gravity wrote:
one thing i've been pondering is a vertical colinear. 1/2 wave over 1/2
wave. i have not modeled it.

is there any free modeling software?

You can use the free demo copy of EZNEC by driving the
collinear with two sources and varying the phase angle
between them. Then you can design an appropriate phasing
network. I don't think the lumped inductive reactance
available in EZNEC will yield an accurate phase shift
and the free demo will not handle enough segments to
model a helical coil.
--
73, Cecil http://www.qsl.net/w5dxp