The battle between the FCC and the Hill over allowing a new terrestrial broadband service adjacent to GPS spectrum is heating up.  

Related: FCC Says Senate Ligado Attacks are Fear Mongering 

In the wake of a Senate Armed Services Committee hearing on the subject that saw the FCC hammered by legislators, military brass, and even iconic pilot Sully Sullenberger, almost two dozen members of the House Armed Services Committee from both sides of the aisle have written to FCC chair Ajit Pai and the other commissioners--the vote to approve the Ligado broadband service was unanimous, though the two Democrats only concurred--to express their "deep concern." 

Lead Signatories on the letter, a copy of which was obtained by Multichannel News, were Sen. Jim Cooper (D-Tenn.), chairman of the Strategic Forces Subcommittee, and Michael Turner (R-Ohio) ranking member.  

Related: Ligado Defends FCC Decision 

They said that while Ligado has argued that DOD assessments of harmful interference from its broadband network is not based on any testing data, they want to make sure that the commissioners have independently confirmed that, preferably via a classified briefing. 

The House mbmers said their committee is pushing DOD to share as much spectrum for 5G as possible, but not if it is a national security threat.  

An FCC spokesperson said the commission had received the letter and was reviewing it. 

They want responses to the following within three days: 

• "Please provide copies of the legal analysis that led the commissioners to their determination despite the unanimous concerns of the national security community, and whether that decision is consistent with the FY17 NDAA requirement to resolve concerns of widespread interference with GPS devices prior to permitting the commercial use of this spectrum. 

• "Did each commissioner receive a briefing from the Department of Defense on the classified test data contained in the classified report of DoD testing to accompany the Department of Transportation Adjacent Band Compatibility Assessment from April of 2018? 

• "For Commissioners Rosenworcel and Starks, you issued a joint statement of concurrence, indicating a less than full endorsement of the approval and said the decision was a close call. Do you believe the concerns of the national security community were adequately addressed? Additionally, you expressed concern about the spectrum decision making process. Were there any specific aspects of this decision that concerned you?"

Despite pushback from GPS entities and some federal agencies, the FCC voted April 20 to approve Ligado's application to deploy a low-power terrestrial 5G network in the L-Band satellite spectrum.  

Related: FCC Approves Ligado Terrestrial Broadband Service 

GPS companies and users had pushed back on the Ligado application, saying they could face interference to critical services, but FCC engineers said that harmful interference could be avoided, including by requiring a guard band of spectrum between Ligado and adjacent-band GPS and a 99% reduction in power levels from Ligado's 2015 application.  

Airline interests including plane builders, pilots, air transport companies and airlines including Jet Blue, Delta, and Southwest petitioned the FCC to dismiss the Ligado application.  

But Pai cited the support for the item of Secretary of State Mike Pompeo and Attorney General William Barr on the one hand to Senator Mark Warner of Virginia and Congresswoman Doris Matsui of California on the other. 

Ligado, formerly LightSquared, the company has been trying to launch a terrestrial wholesale wireless broadband service using spectrum initially licensed for satellite for most of a decade. Back then it was for a 4G network.  

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