I am not claiming to be an RF guy – it’s been 20 years since I took E&M in college and while I occasionally think about getting my ham ticket, I haven’t bothered to put the necessary knowledge into my on-board storage. So I have to take the claims of interference on faith. The theory doesn’t seem to be too badly Out There, at any rate.
I’m not all that worried, in the end, about this, though. If they turn on their network, and it wipes out GPS in a radius measured in 10^2 meters around each of the transmitters, there will be metaphorical torch and pitchfork marches on LightSquare’s HQ. Other elements of government, starting with DoD and continuing with USCG, FAA, Commerce, and NASA will be leading the wave, followed by every owner of a commerical GPS system and their congresscritters; and the incumbent cellular carriers will be cheerfully handing out the torches and pitchforks from the sidelines to bring down an upstart competitor.
GPS doesn’t just tell you to turn left onto the missing ferry across a parking lot. Cellular networks are at least partially dependent on the precise timing signals available from the network, for one. The FAA has more or less replaced all their navigation aids with GPS-based ones, likewise the Coast Guard. The military uses it all over the place. None of these users have the spare money to retrofit filters just because some bright boy found a loophole in the FCC rules. For the purely commercial users, it’s probably cheaper to rent a congressman, and the governmental ones probably have a timeshare in one office or another.
And LightSquare either has to know this or is too stupid to be in this business! They’re pouring Non-Recoverable Expenses into this; at least part of which is their own money. If they do end up degrading GPS to unusability, their ass will be in a sling on a ride to bankruptcy court, regardless of how many waivers they have from the FCC. With only marginally bad luck, they get to be blamed by NTSB for being the last link in a chain of error that brings down an airliner. That could be federal criminal negligence charges AT BEST.
I know it’s not fashionable – but the Hitchhiker’s Guide said it best: