I reinforce what Roy has said with different words: Superposition and
linearity are one and the same. If a circuit or process is linear, then
superposition gives correct results. If superposition works, then the
circuit or process is linear. Power is not a linear process. Power
involves multiplication.

When investigating the results of multiple voltage and/or current sources
(including E or H from an antenna) all at the same frequency, one performs
an addition (vector addition). Then, and only then, one may (note the
permissive form) use the resultant voltage or current or impedance (two of
the three) to calculate (complex) power. (In the antenna case, recall that
Z is near 377 ohms only in the far field.)

73, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Roy Lewallen" wrote in message
snip

I see Cecil is still superposing his waves of average power.

I have an example that's more fun yet.

Take a 10 volt source and connect it through a 10 ohm resistor to another
10 volt source. The positive terminals of the sources are connected to the
ends of the resistor, and the negative terminals are connected together --
"grounded", if you prefer. Turn on one source, leaving the other off. (An
"off" voltage source is a short circuit.) Result: 10 watts of dissipation
in the resistor. Turn off the first source and turn on the second. Result:
10 watts of dissipation in the resistor. Now turn both sources on. Result:
An exercise for the reader.

This is a linear circuit for which superposition holds.

Roy Lewallen, W7EL