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Old February 26th 05, 02:21 AM
Reg Edwards
 
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Arguments about whether the power ammplifier is matched or not matched to 50
ohms arise due to misunderstandings about the meaning of "matched".

Meaning 1.
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The PA has been designed for maximum, linear, undistorted power output when
loaded with Ro ohms and the load reistance has actually been adjusted to
equal Ro. Ro is usually 50 ohms. (There may be additional criteria to
define what constitutes an optimum match.)

Meaning 2.
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The load impedance Z = R+jX has been adjusted to equal the conjugate of the
internal impedance resistance of the PA. (The internal impedance of the PA
is usually unknown but the circuit is assumed to behave as if a conjugate
match exists.)

The two meanings are entirely different from each other. If there is danger
of confusion then the meaning should be stated. Some people already use the
descriptions "Zo match" and "Conjugate match".
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Reg, G4FGQ