47 CFR § 90.691 - Emission mask requirements for EA-based systems.

---
identifier: "/us/cfr/t47/s90.691"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "47 CFR § 90.691 - Emission mask requirements for EA-based systems."
title_number: 47
title_name: "Telecommunication"
section_number: "90.691"
section_name: "Emission mask requirements for EA-based systems."
chapter_name: "FEDERAL COMMUNICATIONS COMMISSION"
subchapter_number: "D"
subchapter_name: "SAFETY AND SPECIAL RADIO SERVICES"
part_number: "90"
part_name: "PRIVATE LAND MOBILE RADIO SERVICES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "47 U.S.C. 154(i), 161, 303(g), 303(r), 332(c)(7), 1401-1473"
regulatory_source: "43 FR 54791, Nov. 22, 1978, unless otherwise noted."
cfr_part: "90"
---


# 90.691 Emission mask requirements for EA-based systems.

(a) Out-of-band emission requirement shall apply only to the “outer” channels included in an EA license and to spectrum adjacent to interior channels used by incumbent licensees. The emission limits are as follows:

(1) For any frequency removed from the EA licensee's frequency block by up to and including 37.5 kHz, the power of any emission shall be attenuated below the transmitter power (P) in watts by at least 116 Log<sub>10</sub>(f/6.1) decibels or 50 + 10 Log<sub>10</sub>(P) decibels or 80 decibels, whichever is the lesser attenuation, where f is the frequency removed from the center of the outer channel in the block in kilohertz and where f is greater than 12.5 kHz.

(2) For any frequency removed from the EA licensee's frequency block greater than 37.5 kHz, the power of any emission shall be attenuated below the transmitter power (P) in watts by at least 43 + 10Log<sub>10</sub>(P) decibels or 80 decibels, whichever is the lesser attenuation, where f is the frequency removed from the center of the outer channel in the block in kilohertz and where f is greater than 37.5 kHz.

(b) When an emission outside of the authorized bandwidth causes harmful interference, the Commission may, at its discretion, require greater attenuation than specified in this section.