Radar Spectrum Below 10 GHz Is Fully Allocated with No Room for New Systems

The electromagnetic spectrum below 10 GHz is the most valuable real estate in radar engineering. These frequencies offer the best combination of atmospheric propagation (minimal rain fade), reasonable antenna size, and target detection performance. Every major radar application — air surveillance (L-band, 1-2 GHz), air traffic control (S-band, 2-4 GHz), weather radar (S-band and C-band, 2-8 GHz), maritime radar (X-band, 8-12 GHz), and military fire control — operates in this range. The problem is that this spectrum is fully allocated, with every MHz assigned to one or more users, and the demand for new radar capabilities (counter-drone, space surveillance, hypersonic tracking) requires bandwidth that simply does not exist in the current allocation framework. The consequence is that new radar systems must either operate in congested bands with degraded performance due to interference, or move to higher frequencies (Ka-band, W-band) where atmospheric attenuation limits range and rain causes severe signal loss. The DoD's proposed Next Generation Over-the-Horizon Radar needs hundreds of MHz of HF bandwidth (3-30 MHz) that conflicts with international shortwave broadcasting and amateur radio allocations. The FAA's planned terminal radar replacement needs S-band spectrum that is increasingly encroached by 5G and WiFi 6E. NOAA's next-generation weather radar needs C-band or S-band bandwidth that is being auctioned to telecom companies. Every new radar program becomes a political battle over spectrum reallocation rather than an engineering project. The structural cause is that spectrum governance treats radar as a legacy user that should yield to commercial broadband. The economic value of spectrum for 5G ($100+ billion in auction revenue) dwarfs the economic value that policymakers assign to radar ($0 in direct revenue, despite underpinning trillions in aviation, weather, and defense value). The National Spectrum Strategy released in November 2023 identified 2,786 MHz of spectrum for study for potential repurposing — much of it currently used by federal radar systems. The DoD and NOAA can object, but the NTIA and FCC face relentless pressure from the telecommunications industry to free up sub-10 GHz spectrum. There is no mechanism to value the societal benefit of radar spectrum in economic terms that can compete with commercial auction revenue.