Since '70, I've had good luck with stranded hard-drawn copper for up to
lambda/2 dipole on 80m (no experience with longer spans). The latest stuff
I've been using is 12ga (268 strand) hard-drawn for a single wire 80m dipole
and now a cage dipole for 80m using 14ga from Davis RF
(http://www.davisrf.com/). They also offer porcelain compression
insulators, so a broken insulator won't bring your antenna down (and leave
the end of the wire dangling in the trees). Nice folks to deal with, too.
Bryan WA7PRC

Roy Lewallen wrote:
"Best" has a number of different definitions depending on the particular
situation. If you want wire that'll never stretch or break and will take
a lot of tension, Copperweld is hard to beat. It's springy and a
nuisance to work with, though.

Roy Lewallen, W7EL

JERD wrote:
I am getting back to the HF bands after some 20 years 'rest'. What is
the
best type of wire to use for long wire antennas? The wire will be under
some
tension to keep it above some local trees!