Cell phone base stations may be free standing towers or mounted on existing structures, such as trees, water tanks, or tall buildings. The antennas need to be located high enough so they can adequately cover the area. Base stations usually range in height from 50-200 feet.
Cell phones communicate with nearby cell towers mainly through radiofrequency (RF) waves, a form of energy in the electromagnetic spectrum between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, they are forms of non-ionizing radiation. This means they cannot cause cancer by directly damaging DNA. RF waves are different from stronger types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light, which can break the chemical bonds in DNA.
At very high levels, RF waves can heat up body tissues. (This is the basis for how microwave ovens work.) But the levels of energy used by cell phones and towers are much lower.
When a person makes a cell phone call, a signal is sent from the phone’s antenna to the nearest base station antenna. The base station responds to this signal by assigning it an available radiofrequency channel. RF waves transfer the voice information to the base station. The voice signals are then sent to a switching center, which transfers the call to its destination. Voice signals are then relayed back and forth during the call.
A cell-phone tower is typically a steel pole or lattice structure that rises hundreds of feet into the air. This cell-phone tower along I-85 near Greenville, SC, is typical in the United States:
This is a modern tower with three different cell-phone providers riding on the same structure. If you look at the base of the tower, you can see that each provider has its own equipment, and you can also see how little equipment is involved today (older towers often have small buildings at the base):
The box houses the radio transmitters and receivers that let the tower communicate with the phones. The radios connect with the antennae on the tower through a set of thick cables:
If you look closely, you will see that the tower and all of the cables and equipment at the base of the tower are heavily grounded. For example, the plate in this shot with the green wires bolting onto it is a solid copper grounding plate:
One sure sign that multiple providers share this tower is the amazing five-way latch on the gate. Any one of five people can unlock this gate to get in.
Cell-phone towers n all shapes and sizes, but I do believe this one in Morrisville, North Carolina, is one of the weirdest looking.
That is one tall, ugly tree!
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