Radio Net

A radio net is three or more radio users communicating with each other on a common channel or frequency. Each user has a call sign to identify themselves. In small nets, users may talk directly to each other, though generally there will be a co-ordinating ‘control’ call sign in a fixed location, through which all radio traffic and information must go and be logged.

Voluntary services will often utilise multiple radio nets at public events, with different teams or resources using different channels. This requires ‘control’ to monitor and respond to teams on several frequencies.

Most radios utilise a half-duplex system (think walkie-talkies), where all units can send and receive messages, but not at the same time. This requires the use of a push-to-talk button, and good radio etiquette to keep messages brief and to complete messages with the word ‘over’ indicating the end of transmission and ensuring that only one party transmits at a time. A disadvantage of this system is that if multiple parties try to talk at the same time, interference occurs, and messages get lost.

The TETRA system uses half-duplex but has the functionality to also be used as a duplex system like mobile phones with both parties able to speak simultaneously.