More radio subsystems
Emergency power
All radio sites, including control points and dispatch centers, require power to operate, so power must be present 100% of the time. Primary power can be interrupted by lightning strikes and other forces of nature, vandalism at the site, automobile accidents, power transmission-line failures, sabotage of the power grid or operator error at the power company. Because most networks cannot tolerate a complete loss of power, they need one of the following emergency power systems:
- Fuel-powered generators
- Battery-operated, uninterruptible power systems
- Fuel cells
- Hydro-electric generators
- Solar-power systems
When selecting a backup power system, be certain that the voltage and current rating match the load from all aspects of the site. Many sites now require backup power for the radio equipment, lighting and the air conditioning that prevents equipment from overheating.
Transfer switches allow backup power to replace primary power without operator intervention, and they can be programmed to test the backup system at regular intervals, such as weekly or monthly. Transfer switches also sense when the primary power is restored and is stable, so the building load can be returned to the primary power source.
Besides the voltage and current ratings of the UPS, generator, or fuel cell, it is important to determine how long the backup system will last in the event of a primary power outage.
Environmental systems
A site requires protection from heat, humidity, lightning, and fire, as well as bugs and other creatures that sting and bite technicians, and destroy equipment. The following items should be considered when contemplating environmental protection systems.
- Air conditioning must be capable of keeping the equipment from being destroyed or malfunctioning due to high temperatures. If the site is staffed by personnel, then workers' comfort must be considered.
- If the interior temperature is too low, then heating must be part of the environmental system.
- Static electricity can damage the circuitry at a site when the humidity is too low, if a worker accidently touches the equipment at the wrong time. Ensure that the humidity inside of the site is controlled to eliminate static electricity.
- Lighting inside and outside of the site is integral and must be included in the site specifications.
- Fire protection is required for most buildings, and local codes will dictate the requirements for a fire-protection system. If electrical equipment and people are at the same site, the system must protect both. In most cases, water will destroy the electronic and electrical systems. FE-30-rated fire extinguishers can be used safely at most sites. Class C extinguishers are designed to suppress fires in electrical equipment when non-conducting agents must be used.
- At many sites, bugs, mice, wasps, snakes and other varmints can hurt personnel and equipment, so buildings must be sealed to keep these pests out of the building.
- A second type of varmint is the two-legged kind — humans — and some will steal or destroy system components and hurt personnel, if given the chance. Alarm, motion-detection and video-surveillance systems will help prevent such situations. In addition, armed guards and personnel may be needed when technicians and operators are at remote locations — especially when a radio system is in a national forest, where local law enforcement does not have jurisdiction.
Connectivity
Most large radio systems have a central control point — where the main switching controller for the system is located — and remote sites scattered throughout the region that the system covers. The systems that tie the remote sites to the central site are called the connectivity of the system. For the system to operate properly, sufficient bandwidth is needed for the central site to communicate to all remotes sites simultaneously.
In the past, systems used copper telephone lines to link remote sites to the central control site. As system bandwidths have increased, copper pairs no longer provide the connectivity that the new systems require.
Some sites use radio linking to achieve connectivity between the sites and the central controller, but bandwidth may be limited. A multiplexed microwave system provides higher bandwidth, but there are many limitations when using microwave connectivity. Fiber-optic systems have tremendous bandwidth, but it is very expensive to get fiber to the various sites, if it is not already present. In all cases, the reliability of the backhaul connectivity must be the most important parameter of the backhaul system.
Maintenance and contracts
Complex systems made up of many components require regular maintenance, and a radio system is no different. A system that is working perfectly can become useless in a heartbeat when a critical part fails. The resulting communications failure can place lives in jeopardy.
Some entities have enough maintenance work to maintain a dedicated radio shop, while others find that it is more economical to outsource such work to a company that specializes in radio system maintenance.
For organizations that outsource radio maintenance, there are two ways to set up the service.
Under the time-and-materials arrangement, the radio-service company charges a fee for the labor, plus an additional fee for the materials used during a service call.
Under the contract method, the service company charges a flat monthly rate for its work, and parts are covered at a rate that is negotiated as part of the contract.
In either situation, if the radio system is critical for the entity's operations, there should be spare parts on hand, so there is minimal downtime in the event of equipment failure. If a system requires 24/7 support, expect to pay a premium charge for this, or for after-hours, on-site support.
Many service companies offer the following three-tier level of support:
- Level 1 – Swap out units and send inoperable units back to the repair depot.
- Level 2 – Bring in a local service company that troubleshoots the problem.
- Level 3 – Bring in an expert for problems that most technicians rarely see. This is often a factory field engineer, consulting engineer, or a specialist in resolving the specific problem.
Conclusion
A radio system consists of many piece parts that go far beyond the basics of the towers, antennas and base stations. The ability to properly specify subsystems — so that they work in harmony with the overall system parameters established by the system designer — is of such importance that it cannot be overstated.