The PNT agency also reported the results of "live sky" tests conducted using a production transmitter set up and operated by LightSquared at Holloman Air Force Base in New Mexico. Among other things, those tests showed that police cars lost their GPS reception within about 600 feet from the tower and ambulances and fire trucks lost service about 1,000 feet away. General Motors' OnStar vehicle navigation systems also were significantly degraded, the agency said.
To mitigate the interference, the PNT group proposed shifting LightSquared service to other frequencies or adding filters to GPS receivers, a solution that the agency noted would be expensive and might affect GPS performance. Other possible solutions were changing LightSquared's antenna patterns and cutting transmitter power.
The RTCA, a nonprofit corporation that advises the Federal Aviation Administration, said its tests showed that LightSquared's operations in one part of its spectrum band would make GPS unavailable to aircraft over a large region of the Northeastern U.S. RTCA recommended LightSquared not be able to use that band, and called for further study.
At the June 9 meeting, LightSquared said there were several possible ways to mitigate the interference, including ones involving the frequencies and transmitting power the carrier uses, and that it had not taken any options for mitigation off the table.
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