---
kind: "section"
citation: "47 C.F.R. § 27.1423"
title: "47"
number: "27.1423"
heading: "Protection of incumbent operations."
url: "https://uscodex.org/cfr/47/27.1423"
---

# §27.1423. Protection of incumbent operations.

- (a) To protect incumbent earth stations from out-of-band emissions from fixed stations, base stations and mobiles, the power flux density (PFD) of any emissions within the 4000-4200 MHz band must not exceed −124 dBW/m 2/MHz as measured at the earth station antenna.
- (b) To protect incumbent earth stations from blocking, the power flux density (PFD) of any emissions within the 3700-3980 MHz band must not exceed −16 dBW/m 2/MHz as measured at the earth station antenna.
- (c) All 3.7 GHz Service licensees, prior to initiating operations from any base or fixed station, must coordinate cochannel frequency usage with all incumbent Telemetry, Tracking, and Command (TT&C) earth stations within a 70 km radius. The licensee must ensure that the aggregated power from its operations meets an interference to noise ratio (I/N) of −6 dB to the TT&C earth station receiver. A base station's operation will be defined as cochannel when any of the 3.7 GHz Service licensee's authorized frequencies are separated from the center frequency of the TT&C earth station by less than 150% of the maximum emission bandwidth in use by the TT&C earth station.
- (d) All 3.7 GHz Service licensees operating on an adjacent channel to an incumbent TT&C earth station must ensure that the aggregated power from its operations meets an interference to noise ratio (I/N) of −6 dB to the TT&C earth station receiver.
- (e) To protect incumbent TT&C earth stations from blocking, the power flux density (PFD) of any emissions within the 3700-3980 MHz band must not exceed −16 dBW/m 2/MHz as measured at the TT&C earth station antenna.

## Notes

### Source

Source: 85 FR 22882, Apr. 23, 2020, unless otherwise noted.

### Authority

Authority: 47 U.S.C. 154, 301, 302a, 303, 307, 309, 332, 336, 337, 1403, 1404, 1451, and 1452, unless otherwise noted.

### Source

Source: 62 FR 9658, Mar. 3, 1997, unless otherwise noted.