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[TowerTalk] re Trapped Tribanders Turned Vertical

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Subject: [TowerTalk] re Trapped Tribanders Turned Vertical
From: " Peter Forbes" <>
Date: Thu, 21 Jun 2007 06:31:40 +1000
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Whilst the esoteric discussion on vertical versus horizotal polarisation is 
interesting, the main focus of the original question seems to have been lost.

Mounting a traditional tribander in a vertical poistion is going to present one 
particular problem that needs to be carefully addressed.  That is the problem 
of water buildup in the traps, particularly after a few months when dust and 
insects have had a chance to enter the traps.

Usually traps mounted horizontally have several drain holes facing downwards, 
whereas traps designed for vertical mounting will have a series of drain holes 
at the base of the trap.

Using  traps designed for horizontal in a vertcal position will be particulary 
susceptible to water entry, especially if the holes face in the direction of 
the prevailing winds (hard to predict as the beam can be turned anyway).

Adding some additional drain holes to one end of the traps will need to be done 
carefully, so as to not interfere with the way in which the outer tube cover is 
attached, as it often forms part of the capacitance value of the trap.

A further  mechanical consideration in mounting a tribander vertical is with 
the element to boom brackets.   

The strength of the bracket relies to some extent on even weight distribution 
downwards on both sides of the element (a little like two people on a see-saw).
In the vertical position, the chances of there being uneven wind forces on the 
element ends is greater, due to the large vertical difference in wind pressure, 
especially if shielding trees are involved. 

There will be a tendency for the element to twist off vertical, requiring 
careful pinning of the element and bracket to the boom to prevent this 


Peter   VK3QI

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