● Covered by 1 source · 1 reportLow impact1 neutral
Military Radar Can Cause Wi-Fi Routers to Switch 5 GHz Channels
Key points
- Routers use DFS to avoid interfering with radar on 5 GHz band.
- FCC rules require DFS to be active on shared 5 GHz channels.
- FAA airport weather radars operate within the 5 GHz Wi-Fi band.
- FCC has fined ISPs for disabling DFS and causing radar interference.
Understanding Dynamic Frequency Selection (DFS)
Dual-band routers occasionally drop their 5 GHz network and switch channels, often indicated by "RADAR" entries in their event logs. This behavior is due to Dynamic Frequency Selection (DFS), a mechanism that allows routers to detect and avoid interfering with radar signals.
DFS ensures that Wi-Fi devices operating on the 5 GHz band yield to priority users such as military radar, satellite communication, and weather radar. In the United States, Federal Communications Commission (FCC) regulations mandate that routers listen for radar on shared channels for 60 seconds before transmitting, cease transmission within 10 seconds of detecting radar, and remain off that channel for at least 30 minutes. DFS is enabled by default and is required to remain active in these shared bands.
Radar Interference and Airport Systems
While military radar is a factor, a common source of interference for US home networks comes from airport-based radar systems. The Federal Aviation Administration (FAA) operates 45 Terminal Doppler Weather Radar (TDWR) systems at 46 major airports. These systems detect wind shear, a hazardous weather phenomenon, and transmit between 5600 and 5650 MHz, which falls within the 5 GHz Wi-Fi band.
Since their commissioning in 1994, TDWR systems have prevented wind shear-related aviation accidents at protected airports. However, in 2009, the FAA began detecting interference from unlicensed 5 GHz equipment, leading to investigations and enforcement actions.
Regulatory Enforcement and Compliance
The FCC has taken action against entities that fail to comply with DFS regulations. In August 2019, the FCC proposed $25,000 fines against three wireless ISPs—Boom Solutions, Integra Wireless, and WinPR—for their equipment interfering with weather radar at San Juan International Airport. These companies had reportedly disabled DFS on their devices. The penalties for WinPR and Boom Solutions were confirmed in late 2019 and early 2020, respectively. These cases, while involving outdoor point-to-point links rather than home routers, illustrate the importance of DFS compliance.
✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →
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Reporting from
Wi-Fi routers may drop their 5 GHz network and switch channels due to Dynamic Frequency Selection (DFS) responding to military, satellite, or weather radar signals. This is a regulatory requirement, particularly in the US, to prevent interference with critical radar systems like those used by the FAA at airports.