For DX or anything beyond a few hundred miles, you shouldn't make your
vertical taller than about 5/8 wavelength. At greater heights, the
radiation at low angles decreases and the radiation at high angles
increases. So taller isn't always better. You probably won't be able to
construct a single vertical that's reasonably efficient on the lower
frequency bands without being too long for low angle radiation on the
higher frequency bands, unless you include some sort of trap(s) to limit
the length of the radiating portion on the higher bands.

Roy Lewallen, W7EL

Reg Edwards wrote:
Jerry, KISS

The best vertical is an approximately vertical wire, rod or mast, as tall as
possible . . .