[TowerTalk] Preventing Water Penetration (was Aruba corrosion)

[Frank Donovan]

Vertical antennas constructed of telescoping tubing are difficult
to protect from water intrusion in any climate; however, its
particularly important to protect telescoping tubing joints and
screw or rivet holes from salt water intrusion near the ocean.

Examine any vertical object in a heavy rain (tower, vertical, coax
cable or anything else), and you will discover a steady stream 
of water flowing down the object.  Flowing water enters the
penetration points (e.g., telescoping tubing joints or screw holes),
and washes away Noalox or other materials in the joints.
Near the ocean, salt will be deposited in the joints and screw
holes.

A particularly effective way to solve this problem is to cover 
joints and screw holes with shrink tubing.  The best choice
is adhesive shrink tubing, but almost any product will work 
well.  Near the ocean, its wise to use shrink tubing over all
joints and screw or rivet penetrations of horizontally polarized 
antennas as well.  Be sure to leave openings at the end of the
elements that allow water to easily flow out.

In a temporary installation, use good quality electrical tape,
properly lapped so that water flows over each overlapping
layer of tape (the tape should should look like overlapped
roof shingles after the last layer is applied).

The same protection issue applies to outdoor coaxial and other 
cable connectors.  Its wise to place outdoor connectors in a 
horizontal position, to prevent flowing water from entering the 
connectors.  The cable at each end of the connectors should
turn downward, to form a drip loop.  Its more difficult to 
prevent flowing water from entering connectors if they are 
oriented vertically or if they are not protected by drip loops.

73!
Frank
W3LPL
donovanf at erols.com