A two-way radio is an electronic device that can both send and receive voice broadcasts. The first radios were used by ships at sea during the early 1890s. Radios became commonplace in the 20th century, and are used today for recreational, business and emergency purposes. Some two-way radios are designed to be installed in vehicles, while others are handheld and can be easily carried. No matter the design, all radios operate using the same fundamentals.
All two-way radios depend on radio waves for communication. A radio wave is a type of energy, just like the light from a lamp. Unlike visible light, however, radio waves cannot be seen by the naked eye. Even though they are invisible, radio waves can be detected when they pass through an antenna and cause it to oscillate. The pattern of these oscillating waves can include a coded message. A two-way radio uses its small antenna to detect radio waves in the air. An electronic circuit inside the radio converts the pattern of the oscillating waves into sound. In order to reduce interference from many different radio signals, a two-way radio can be tuned to a specific frequency. This means that it listens for only one pattern of radio waves, and ignores signals on different frequencies.
A two-way radio can transmit a message by reversing the process used during reception. Each radio unit has a microphone, which converts sound vibrations into an electronic signal. The coded signal is then amplified and sent through the antenna. Radio waves continue to travel through the air once they have been emitted from the radio's antenna, and can be received and decoded by nearby radio units. Unlike a telephone, a standard two-way radio cannot receive and transmit at the same time. When the transmission circuit is active, incoming signals will not be detected. Radio operators must release the transmit button when they are finished talking, and take turns talking back and forth.
The primary feature that users must consider is the frequency. In order for a pair of radios to be compatible, they must be designed for the same radio frequencies. A Citizen's Band radio, such as the Midland Model 75-822 carried by Radio Shack, will operate at around the 27 megahertz frequency. This frequency allows for fairly long-range communications under ideal conditions, but can be prone to erratic interference and poor audio quality. Some two-way radios operate at higher frequencies. Radio Shack's Motorola MJ270 model, for instance, uses the Family Radio Service band. This type of radio can transmit and receive on frequencies between 462 and 467 megahertz. FRS radios typically have a shorter maximum range than CB radios, but have superior voice quality and more predictable performance.
Some two-way radios have additional features that make them more user friendly. Motorola Model MS350R radios, for example, include the ability to set privacy codes. When two of these radios are set to the same privacy code, they will ignore signals from nearby radios, even if the transmissions are on the same frequency. This helps eliminate unwanted interference in crowded areas, and allows users to only hear important conversations. Many radios can receive special broadcasts. The Motorola MS350R is one of several units that can be tuned to the government-run weather reporting frequencies. Users can listen to forecasts and reports from the National Oceanic and Atmospheric Administration, and hear an alert if severe weather is present.
- Thinkstock Images/Comstock/Getty Images