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[TowerTalk] 1.9" masts

To: <>
Subject: [TowerTalk] 1.9" masts
From: "Jim Thomson" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Thu, 18 Mar 2010 21:54:32 -0700
List-post: <">>
For years I had a 1.5 with a 1.25 telescoped inside and welded on both  
> ends.  All was fine with a very large monobander just above the top of  
> the tower until a big ice storm broke one side of a boom truss.  Then  
> the imbalance bent the mast.  Had the truss support remained intact,   
> I think all would be fine.  Certainly I believe using an expensive  
> mast on a tribander of any size mounted right at the top of the tower  
> is a waste of money.
> Stan, K5GO

##  Here's a good one.   Should the yagi  have it's own truss support,
IE: it's own riser,    OR  should you terminate the pair of truss lines
on the mast ?? 

## IF it had it's own riser,  and you lost  1/2 of the truss,  the bending
moment would be right at the boom to mast plate... which in stan's case
was just above the top of the tower.    Now, if you terminate to the
mast instead..say 3' above the boom, now your bending force is
on the mast... and 3' above the boom  to boot. 

later... Jim  VE7RF

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