When the city of Miramar, Fla., decided to implement an information-based system to communicate to residents, they began investigating radio frequencies to broadcast their messages. They were aware of another local community that used highway advisory radio (HAR) to broadcast messages about city events as well as parks and recreational activities. The challenge for the city of Miramar, however, was to find a system that could broadcast messages throughout the entire city, not just in a localized area such as a park or only one section of the city.
The answer? Miramar is using an AM transmitter with advanced GPS technology to communicate messages to its residents from Highway Advisory Radio Inc., (HIS) Durham, N.C., whose system utilizes an AM radio frequency to broadcast messages to motorists, residents or event attendees. The messages typically cover a 4- to 6-mile radius and are often used for safety information, local points of interest, public events, construction zones or frequently congested traffic areas. The city of Miramar researched their options for radio stations (AM and FM) as well as a system that would synchronize their messages throughout the city. During the city of Miramar’s research, they came across HIS, a Quixote Transportation Technologies company that provides HAR systems.
The GPS-synchronized system provided by HIS allowed the city of Miramar to have seamless broadcast coverage throughout the city with no interference between the overlapping signals. The city of Miramar is about 13 to 14 miles long, but only about 2 miles wide. They initially purchased two stationary HAR systems and shortly thereafter added a third system to complete their coverage.
All three stationary HAR systems are linked together using GPS technology. HAR systems using GPS acquire a signal from three or more satellites to provide a highly accurate time source, which is used as a reference point. Using the GPS signal allows the frequencies from multiple transmitters to be synchronized and kept phase-locked indefinitely. The audio is then synchronized using the same GPS signal, so all the radio stations in the array can launch their messages within 1 millisecond of each other. There is no limit to the number of transmitters that could be used in this system. By having a decentralized system such as this, communications costs are minimal. Using a GPS-synchronized array of HARs to cover a large area seamlessly also provides for scalability. As demand for coverage increases, additional transmitters can be added to the array to increase coverage.
The city of Miramar placed the HAR systems at each end of the city as well as one system in the middle. The broadcast coverage is clear from one end of the city to the other, and the same message is heard by residents across the city. The residents and motorists in effect hear one signal covering their entire city.
The city of Miramar uses the GPS-synchronized HAR system to inform residents about upcoming events, parks and recreation activities, announcements about traffic and general safety messages. They even used the system during Hurricane Katrina when it passed over Florida. The city changes the messages as regular events change, and they keep a library of safety messages and rotate them as well.
“The system is definitely a value for the city of Miramar and its residents,” reported Tom Good, administration officer for the city of Miramar. “Miramar is one of the top three fastest-growing cities in Florida and has quickly gone from a small, sleepy town to a mature city.”
The GPS system is still in its infancy for the city of Miramar, and it plans to expand use of the product by working with the fire department to broadcast messages about fire prevention and has even considered using the frequency for elected officials to communicate city-related messages.
