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Association of Telecommunications Officers and
<br />Administrators, the U.S. Conference of Mayi3rs, the National
<br />League of Cities, and the National Association of Counties have
<br />filed similar objections.
<br />
<br /> Nature of the Technology
<br /> Low-power mobile radio communication, also known as cellular
<br /> communication, is accomplished by linking a wireless network
<br /> of radio wave transmitting devices (portable phones, pagers, or
<br /> car phones) to the conventional ground-wired communications
<br /> system (telephone lines) through a series of short-range,
<br /> contiguous cells that are part of an evolving cell grid.
<br /> For example, a portable phone transmits a signal to the
<br /> nearest cellular antenna. The call is relayed from the antenna to
<br /> the nearest land-based telephone line or microwave dish, and
<br /> then to a central switching computer. From there, the call is
<br /> sent to its destination, either a land-based telephone via the
<br /> land-based line or another mobile communication device via the
<br /> closest cellular antenna.
<br /> Calls can originate or be received from a wireless source
<br />because antennas share a fixed number of frequencies across the
<br />cellular grid. In other words, while a caller may dial her destina-
<br />tion number from within the radius of one cell antenna, she may
<br />travel into the radius of another during the call. The call proceeds
<br />uninterrupted as the transmission is "patched" from one antenna
<br />to the next. While the caller is moving, the cellular antennas are
<br />automatically locating an unoccupied frequency on the next
<br />antenna, thus enabling continued transmission.
<br /> When a caller cannot successfully place or maintain a call,
<br />either he is out of range or the nearest antenna is at full
<br />capacity. Cellular tower technology differs from satellite,
<br />microwave, or land-based communications in that it is based on
<br />a network of short-range cell sites with a fixed capacity. If the
<br />cells are not linked by cellular towers, microwave dishes, or
<br />ground-wired towers, transmission will fail. Similarly, if a cell is
<br />crowded by too many users, it must be "split" into two cells,
<br />each having its own radius; thus, only the cellular antenn~/s of
<br />separate carriers can share space on the same tower. It is
<br />physically impossible for a single carrier to deliver service
<br />successfully if irs antennas are not dispersed.
<br /> Most local regulations require that all technically available
<br />space on existing towers within the jurisdiction be used before
<br />new towers are erected. In other words, cellular carriers must
<br />lease space to other carriers on their towers; the cellular industry
<br />considers this leasing arrangement to be a less-than-ideal
<br />solution. As the demand for cellular telecommunications
<br />increases, cells in a' given area must be subdivided, or additional
<br />carriers must be permitted to operate there. The end result is the
<br />need for more towers.
<br />
<br />Towers and A.tennas
<br />Towers may need to range in height from 50 to 200 feet so that
<br />antennas can overcome the challenges posed to communications
<br />by local topography. The required height is usually proportional to
<br />a combination of the distance antennas can cover and the demand
<br />within their radius. Higher towers generally cover a larger
<br />geographic area, but have a lower service demand, and are known
<br />as coverage sites. Shorter towers, known as capacity sites, cover
<br />smaller areas with a more concentrated demand. Tower height can
<br />also vary according to engineering requirements for a specific site
<br />or the technical capabilities of the antennas being mounted.
<br />In addition to dedicated, free-standing cellular towers
<br />(monopoles), there are guyed towers (anchored with guy wires)
<br />
<br />and lattice, or self-support towers, which have three or four
<br />sides of open-framed steel supports. Some cellular antennas can
<br />occupy space on other types of communication towers when the
<br />engineering is feasible. This is known as using a donor site to
<br />troubleshoot a small gap or dead spot within the grid. A micro-
<br />celt or repeater facility is installed on a preexisting tower to
<br />ensure that transmissions within that area are clear. Antennas
<br />can also be placed on rooftops and other building features if the
<br />building's height can accommodate their service area. In
<br />addition, antennas have been mounted on silos, water tanks,
<br />windmills, and smokestacks. As cellular use proliferates and the
<br />technology improves, the trend toward shorter towers and less
<br />obtrusive mounting fixtures is likely to prevail.
<br /> Antennas are of three types: omnidirectional, directional, and
<br />microwave. Omnidirectional antennas, also called whip
<br />antennas, serve a 360-degree area. Directional antennas, also
<br />known as panel antennas or rectangular antennas, are used to
<br />achieve transmission or reception in a specific direction.
<br />Microwave antennas are used to link different types of
<br />telecommunications facilities, such as when a portable phone
<br />user calls a conventional telephone number.
<br />
<br />Screening, Landscaping, and Setbacks
<br />The most common objection to cellular towers and antennas is
<br />their aesthetic impact. Residents, many of whom use the
<br />technology, do not want to see the towers cluttering their
<br />landscape or degrading property values. Planners and industry
<br />professionals have gone to great lengths to screen, conceal, and
<br />set back towers and their associated buildings. All the
<br />ordinances reviewed contain some sort of requirement for
<br />maintaining existing vegetation or installing landscaping for the
<br />purpose of screening the base of the tower and the storage
<br />building. Towers can also be camouflaged to blend with the
<br />surrounding environment through the use of color, materials,
<br />and design. For instance, Jefferson Parish, Louisiana, requires
<br />that all cellular towers be disguised as trees:
<br />
<br /> 1. The entire facility must be aesthetically and architecturally
<br /> compatible with its environment. The use of residentially
<br /> compatible materials such as wood, brick, or stucco is
<br /> required for associated support buildings, which shall be
<br /> designed to architecturally match the exterior of residential
<br /> structures within the neighborhood. In no case will metal
<br /> exteriors be allowed for accessory buildings.
<br />
<br /> 2. The tower itself must be of such design and treated with an
<br /> architectural material so that it is camouflaged to resemble a
<br /> woody tree with a single trunk and branches on its upper part.
<br />
<br /> Setback distances can be guided by aesthetic and safety
<br />concerns. Most are expressed as a percentage of the tower
<br />height. In the Pensacola, Florida, ordinance, the setback serves a
<br />primarily aesthetic purpose:
<br /> [T]he distance bev,veen the base of the communications towers
<br /> and any residential zoning district or any historical or
<br /> architecturally significant building must equal 20 percent of the
<br /> tower height.
<br />
<br /> Safety-oriented setbacks establish a clear zone for falling
<br />tower debris or the worst-case scenario, the tower's collapse.
<br />Falling zones for towers vary with their design. At most, they
<br />will collapse to a distance equal to their full height, but many
<br />are designed to collapse first toward their base. The Oldham
<br />County, Kentucky, setback provisions are designed with falling
<br />zones in mind:
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