Getting feeder, even a balanced one, thru a wall is not a big problem. You
can cross even metal window frames at right angles. You just cushion the
parallel feeder of the insulated type with either foam strips above and
below it, or make an insulated insert to go under the window sash lower
edge. Screw in a block above the top of the sash to keep the unlocked
window from being raised above the added feeder pass thru board.
Other solutions are to drill exterior and interior wall for a plastic tube
sold by Radio Shack for twin lead TV feeder. That will pass the
transmitting 300 ohm line as well.
Since you use either 450 ohm line or 300 ohm line with a tuner anyway for
multiband doublets, you can tune out the small effect of crossing the metal
window frame. You can also combine 450 ohm line and a short pass thru of
300 ohm line, and tune out the cumulative effect of that impedance bump on
the total transmission line. You can go from 450 ohm to 300, and back to
450 outside.
If you have a short run from the outside wall to the rig, you can even
locate a balun outside, and transition to tuned coax to tuner and then the
rig. Of course, high swr will have some loss in the tuned section of coax,
but that is usually of no major effect, if the run is short enough.
73,
Stuart
K5KVH
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