...With 80m of wire up, you can make a 160m EFHW and run it on 80m also (and of course other harmonics too).
Just a note that, while you may have a low SWR running a
160m EFHW on 80m, you might not get the performance you
are expecting, depending on who you are trying to talk to.
I had a 160m EFHW wire coming in the upstairs window of
the house at one point. On the local 80m net is was rather
mediocre, but afterwards a station 250 miles away called me
to ask what type of amp I was using. (I was barefoot at 100W.)
Turns out that the 160m EFHW used on 80m has an overhead
and broadside null in the pattern (typical of a 1-wavelength
antenna not fed in the center, so it also applies to an OCFD).
Most of the local stations were in that null, so signals were weak.
Maximum radiation was at an angle of about 50 degrees
off the
ends of the wire, which happened to be pointed at the more
distant station.
That's not to say that either antenna is "good" or "bad", just that
the radiation patterns are significantly different, and which one is
"better" depends on your specific application.
