who is used to active filters and has yet to
see their limitations, or maybe more importantly, are unaware of what's
normally done at RF. A coil is pretty bulky at 1KHz, but at 10MHz it's
downright easy to wind.

And I do find it interesting, to see fairly complicated answers for
problems that were solved a long time ago, simply by coming from a different
angle.

Michael VE2BVW