Floating Cell Phone Signals

• Although cell phones may seem like magical devices with signals that float through the air, there is a complex science behind this phenomenon. Cellular signals are actually electromagnetic fields which travel at specific frequencies. The ability for cellular phones to pick up these frequencies is based upon the availability of a cellular network in the area where the phone is being utilized.
  
  

Radio Waves

• Cell phone signals are actually a type of radio wave. Radio waves are electromagnetic waves, which are encoded sound waves. Unlike sound waves, electromagnetic waves can travel great distances with little degradation in sound quality. Compare shouting at someone miles away versus using a cell phone to communicate with that same individual. This difference illustrates why the sound waves must be encoded into radio waves to transmit audible signals.
  
  

Sound Waves

• A combination of height (amplitude), length and speed (frequency) create a sound wave, which is then encoded into a radio wave, transmitted to the speaker and decoded. In this model, cell phones encode and decode the signals, while cell phone antennas and base stations transmit the signals between the devices.
  
  The sound waves or frequencies utilized by cell phones are between 824 MHz and 894 MHz, with different frequencies used for sending and receiving. The use of a range of frequency bands allows separate conversations to occur simultaneously with little interference.
  
  

Cell Phone Networks

• While radio networks use towers to broadcast outwards to the receivers (radios), cell phone networks are comprised of cells, where the signals travel inwards from antennas to a central base station. Cells cover a specific geographical area and resemble a cluster of hexagons. The most common cell configuration employs a cluster of seven hexagons, as this allows for an optimal set of frequencies and thus maximizes the number of separate conversations.
  
  Cell phone base stations are located in the center of the hexagons, with antennas placed along the points. When someone speaks into a cell phone, the signal travels though the air to a nearby antenna. The signal is then transmitted to the base station, where it is re-encoded and sent back out through a series of antennas, until it is received by the listener's phone.