2 Way Radio Service - Experience – Expertise! A two-way radio is a radio that can both transmit and receive (a transceiver), unlike a broadcast receiver Two-way radios are available in mobile, stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies or handie-talkies. A push-to-talk or Press To Transmit button is often present to activate the transmitter. History Installation of receivers and transmitters at the same fixed location allowed exchange of messages wirelessly. As early as 1907, two-way telegraphy traffic across the Atlantic Ocean was commercially available. By 1912 commercial and military ships carried both transmitters and receivers, allowing two-way communication in close to real-time with a ship that was out of sight of land. The first truly mobile two-way radio was developed in Australia in 1923 by Senior Constable Frederick William Downie of the Victorian Police. The Victoria Police were the first in the world to use wireless communication in cars, putting an end to the inefficient status reports via public telephone boxes which had been used until that time. The first sets took up the entire back seat of the Lancia patrol cars. As radio equipment became more powerful, compact, and easier to use, smaller vehicles had two-way radio communication equipment installed. Installation of radio equipment in aircraft allowed scouts to report back observations in real-time, not requiring the pilot to drop messages to troops on the ground below or to land and make a personal report. In 1933, the Bayonne, New Jersey police department successfully operated a two-way system between a central fixed station and radio transceivers installed in police cars; this allowed rapidly directing police response in emergencies. During World War II hand-held radio transceivers were extensively used by air and ground troops. Early two-way schemes allowed only one station to transmit at a time while others listened, since all signals were on the same radio frequency - this was called "simplex" mode. Code and voice operations required a simple communication protocol to allow all stations to cooperate in using the single radio channel, so that one station's transmissions were not obscured by another's. By using receivers and transmitters tuned to different frequencies, and solving the problems introduced by operation of a receiver immediately next to a transmitter, simultaneous transmission and reception was possible at each end of a radio link, in so-called "full duplex" mode. Early two-way schemes required training operators to learn and use Morse code; in ship-board installations the radio operating officer typically had no other duties than handling radio messages. When voice transmission became possible, dedicated operators were no longer required and two-way use became more common. Today's two-way mobile radio equipment is nearly as simple to use as a household telephone, from the point of view of operating personnel, thereby making two-way communications a useful tool in a wide range of personal, commercial and military roles. Two-way radio frequencies In an analog, conventional system, (the simplest type of system,) a frequency or channel serves as a physical medium or link carrying communicated information. The performance of a radio system is partly dependent on the characteristics of frequency band used. The selection of a frequency for a two-way radio system is affected, in part, by:
It is necessary to identify which radio service is under discussion when specifying a frequency by its channel number. Organizations, such as electric power utilities or police departments, may have several assigned frequencies in use with arbitrarily assigned channel numbers. For example, one police department's "Channel 1" might be known to another department as "Channel 3" or may not even be available. Public service agencies have an interest in maintaining some common frequencies for inter-area coordination in emergencies. CONTACT BARTRONICS TODAY – WE CAN HELP! 219.929.4277 |
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which only receives content.
Two-way radios can operate on many different frequencies, and these frequencies are assigned differently for different users. Typically program channels are used, so that operators need not tune equipment to a particular frequency, but instead can use one or more pre-selected frequencies, easily chosen by a pushbutton or other means. For example, in the United States, there is a block of 22 channels (pre-selected radio frequencies) assigned, collectively, to the General Mobile Radio Service and Family Radio Service.
