On Jun 13, 1:20*pm, Richard Clark wrote:

How linear is linear? *Give me a technical criteria...

A truly linear device does not produce r-f intermodulation products
when signals of different frequencies are applied to it at the same
time.

For many practical uses a linear device does need to be perfectly
linear. Let's say that the IM products need to be only - 20 dB w.r.t
the lowest amplitude value of the various input frequencies. The
Mendenhall paper I quoted conclusively shows that even such nominally
linear performance is not an attribute of Class C vacuum tube r-f
amplifiers -- especially at, and near the center frequency of the PA
output tuning/matching network.

That Mendenhall paper also shows that such r-f amplifiers do not
present a functional, 50+j0 termination to r-f energy entering via the
tx output connector. That is the reason why such energy is present in
the PA plate circuit, giving rise to r-f intermodulation and/or
changing the power dissipation there.

RF