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Old May 10th 04, 08:52 AM
Reg Edwards
 
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Jack, I think you know what you are about. But you may be doing the right
things for the wrong reasons.

The ONE and ONLY purpose of the SWR meter is to facilitate the
antenna-plus-line (plus tuner if you use one) to be adjusted such that the
transmitter is loaded with its design impedance of 50 ohms, plus or minus 20
percent or thereabouts.

What the SWR on the line may be is not relevant. It can be anything you
like! It doesn't matter insofar as the adjusting process itself is
concerned. And it is not of great consequence anyway.

The meter, Bird or MFJ or otherwise, does NOT indicate SWR on the feedline.
This is a popular misconception - a very old Old Wives' tale. It merely
indicates whether or not the impedance looking into the transmitter end of
the line is 50 ohms or is not 50 ohms. If it is not 50 ohms it won't even
tell you what it actually is.

So after adjusting line input impedance to be 50 ohms by some means or
other, you may be quite happy to retire under the impression the SWR is a
nice 1-to-1 and the antenna input impedance is what you think it is. Whereas
it very likely isn't.

But you will have achieved the true objective - the transmitter will be
correctly loaded with 50 ohms within plus or minus 20 percent even after
taking so-called SWR meter uncertainty into account.
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Happy adjusting, Reg, G4FGQ