The problem is in making the 90 degree phased array on 20, which I recall
you wanted to do. (If not, disregard the rest.) The feed system for that
pattern will work only on the one band, so you'll have to switch it out on
the other bands. The L network feed systems described in the _Antenna
Book_ use equal length lines plus an L network for doing 90 degree feeds.
So you could use the L network on 20, and switch it out but use the same
feedlines for the other bands to get two in-phase elements on those other
bands. You would need a tuner, though, since the impedance at the common
feed point will be different on each band.

Roy Lewallen, W7EL

Ok, thanks, as soon as I have the possibility to assemble the antenna, I'll
let you know. This newsgroup is great, as your kindness.
Francesco ik8vwa