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[TowerTalk] Mast loading

Subject: [TowerTalk] Mast loading
From: Rick Wheeler <>
Date: Wed, 16 Jun 2004 08:27:20 -0700 (PDT)
List-post: <>
I have a 50' 18" face Glen Martin tower (Hazer) with a 2 element 5 band
Lightning Bolt Quad (6 sq/ft area; flat or round?) and a DB-420 (3.33
sq/ft flat plate) on top of the mast for my IRLP repeater (node 8910). 

The present steel 10' mast I currently have is too short as the bottom
of the Quad does not clear the top guys when rotated. Of the 10' mast
currently installed 4' is in the Hazer (bottom of the 4' is a T2X rotor
and the top 4' is the thrust bearing) and 5' clears the top of the
tower when the Hazer is hoisted to the top position. The Quad really
needs to be about 8' or so mounted above the top of the tower for
clearance of the guys when rotated which means I need at least a 13' or
so mast. The DB-420 can mount right above the Quad and probably needs
only a foot or so for mounting. 

My question is how high can I get away with mounting the antennas? 

I have access to a 24' section 2" diameter 1/4" wall 6061 tube. It seem
obvious trying to use all 24' of the tube for the mast would be a bit
of stretch for the loading on the Hazer! So of course I will probably
have to cut the tube somewhat to get within reasonable loading figures.
But to what length?


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