Sure you can. You can make a 80/40 dipole that is the same length as the 40
meter. THis is the basis for the old Mor-Gain dipole. You wrap the 80
meter wire around the 40 meter dipole
almost like a folded dipole that is open at the bottom. Just like Mor-gain
you can add other bands as parallel wires. There is little interaction.
Jim West of Antennas West built a version called the PM Dipole and found the
40 meter lower band portion was broadened ...I have one Mor-Gain and one
homebrew and find the 80 meter is at least 100Khz and the 40 is less than
1.2 across the band. K4TWJ had a more recent version in his column last
fall using ladder line.
I plan to add 60 meters to one of my dual banders.
73 Dave K4JRB

W4UDX wrote in message
...
Hi guys.
Quick question. I have in the past made 80 and 40 meter multiband dipoles
using parallel wires and they worked fine with little 80/40 interaction.
My
question is, can a make one with a set of wires on it for 30M also? or
will
the 40M and 30M parallel wires interact too much?

Mark W4UDX