Dwight Stewart wrote in message ...
"Brian Kelly" wrote:

A shallow concrete slab will not support any
tower unless the tower is well bracketed to
the house. There are only two choices: A large
block of concrete for the base or a slab with
a house bracket.


The word "slab" was probably a poor choice. I was mainly referring to the
width, not depth, of the concrete. The concrete will pretty much fill the
entire hole below the ground surface.

OK.

Use a mast made from steel pipe. I've used 'em
several times, works fine. Assume the bottom
section of the mast is made from a full length
of standard 2.5" Schedule 40 galvanized steel
pipe x 21 feet long. Top the base section with
a couple 10-12 foot lengths of smaller diameter
pipe and assemble the mast & antennas. Drive a
five foot length of 3" pipe into the ground,
clean it out, raise the mast to a vertical
position and drop it into the 3" pipe. (snip)


To make it freestanding, one would have to use some fairly thick steel
pipe (both wall thickness and pipe diameter), especially for longer lengths.

That's nonsense. If you want a properly-designed pipe mast you do it
by the numbers, not with amateur "eyeball structural engineering"
and/or broad-brush statements like "have to use some fairly thick
steel pipe . . ". You won't know a thing about any pipe sizes until
and unless you run the numbers. A 40 foot pipe mast analysis is as
simple as it gets in the field of applied mechanics, any sophomore
student in any engineering discipline including the EEs who brought
you your HT can handle the job. A pipe mast is just a classic
cantilever beam.

And pipe that heavy would almost require a crane to move it around. Because
of that, steel pipe might be fine for shorter masts (or guyed taller masts
using thinner pipe), but wouldn't really be feasible for a taller
freestanding structure (unless one owned a crane, but then the crane itself
could just be used to support the antennas).

You gather up five buddies. You hang a pulley near the house bracket.
Run a rope from the ground, thru the pulley then down to the midpoint
of the mast. There's your "crane". Three guys walk the mast up and two
pull on the rope and up she goes.

Dwight Stewart (W5NET)

http://www.qsl.net/w5net/

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