A new cellular broadband provider with plans to harness the radio spectrum immediately adjacent to that used by the Global Positioning System (GPS) could end up jamming GPS signals and threaten the viability of satellite navigation systems across the U.S., according to a new industry group formed to protect GPS interests.
The Coalition to Save Our GPS (www.saveourgps.org) was formed after LightSquared Inc. (www.lightsquared.com) received a tentative license in January from the Federal Communications Commission (FCC) to use the 1525 to 1559 megahertz (MHz) spectrum for its hybrid land and satellite-based high-speed broadband system. LightSquared officials have said that its system will include 40,000 land-based transmitters, in addition to a satellite already orbiting over the U.S.
The FCC charged LightSquared to work with the GPS industry to resolve the question of whether and its amplified signals would interfere with relatively low-powered GPS satellite transmissions. Coalition members are participating with LightSquared to evaluate interference issues, but have criticized the FCC for issuing the preliminary license prior to extensive testing.
Experimental testing by Garmin, the large consumer and aviation GPS company, showed that a typical consumer level GPS device began being jammed at a distance of about 3.6 miles from a simulated high-power cellular transmitter. It lost its fix at just over a half mile from the transmitter. An aviation receiver began being jammed at a distance of 13.8 miles and lost its fix at 5.6 miles. LightSquared officials said the Garmin test transmitter did not use the filter technology it plans to harness to eliminate interference.
“LightSquared's plans to build up to 40,000 ground stations transmitting radio signals one billion times more powerful than GPS signals as received on earth could mean 40,000 ‘dead spots’ – each miles in diameter – disrupting the vitally important services GPS provides,” according to a coalition statement released in mid-March.
Several agricultural companies and associations are part of the coalition, including the Association of Equipment Manufacturers, Case New Holland, Caterpillar Inc., Deere & Company and Trimble.
The coalition is asking GPS users to contact the FCC with their concerns about GPS interference. Instructions are available at www.saveourgps.org/voice-your-concern.