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Old May 28th 04, 01:44 PM
Cecil Moore
 
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alhearn wrote:
If you read Chapter 13, "RF Power Amplifiers and Projects", in the
2004 ARRL Handbook, there are pages and pages of discussion of
matching plate or transistor output impedances to 50 ohms output and
not once do they ever refer to output networks dissipating or
reflecting reflected power.


However, the 15th edition of the ARRL Antenna Book goes into great
detail about how a match point reflects rearward-traveling waves.
If you are designing RF Power Amps, you can simulate load conditions
with lumped components. If you are trying to figure out what happens
on a transmission line (distributed network) you need to take
reflections into account.

Transmission lines have reflections; output matching networks and
tuners don't. The reflections on transmission lines don't make it past
the end of the transmission line -- that's where the reflections take
place. Beyond the end of the transmission line, the reflections are
seen as mere impedances created by standing waves, which are created
by reflections, assuming mismatch.


Impedances created by standing waves are merely V/I ratios, i.e. virtual
impedances. They are the result of standing waves and not the cause of
anything. Physical impedance discontinuities are the cause of reflections
that cause standing waves.
--
73, Cecil http://www.qsl.net/w5dxp



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