[Antennas] Mast design equations & rules of thumb?

Thu, 04 Mar 2004 23:19:03 -0800

I have heard of but have not found a source of long and I mean long marine SS 
whips.  These are a lot longer than CB whips.

Have you looked at using good spruce to make a tip-over then put wire and whips 
on it for your antenna?

Chris opr VE7HCB

From:           	"JAKidz" <[email protected]>
To:             	<[email protected]>
Subject:        	[Antennas] Mast design equations & rules of thumb?
Date sent:      	Wed, 3 Mar 2004 08:08:18 -0800

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.

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