Power Output
PowerAn antenna transmits and receives radio-frequency signals, allowing a two-way radio to communicate. Antenna type, frequency, height and location can all affect radio performance and coverage. Output is the amount of radio-frequency energy a two-way radio’s transmitter produces when it transmits a signal. It is normally measured in watts (W).
Power output is one factor that affects radio coverageRadio Coverage is the geographical area in which a two-way radio system can provide reliable communication. Coverage depends on the radios, antennas, frequency, terrain, buildings and system infrastructure., but higher power does not automatically mean greater usable range. AntennaAn antenna transmits and receives radio-frequency signals, allowing a two-way radio to communicate. Antenna type, frequency, height and location can all affect radio performance and coverage. performance, frequencyAn antenna transmits and receives radio-frequency signals, allowing a two-way radio to communicate. Antenna type, frequency, height and location can all affect radio performance and coverage., terrain, buildingsAn antenna transmits and receives radio-frequency signals, allowing a two-way radio to communicate. Antenna type, frequency, height and location can all affect radio performance and coverage., interferenceRadio interference occurs when unwanted radio-frequency signals or electrical noise disrupt two-way radio communications, causing distorted audio, broken transmissions, reduced coverage or loss of communication. and whether a repeaterA Repeater receives a two-way radio transmission and retransmits it, usually from an elevated location, to extend the coverage and reliability of a radio communication system. is being used can all have a significant effect on communication range.
What is power output?
When a two-way radio transmits, its transmitter generates a radio-frequency signal.
The power of that transmitted signal is referred to as the radio’s power output.
For example, a radio may have a transmitter output of:
- 1 watt
- 2 watts
- 4 watts
- 5 watts
- 25 watts
- 50 watts
The available output depends on the type of radio and its intended application.
Power output and radio range
Power output can affect how far a radio signal can travel.
Increasing transmitter power can improve the strength of the transmitted signal at a receiving location, potentially improving coverage where the original signal was marginal.
However, the relationship is not simply:
More Power = More Range
Other factors can have a greater influence on practical coverage.
Factors affecting radio coverage
The usable range of a two-way radio depends on factors including:
- Transmitter power
- FrequencyFrequency is the number of cycles a radio wave completes each second, measured in Hertz. In two-way radio, frequency determines where a transmission operates within the radio spectrum.
- Antenna
- Antenna height
- Terrain
- Buildings
- Vegetation
- Atmospheric conditions
- ReceiverA Receiver is the part of a two-way radio that detects and processes incoming radio signals, converting them into audible voice or usable data for the user. sensitivity
- Interference
- Repeater coverage
This is why two radios with similar power output can provide very different levels of coverage.
Portable radio power output
A Portable RadioA Portable Radio is a battery-powered two-way radio designed to be carried and operated by an individual, providing mobile communication for professional and operational users. generally has a lower transmitter power output than a vehicle-mounted or fixed radio.
This is partly because portable radios need to operate from a relatively small battery and are designed to be carried by users.
Typical professional portable radios may provide several watts of transmitter power, depending on the model and configuration.
The exact output should always be checked against the manufacturer’s specifications.
Mobile radio power output
A Mobile RadioA Mobile Radio is a two-way radio designed to be installed in a vehicle. It normally uses the vehicle's power supply and an external antenna to provide reliable communication while travelling or working in the field. installed in a vehicle can generally use more transmitter power than a handheld radio.
The vehicle’s electrical system can provide substantially more power than a portable radio battery.
A mobile radio can also use an externally mounted vehicle antenna, which can provide advantages over the small antenna normally fitted to a handheld radio.
Base station power output
A Base StationA base station is a fixed two-way radio installed at a permanent location, allowing an operator to communicate with handheld or mobile radios across a site or operating area. can use higher transmitter power and a more effective antenna installation than a portable radio.
Because the antenna can often be mounted at a greater height, a base station can provide significantly greater coverage.
However, the permitted transmitter power is determined by the applicable radio authorisation and system design.
Power output and repeaters
A Repeater can provide a much greater improvement in coverage than simply increasing the power of individual handheld radios.
A repeater is normally positioned at a strategically useful location, often at height.
For example:
Portable Radio → Repeater → Portable Radio
The repeater receives a relatively weak signal and retransmits it from a better position.
This can provide coverage across large sites or difficult terrain.
Power output and antenna height
Antenna height can have a major effect on radio coverage.
A higher antenna can provide a clearer path for radio signals and improve the area that can be reached.
For this reason, installing a suitable antenna at an elevated location can sometimes provide more practical benefit than simply increasing transmitter power.
Power output and frequency
Radio frequency affects how signals propagate through the environment.
Lower frequencies can have different propagation characteristics from higher frequencies, particularly around buildings and over terrain.
Power output therefore needs to be considered together with frequency when designing a radio systemA Radio System is a complete communication solution comprising two-way radios and, where required, equipment such as repeaters, antennas, base stations, mobile radios and network infrastructure..
Power output and buildings
Buildings can weaken or obstruct radio signals.
Materials such as reinforced concrete, steel and other structures can significantly affect radio coverage.
Increasing power may help in some situations, but it will not necessarily overcome substantial building attenuation.
A repeater or appropriately positioned antenna may provide a better solution.
Power output and terrain
Hills, valleys and other geographical features can obstruct radio signals.
A high-power radio may still have difficulty communicating with another radio when a significant physical obstruction exists between them.
Repeater positioning can help overcome these limitations.
Power output and line of sight
Radio communication is often affected by whether there is a reasonably clear propagation path between the transmitting and receiving antennas.
This is particularly important at higher frequencies.
A radio with greater power cannot always overcome an obstructed path.
Power output and receiver sensitivity
Radio communication depends on both the transmitted signal and the receiving radio.
A sensitive receiver can detect weaker signals.
This means that improving the receiving side of a radio system can sometimes provide a greater benefit than increasing transmitter power.
Power output and antenna efficiency
The antenna is a critical part of a radio system.
An efficient, correctly installed antenna can improve the way transmitted power is converted into a useful radio signal.
A poorly positioned or unsuitable antenna can reduce performance even when the transmitter has relatively high output power.
Power output and ERP
Radio systems may be described using Effective Radiated Power (ERP).
ERP takes into account transmitter output and antenna characteristics, including antenna gain and losses in the transmissionTransmission is the process of sending voice, data or signalling from a radio using a radio-frequency signal to another radio, repeater or communication system. system.
As a result, transmitter power alone does not always describe the effective strength of a radio signal being radiated.
Power output and EIRP
Effective Isotropic Radiated Power (EIRP) is another measurement used when describing radiated radio power.
EIRP uses an isotropic antenna as the reference, whereas ERP uses a half-wave dipole as its reference.
The distinction is important when interpreting technical specifications and regulatory limits.
Power output and battery life
Higher transmitter power can increase the amount of energy consumed when a portable radio is transmitting.
This can reduce battery operating time if the radio spends significant periods transmitting at higher power.
Professional radio systems therefore often provide different power settings.
For example:
Low Power → Reduced Energy Consumption
High Power → Greater Transmitted Signal Strength
The available settings depend on the radio model.
High-power and low-power settings
Some professional radios allow users or administrators to select different transmitter power levels.
Lower power may be suitable where coverage is already strong.
Higher power may be appropriate where additional signal strength is required and the radio system permits it.
The radio should be configured within the authorised operating conditions.
Power output and heat
Transmitting at higher power can generate more heat within the radio.
Professional radios are designed to manage the heat generated during normal operation.
Extended high-power transmission can nevertheless increase energy consumption and thermal load.
Power output and interference
Increasing transmitter power can increase the potential for interference with other radio systems.
This is one reason transmitter power is normally controlled as part of radio-frequency management.
Users should not increase the power of a radio beyond the authorised or manufacturer-specified limits.
Power output and Ofcom
In the UK, professional radio systems may operate under an Ofcom Business Radio LicenceAn Ofcom Business Radio Licence authorises businesses and organisations in the UK to use specified radio frequencies for professional two-way radio communication, subject to the licence conditions..
The applicable licence can specify technical conditions governing how the radio system operates, including parameters associated with transmitter operation.
Users must operate radios within the conditions of the relevant authorisation.
Power output and licensed radio
A radio capable of transmitting at a particular power level is not necessarily authorised to use that power in every situation.
The permitted power depends on the radio service, frequency allocation, licence conditions and system configuration.
Technical capability should therefore not be confused with legal authorisation.
Power output and licence-free radio
Licence-free services such as PMR446 are subject to specific technical requirements.
Equipment used for PMR446 must comply with the applicable restrictions, including transmitter power and other technical characteristics.
A higher-powered professional radio cannot simply be used on a licence-free frequency outside those requirements.
Power output and DMR
Digital Mobile Radio (DMR)Digital Mobile Radio (DMR) is an ETSI digital radio standard for professional two-way communications, supporting voice, group calling, data and other features on compatible radio systems. equipment is available in different classes and configurations.
Power output varies between portable, mobile and fixed equipment.
DMR itself does not mean that all radios operate at the same power level.
The appropriate output depends on the radio and the system in which it is being used.
Power output and analogue radio
Analogue two-way radios are also available with different transmitter power levels.
As with digital radio, output power is only one part of the overall radio system.
A well-designed lower-power system with good antennas and repeater coverage can outperform a poorly designed high-power system.
Power output and digital radio quality
Increasing transmitter power does not directly improve the quality of a digital radio signal in the same way that it may improve a weak analogue signal.
Digital systems generally provide clear audio while the received signal remains within the system’s usable operating range.
Once the signal becomes too weak or corrupted, communication can fail relatively quickly.
Power output and radio hire
Professional Radio HireRadio Hire is the temporary rental of two-way radios and related communication equipment for events, projects and operational requirements, providing professional communication without purchasing the equipment. companies can supply radios configured for the required application.
The transmitter power will normally be set or selected according to the equipment and authorised radio system.
Customers should not attempt to modify transmitter power settings on hired equipment without permission from the supplier.
Power output and construction
Construction sites can contain substantial obstacles and sources of interference.
Selecting an appropriate radio power level can help, but coverage planning is usually more important than simply choosing the highest-power handheld radio.
Large sites may benefit from a repeater and suitably positioned antenna.
Power output and agriculture
Large farms can have significant distances between working areas.
A higher-power mobile radio, suitable antennas and a repeater can be used as part of a wider farm communication system.
The most effective solution depends on the terrain and required coverage.
Power output and events
Events may require reliable communication across large or crowded areas.
Rather than simply increasing radio power, a professional event system may use:
Portable Radios + Repeater + Suitable Antenna
This can provide more consistent coverage while maintaining appropriate radio-system parameters.
Power output and security
Security teams may operate across large buildings or outdoor sites.
A suitable combination of portable radio power, antenna performance and repeater coverage can provide reliable communication between officers and control rooms.
Power output and radio system design
Power output should be considered as part of the overall radio-system design.
A professional assessment can consider:
- Required coverage.
- Frequency.
- Radio type.
- Antenna.
- Transmitter power.
- Terrain.
- Buildings.
- Repeater requirements.
- Interference.
- Licensing conditions.
Power output and coverage testing
A Site SurveyA Site Survey is an assessment of a location to determine whether a two-way radio system will provide the required coverage, reliability and performance. can help determine whether the proposed radio system provides sufficient coverage.
Testing can identify weak areas or Dead Spots before a system is deployed.
This allows engineers to determine whether the solution requires changes to:
- Radio power
- Antennas
- Radio frequency
- Repeater location
- NetworkA Network is a connected system of radios, equipment and infrastructure that allows users to communicate across a defined area. Radio networks can range from simple radio-to-radio systems to large multi-site networks. design
Power output limitations
Higher transmitter power cannot solve every coverage problem.
It cannot necessarily overcome:
- Physical obstructions
- Poor antenna positioning
- Severe interference
- Insufficient receiver sensitivity
- Network failures
- Incorrect frequency selection
For this reason, radio coverage should be approached as a complete system-design problem.
Power output and DCS
DCS can help determine the appropriate transmitter power and overall radio-system design for a particular application.
Rather than simply selecting the highest available power, we consider the required coverage, radio type, frequency, antenna, repeater requirements and applicable licensing conditions.
The aim is to provide reliable communication while keeping the radio system within its technical and regulatory limits.
