Potential Interference with Critical Defense Radars Sparks Alarm
A new report from the Center for Strategic and International Studies (CSIS) warns that proposed congressional actions to open the S-band spectrum—specifically the 3.10–3.45 GHz range—to commercial 5G networks could severely disrupt vital military radar systems. The initiative, tied to President Donald Trump’s Golden Dome missile defense plan, risks jamming or degrading the performance of key defense radars across several branches.
The ‘Goldilocks’ Band at Risk
The S-band, in the 3.10–3.45 GHz range, has long been designated exclusively for Department of Defense (DoD) use by the Federal Communications Commission (FCC). Experts regard it as the “Goldilocks zone” for radar — a sweet spot that operates effectively in all weather conditions and can detect even small targets at great distances. Radars such as the Navy’s Aegis SPY family, the Army’s TPQ-53, the Marine Corps’ Ground/Air Task-Oriented Radar, and the Space Force’s Long Range Discrimination Radar rely heavily on this spectrum.
Risks to National Security and Missile Shield Operations
The CSIS report warns that sharing this spectrum with commercial 5G operators, especially through dynamic spectrum sharing schemes, could introduce ambient noise and interference. “High-power radars required to track faint missile signatures thousands of miles away would be adversely affected,” the study states. Such interference could compromise missile defense capabilities, border security, and national airspace monitoring.
Legislative Tensions and Spectrum Negotiations
The ongoing legislative process features competing visions. The House’s reconciliation bill proposes auctioning 600 MHz of spectrum for 5G expansion, but explicitly exempts the 3.10–3.45 GHz band. Conversely, the Senate’s version, led by Senator Ted Cruz (R-Texas), initially included that band, provoking warnings from members of the Senate Armed Services Committee (SASC).
Senator Maria Cantwell (D-Wash.) recently demanded a detailed DoD assessment of the risks associated with auctioning the lower S-band and the 7–8 GHz band used by military satellites. Meanwhile, Senator Mike Rounds (R-S.D.) and Deb Fischer (R-Neb.) have been pushing to block the auction, citing national security concerns. Rounds indicated progress toward a compromise, but recent reports suggest disagreements over frequency exclusions persist.
Industry Advocates for Dynamic Sharing
Supporters of expanding commercial use argue that “dynamic spectrum sharing”—which coordinates spectrum use in real time—could mitigate interference without resorting to exclusive allocations. However, the CSIS report counters that such schemes are unproven and unlikely to reliably prevent interference.
“Rigorous testing shows incompatibility between 5G and high-powered radars,” the CSIS study asserts. “During operation, 5G must be turned off for radar to function, and proposals for sharing do not account for the need for continuous airspace surveillance.”
Expert Concerns and Caution
Tom Karako, director of CSIS’s Missile Defense Project, emphasized the risks: “Until dynamic sharing is definitively proven, the stakes are just too high to jeopardize missile defense, border security, and other critical capabilities by allowing high-power radars to be jammed or impeded.” He urged caution, warning that a spectrum sale or sharing scheme that diminishes radar effectiveness could leave the U.S. vulnerable.
As negotiations continue and staff for key senators declined to comment, the debate underscores the delicate balance between advancing commercial 5G and safeguarding national security assets. The outcome could have significant implications for military readiness and technological sovereignty in the years ahead.
