David Forsyth wrote:
I read somewhere (I think it might have been in reference
to crystal sets) that you can use coax for an AM lead-in. Would this be
better for a longer/more convoluted lead-in?

Not necessarily. If you need shielding for noise purposes that might be
worthwhile but apart from that there's no advantage over just a single
wire. The radios you're typically working on have high impedance inputs.

In a random-wire installation, the total length of the wire IS the
antenna. There is no lead-in per se. By using a shielded cable you are
effectively shielding that portion of your antenna. I think you might
find it won't work as well on BCB with the shield grounded and you would
have to lift that at the radio end negating having it there in the first
place.

On shortwave freqs the loss of the cable in a mismatched state such as
feeding a random wire (or an old hi-z radio) may also work against you.

I'd go with the plain wire unless there is a noise problem that is being
picked up by the vertical portion of the antenna.

My 2c.

-Bill