wrote in message ...
I am planning to construct a vertical dipole array for 20m. The
electrical calculations are complete (with help from LB Cebik) and now
I'm looking for some advice on the physical construction. I'd like to

Here's one link:

http://k7nv.com/notebook/id3.htm

For 20m (unguyed), the base can be thinner than 1.25". To get an idea,
look at the taper schedule for 20m yagi elements...there the center
section is often 1" or even 7/8".

I don't agree. A 20M yagi half-element is around 17 feet long, a
self-supporting 20M vertical is around 34 feet tall. In your context
he needs to look at the taper schedule for a 40M yagi to get the
drift. The stress in a fixed end cantilever beam like a vertical
antenna goes up as the square of length (stress is proportional to
WL^^2 where W is the wind load). Without actually running the stress
analysis I suspect he'll need a base tube which is around 2.000"
diameter, maybe even 2.500" diameter x 0.058 wall 6061T6 aluminum.

Torsten
N4OGW

Brian w3rv