Repeater applications explained!

In its own right a repeater can be a useful tool to increase the operating range of your radio system. With its relatively high transmitting power & external antenna, a well-sited repeater will provide an excellent platform to boost signals beyond the range of non-repeater networks. Whether it is sited at the centre of your operating network or at a location prone to weak coverage, the repeater will instantaneously re-transmit received audio without any noticeable delay. This high power re-transmission improves your operating range as the original signal effectively gets a piggy back ride.

In addition to the basic advantages associated with a repeater, you can further enhance your radio network by personalising repeater operation to suit your requirements:-

Multi-User Groups/Community Base Station (CBS)
If you operate a large number of radios on your network, you may want to improve the efficiency of the system by splitting these radios into user groups i.e. managers, maintenance, catering, deliveries etc. Radios on the network can be programmed to communicate only within their own group or with certain other groups. Other groups will not hear communications not intended for them and thus can continue work without unnecessary distraction or delay.

Even if you do not operate a large system, why not share your repeater with other users in your area - delivery companies, taxi firms, security guards etc. could all benefit from such a system. You could sell radios to these users and quickly recoup your initial outlay or hire radios to have a regular monthly income. Clever management of the user groups would allow a higher volume of operators to be spread over a whole 24hr day without saturating the radio channel i.e. security guards at night, delivery firms early in the morning etc. Remember that as network owner/manager you still have complete control over the system and can add/remove clients or adjust operation to suit your changing requirements.

Telephone Interconnect
By adding a telephone interconnect or telephone patch (telepatch) to your repeater system you can allow authorised users to place and receive telephone calls to the PSTN or PABX - whichever is connected to the repeater. When not in telepatch mode the system acts as a conventional repeater, providing improved operating range for your radio users. To access telepatch mode, an authorised user will transmit an access code to the repeater, a valid code will trigger the repeater to transmit a dial tone over the radio channel. The user can then dial into the telephone system using the repeater as an interface. Upon connection of a successful call, the radio user assumes full control of the conversation - this is because the radio can only talk or listen, not both together (semi-duplex). To end a call, the radio can transmit the access code or wait for the system to time-out and return to repeater mode. If the repeater is called over the PSTN or PABX, it will transmit a ringing tone over the radio channel to indicate to the radio users that a telephone call is present. To answer the call, an authorised user simply needs to transmit the access code to be connected to the telephone caller.

Multi-User Groups or Community Base Station (CBS) with Telephone Interconnect
Combine the advantages of a repeater with multi-user group system and telephone access - the best of both systems.

Trunking System
A Trunking system is a more advanced radio network, typically for much larger or high-usage operators and basically comprises of a number of repeaters interfaced together at a single site, although multiple sites are also possible. Trunking systems are inherently more expensive but they do offer far more flexibility over a conventional repeater system. The limitations of a conventional repeater system are that they use a single radio channel which when busy can not be used by other radios, who subsequently have to wait for the channel to become free. It is therefore essential that such systems maintain a strict operating procedure to ensure conversations are kept as short as possible to free up the radio channel for other users. A trunked radio system overcomes this problem by having multiple channels available for use simultaneously - if a channel is busy the system will switch to another. While there are many trunking networks available, a widely used common system is offered under the MPT 1327 protocol - this is an operating procedure that allows any MPT 1327 equipment to integrate together regardless of the manufacturer.

Individual calls (group calls are also possible) made on a trunking system are fully private i.e. only the caller & callee will hear the conversation. This is also true for trunking networks which have a telephone interface fitted - a popular option, sometimes even standard equipment. Trunking sites can also be linked together to allow inter-site or roaming communications - typically these links are either via conventional telephone line or microwave link.

26/05/2004