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Potential Spectrum Interference Associated with Military Land Mobile Radios.



GAO-06-172R December 1, 2005

To address homeland defense needs and comply with government direction that agencies use the electromagnetic spectrum more efficiently, the Department of Defense (DOD (1) (Dial On Demand) A feature that allows a device to automatically dial a telephone number. For example, an ISDN router with dial on demand will automatically dial up the ISP when it senses IP traffic destined for the Internet. ) is deploying new Land Mobile Radios to military installations across the country. The new Land Mobile Radios operate in the same frequency range--380 Megahertz One million cycles per second. See MHz.

MegaHertz - (MHz) Millions of cycles per second. The unit of frequency used to measure the clock rate of modern digital logic, including microprocessors.
 (MHz) to 399.9 MHz--as many unlicensed low-powered garage door openers, which have operated in this range for years. While DOD has been the authorized user of this spectrum range for several decades, their use of Land Mobile Radios between 380 MHz and 399.9 MHz is relatively new. With DOD's deployment of the new radios and increased use of the 380 MHz-399.9 MHz range of spectrum, some users of garage door openers have experienced varying levels of inoperability that has been attributed to interference caused by the new radios. Nevertheless, because garage door openers operate as unlicensed devices, they must accept any interference from authorized spectrum users. This requirement stems from Part 15 of the Federal Communications Commission Federal Communications Commission (FCC), independent executive agency of the U.S. government established in 1934 to regulate interstate and foreign communications in the public interest.  (FCC (1) (Federal Communications Commission, Washington, DC, www.fcc.gov) The U.S. government agency that regulates interstate and international communications including wire, cable, radio, TV and satellite. The FCC was created under the U.S. ) regulations. Garage door openers and other unlicensed devices are often referred to as "Part 15 devices." Congress requested that GAO review the potential spectrum interference caused by DOD's recent deployment of Land Mobile Radios. Specifically, Congress asked us to (1) determine the extent of the problem of spectrum interference associated with the recent testing and use of mobile radios at military facilities in the United States, (2) review the efforts made by DOD during the development of its Land Mobile Radio system to identify and avoid spectrum interference, and (3) identify efforts to address the problem.

Since DOD began its rollout of the new Land Mobile Radios in 2004, a number of complaints have been reported at several locations near military installations--notably, Eglin Air Force Base Eglin Air Force Base is the home of the United States Air Force 96th Air Base Wing of the Air Force Materiel Command, and is also headquarters for more than 45 associate units. , Florida; Defense Distribution Depot Susquehanna (DDSP DDSP Disability Development Services Pursat (Cambodia)
DDSP Distribution Depot Susquehanna Pennsylvania
DDSP Defense Distribution Depot Susquehanna Pennsylvania
DDSP Defense Development Sharing Program
) near New Cumberland, Pennsylvania New Cumberland is a borough in Cumberland County, Pennsylvania, United States. New Cumberland was incorporated as a borough on March 21, 1831. The population was 7,349 at the 2000 census. ; and Ft. Detrick, Maryland. As of August 2005, manufacturers had received over 1,300 customer complaints of affected garage door openers that they attributed to interference from Land Mobile Radios. One major manufacturer also estimated that its distributors had received between 7,000 and 10,000 complaints. However, the extent of interference experienced by users of garage door openers from DOD's Land Mobile Radios is difficult to quantify because interference problems may not be reported or may be reported to several different organizations, including garage door opener A garage door opener is a motorized device that opens and closes garage doors. Most are controlled by switches on the garage wall, as well as by remote controls carried in the garage owner's cars.  manufacturers and retailers, government agencies, or congressional representatives. According to DOD and garage door opener manufacturers, the nature of the interference that has occurred varies by location. In some locations where the radios were rolled out, no occurrences of interference have been reported. Where interference has been reported, the problems range from intermittent inoperability to situations where the garage door may not open at all with the remote control device. DOD has reported a decrease of interference complaints. They attribute this decrease, in part, to consumer awareness of the problem and the completion of the Land Mobile Radio testing phase, at each site. In early 2005, following reports of interference, the National Telecommunications and Information Administration's Office of Spectrum Management and the FCC's Office of Engineering and Technology established a working group with representatives from DOD and the major manufacturers of garage door openers to develop short- and long-term solutions to the spectrum interference problem. The group has met several times, and as a result, DOD and the manufacturers report that progress has been made in terms of coordination and information sharing. For example, DOD has provided the Land Mobile Radio rollout locations to manufacturers and the ranges of spectrum to be affected through fiscal year 2010. DOD has also conducted analyses showing the likely extent of potential interference from Land Mobile Radios in several populated areas where the radios will be deployed and has given the findings to major manufacturers. For their part, manufacturers are offering retrofit kits to change the frequencies of existing garage door openers that would cost consumers $50 to $80, excluding installation. Furthermore, for new devices, one manufacturer is moving off of the 390 MHz spectrum range, and another plans to go to a multi-frequency approach using 390 MHz and other spectrum in order to minimize potential interference problems in the future.
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Publication:General Accounting Office Reports & Testimony
Date:Feb 1, 2006
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