Towers benefit local efforts at revitalization and growth Aesthetics draw citizen support for tower projects. How’s that again? Attractive towers overcome objections to allow optimum placement to support greater coverage and to generate maximum rental inc

Many cities are struggling to reverse the devastating effects of urban flight, which leave them with decaying neighborhoods, abandoned buildings and shrinking tax bases. Many times, city-owned properties, such as athletic fields and parks, become neglected, run-down centers for criminal activity that hinder any revitalization effort. Jackson, MS, took a bold step to combine revitalization with a dramatic improvement to its city government telecommunications. The city placed a 503-foot tower at an abandoned, city-owned athletic field that became the primary site in its new trunked radio system. The tower’s aesthetic design helps to convert a previously unproductive site in a manner that brings beauty and distinction to the neighborhood. Already, an adjoining land parcel is being developed for new housing. More growth will undoubtedly follow.

Although urban flight represents a growing problem, progressive cities such as Jackson, MS, and Mesquite, TX, have taken steps to prevent it. Preventing urban flight can be made more complicated when citizens object to towers. Towers, through the communications that they carry, are absolutely necessary to maintain city services, to protect personal safety and property, to satisfy consumer communications demands and to attract and retain businesses.

Central location Maximum coverage and penetration for radio-based telecommunications such as public safety radio communications, private wireless business networks and cellular telephone require a transmission site to be carefully located. Towers need to be central to the city to provide a wide service radius. Decisions about tower placement cause turmoil. A city government can expect a battle between citizens and service providers over every tower construction permit. Some permits have been delayed as long as six years because of citizen opposition. Some permits eventually are denied. Usually, citizens suffer the most from delays and denials because necessary communications systems are not implemented on a timely basis. What can be done to change the people’s minds about towers in their neighborhoods? The Mesquite Independent School District (MISD) needed a tower for its KEOM-FM radio station, a tower that could be shared by city government and private communications services.

Overcoming opposition Mesquite citizens had expressed opposition to the prospect of towers popping up everywhere across the city. As a result, the MISD leadership enlisted the aid of the City of Mesquite so their combined radio communications requirements and those of private service providers could be met with one project.

A study group determined that the combined requirements included the following: reliable 9-1-1 services. back-up power. minimum maintenance. privatization of the site technical management. security. expandability. strength and stability for microwave antennas. monitoring of the tower, equipment environment and fence. aesthetics.

The tower shown in Photo 1 on page 10 was chosen as the type that would best meet these requirements. The communications complex was planned so one large facility could serve the entire area instead of using multiple smaller towers throughout the city. The basis for the patent that covers the tower is the tower’s ability to be upgraded and its ability to carry superior payload per pound of steel for a comparable structure. Rental revenue

Tower rental space for wireless communications service providers is bringing a return on the joint investment made by the City of Mesquite and the MISD. By constructing the central communications complex, the city and the MISD have turned one of its problems into a revenue source.

The tower’s wash lighting at night enhances the beauty and character of the city and has made the tower popular. It’s wide stance virtually eliminates twist and sway, making it ideal for microwave transmissions. The wide stance and triple-leg truss design makes the tower reliable with respect to wind loading and seismic safety factors. The structure’s folded-plate “U”-shaped leg members allow coaxial transmission lines to be placed inside the leg members where they are protected from wind loading, ice loading and rifle fire. (See Figure 1 on page 11.) Where they are routed between the tower legs and the transmitter building, the cables are protected by tunnels. (See Figure 2 on page 11.) Aside from security, the tunnels resolve three other important considerations: (1) The coaxial cables have room to make large sweeping turns that avoid kinks in the line. (2) The tunnels allow the elevators in each leg to be stationed at an elevation of only six inches above the concrete foundation for easier loading and unloading. (3) Placing the coax below ground level prevents it from carrying a portion of the tower’s high voltage gradient caused by lightning. For example, with a potential voltage gradient of 300,000V between the top of the 515-foot structure and the ground during lightning strikes, coax routed at ground level would be suspended in a voltage gradient of about 5,000V. Safeguarding workers and equipment from potential injury or damage from voltage on the coaxial cable would be an additional requirement that is avoided by using the tunnels.

After studying several lightning-deterrent systems, my company’s engineers chose the system manufactured by Lightning Deterrent, Wilmington, IL. They thought the system would give the overall best protection, and after two years of operation, the system has proven to be satisfactory.

The need for security and efficiency led to the use of two tower-mounted equipment rooms. (See Photo 2 on page 11.) The lower equipment room is at 310 feet, and the other is at 400 feet.

Elevated equipment rooms Although some RF equipment is in the building at ground level, there are many benefits to placing equipment at elevation. Less transmission line is required to reach the antennas, reducing the line cost and improving the effective radiated power (ERP). The tower-mounted room’s galvanized steel top, bottom and inside wall provide good protection in that, electronically, they resemble a faraday cage. Each room is provided with the following: 15 tons of air conditioning. electric toilet. halo grounding system. 200-pair telephone punch down block. dual-protection fire alarm system. fire-suppression systems consisting of 7% Halon (CO2 in the ground building). 12 windows to prevent claustrophobia. 400A, 440V primary power service and 100A emergency power 3/4″ plywood floors. 1/2″ drywall interior vertical surfaces. insulation on floors, back walls and ceiling. individual circuit breakers for each radio duplex outlet. fluorescent lighting system.

The landing platforms at each elevated room span the space between the room and the interior of the tower. (See Photo 3 to the left.) Both top and bottom landing platforms are equipped with counter-balanced hexagonal doors in the grating for easy opening. The heavy-duty freight elevator passes through these openings as equipment is hoisted to the various equipment room levels. (See photo 4 below.)

Each equipment room has about 1,000 square feet of air-conditioned floor space that permits ample room for radios and microwave antennas. One customer has installed 11 eight-foot-diameter microwave antennas in the lower room, and there is much more space still available. The fact that the wind-tunnel-tested aerodynamic drag coefficient will not be altered by the 11 antennas makes the selection of the tower-mounted equipment room for this structure even more credible. The 44-foot diameter rooms have nine feet of inside vertical clearance to the ceiling. These dimensions allow ample horizontal spacing for antennas mounted on the room’s top railing and ample vertical space for RF equipment installation. The elevated rooms allow easy access to the associated antenna.

Elevator access Access to the rooms normally is by cable-drawn lift units. Most cable-drawn elevators are subject to a certain amount of wind movement. Together with other undesirable factors associated with cable-drawn tower elevators, instability in windy conditions led to a two-year development program that included 30 years of life testing for a new type of tower elevator. The new lift includes the following attributes: no cables or gear racks. runs on curved surfaces as well as straight surfaces. operator-controlled from inside the cab. tambour doors for complete enclosure while in motion. speeds from 0 to 100 feet per minute are possible. choice of power supplies (electric Duct-O-Bar or gasoline engine). extensive list of accessories.

The lift is designed for retrofitting into any tower. Plans are being considered to replace at least one of the three existing elevators in the MISD communications complex with the new lift. Construction financing

Financing is frequently an issue. A large tower, especially one that is part of a city, county or state communication complex, usually qualifies for traditional infrastructure financing, such as special-purpose bonds. Where infrastructure financing is unavailable or politically sensitive, the “personal property” character of a boltdown tower, loaded with equipment and accessories, substantially qualifies for traditional lease-financing. Some investment banking firms specialize in underwriting bond issues that directly or indirectly carry the backing of the municipality or other governmental unit. Similarly, some large asset-based lenders actively seek lease-financing deals for infrastructure projects that have the character of “equipment” and some form of backing by the governmental unit primary user. Finally, to the extent that capacity is built into the tower to accommodate outside revenue producing lease space, revenue-based financing options are made possible by using the future lease cash flow as security for the financing.

The MISD facility is a good example of a system that meets communications needs well into the next century. The initiation of this project exemplifies the progressive direction and management of Dr. John Horn, who has served as MISD superintendent for many years, and the skills of the district’s systems engineer, Dennis Hevron.