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LightSquared GPS Interference Test Brings Mixed Results

Reports are appearing about testing done to determine if the LightSquared mobile broadband terrestrial network will interfere with GPS reception on adjacent frequencies.

Tests at Holloman Air Force Base in New Mexico last month knocked out the GPS receivers used by first responders. However, more recent testing in Las Vegas has not resulted in any interference problems, so far.

Bob Brewin describes the New Mexico results in the article LightSquared cell network knocks out first responders' GPS in tests. The article quotes Bill Range, director of the State of New Mexico E911 program, saying 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 article notes that New Mexico State Police reported that when parked directly under the LightSquared tower, GPS equipment experienced "system failure," and while driving around the test site they [GPS devices] "continued to [be] incorrect during the test period." The article states, "GPS receivers in ambulances from Otereo 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."

The Las Vegas Sun, in the article Test of speedy wireless network running smoothly, officials say by Steve Kanigher, quotes Officer Bill Casell, a Metro Police spokesman, as saying "There have been no anomalies, nothing. We've been watching it and there has been absolutely nothing shown on our radar attributable to it. It's business as usual."

No other agencies, including the Clark County Aviation Association, reported any problems. The Las Vegas Sun article reported Coalition to Save our GPS spokesman Dale Leibach observed that it was "difficult to draw conclusions from the Las Vegas testing so far because LightSquared is monitoring possible interference with GPS signals in a way that may not be noticeable to airplane pilots and emergency first responders."

He added that it was not intended "to blanket Las Vegas with a signal and then wait to hear who might be impacted."

Without more details on the testing, it's difficult to say if the Las Vegas tests really show that there are no issues with GPS interference. The New Mexico testing seems to indicate that there should be problems. As the testing wraps up, more information should become available. I'll cover it here.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.