[Antennas] Mast design equations & rules of thumb?

[Don Havlicek]

John,
Back in the late 70's, Dentron marketed a 40m vertical 1/4-wave whip 
antenna that had a very good, insulated mount and a fairly heavy-walled 
bottom section.
The mount was shaped like this :   ]  with a hole in the top flange, 
through which the vertical passed, insulated by plastic tubing [might 
even be PVC, not sure].
They mount on a pipe driven in the ground, and have SO-239 connector at 
the base.
It would be easy to fabricate a 'fold-over' connection at the base by 
paralleling another flat plate that would be mounted to the 
ground-driven pipe and connected with spacers, which could be connected 
by bolts/lockwashers/nuts .. then, you could simply remove all but one 
of those bolts to allow the antenna to fold down.
I have five of them [none for sale].
Don
N8DE


JAKidz wrote:
> Greetings:
> 	I'd like to build a tip up, free-standing 1/4 wave 40m vertical,
> base at 11 feet, out of small town available materials (e.g., chain link
> fence rail, electrical conduit, water pipe). No guys (small lot with a
> bunch of house stuff in the way) so support has to be close to the base.
> Due to CC&R's, I have to tip it up for use and down the rest of the time
> so wind loading would be moderate at most. What diameter and wall
> thickness does the base need to be to withstand repeated bending from
> being pushed up but not overkill? Only one old guy is the pushup force
> so it can't be 34 feet of 3 inch water pipe on top of the 11 foot base.
> I'm guessing that for less weight but adequate rigidity, it is best to
> have reduced cross-sections with height but how many and how long for
> each is optimum? I figure a Radio Shack steel CB whip can top it off.
> Any good thumb rules or design equations for such things? As fence rails
> and metal electrical conduit come in a variety of wall thicknesses, I'd
> like to run the numbers for some confidence that the thing isn't like to
> make a big dent in my noggin or my roof.
> 
> 	Thanks and 73,
> John, K7JG.
> 
> - - - 
> 
> Your moderator for this list is:
> Larry Wilson KE1HZ antennas-owner@mailman.qth.net
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