It's interesting to note (and rightfully so) that space has been given to
Walt in a League publication. Could they possibly believe there may be some
truth in what he's been advocating all along?
-Paul, W9AC
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "Phil Clements" <philk5pc@tyler.net>; "AMPS" <amps@contesting.com>; "Jon
Ogden" <na9d@speakeasy.net>
Sent: Friday, May 11, 2001 20:38 PM
Subject: Re: [AMPS] Conjugate Matching In Class B and C Amplifiers
>
> > > As I understand it, Mr. Maxwell asserts that linear amplifiers are
> > > conjugately matched. If this is true, the efficiency could not
> > > exceed 50%.
> >
> > OK. You are correct Rich. If conjugate match occurs, then an equal
> > amount of power is absorbed by both source and load - hence the 50%
> > efficiency.
>
> That is not correct, although it has crept into recent texts. I think
> that concept comes from taking a Thevenin model literally, as an
> actual circuit with a dissipative resistance in series with a source.
>
> It's unfortunate that electrical engineers used the same term
> (resistance) to describe the ratio of across-to-through vectors as
> we use to describe the characteristics of a resistor.
>
> Even more unfortunate, we now are assuming a Thevenin model is
> actually the real world system with a dissipative resistance.
>
> I did load pulls on class C PA's with more than 70% efficiency, and
> the load-pull indicated a conjugate match (50 ohm source) when
> efficiency was maximum. There is nothing that says PA's must be
> operated at a conjugate match, just like there is nothing that says
> efficiency is only 50% when the PA is conjugately matched.
>
> It isn't that difficult to measure a PA and prove this, yet most
> people spend far more time arguing than measuring.
>
>
> 73, Tom W8JI
> W8JI@contesting.com
>
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