Knowledge Base
Answers to Your Questions about Radio and Wireless Voice Communications

Range: Licenced or Licence Free (PMR446)

01 January 1970

Licensed radios will transmit at around 5 watts and licence free radios around 1/2 watt (500mW). So it might seem that if licensed radios transmit at 10 times the power then range will be 10 times further?. Unfortunately this is not the case because radio signals follow the Inverse Square Law.

Doubling range requires 4 times the power and tripling range requires 9 times the power. So all things being equal a licensed radio will give just over three times the range at best over Licence free radios. Unfortunately all things are not equal. Small changes in the Receive Sensitivity of radios have a greater effect on range than large changes in transmit power. So do aerials, some perform better than others. Finally and most important: The local environment affects range. An urban environment has far greater effects than in rural locations. As well as all these factors the audio quality has a influence; even a reasonable signal is useless if it is distorted and hard to understand because of poor audio quality.

In the real world this means good licence-free PMR446 radios can out perform poor quality licensed radios. Digital licence-free radios will almost always match or outperform analogue licence free radios because audio quality is better with weak signals.

Throwing money and transmit power at a radio system is not always cost effective or necessary. What licensed radios do offer is the ability to upgrade to repeaters which really can achieve 10 times the range over simple back-to-back radios such as PMR446 radios.

Before you choose a radio based on licensed or licence-free look at other features such as signalling which is not available on all radios.

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