Somewhere around 100T of #24.
Try
http://www.lalena.com/Audio/Calculator/Inductor/ or google for an
inductor calculator if you don't like that one.
Your best bet would be to wind maybe 130T turns and addd taps every 10T
starting at about 70T, or unwind turns until you get the right tuning
range.
If you add more taps, who knows, you might pickup some shortwave
depending on antenna, ground, and receiving conditions in your area.
When I was a Boy Scout, we would make variable inductors. Take a TP roll,
and wind some manageable magnet wire around it, maybe #32-#36; close-
wound. Leave about 1/4"-1/2" of naked roll at the ends. Secure the
wire, do whatever you need to do to the leads, and fasten it down
to your board. I mean board, as in wood. Then, mount a post a few inches
away from it, that's as tall as the diameter of the coil. Get a strip
of tin, like from a coffee can lid or so, put a hole in one end, and
bend the other end into a "v" shape, lengthwise, as if it were a little
scoop. Make the 'v' long enough to accommodate the next step. With some
fine sandpaper, clean the enamel off the wire at the top of the coil.
Mount the tin strip with a screw through its hole into the top of the
post, and the 'v' on top of the coil, making contact.
Voila! Variable inductor!
If you've got the patience, you could make your own capacitor with
aluminum foil and Saran wrap. ;-)
Cheers!
Rich