The distance over which radio equipment can operate depends on the power
output of the transmitter, the frequency it operates on, antenna type, (and
also the time of day). Generally the lower the frequency the better the
range. The military have frequencies all over the spectrum, ranging from
line of site microwave equipment (many GHz) to very low frequencies which
travel thousand of miles.
In relation to broadcast frequencies, in the UK, 1.5 MHz is roughly the AM
or MW broadcast band. 12 MHz is "short wave" - obviously used for
international high power transmission. I think dividing up such a small band
into short/med/long range is a bit specific. A lot depends on other factors.
just my personal 2p worth.
Richard H. Evans R&D Engineer
Mail: BBC R&D Department, Kingswood Warren, Tadworth, Surrey, KT20 6NP
Tel: +44 1737 836678
Fax: +44 1737 836667