Now that you have completed all of the engineering and have installed the system, the next area that you must look at is maintenance — both short- and long-term. This article details some of the items that you must consider as you plot your maintenance strategy. Let’s start with site maintenance.

There are other items beyond the site equipment that you will have to maintain. These items include the tower, tower-lighting system (if one is required), building, fence, generator or uninterruptible power system, access gate, and roads.

One always can tell a tower that hasn’t been maintained. It is rusty, has overgrown vegetation at the base or lights that do not work. It will be the one that eventually crashes to the ground — or is already on the ground rather than standing tall into the air.

As a structure made of steel, the tower’s biggest enemy is rust. The tower should have been hot-dip galvanized, but the galvanization coat can be broken and rust can take hold in the area where this occurs. Painting the tower with rust-resistant paint helps to eliminate this threat.

Because you cannot transport a full-size tower using a truck or railroad car, almost all towers are made in sections, and these sections are bolted together once they are at the tower site. Bolts come loose over time, so a periodic inspection — at least one or two times a year — will ensure that the nuts and bolts remain tight. You must use the required calibrated torque wrenches when tightening nuts. If the tower is guyed, you also are required to measure the tensile pull strength of the guy wires — each and every one. In addition, a tower can be weakened if one or more of the guy wires are too tight, which causes one or more of the sections to not be exactly vertical.

The requirement to light or paint a tower generally falls into one of two categories. If the tower is taller than 200 feet, then it must be painted or illuminated. If the tower is under 200 feet, but within 20,000 feet of an airport, then it also must be illuminated. If you do not have strobe lights for daytime operation, then you will need to paint your tower whenever the white or international orange colors fade. There are color charts available that detail the limits of the fading.

If your tower does need lighting, you are required to inspect the tower daily to confirm that the lights are working properly. This can be done by a person who makes a visual inspection of the tower sometime after sunset, or by electronic sensors that will initiate an alarm sequence if a tower light or strobe does not work as designed. FCC rules [47CFR Part 17.47(b)] require that automatic monitoring systems be inspected every three months to ensure that the system is working properly and that an inspection/maintenance log be kept. In addition, if the tower lights are not working correctly, the Federal Aviation Administration must be notified and a log must be kept of the notification and the subsequent repair.

Buildings require maintenance, just as towers do. If you neglect the building, eventually it will not be safe to enter for several reasons. The items that require attention include: doors, alarms, air conditioners and heating units, insects and other vermin, and vegetation overgrowth.

The doors provide security to keep thieves and other predators out of the building. As the building ages, the weather stripping eventually will dry out and allow insects, rodents and snakes to get into the building. These vermin can cause damage to the equipment and to anybody who visits the building. Examples include: wasp and bee stings, centipedes and scorpions, mice and rats — which carry diseases and whose bodily fluids can destroy equipment — and poisonous snakes that can cause lethal injuries to unsuspecting technicians who visit the sites.

Alarms can notify the operations personnel of problems with the equipment, the temperature of the building and equipment, the opening of the door by unauthorized people, tower lighting problems, and anything else that requires remote notification of an event or status.

While heating and air conditioning is nice for your personnel, it is essential for the equipment, as the microprocessors and solid-state components must be kept at a constant temperature. Just as in your homes, system filters occasionally must be cleaned or replaced, and the coolant in the air conditioners eventually will need to be recharged.

It is vital that you clear any vegetation that is close to the building. The only way to even have a chance that your building will still be standing and operating in the aftermath of a forest or range fire is to make sure that there is NO vegetation near the building.

Now let’s examine the site’s power needs. The primary power that feeds a site normally is very reliable, but lightning is its worst enemy. Ironically, when commercial power is lost, that is when the radios that operate on the system are needed the most. So, most sites use a combination of batteries and generators to provide backup power to the site.

Batteries will provide uninterrupted operation of the equipment when the primary power is lost. Some equipment can be operated directly from the DC voltage of the batteries, but other equipment only works with 120 VAC, so a UPS inverter is required.

Because the batteries eventually run out of juice, a means must be in place to replace the primary power relatively quickly once a failure occurs. A generator will perform this function for most sites. The generator will run as long as the fuel for that generator is available. Keep in mind that the generator’s fuel capacity and type of fuel must match the environment and also the availability of that fuel for your geographical area.

All generators must be sized for the site. For instance, if your equipment requires 20 kilowatts of power, a 5-kW generator will burn up in just a few seconds. Besides protecting the equipment, many sites will need the air conditioner to remain operational during an extended power failure. In addition, if you have a lighting system, be sure to have enough reserve power capacity for the lights and any test equipment or peripheral equipment that might be at the site.

The transfer panel is the device that switches the building between the commercial power and the generator. Some transfer panels must be manually switched by an operator or technician at the site, while other transfer panels can sense that the main AC commercial power has been lost. In the latter instance, the generator automatically is started; once the voltage is stabilized, which usually occurs within 5 to 10 seconds, then the power for the building is transferred to the generator.

With many of transfer panels, the generator will be kept running and online until the sensor has determined that a minimum of two minutes of stable commercial power is available again. At that point the site will be transferred back to the commercial power and the generator will be commanded to turn itself off. Many of the newer transfer panels can be scheduled to provide a daily, weekly or monthly test of the generator, or transfer power to the generator for a programmed length of time.

Fences are used to keep people and livestock away from your building and off your tower. The tower owner is liable if someone easily can walk up to the tower, climb it and then fall off. A cheaply made fence easily can be destroyed by a cow or horse. Under normal circumstances, you do not need razor wire or barbed wire on your fence, but if trespassers are a problem, then you might need to add them.

Fence gates should be wide enough to accommodate people and equipment. The mechanism can be as simple as a single lock or a chain with cascaded locks so that each tenant of a shared site can have their own lock. In addition, the power utility company usually prefers to have its own lock. The chain should be heavy enough to keep someone from going to their local hardware store and buying bolt cutters that easily can cut the chain.

If you operate your radio system in the United States and your tower is more than 200 feet tall, or is required to be illuminated because it is in close proximity to an airport, you are required to register your tower with both the FAA and FCC. As part of your registration, you will be assigned an Antenna Structure Registration number, which must be able to be read from the street where your tower is located. Many tower owners also put a sign directly on the tower, near the base.

If there is more than 1,000 watts of aggregate power from the transmitters on the tower, and at least one of the antennas is less than 10 meters (about 33 feet) above ground level, then you also are required to do an RF safety study and post the appropriate signage for the amount of radiation that exists at ground level. Most tower owners will post a blue sign to indicate an RF-radiation hazard, and a yellow sign to caution of a potential hazard.

If your site is on a building rooftop and the aggregate power exceeds 1,000 watts, then you are required to follow the FCC Office of Engineering Technology Bulletin OET 65, which details what areas must have signs, locks and access restrictions. Severe fines can be meted out for failure to meet these requirements. Even amateur radio and U.S. military sites operating are not exempt from these RF safety rules and regulations. This subject is taken seriously by the FCC and OSHA.

There are many sites that cannot be accessed during part of the year due to climate issues that render roads impassable. Remember that in the U.S., the licensee always is responsible for having positive control of any transmitter; consequently, you must have a means to disable an errant transmitter at any time, regardless of conditions.

In terms of what is required to maintain the equipment over its lifespan, documentation is at the top of the list. In most systems, the following documents are needed:

  • As-built wiring diagram
  • System-level diagrams
  • Maintenance procedures
  • Special notes for the particular site

By having good documentation at the site, any competent engineer or technician can perform any repairs or maintenance procedures. Be sure to protect the documents from potential damage from water leaking in the building or any vermin such as ants, rats, snakes or thieves.

As LMR systems have become more sophisticated, with complex features and modulation schemes, it has become almost impossible to properly maintain such systems without advanced training. Unfortunately, many trade schools, military schools and junior colleges do not adequately prepare their graduates for properly maintaining the equipment that is being deployed today. For this reason, the manufacturers almost always provide training on their equipment that covers the following areas:

  • System block diagrams
  • Equipment programming
  • Level-setting procedures
  • Ongoing maintenance items

Once the system has been accepted, is placed into service and is working to the satisfaction of all involved, maintenance is what keeps the system operating as it was conceived, engineered and installed. A system that is not properly maintained eventually will have problems develop — and eventually will quit working.

Nearly every manufacturer publishes a list of recommended test equipment. While such equipment is essential for system maintenance, it will be ineffective unless it is kept in good calibration. Just because your test set gives you a value on the meter or instrument does not mean that it is correct. Indeed, some of the test sets are so complicated that you will need to be trained on them just to operate the controls.

Ed: This is the final installment of our series on land-mobile radio. We will be publishing articles from Ira Wiesenfeld and Bob Shapiro on other topics in future issues of Urgent Communications. We welcome your feedback on these articles and also your suggestions on future topics. Please send them to Ira and Bob at the e-mail addresses below.

Part 1: Class is in session: Basic LMR and FCC definitions
Part 2: Start at the beginning: Understanding LMR user needs
Part 3: The devil's in the details: Conducting a user-needs survey
Part 4: Decisions, decisions: Understanding the LRM procurement process
Part 5: Let's get started: System engineering begins with RF planning
Part 6: The lynchpin: Receiver planning and noise interference
Part 7: Connecting the dots: How to connect LMR sites
Part 8: The next piece of the puzzle: Understanding dispatch communications
Part 9: Now the real work begins: How to select a suitable LMR site
Part 10: The bane of your existence: How to deal with RF interference
Part 11: Winning the battle: More causes of RF interference
Part 12: Now the fun begins: Installing the LMR system
Part 13: Dotting Is and crossing Ts: Choosing the LMR project, program managers

Ira Wiesenfeld, P.E., is a consulting engineer who has been involved in the radio communications business since 1966. He is a senior member of the IEEE and has been a licensed amateur radio operator since 1963. He can be reached at iwiesenfel@aol.com.

Robert C. Shapiro, P.E, is the senior manager-systems engineering for Cassidian Communications, an EADS Company. He serves on the TIA TR8 committee as TR8.18 vice chair and is a senior member of the IEEE. He can be reached at bob.shapiro@eads.com.