>For starters, look at the antenna patterns for a G5RV and
>80 Meter Dipole when used on higher bands in any ARRL
>Antenna Book or Handbook.
The pattern of a G5RV on 20, 17, 15, 12, and 10 meters can be made
nearly omnidirectional by leaving the central 20 meters (of the
overall wire length of 30 meters) horizontal, and dropping the last 5
meters on each end vertically. I did this; the central, 20-m,
horizontal, flat-top of my G5RV is 10 meters above ground; thus, each
vertical end drops to 5 meters above ground.
Analyze this configuration in NEC or EZNEC, and you'll see what I
mean. If anyone asks, I'll email directly to him the pattern plots
made by NECPLT from the NEC-4 output files. What the plots show, as
you might guess, is that vertically-polarized radiation from the
two-element array formed by the two 5-m vertical wire sections fills
in the nulls of the pattern of the horizontal 20-m wire.
I've been using this configuration very successfully on all bands 10
through 80 meters for years.