On Tuesday, the Federal Communications Commission (FCC) dealt a near fatal blow to LightSquared’s ambitious attempt to bring a nationwide 4G broadband network to rural America. Following months of tests and attempts at a fix, LightSquared proved unable to keep its signal from interfering with global positioning system (GPS) receivers, which are increasingly employed in farm machinery.

Besides agriculture, the network was also opposed by representatives of other GPS users including the U.S. military, aviation and emergency services.

“LightSquared’s proposal to provide ground-based mobile service offered the potential to unleash new spectrum for mobile broadband and enhance competition,” said Tammy Sun, FCC spokesperson. The FCC “clearly stated from the outset that harmful interference to GPS would not be permitted.”

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That is why the conditional waiver granted to the telecommunications company -- issued in January 2011 after the GPS/LightSquared spectrum conflict came to light – “prohibited LightSquared from beginning commercial operations unless harmful interference issues were resolved,” said Sun.

That FCC waiver will now be revoked, keeping LightSquared from continuing to build infrastructure. The company’s only recourse may be to take the FCC to court.

The reason for the FCC’s conclusion was largely based on tests conducted by the National Telecommunications and Information Administration (NTIA), which operates under the U.S. Department of Commerce. Those tests concluded last November and a report was written based on the findings.

“The NTIA found that there was significant interference between the LightSquared towers – or the network the company wanted to pursue – and GPS receivers,” said RJ Karney, American Farm Bureau Federation (AFBF) director of congressional relations on Wednesday. “The FCC then decided not to allow LightSquared to continue working under the waiver.

“To recap, the waiver allowed LightSquared to proceed with the building of its network as long as there was no interference with GPS receivers. That led to the back-and-forth between LightSquared and GPS industries throughout almost the entirety of 2011.

“The NTIA also reported on LightSquared’s timeline. I believe that involved them rolling out their network” during the first half of 2012. “With that tight of a timeline, the NTIA concluded that even if a technical fix was possible, the amount of time and money it would take to retrofit the millions of GPS receivers being used would be too prohibitive and LightSquared shouldn’t be allowed to proceed.”

Indeed, the FCC’s Sun said the NTIA “concluded that there is no practical way to mitigate potential interference at this time. Consequently, the Commission will not lift the prohibition on LightSquared.”

The FCC will soon seek public comments on its proposals.