Following extensive reports of GPS interference, LightSquared announced last week that it would vacate its L-Band frequency adjacent to GPS and move to one further away to greatly reduce, but not eliminate, interference with satnav signals.
In May, Eurocopter’s proof-of-concept compound, the X3, reached 232 ktas, a speed it sustained during five minutes at 8,500 feet. It also demonstrated a rate of climb greater than 5,000 fpm. The crew flew pitch-up attitudes in the 30- to 50-degree range. Roll angles were taken to 80 degrees of bank.
A study released by the Save Our GPS Coalition warns of “serious repercussions for the U.S. economy” if LightSquared is allowed to broadcast 4G broadband signals that cause interference with GPS. According to the study, more than 3.3 million U.S.
Since early reports indicate that LightSquared’s transmitters do, in fact, interfere with GPS signals, LightSquared yesterday announced that it would vacate the frequency that caused major GPS interference and move to one farther away, where tests had shown minimum interference. However, some GPS receivers would still be affected by the company’s 4G signals even in this frequency band.
“The test data discussed today makes clear that there is substantial interference to GPS if LightSquared turns on high-powered terrestrial facilities in the spectrum next door to GPS,” Trimble vice president and general counsel Jim Kirkland said today at an event sponsored by the National Space-Based PNT Advisory Board. Kirkland is also a founding member of the Coalition to Save Our GPS.
The controversy over potential interference to GPS from LightSquared’s planned nationwide network of powerful 4G broadband retransmitting stations has now drawn Congress into the dispute. Letters expressing concern about adverse effects of the LightSquared network on GPS have been sent to the FCC by House and Senate members.
Two events last month intensified the confrontation between LightSquared, a private U.S. communications company, and U.S. government and industry GPS interests.
Satellite communications provider Inmarsat and aviation standards organizations have been working on a solution to a lesser-publicized aspect of the planned LightSquared broadband wireless network–the potential for the system’s high-power transmitters to interfere with satcom as well as GPS navigation signals.
LightSquared documents submitted to the FCC last week reveal that its transmitters were transmitting at only half power during the tests recently conducted in the Las Vegas area to check for interference with GPS receivers. This means that any interference detected by the GPS units could be as much as half that expected when the LightSquared transmitters operate at their eventual planned power levels.