My outdoor longwire antenna works just about as well as I could imagine.
Very long wire, very high, attached to shielded 50ohm coax about 40 feet
from the house to avoid all the noise, and connected through a MLB. I get
amazing reception on all my radios.

So now I have a second "listening post" on another floor, and have decided
that I'll feed a high-impedance antenna to that spot. Some radios, mostly
my older ones, don't have a low-impedance input, just the normal
slotted-screw antenna wire hookup. This will give me an easy way to play
with these.

I might try a slinky outside, or maybe not. (Any real-world opinions on a
slinky vs. long wire?)

My real question is this: Can I use similar 50ohm shielded coax as my
feedline, to take advantage of the shielding and get the antenna away from
the house? I would of course not use the balun or even the connectors, just
connect the antenna to the center conductor, and strip away enough inside
the house to connect the center conductor directly to the radio. Will this
work? Is it a sound design?

Thanks,
Jeff