"Telstar Electronics" wrote in message
...
You mean to tell me that you take a clean sine wave... pass it
through... say a single-ended class A amp... and you can put a tank on
the output of that amplifier... and tune for a harmonic? You will get
nothing.

Class A means that plate current is flowing throughout the entire cycle of
the input wave with the tube operated between cutoff and saturation. It
says nothing about the linearity of the tube's transconductance (plate
current as a function of grid voltage). With real devices, the
transconductance curve is ALWAYS nonlinear to some degree, producing
distortion (and harmonics). As you decrease the drive to a single-ended
Class A amplifier, you are working on a smaller and smaller portion portion
of the transconductance curve which decreases distortion. In the limit
where only an infinitesimal part of the transconductance curve is used, you
will get no distortion and no harmonics. Of course, in this situation the
tube produces NO output.while drawing current from the power supply.

The scheme that I was talking about, known as a push-push doubler,
generally uses the tubes operated in Class B although AB operation will
work too, but it produces less harmonics. The real advantage of a
push-push doubler is that odd order harmonics and the fundamental cancel
out, making the resultant waveform easier to filter.

73, Barry WA4VZQ