> The biggest problem I see people having with OWL is that they
> want to run "tuned lines" at high SWR. This can be problematical
> and is not covered in any of the books on the subject.
>
> Rick N6RK
It's out there -- you just have to go back in time to find it. High power
and high SWR can co-exist nicely when the transmission line concepts are
understood.
All too often, an op chooses some random length of open/ladder line into
some random length of dipole for multi-band operation from a mediocre "T"
type tuner, not knowing the feedpoint Z, nor the Z at the Tx end of the
line. (the so-called "McCoy Dipole" is a perfect example). Constructing a
dipole that way results in "performance by chance," not by design.
You've got to have some clue about those factors in order to have a
reasonably efficient multi-band dipole system. Not only does open-wire line
loss increase as line SWR increases, but tuner losses also increase,
especially when a "T" type tuner is used with questionable Q of the C and L
components and small output C values. In many cases, keeping the line to
load mismatch at less than 8:1 and changing the feedline length to function
as a variable transformer can make a world of difference when high power is
used, especially when a commonly available "T" tuner is used.
Paul, W9AC
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