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Old 13-Jun-2013, 2:16 PM   #24
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 123
Longer Reinforced Mast

If higher gain antennas were to occupy the top position on the tower, then a taller mast may be required. For maximum stacking gain, individual antennas with higher gain require increased stack spacing. At that time, the existing mast was 10.5 feet of SS-20 (heavy duty), 1 & 3/8 inch outer diameter top fence rail.

Realizing that if a longer mast was ever bent by wind force, with unreachable antennas installed, it might be difficult to remove.

To maintain highest rigidity and minimize weight, a mast was configured of three parts:

Full-length Outer – 15.5 feet of SS-20, 1 & 3/8 inch outer diameter
Inner – 10 feet of Schedule 40, 1.064 inch outer diameter
Lower-Outer - 6.5 feet EMT, 1.5 inch outer diameter.

The mast thickness were:

Bottom portion was 3 pipes thick (EMT, SS-20, & Sch 40)
Mid-section was 2 pipes thick (SS-20 & Sch 40)
Top portion consisted of one pipe (SS-20)

The Inner was positioned inside the Full-length Outer, such that it did not reach the top ~ 4.5 feet. In other words, the top 4.5 feet consisted of only the SS-20 pipe. Also, the Inner pipe did not extend all the way to the mast bottom, but there was pipe overlap inside the tower.

The Lower Outer (EMT) was positioned to reinforce the lower part of the mast, up to ~ 4 feet above the tower top.

The Full-length and the Inner mast were assembled with stainless steel screws. The Lower-outer was to be added after the assembly was in place. The assembled mast (without antennas) weighed 35 pounds.

A sort of a ‘gin pole’ (lightweight pipe with upper loop) was temporarily fastened to the tower top as an aid during installation. The top end of mast was fed up through the loop to help balance and stabilize it during installation (especially with air movement). This additional stability was probably most critical when inserting the lower end of mast into the tower top.

Below is an image of the mast on the tower without the Lower-Outer portion. Later when antennas and the Lower-Outer mast portion were installed, the mast was raised a bit higher. The install support ‘gin pole’, is also shown but was later removed.

Attached Images
File Type: jpg Longer Reinforced Mast.jpg (40.7 KB, 5992 views)

Last edited by tripelo; 13-Jun-2013 at 2:19 PM.
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