Some observations on this subject...
1) Some participants come to the discussion wanting
to support a specific set of antennas and some come
to the discussion wanting to erect a mast "for all time".
Those that look to the ultimate approach tend to recommend
2", 20'-24' chrome-moly mast. Erecting such a mast
is pretty much at the limit of most hams, sans a crane.
It is about the strongest 2" mast you can afford & erect.
2) 3" mast would be ideal, but that would necessitate
swapping out boom to mast and rotor to mast clamps -
an additional expense. 3" mast is *much* stronger that
a 2" mast of the same material & wall thickness
(or even weight).
3) If you are mounting an antenna less than 1.5' above
the top of the tower, most any mast material will do.
4) If you are mounting hf antennas 5'-15' above the
top of the tower, you'd best be doing some engineering
calculations.
Tom - N1MM
P.S. My mast - 2" schedule 40 water pipe with
a TH-7 mounted just over the top of the tower.
I won't be buying a 2 el 40 until I buy a new mast.
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