PMR446

- summary, overview or tutorial about the basics of PMR446, the PMR446 frequencies and channels used, PMR 446 range expected and the PMR446 walkie talkie.

PMR446, (Personal Mobile Radio, 446 MHz) is a license free radio communications system, that is available for use in most countries of the European Union. It is aimed at enabling the provision of a basic but effective radio communications service for both business and non business users. It is ideal for providing fixed, portable or mobile radio communications over short distances; such as within office buildings, factories and building sites.

There are a few overall limitations to the PMR446 service:

• The radio communications equipment must be hand-portable



• Only speech transmissions are allowed.

PMR446 range

One particularly important factor of PMR466 for the users is the achievable range. This cannot be specified because it is dependent upon many factors including the height, antenna, location and local terrain, transmitter power, obstructions in the signal path, etc.. With the antenna size being limited and the transmitter maximum power level set, the PMR466 range is not likely to extend too far. Typically the PMR466 range may be anywhere from a few kilometres if both walkie-talkies are located on hilltops in sight of each other, or it may be as little as a hundred metres if there are obstructions in the way, e.g. if there are buildings in the way, or the PMR466 equipment is being used within a building.

PMR446 frequencies

There is a total of eight PMR466 channels or PMR466 frequencies that can be used. These are spaced 12.5kHz apart from each other. As the name of the system suggests, the PMR446 frequencies are in the UHF portion of the radio spectrum and located around 446 MHz.

PMR466 Channel	Frequency (MHz)
1	446.00625
2	446.01875
3	446.03125
4	446.04375
5	446.05625
6	446.06875
7	446.08125
8	446.09375

PMR446 frequencies and channels

PMR446 technical specification

The idea of PMR446 is that the radio communications equipment should be easy to use by all people. There are very few regulations that must be known by the users, instead the equipment must be designed and built to meet the required regulations. Essentially the PMR 446 radio communications equipment must be hand-portable. It must have an integral antenna and the maximum power transmitted must be within 500 mW ERP. The full definition for the PMR446 equipment is contained within ETS 300 296 to which the equipment must be compliant.

Although the idea of PMR446 is to enable straightforward radio communications devices to be used license free by untrained users, there are a number of facilities in addition to the basic transmit and receive functions that are allowed. Privacy measures including speech inversion are permitted with PMR 446 radios. In addition to this the inclusion of broadcast (AM/FM) radio receivers in PMR446 radios is allowed where there is no provision for the received broadcast signal to be re-transmitted on the PMR 446 radio frequencies.

A variety of accessories can be used with PMR 446 radios:

1. External microphones including VOX type microphones



2. Earphones, headphones and external loudspeakers; and



3. DC power sockets, charge sockets and battery packs.

These accessories can be used provided that they are connected using appropriate sockets installed by the manufacturer at the time of manufacture and conformance evaluation. The use of these accessories must not affect the RF characteristics of the radios. In all cases, the use of these facilities must not cause any change to, or effect on, the performance characteristics of the PMR 446 radio, as permitted under the Wireless Telegraphy (Exemption) Regulations (SI 1999/930).

it is also not allowed for PMR446 radios to be connected to the Public Switched Telephone Network (PSTN) or other telephone networks.

Summary

PMR446 radio equipment is widely available, and for a very low cost. This makes it ideal for a variety of short range radio communications applications. Not only can PMR 446 be used for business, but it is also open for domestic or non-commercial use as well.