A standard dipole will only work well on one band. However, if you put
several different dipoles together in parallel, you can have antennas for
different bands using the same feedpoint.
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A single dipole will work well on many bands ,provided a balanced feeder of
300 - 450 or 600 Ohms (to name a few) is used ,obviously with a balanced to
unbalanced matching unit.
For this purpose I successfully use a 2 times 21 metres (68 ft) dipole with
a 450 Ohms ribbon feeder on all bands from 1.8 to 30 MHz. The length is not
all that critical although the dipole should preferably be half a wavelength
for the lower freq band used.
Because of its balanced behaviour the feeder does not radiate . In my case
the feeder runs into and over the loft into the lower level shack without RF
interference problems .

Frank GM0CSZ / KN6WH