Doug Lung /
05.26.2011 03:30 PM
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.

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Posted by: Brian Smith
Thu, 05-26-2011 06:54 PM Report Comment
errors within SIXTY YARDS of the transmitter? SIXTY YARDS? If they can't find something within sixty yards of where they're at, somethings seriously WRONG - with the person doing the driving/navigating, once they're THAT close, they're within the standard GPS error, anyway!
Posted by: Brian Smith
Fri, 05-27-2011 11:39 AM Report Comment
Eric Gakstatter reports on matters of precision survey for GPS World Magazine. GPS survey equipment is capable of sub-meter accuracy. Mr Gakstatter contends survey devices were disrupted a mile away from a Lightsquared test tower. Potentially making matters worse, the Boulder City test tower might have been transmitting at half power. That information was presented at the 26 May GPS World Magazine Webinar. By nature of their design, high precision receivers see into wider bandwidth than do general location receivers. Therefore, they are more susceptible to overload from the Lightsquared network. FCC went wrong when they failed to analyze the effects of a totally altered electromagnetic environment upon a diverse installed user base. Consequently, the Lightsquared license modification has become a politically sensitive matter.
Posted by: Brian Smith
Tue, 05-31-2011 12:19 PM Report Comment
When they are trying to locate the corners of your property, is 60 yards close enough for you?

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