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Old April 6th 05, 10:48 PM
Jim Kelley
 
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Richard Harrison wrote:

Cecil, W5DXP wrote:
"If we simply amplify the receiver voltage through a near infinite
impedance FET with virtually no load on the signal, do we get the signal
information?"

Not as much as possible.

Just as the reactance must be tuned out of an antenna to receive maximum
available power, to get maximum received carrier power, the resistance
of the load in the antenna must be reduced to only that matcing the
radiation resistance. Walter Maxwell, W2DU has had it right all along.
Maximum power transfer requires a conjugate match.


I happend across this just the other day. On page 1426, "Physics:
Volume Two Electricity, Magnetism, and Light", Ronald Blum/Duane E.
Roller it reads "Note that the optimum power transfer occurs when p=0,
R=Z0, and t=1. [p and t are reflection and transmission coefficients]
In general, for lossy lines, this takes place when the load impedance in
the complex conjugate of the characteristic impedance, just as with
lumped circuits."

Seems to be the only way for p = (R-Z0)/(R+Z0) = 0 and
t = 2R/R+Z0 = 1 to hold true for any Z0.

ac6xg

ac6xg

Best regards, Richard Harrison, KB5WZI




 
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