The first thing that must be agreed is that if the device conducts less than
180 degrees then it is Class C. I submit that this is not nonsense, it is
the agreed upon definition of what determines a class of amplifier. There
is nothing cast in stone that requires the output in class C to be
non-linear, the text simply says it typically is not. That leaves a lot of
room for how to view new ideas and techniques.
Back in the days when I learned the hard and fast rules (and definitions) of
that time, things like "pre-distortion" were never taught let alone
executed. Modulating the bias of a tube with a complex feedback loop
tailored towards improving linearity was also never considered (that I came
across anyway). Another thought to ponder is that if the general consensus
agrees that less than 180 degrees of conduction defines Class C, just which
180 degrees are under consideration? Does it have to be less than 180
degrees continious, or less than 180 degrees total?
I am not necessarily discussing the current topic, but think for a moment of
a digital word that defines polar coordinates on a graph. The definition
and transmission is purely digital, but when you connect the dots that those
coordinates define, you can have a reasonable reproduction of an analog
waveform. My point in saying this, is that a lot of times it becomes a
matter of how you look at something that determines how you define it.
I do not consider my teachers to be incorrect, but then neither is Manfred.
Mark Bitterlich
wa3jpy
----- Original Message -----
From: "Bill Turner" <dezrat@outlook.com>
To: "Amps group" <amps@contesting.com>
Sent: Friday, June 09, 2017 10:59 PM
Subject: Re: [Amps] LDMOS availability
------------ ORIGINAL MESSAGE ------------(may be snipped)
On Fri, 9 Jun 2017 20:56:33 -0400, Mark wrote:
But the bottom line is simply that if the device conducts less than 180
degrees it is class C. If any method at all can be used to increase
linearity this does not change the class of amplifier, it just improves
the
linearity.
REPLY:
Nonsense. If the amp conducts less than 180 degrees it can not
possibly be linear because the output in NOT a replica of the input.
That's the definition of "linear".
If you "modulate" the bias to make it linear, it is no longer Class C.
Don't try to make things more difficult than they are. What you were
taught years ago was and is correct.
73, Bill W6WRT
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