Ian Jackson wrote in
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That is indeed very interesting - and illuminating. I've always
assumed that, for electrically long feeders, most of the power got
lost at the input end - but I didn't realise that the effect was so
dramatic. I must do a few calculations for myself!

I chose a case that would be clear. When the line loss is low, it is not
so dramatic. Trying to find Rules of Thumb in all of this is fraught
with problems.


And as for electrically short feeders, I do see how the greatest power
loss is where there are current nodes etc (although, presumably,
averaged over a halfwavelength, the power loss will still be greater
towards the TX end). But I now recall that some time ago, there was a
lengthy discussion (in this NG, I'm sure) about how a matched
low-impedance feeder could actually have more loss than a mismatched
relatively high-impedance feeder.

Well, if you do some calcs yourself, what you learn will stick in your
mind. Just be sure that your study is reasonably comprehensive so you
don't come away with some new, but flawed, Rules of Thumb (RoT).

You could persue the dummy load example a little further. How long does
the line need to be for VSWR1.1, and if the continuous dissipation
limit of RG58 is say 6W/m, what is the continuous power rating?

Owen