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Old July 8th 15, 11:04 PM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,898
Default An antenna question--43 ft vertical

Ralph Mowery wrote:

wrote in message
...

Once again, SWR is defined in terms of SOURCE impedance and LOAD
impedance. The normal LOAD for a transmitter is one end of a piece
of coax with an antenna on the other end.

The SWR at the near end of a piece of coax may or may not be the
same as the SWR at the far end of the coax.


--
Jim Pennino


Can you show any place where the SWR definition mentions the Source
impedance ?


I have several times now, but once again:

SWR = (1 + |r|)/(1 - |r|)

Where r = reflection coefficient.

r = (Zl - Zo)/(Zl + Zo)

Where Zl = complex load impedance and Zo = complex source impedance.

https://en.wikipedia.org/wiki/Reflection_coefficient

http://www.antenna-theory.com/tutori...nsmission3.php

I have never seen anything that mentions the Source impedance. Just the
ratio of the voltage or current going forward and reflected.


It is generally not mentioned in Amateur publications.

The SWR has to be the same at any point on the coax or transmission line
minus the loss in the line. A simple swr meter may show some differance
because of the way that kind of meter works. By changing the length of the
line , the apparent SWR may be differant at that point.


There is no such thing as apparent SWR. It is what it is in a given
place.

Transmission line transformers.

http://highfrequencyelectronics.com/...TraskPart2.pdf

Impedance matching.

https://en.wikipedia.org/wiki/Impedance_matching


--
Jim Pennino
 
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