wrote in message ...
But in emergency/expedient situations, it would be really handy if one
could pass at HF, say, 100 watts of RF energy through a window (I
visualize some foil strips and an inductor or two to "tune out" the
capacitance) to an external antenna.

In an emergency I'd say... uh... just leave the window open? :-)

Over on eHam.net there's a recent article on building yourself a simple
rectangular wooden panel to stick in the frame of an (open) window. You then
just drive holes in the panel as needed to run cables, etc. I've even seen
people who didn't have, e.g., a drill or jigsaw do the same thing using a
thick-ish chunk of stiff foam (insulation material or even presentation poster
board) and an X-acto knife.