"K7ITM" wrote in news:1175574896.245112.244360
@y80g2000hsf.googlegroups.com:

On Apr 2, 4:52 pm, Cecil Moore wrote:
K7ITM wrote:
....
seen a great many examples of it. I gave a few of them earlier. I've
also worked on the design of broadband RF amplifiers which are
designed specifically to be 50 ohm resistive sources, through the use
of feedback to set that impedance. You don't need brute-force

Tom, I suggest that amplifiers with a specific equivalent source
impedance to low tolerance don't happen by accident or by magic of a PI
coupler, they require design measures that are not usually applied to
amplifiers for SSB telephony.

The assertions here that "conjugate matching" occurs naturally as a by-
product of peaking the PA is not consistent with the realities of design
of amplifiers with specific equivalent source impedance.

The amplifier configuration I used as an example was a single ended class
B valve RF linear with PI coupler for SSB telephony for comparison with
Walt's test. A push pull class B bipolar transistor amplifier with
broadband transformer coupling and high pass filter will behave
differently, and some of those designs include negative feedback which
reduces the equivalent source impedance. (I am not talking ALC here, ALC
is in the form of dynamic power control rather than reducing the
equivalent source impedance, though you could be fooled by some steady
state tests into thinking it has reduced the equivalent source
impedance.)

Owen