RFM Underground Radio System - GAI-Tronics - #1

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GAI-Tronics Mining R.F.M. Underground Radio System • VHF high band (151- 173MHz) • Multi channel • 25km of cover • Telephone interconnect • Speech, signalling and data • Intrinsically safe • 40 years of experience The RFM underground radio system is designed to enable VHF radio frequencies to be transmitted and received in underground roadways and tunnels up to 25 km in length. The age-old problem of strata absorption has been overcome by using a radiating cable with 2 way repeater amplifiers at 500 metre intervals. The system comprises a Base Station, Radiating Cable (Leaky Feeder), in line Repeater amplifiers, Passive Splitters, Terminators and mobile radio transceivers. Various interconnect facilities are offered to enable integration to other radio systems and other types of communication systems. With the RFM system, GAI-Tronics has taken the opportunity of using standard off the shelf pocket phones for intrinsically safe and non-intrinsically safe applications. A rugged, robust loudspeaking transceiver, Transcom, is offered for mounting on mobile vehicles such as locomotives, free steered vehicles or rope driven haulages. The Repeaters are powered from the base station and additional power is only needed for complex long distance systems. Interface circuitry is offered to allow radio telephones to be used and connection to other types of communication systems for loudspeaking Public Address. BASE STATION A variety of Base Stations are offered to suit individual customer applications. The Base Station houses the necessary transmitters, receivers and other interface circuitry. Power for the Repeater amplifiers is supplied from the Base Station via the radiating cable. RADIATING CABLE The cable is of co-axial construction specially designed to allow signals to radiate and allow signals to be accepted from portable radios anywhere along its length. REPEATERS The Repeater circuitry is the heart of the system. This design ensures the signal strength to is consistent throughout the whole network. The repeater acts as a two way amplifier simultaneously capable of handling multiple channels. These would normally be spaced at 500 metre intervals. PASSIVE SPLITTER Because most underground complexes are made up of many tunnels, it is necessary to be able to split the system at roadway junctions. The passive splitter allows this to happen without significant loss of signal strength.