The Pentagon and the GPS industry fear the system will interrupt navigation systems nationwide if it wins FCC approval.
Initial tests of a controversial cellular broadband network planned by LightSquared showed the company's system knocked out Global Positioning System receivers used by first responders.
LightSquared of Reston, Va., tested its system last month at Holloman Air Force Base, N.M., with the participation of state police vehicles and county ambulances, both of which experienced outages from the company's cell tower, according to Bill Range, director of the State of New Mexico E911 program.
LightSquared cell system operates in the 1525-1559 MHz and 1626.5-1660.5 MHz bands, and the Federal Communications Commission directed the tests to determine if the network interfered with GPS systems that operate in the nearby 1559-1610 MHz bands.
Range, in a May 11 letter to Col. Bernard Gruber, director of the Air Force Global Positioning Directorate, said the results of the April tests, "substantiate concerns that the LightSquared network will cause interference to GPS signals and jeopardize 911 and public safety nationwide."
The New Mexico State Police reported that when parked directly under the tower, their GPS equipment experienced "system failure," and while driving around near the test site in Alamogordo, N.M., they "continued to incorrect during the test period."
GPS receivers in ambulances from Otero County, N.M., which includes Alamogordo, could not establish any connection with the GPS satellites within 60 yards of the tower in the April tests.
LightSquared, the GPS industry and numerous federal agencies are conducting tests through June to determine the extent of interference from the company's system to GPS receivers. The Federal Aviation Administration said another test of the LightSquared system started this Monday in Las Vegas and will continue through May 27. FAA warned of potential GPS outages within 300 miles of the LightSquared tower in Boulder City, Nev., 25 miles southeast of Las Vegas.
The Defense and Transportation Department have serious concerns about the impact LightSquared's national network of 40,000 cell towers will have on GPS receivers. LightSquared maintains the interference is not caused by its system, but by sensitive GPS receivers that "see" into the frequency band the network uses.
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