Registered
Charity Number: 1008250
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Patron: Lord Montagu
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The EquipmentPrivate Mobile Radios (P.M.R.'s) are two-way radio sets that allow operators to communicate over relatively long distances, efficiently, cheaply, and privately. Before you can use a P.M.R. you must have the correct equipment set up. This consists of:
Radio SetThe radio set is basically the box that sits in the middle, with the rest of the items listed below connected to it. This is the bit that does all the work. It's job is to take sound signals from the microphone and transmit them over radio waves, and to receive radio waves and send them as sound signals to the speaker. There are basically three categories of Radio Set, these being Base Station, Mobile, and Hand-Held (HH). They all work in exactly the same way, the only differences are size and performance. Base StationBase Station radio sets tend to be physically bigger than mobiles and HH sets. There are two reasons for this. Firstly, they are designed to plug into a mains power supply, and therefore need to have a transformer inside them to convert the 240 volt AC mains supply to 12 volt DC. Secondly, as a rule it costs more to make things small, and if the radio is going on top of a desk in an office instead of under the dash of car it doesn't matter if it's a bit bigger. Base Station sets tend to have base station antenna's too, and because of this their performance is usually better than that of mobiles and HH sets.
MobilesMobile sets are very similar to base stations, but being design to be installed in vehicles they tend to be smaller. They are designed to be run from a car battery, and therefore do not need a transformer. If you wish to run a mobile set in a base station environment, you can buy a power transformer (power pack) to allow you to run the set from the mains (see the note above about the license). Hand-HeldHand-Held (HH) sets are quite a different type of set. These sets are designed to be as small and light as possible, and to be totally self-contained. To do this, the microphone, antenna, and a battery pack are all built into the case of the unit. Their purpose is to allow the operator to be totally free to move around. Because of the restrictions on the size, weight and power, HH sets tend to have a lower transmission strength (the stronger the transmission the more the power drain) and therefore a shorter operating range. Also, because they use internal battery packs they have a shorter operating time (1 car battery will last for days, whereas battery packs only last a few hours each). Because they are free to move around, but have limited range and operating time, HH sets are better suited to small local events such as county shows, rather that more disperse events such as marathons.
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