Cecil Moore wrote:
Walter Maxwell wrote:
I hope this helps in understanding why the SWR at the input of the 72-ohm line
is 1.44:1, and NOT 1:1.

Very good stuff, Walt, as usual. It is possible that Gary
misunderstood the question. He apparently thought the question
was: What SWR will a 50 ohm SWR meter indicate and of course,
a 50 ohm SWR meter will erroneously report an SWR of 1:1 at
the 50 ohm (current maximum) point on the 72 ohm feedline. If
we move the 50 ohm SWR meter to the 103.7 ohm (current minimum)
point on the 72 ohm feedline, it will erroneously report an SWR
of 2.1:1. But, on the 72 ohm feedline, the SWR is, of course,
1.44:1 at both the 50 ohm point and the 103.7 point and at all
other points up and down the feedline (neglecting losses).
--
73, Cecil http://www.qsl.net/w5dxp


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Yep, it is possible I did, won't be the first time. The orginal
question stated that the swr was somehow measured at the source, how
else could one know it was 1:1. The measurement instrument was not
specified. Assume that it is the average ham with a 50 ohm swr bridge,
an antenna analyzer, and a 50 ohm RLB. If one changes to 1/2 wave 72
ohm cable, using the same measurement instrument you get the same
results.
I understand the mechanics of the actual VSWR on mismatched lines,
but I intrepreted the the question differently I guess. My handy Smith
Chart program reports a 1:1 VSWR, of course it is only at the source,
at 90 degrees it reports 2:1. Wonder what that program uses to
calculate swr?
Gary N4AST
Gary N4AST