Bob McGraw makes good points on using a dipole fed with parallel
(balanced) line. This will work for twin lead or for either the open
wire line, or coated ladder line.
I successfully use some pipe insulation, slotted for my balanced line
and placed under the metal sash and on top of the metal frame of the
window unit. The balanced line is about an inch from the metal in each
direction, supported by the slot in the pipe insulation and crosses it
at right angles. A screw on window lock and insulation stuffed into the
top of the sash insulates the window and the lock restores security of
that window. The window sash slightly compresses the pipe insulation to
hold it in place across the width of the sash.
For bringing parallel line down from the attic for an operating position
on an interior wall, you can just drill two holes the spacing of the 450
ohm line, or even a bit one way of the other apart, in the ceiling above
the tuner. Use long bolts or all thread to make attachment points in
the attic and at the top of ceiling for the parallel line. This makes a
direct drop to the back of the tuner, and if you ever want to
discontinue use of the operating position, close the two holes with
spackling compound, and you are done, unless you have to paint the
ceiling points with color. The holes don't have to be exactly the
spacing of the feedline, because using a tuner, you tune the line and
the antenna for a match.
-Stuart Rohre
K5KVH
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