I wonder why they just didn't use the same antenna as the AM
and FM bands, like my old 8-band radio did? Jim -- any ideas? Why the
extra antenna on a receive-only unit?

Well, first of all, the AM and FM bands don't use the same antenna - the AM
antenna is probably built inside of the radio. The FM and airband
frequencies are close, but still an antenna optimized for air band would
need to be a slightly different length than an FM antenna. Finally, using
the same antenna to simultaneously listen to one frequency and scan through
a list of other frequencies, while possible, is not easy. It is much
simpler to just use two antennas.

- Ray