On May 31, 2010, at 10:55 PM, <wow_chf@hotmail.com> wrote:
It is interesting how a simple fix for these problems doesn't seem
to be
well known.
I submitted the article draft to QST, and it was questioned by the
Technical
Review folks, and although I have been published in QST before, they
could
not see how this would "transform" the apparent input SWR.
I have received hundreds of emails on how this technique worked for
radio
amateurs all over the world.
I can't prove it mathematicaly, but I can give you a logical
explanation. If you look at as a short wire, it probably has no effect
in the circuit that you can model, or measure. If you look at it as
part of the entire circuit including the finals of the radio and the
input of the amp, it changes things. In effect it acts a delay line,
which just shifts exactly where in the circuit things are.
Everyone can easily understand that a wave has it's voltage peaks at
1/4 and 3/4's it length, and it's low points at begining and the
middle. It's what happens in between that is less obvious and less
understood.
So if you look at the entire circuit and see that at a particular
frequency, the combination has a "bad" impedance, changing it would
give you a "better" (or even "good") one. In the days of tunable
finals on transmitters, or tunable input circuits in amps, then you
could just slightly tweak one to change things.
Now the only way to change the effective impedance of the circuit is
to add or subtract a little delay, moving where along the wave things
are.
Geoff
--
geoffrey mendelson N3OWJ/4X1GM
Jerusalem Israel geoffreymendelson@gmail.com
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge
or understanding, as in he has a sub-wikipedia understanding of the
situation. i.e possessing less facts or information than can be found
in the Wikipedia.
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