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What Are Cellular Phone Towers?
The widespread use of cellular telephones has led on to
the placement of cellular telephone towers in several
communities. These towers, also called "base stations,"
consist of radios, computerized switching kit, and antennas
that receive and broadcast radiofrequency ( RF ) signals.
When a person makes a cellular telephone call, a signal is
sent from the telephone's antenna to the base station
antenna. The base station replies to this signal by alloting
it an available radiofrequency channel. Transmission and
reception of these radio signals transfer the voice info to
the base station. Next, the voice signals are sent to a
switching center, which transfers the call to its
destination. For further info on the telephones themselves,
please see the American Cancer Society document, "Cellular
Phones." Cellular telephone towers are typically mounted
either on top or on the side of existing structures, for
example trees, water tanks, or tall buildings. The antennas
have to be positioned high enough so they can adequately
cover the area.
Base stations generally range in height from 150-270 feet.
Cellular telephones operate at the radiofrequency ( RF )
part of the electro-magnetic range. This is non-ionizing
radiation. Other examples of the non-ionizing part of the
electric range include AM and FM radio waves, microwaves,
and infrared waves from heat lamps. Unlike x-rays and gamma
rays ( which are examples of ionizing radiation ), radio
waves have not enough energy to smash the bonds that hold
molecules ( like DNA ) in cells together. In a similar
fashion , since RF of this frequency contains comparatively
low energy, it doesn't enter tissues.
At extremely extreme levels of exposure, RF could cause
warming of tissues, much as a heat lamp does. The wavelength
of cell telephone waves is about one foot and the frequency
is roughly eight hundred to 900 MHz, though newer models may
use higher frequencies up to 2,200 MHz. How Are Folks
Exposed to Radiofrequency power from Cellular Telephone
Towers? As folk use cellular telephones to make telephone
calls, signals are transmitted backwards and forwards to the
base station.
The radio waves produced at the base station are emitted
into the environment, where folk can be exposed. The power
from a cellular telephone antenna, like that of other
telecommunication antennas, is directed toward the horizon (
parallel to the ground ), with some downward scatter. Base
station antennas use higher power levels than other sorts of
land-mobile antennas, but lower levels than radio and TV
broadcast stations.
The power density decreases with enlarging distance from the
antenna. As a consequence, the level of exposure to radio
waves at ground zero is terribly low compared to the level
near to the antenna. Public exposure to radio waves from
cellular telephone antennas is slight for many reasons. The
power levels are comparatively low, the antennas are mounted
at way above ground level, and the signals are broadcast
intermittently, instead of continually. Agencies like the
nation's Council on Radiation Protections and Measurements,
the Intnl Radiation Protection organization, the Institute
of Electric and Electronics Engineers, and the American
National Standards Institute, have established axioms for
exposure to RF radiation originating from cellular
communications base stations. These guiding principles were
engineered to protect employees, as well as the public, from
most likely damaging radio frequency.
The suggested exposure boundaries are in the range of
.41-.45 milliwatts per square centimeter ( mW / cm2 ) for
cellular radiofrequencies.
Exposures that surpass these commended standards can
occasionally be encountered on the rooftops of buildings
where base stations are mounted. If this is the case, access
to these areas should be limited. The power density within
buildings where a base station is mounted is often ten to a
hundred times lower than the level outside depending on the
construction materials of the building. Wood or cement block
decreases the exposure level of RF radiation by an element
of roughly 10. The power density behind an antenna is
hundreds to thousands of times lower than in front. , if an
antenna is mounted on the side of a building, the exposure
level in the room at once behind the wall is often well
below the endorsed exposure boundaries. |
