• Known radio communication problems exist in metal and multi-layered structures
Rockford police and fire union representatives and administrators agree their radio communication system improved significantly during the past two years. However, more improvements in the form of mobile repeater units may be installed to bring the system closer to its potential, which is limited by laws of physics and economic reality.
Doug Block, union president of Rockford Unit 6 of the Policemens Benevolent and Protective Association of Illinois, said of Rockfords police radio system: Its an issue thats really behind us, and that if there are current radio communication problems, they havent been brought to Blocks attention.
Questions about the effectiveness of the Rockford Police Departments radio system were raised by Alderman Dave Johnson (R-4) several years ago and again last summer, after Johnsons son, former Rockford Police Officer Steve Johnson, was called before the Rockford Police and Fire Commission for a hearing.
The bizarre circumstances regarding Steve Johnsons hearing and his eventual termination from the police department were described in detail in The Rock River Times July 2, Aug. 27, 2003, and Jan. 24, 2004, articles. The legality of Steve Johnsons firing is being challenged in court.
Radio coverage and limitations
Block said the radio system improved from 80 percent coverage a few years ago to between 90 to 95 percent coverage, as a result of Rockford aldermens efforts that called attention to radio communication problems. Block and Rockford Fire Department Chief Bill Robertson said the improvements may be attributed to installation of a new antennae tower on Newburg Road in 2002, installation of at least six repeater stations, and directional adjustments to antennae.
Tom Eckels, professional engineer and vice president of Seattle-based Hatfield and Dawson Consulting Engineers, said 90 to 95 percent coverage for public safety radio systems is about all that is physically and economically possible for any municipality, whatever frequency is used for signal transmissions.
Eckels added that because of the nature of radio waves, which are described by statistical mechanics, 100 percent coverage in an area is not realistically achievable. Rockfords 90 to 95 percent coverage means that in any area, at any time, within the sector of coverage, there is a 5 to 10 percent chance that an emergency transmission will not be received. For comparison, Eckels said most cellular phone transmissions achieve 80 percent coverage in their areas.
To increase the probability an emergency signal will be heard despite physical limitations, a message often needs only to be repeated to be received. However, the same remedy is not possible in areas that are known as dead zones, which are described later in this article.
Repeaters and buildings
Eckels explained that repeater units convert weaker radio signals into stronger signals, which may be more easily received.
Peter Roy, deputy chief technology officer for Washington, D.C., said the District addressed its radio communication problems by installing mobile repeater units on police and fire vehicles for a fraction of the cost of installing new antennae towers.
Roy said public safety radio systems with higher frequencies that operate near the cellular phone frequency band cost millions to tens of millions of dollars. However, Roy said using lower frequency transmissions in combination with repeater units may solve a municipalitys radio communication problems for thousands instead of millions of dollars.
Roy said the Districts radio communication difficulties were primarily from inside multi-walled and multi-floored buildings, and thick-walled structures, where portable, 5-Watt radios were trying to communicate with mobile, 30-Watt radios and macro radio units.
Robertson and Block said Rockford uses a similar radio system. However, Rockfords radio system operates on a much lower frequency than D.C.s.
Roy said their radio system improvements have worked well, and he encouraged Rockford and other public safety officials to contact him for further information. Robertson said his department is looking into the use of mobile repeater units, and indicated he was interested in contacting Roy.
Robertson added that the fire department does not use mobile repeater units. According to Block, Rockford police decided not to use mobile repeater units due to the potential of one channel frequency overpowering another at a scene, which could increase communication problems.
Nearly all public safety radio transmissions are broadcast in the 150, 450 or 800 megaHertz (MHz, or millions of cycles per second) frequency range. Analog cellular phones operate between 869 to 893 MHz and are suspected of interfering with public safety signals that operate in the 800 MHz range, according to Roy and Eckels.
Many municipalities, such as Madison, Seattle, Kansas City, Denver, Hawaii and Washington, D.C., recently moved from the 150 and 450 MHz frequency range to the 800 MHz band because of the availability of more communication channels and greater ability for signals to penetrate buildings.
The 150 and 450 MHz radio systems are not affected by cellular phone transmissions.
According to Roy, eventually many municipalities plan to use the 700 MHz (ultra-high frequency band or UHF), after the band is vacated by television broadcasters when they change from analog to digital transmissions. Roy said the 700 MHz band provides not only greater channel availability, but the possibility to simultaneously transmit audio and video information.
Rockford police transmit on two channels at 155.565 and 155.625 MHz. Rockford fire officials also transmit on two channels, at 154.235 and 154.19 MHz. In response to increased demand, Robertson said the fire department will begin using a third channel within the next year.
Typically, public safety radio transmissions are made between macro, mobile and portable units. However, in some areas, commonly referred to as dead zones, transmissions are difficult or impossible. The dead zones are unlike the random areas where the probability to hear a transmission is due to the nature of wave mechanics, according to Eckels.
Eckels said dead zones are usually stationary, and are more common in areas of rolling terrain. Block said he has not been notified of any significant police radio transmission problems since the new system was installed, but said he had transmission difficulties at Valley View Apartments, which is a 13-floor, 120-foot high-rise located in a valley at 3303 E. State St.
Rockford firefighters, who wished to remain anonymous, said they have problems transmitting signals from their portable units inside hospitals to the downtown dispatchers macro unit.
Tony Camella, Rockford firefighters union president, said there were transmission problems inside structures before the new system was enacted. However, Camella said: We think the system is satisfactory at this time. Camella referred other questions to Robertson.
Block and Robertson said transmission problems have been reported in metal buildings. However, neither report any significant complaints since the new radio system was activated in 2002.
Sept. 11 attacks
The New York Times reported in a November 9, 2002, article about the September 2001 terrorist attacks: New York City said the devastating breakdown in fire communications at the World Trade Center was largely caused by the failure of an electronic device in the complex called a repeater.
According to the article, the most stinging of all questions about fire operations that day was even though the north tower stood 29 minutes longer than the south tower, at least 121 firefighters did not escape from it. While chiefs in the north tower lobby issued orders to come down, they received no response. …
Witnesses said that scores of firefighters, unaware of the peril, were resting on the 19th floor of the nort
h tower during its final minutes, the article reads.
The Associated Press later reported the repeater system on top of 5 World Trade Center was taken out by falling debris, a problem that may have been averted had mobile repeater units or other types of repeaters been utilized.
At the time of the attacks, the Fire Department of New York (FDNY) in Manhattan used a dispatch frequency of 154.010 MHz, and a portable unit frequency that operated at 153.830 MHz. Manhattan police used frequencies between 453- to 477-MHz. The percent coverage for the area that was under attack is not known.
A report issued by the FDNY suggests New York should test and deploy portable, mobile or air-based repeaters, which mitigate communications difficulties in high rises. The report also suggests New York accelerate testing and deploying 700 MHz/UHF radio units.
Good for now
Several dozen buildings with more than 10 floors dot the Rockford area landscape. However, none of those structures has more than 20 floors. When questioned about high-rise communications, metal buildings, and multi-layered structures, Robertson summarized Rockfords radio system by saying: The whole communication system is probably as good as we can make it right now, and added that the fire department is diligent about addressing problems and conducting tests.
Block said prior to several Rockford aldermens efforts to improve Rockfords public safety radio system, there were no west-side repeater systems. However, thanks to their efforts, Block said there are now six repeater units on the west side and six on the east side. Block said the police departments goal is to install 24 repeater systems12 on the west and 12 on the east side of the Rock River.
Eckels emphasized that there will always be areas that will not be adequately covered, and every municipalitys public-safety radio system needs are unique. As a result, Eckels said it is nearly impossible to easily determine solutions to a radio systems deficiencies unless each system is assessed individually.