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Old January 30th 05, 07:34 PM
Cecil Moore
 
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Jaggy Taggy wrote:
My first reaction was Oh my God, I am soo proud of my decent SWR at the
input of my antenna feedline and in reality I could have a really bad
mismatch between the antenna and the transmission line and wouldn't even
know about it.


Yep, 200 ft. of RG-58 used on 440 MHz will result in an SWR close
to 1:1 whether the antenna is attached or not. :-)

And my second thought was what is happening to the energy, since an SWR
gives me an indication of how much power reaches the antenna and how much is
either radiated from the feedline or lost as heat and here I have two
different SWR in the system, one at the antenna and one for the
antenna/feedline system.


The RF can indeed be lost as heat in the transmission line. The
maximum current in a feedline depends upon the SWR. The losses
in the feedline depend upon the current. The maximum voltage
in a feedline depends upon the SWR. The losses in a feedline
depend upon the voltage. At HF, the current losses tend to
dominate.
--
73, Cecil http://www.qsl.net/w5dxp


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