I don't have an outdoor antenna installed at my house, but would like to
connect one to my basement lair. The question is what's the best way to
connect to the outside without causing permanent damage to the house, or
leaving a window open.

One former basement window has been replaced by an aluminum sheet, from
which have been cut openings for at least two gas chimneys (boiler & hot
water). This is the obvious way to route some cable out. But I don't
think putting coax through a hole in metal (insulation against the metal
edges of the hole) is a great idea. I'd rather have some kind of
feed-through connector that has back to back coax jacks on either side,
so I can plug in a jumper to the radios on the inside and simply plug in
an antenna on the outside. BNC would probably be the ideal connector
type for this but crufty old UHF (SO-239s) could work too.

Anyone have any suggestions or pointers? Thanks.
fred k1io