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Old November 6th 07, 03:10 AM posted to rec.radio.amateur.antenna
Jim-NN7K[_2_] Jim-NN7K[_2_] is offline
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First recorded activity by RadioBanter: Sep 2007
Posts: 52
Default question about wire antenna and tuner

Think, this is the same thing that one "Kurt N.Sturba" says in
his columns, about swr: It Isn't LOST power
(Heating the final or , dissipated in the final),
but is redirected to the load (again). Tho might be sticking
my foot in mouth again, but the ONLY effect of SWR, would
be on the Transmission Line (because of the loss of THAT line)
First, because of the loss, to the load.
Second , because of the Reflected LOSS (again!)towards the Source.
And then The loss, as it is again redirected towards the
load! In short, SWR, doesn't effect the power-- the FEEDLINE does
and the higher the swr- the higher the loss the feedline presents to
the load! See World Radio magazine for his tomes! In short ,
MAXIMUM power transfer occurs when the impedence of the source= the
impedence of the load. But that doesn't mean that the power is lost
at the SOURCE as (heat, loss, ect). ANY loss must be in the (devices)
between the source , and the load! Jim NN7K

Roy Lewallen wrote:
Sal M. Onella wrote:

What did I say wrong?


As always, Ian has done a much better job than I could have, so there's
not much point in trying to repeat what he said.

But I did write up a lengthy essay several years ago, in response to the
same insistent rantings about reflecting waves of average power that's
still going on in this newsgroup, and it has some numerical examples
with a very simple circuit which illustrate the problems with what you
said. You can get it at http://eznec.com/misc/Food_for_thought.pdf. A
little past half way down is "Food for thought: Forward and reverse
power". If you're not interested in the math, scroll down a few
paragraphs from there to the table in Courier font. It and the text
below explain how it shows where the source dissipation is higher,
lower, and about the same when the load is matched, for three different
loads all having the same "reverse power". Another entry in the table is
an example where the "reverse power" equals the forward power (an
infinite SWR) yet the source dissipation is zero. People who believe
that "reflected power" ends up heating up the transmitter should take a
careful look at this, and see if they can explain it.

The established transmission line theory that's been well established
for over a century and that Ian, I, and countless others use daily for
solving real problems will, as shown in the example, tell us exactly how
much power is where and why. The "power is absorbed in the load" folks
can point to transmitters that get warm (sometimes) when working into
(some) mismatches. But they can never come up with a coherent reason for
the results shown in the essay table, or equations which will predict
just how much "reflected power" a transmitter will absorb and when. And
the reason is just as Ian said.

Unfortunately, some people, when presented clear evidence that the
concept is wrong, cling desperately to it nonetheless. For those,
explanations and evidence are a waste of time. But hopefully there are a
few readers out there who will see the problems in resolving their
theory with the evidence and redirect their thinking.

Roy Lewallen, W7EL