KB9CRY - 2003

120 ft. Tower

LINKS:    TOWER     TRAM     ANTENNA     VIEWS

 

A new KLM 3 el. 40M Yagi was installed on a new Rohn 45 120 ft. Tower. Click on the links above to link to more information. See below for tower information and a link to pictures of the tower installation.

The tower is 120 feet of Rohn 45. Virtually all sections were purchased used; all were wire brushed (using electric drill) and painted with Cold Galvanizing paint (heavily loaded zinc material made by Crown from McMaster Carr). The bottom section is a new Rohn tapered base. This incorporates a pier pin (allows tower to twist from wind torque on the antenna up top) and a tapered base (allows tower to lean over when guys stretch in high winds). The tower was erected using a gin pole, a climber, and a bunch of hoisting crew below. The guys are 3/8 inch non-conductive Polygon structural fiberglass guys (13,600 # tensile versus 11,000 # tensile for 5/16 EHS) and terminate at each end using Preformed Products' Big Grips. These grips are great; no clamps to tighten, maintenance free, and very clean installation. They are made specifically for the guy diameter and material. One winds one end onto the guy end and then the other leg is wound over that for a very tight fit. They work on the same principal as those Chinese finger torture toys we used to use as a kid; the harder you pull, the tighter the grip. The lower 15 feet of each guy is made of EHS for physical protection. The anchors are Rohn in-ground anchors which extend below grade into about 2 yards of concrete. A surveyors transit was used to plumb the tower; when checked a month after installation, the maximum deviation was found to be 1/2 inch off plumb. A Loos tension gauge is used to determine and check guy wire tension.

The tower is grounded as follows. Each leg is connected to six ground rods, three 8 footers and three 5 footer. All are connected with #4 bare solid copper wire and all connections are CadWelded to the rods. The coax shield is grounded to the base of the tower using a ICE grounding block. Also, the mast is grounded to the tower before the rotator with #4 welding cable. All cables are grounded to the single point ground rod (SPG) outside the basement shack with ICE lightning arrestors.

 
Thanks to the following who donated their time helping assemble the antenna, guy assemblies, tower erection, and antenna installation: AF9R, AI9L, K9FY, K9IDX, K9NU, N8KWX, N9AOL, NA9D, W9UZ, W9WU, W9YYG, WA9YYY. Thanks to the following for equipment and technical assistance: N6ND, K9HMB, W0UN. Finally special thanks to KS9W for his expert tower assembly and antenna tramming help; I couldn't have done it without you Bob.

 

Click here for tower installation pictures.

 

 



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