The ARRL Antenna Book (19th ed.) has an interesting design on p 6-32 for a
40M sloper that could easily be scaled to 20M. Measurements show the 40M
version providing up to 20dB f/b and about 4 dB forward gain. The rear null
can be positioned. The antenna would require a center support about 35 feet
high for 20M. Five dipoles slope away at a 30 degree angle. The feedpoints
are conected to a switchbox containing DPDT relays which are used to select
the active dipole and position the rear null. The others serve as
reflectors. Anchors for the five 20M slopers would fit in a circle about 35
feet in diameter. The article doesn't say anything about radiation angle. It
does explain how the antenna can be constructed with less wire and no relays
for a fixed direction.

I would be interested in the experience of anyone who has used this antenna.

Tom, N3IJ



"numeric" wrote in message
...
Looking for the best 20m vertical antenna design; without radials or
buried
ground wires. There is no restriction on the antenna height; except, that
I
would like to support the antenna at its base and mounted on the roof. I
am
more concerned about a design that optimizes the antenna efficiency and
provides a low angle of radiation rather then for a 50 ohm impedance. The
ground is basically sand, not much conductivity.

Any Ideas?

Thanks.