A two-way radio is a radio that receives and transmits content. The operator in possession of the radio can participate in a conversation with other operators having a two-way radio, which
operates on the same frequency or channel. A two-way radio is also referred to as a walkie-talkie.
The operator of a two-way radio can either transmit or listen all at once. This mode is usually referred to as a half-duplex mode. If the operator desires to talk, but he was originally listening, then all that he has to do is to push the Push to Transmit Button. On the other hand, a mobile phone has a full-duplex mode, which means that you can both receive and transmit conversation simultaneously. This is because mobile phones work on two frequencies - whereas a two-way radio works on only one frequency.
There are only certain frequencies by which two-way radio systems can operate. Every country assigns this specified frequency for such radios and therefore these frequencies differ from country to country. For instance, a whole block of 22 channels are assigned by America to the general Mobile Radio Service. Operators can communicate on their two-way radios using any of these frequencies.
The government allocates the frequency based on its own policies and regulations and on a number of factors. First, it checks the traffic-per-frequency and determines the frequency availability. Then it checks the topography and checks how radio signals will travel in forest and urban areas. It makes calculations on noise intrusion and congestion, and also considers other technical aspects. Finally, it creates a proposal that must be approved by a special technical committee.
The government would then assign the frequency after you have obtained the approval. Numbers and titles are given to frequencies for easy recall, - for example, Channel 10 is easier to recall than 27.695 MHz. The frequency assigned for two-way radios acts as a bridge between two-way radios. Utility companies and government departments like the police have many frequencies assigned for their use. This is necessary because these organizations provide critical services and their two way radios must always be prepared for use at any and every point in time. Although channel numbers are used by utility companies and other organizations, amateur radio operators on the other hand work with various frequencies since they are not required by law to make use of a fixed channel.
The robustness of the frequency is one huge factor that affects the quality of the conversation between two-way radios. There are many factors that can affect the range of a two-way radio-system. Some of these factors include the noise in the atmosphere, atmospheric refraction and reflection, antenna characteristics, transmitter power, signal-to-noise ration, type of receiver and the height at which the antenna is positioned.
You will find that majority of two-way radio systems operate in the UHF and VHF bands, which is also the one used by mobile systems. Since a two-way radio makes use of line-of-sight broadcast, communication can be blocked by tall buildings that are within the line-of-sight. Atmospheric noise, weather and the frequency that is used are some more factors that can impact the quality of the conversation. There are a variety of applications by which two-way radios are used. Utility company workers, cops, hobbyists, hotel employees, as well as amateurs make use of 2-way radios.
These are the fundamentals of two-way radios.