In theory, in identical conditions, the narrower channel width of a 6.25kHz FDMA system would allow a signal to achieve better coverage than a 12.5kHz TDMA (or FDMA) system when transmitted at the same output power. This is because the noise floor of any receiver is proportional to the filter bandwidth. Therefore, the smaller the bandwidth, the smaller the signals that can be received.

In real world use, various factors such as topography, antenna height of base stations, fixed structures and surrounding buildings all affect coverage whether you are transmitting in UHF or VHF, so without specific comparison tests, neither system can claim to provide better coverage than the other. What can be said is that a digital signal will comfortably out-perform an analogue signal at the extremes of the communication range; providing clearer, more reliable audio over a greater total area, even if the coverage footprint is the same as analogue.

It should be noted that all equipment for use on PMR446 frequencies, whether analogue or digital (dPMR and DMR 446), is generally required to be in hand portable form, feature a fixed integral antenna and operate with an effective radiated power not exceeding 500mW (0.5 watts), while the use of range extending repeaters, IP gateways or more powerful base stations and mobile radios is specifically excluded. Licensed two-way radio formats such as those certified for dPMR Modes 1, 2 and 3 are not subject to the same restrictions, for example a dPMR hand-portable would typically have a maximum output of 5 watts while a mobile unit would have a maximum output of 25 watts, so coverage will be largely dictated by line of sight factors, system infrastructure and the type of license granted to the user by its national licensing authority or telecommunications regulatory body.

But don’t let all these variables confuse you, the question of coverage is usually less complicated than it first appears, and if you would like to discuss your specific coverage requirements for a dPMR system, please get in touch with us.

Coverage Profile