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Old December 23rd 05, 12:07 AM posted to rec.radio.amateur.antenna
Roy Lewallen
 
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Default Standing Waves (and Impedance)

Reg Edwards wrote:

. . .


The only way to "measure" SWR is to place the meter at the antenna end
of the line. You know that as well as I do.

The SWR does not apply to any particular point on the line. It applies
to the WHOLE line.


I disagree with both of those statements, and both can be shown to be
incorrect.

If a line is lossless, the SWR is the same all along the line. An SWR
meter of the line's impedance will measure the SWR correctly when placed
anywhere along the line, including at either end.

If a line has loss, the SWR varies along the line, being the greatest at
the load and decreasing toward the source. (The concept of SWR at a
single point is well understood and widely used and accepted, even
though it deviates from the original literal definition.) In that case,
the meter will correctly read the SWR at the position where it's placed.
That position can be anywhere along the line including either end.

Roy Lewallen, W7EL