"Robert Morein" wrote in message

CATV amplifiers operate into a controlled impedance. The requirement that
they must survive a short is not equivalent to the challenge which audio
amplifiers encounter, where the load is an electrodynamic mechanical system
that provides a load to the system which is a function of frequency, and,
when accounting for nonlinear effects, amplitude and mechanical state.


Yes, a speaker systems provide a load that is a complex impedance, and
one that can change slightly due to nonlinear effects.

The RF amplifer can see a greater load variation. It must of stable
with an accidental low impedance (short) located anywhere along the
transmission line. RF amps are typically tested by sliding a low
impedance (about 1 Ohm) along a sloted line, on the output of the
amplifier. Here is the impedance variation the RF amplifier sees as
the resistor is moved along the sloted line:

Wavelengths Impedance

0.025 1.0 +j 12
0.050 1.1 +j 25
0.075 1.2 +j 38
0.100 1.5 +j 55
0.125 2.0 +j 75
0.150 2.9 +j 103
0.175 4.9 +j 147
0.200 10.5 +j 230
0.225 40.6 +j 470
0.250 5625.0 +j 0.00
0.275 40.6 -j 470
0.300 10.5 -j 230
0.325 4.9 -j 147
0.350 2.9 -j 103
0.375 2.0 -j 75
0.400 1.5 -j 55
0.425 1.2 -j 38
0.450 1.1 -j 25
0.475 1.0 -j 12
0.500 1.0 -j 0.00


This variation of impedance (going from short, to inductive, to open,
to capacitive) is much greater than an audio amplifier would ever see
from and electrodynamic mechanical nonlinear system.

Bob Stanton