Regulatory Compliance News

FCC Formalizes Final Rules Authorizing Wireless Multichannel Audio Systems (WMAS) Across Broadcast and Auxiliary Bands

The Federal Communications Commission (FCC) published its final rule in the Federal Register under Document No. 2024-23959, codifying technical updates across 47 CFR Parts 15 and 74 to govern wireless microphone operations. Arising from ET Docket No. 21-115 (FCC 24-22), the regulatory framework officially permits Wireless Multichannel Audio Systems (WMAS) to operate on both a licensed and unlicensed basis across designated broadcast television bands (VHF and UHF), the 600 MHz guard band and duplex gap, as well as higher auxiliary frequencies including 941.5–944 MHz, 944–952 MHz, 952.850–956.250 MHz, 956.45–959.85 MHz, 1435–1525 MHz, and 6875–7125 MHz. In addition to establishing operational rules for wideband microphones, the Commission updated administrative provisions to formally reflect the conclusion of the post-Incentive Auction transition period, removing sunsetted 600 MHz transition rules from the Code of Federal Regulations.

The introduction of WMAS represents a major technical advancement in spectrum efficiency for high-density audio deployments, such as large-scale theatrical productions, live concert venues, sporting events, and broadcasting centers. Unlike traditional narrowband wireless microphones that transmit each audio channel on a separate 200 kHz frequency, WMAS utilizes wideband RF channels—up to 6 MHz in the TV bands and up to 20 MHz in select auxiliary bands—to multiplex dozens of audio channels over a single radio link. The revised regulations harmonize U.S. technical criteria with European standards by incorporating ETSI EN 300 422-1 measurement methodologies, defining precise power spectral density limits, out-of-band emission masks, and dynamic channel power limits. To protect existing users, the rules maintain a dual framework that permits licensed Low Power Auxiliary Station (LPAS) operators to utilize higher transmit power limits while authorizing unlicensed WMAS deployment under Part 15 power caps, all without altering the legal rights or operational rules of legacy narrowband microphone hardware.

Following administrative corrections published under an FCC Erratum (DOC-406329A1) to rectify rule cross-references, the WMAS regulations took full legal effect, establishing a clear equipment authorization pathway for pro-audio equipment manufacturers and compliance managers. Telecommunications Certification Bodies (TCBs) processing new FCC Certification applications under Part 15 Subpart C or Part 74 Subpart H must ensure laboratory test reports verify strict compliance with wideband spectral density limits and adjacent channel attenuation profiles. Audio manufacturers expanding into the U.S. market can now secure certifications for next-generation WMAS hardware, enabling venue operators to maximize channel counts in spectrum-constrained metropolitan areas while maintaining full coexistence with incumbent broadcast television stations and primary radio services.