PMR446 Two Way Radios - Are They Effective?

LICENCE EXEMPT (PMR446) radios.

These "inexpensive" radios are often seen as a cost effective solution to all radio communications needs.

Unfortunately, they are not all they seem. A large number of these systems are replaced, due to inadequate performance.

We call them "Argos specials!"

The advertising claims for these units can be quite misleading.

"Up to 3 miles range." Means just what it says... It MIGHT work 3 miles! (Probably downhill, with a back-wind.)

Additionally, even within the PMR446 market there are both "toys" and "professional" grade equipment.

The specifications allow for a transmit power of 500mW (1/2 Watt). However. equipment can be produced more cheaply with a much lower rated transmit power, which are invariably the "toys" which can be purchased very cheaply on the High Street.

Time for a little history:

In 1997 Europe decided on a section of the 446MHz frequency band to be used for a new licence exempt short range radio communication system. The UK introduced the PMR446 service in early 1999, so PMR446 is quite a mature, reliable system.

The distance covered, or range, of any radio depends on a number of factors. Obstructions such as buildings will restrict range, whereas in open areas range will increase. The height of radios above the surrounding terrain will also improve performance.

Range could also normally be improved by increasing transmit power or fitting a higher performance antenna, but with PMR446 equipment these options are prohibited, in order to comply with the PMR446 regulations. Remember this system was intended to be "short range".

Range can extend many kilometers between high vantage points, or be limited to only a few meters or a few hundred meters, if a hill or large building is between radio units.

There are eight channels available, with a number of signalling options, so you don't hear other users who are sharing your selected channel.

Note: the other users are still there, and you will cause interference to each other if you transmit at the same time. Your radio is just kept quiet whilst you aren't in conversation.

Strangely, when thought about in this way, the extra signalling is only in use while the radio is not being used.

The bottom line with PMR446 is that it can be perfectly adequate for strictly short range, non-critical applications.

The most usable areas for PMR446 tend to be outside large conurbations, where the available 8 channels can get quite congested.