#### § 90.187 Trunking in the bands between 150 and 512 MHz.

(a) Applicants for centralized and decentralized trunked systems operating on frequencies between 150 and 512 MHz (except 220-222 MHz) must indicate on their applications (radio service and class of station code, instructions for FCC Form 601) that their system will be trunked. Licensees of stations that are not trunked may trunk their systems only after modifying their license (see [§ 1.927 of this chapter](/on/2024-09-20/title-47/section-1.927)).

(b) Except as provided in [paragraphs (c)](/on/2024-09-20/title-47/section-90.187#p-90.187(c)) and [(d)](/on/2024-09-20/title-47/section-90.187#p-90.187(d)) of this section, trunked systems operating under this section must employ equipment that prevents transmission on a trunked frequency if a signal from another system is present on that frequency. The level of monitoring must be sufficient to avoid harmful interference to other systems.

(c) The monitoring requirement in [paragraph (b)](/on/2024-09-20/title-47/section-90.187#p-90.187(b)) of this section does not apply to trunked systems operating in the 470-512 MHz band that meet the loading requirements of [§ 90.313](/on/2024-09-20/title-47/section-90.313) and have exclusive use of their frequencies in their service area.

(d) The monitoring requirement in [paragraph (b)](/on/2024-09-20/title-47/section-90.187#p-90.187(b)) of this section does not apply if the application is accompanied by written consent from all affected licensees.

(1) Affected licensees for the purposes of this section are licensees (and previously filed pending applicants) meeting both a spectral and a contour overlap as defined:

(i) *Spectral overlap.* Licensees (and filers of previously filed pending applications) with an assigned (or proposed) frequency having a spectral separation from a frequency of the proposed centralized trunked station that does not exceed these values:

| Proposed station | Incumbent authorized bandwidth | | |
| --- | --- | --- | --- |
| *25 kHz* | *12.5 kHz* | *6.25 kHz* |
| *25 kHz* | 15.0 kHz | 15.0 kHz | 15.0 kHz |
| *12.5 kHz* | 15.0 kHz | 7.5 kHz | 7.5 kHz |
| *6.25 kHz* | 15.0 kHz | 7.5 kHz | 5.0 kHz |
| | | | |
| --- | --- | --- | --- |
| *The left column is the authorized bandwidth requested for the proposed trunked station. The second row is the authorized bandwidth of the incumbent. The other cells in the table show the frequency range above and below the frequency of the proposed centralized trunked station that must be considered.* | | | |

(ii) *Contour overlap.*

(A) Licensees (and filers of previously filed pending applications) with a service contour (37 dBu for stations in the 150-174 MHz band, and 39 dBu for stations in the 421-512 MHz band) that is overlapped by the proposed centralized trunked station's interference contour (19 dBu for stations in the 150-174 MHz band, and 21 dBu for stations in the 421-512 MHz band). Contour calculations are required for base station facilities. Contour calculations are required for associated mobile stations only in the 150-174 MHz band, with the associated base station's service contour used as both the mobile station's service contour and its interference contour.

(B) The calculation of service and interference contours shall be performed using generally accepted engineering practices and standards, including appropriate derating factors, agreed to by a consensus of all certified frequency coordinators. Frequency coordinators shall make this information available to the Commission upon request.

(C) For purposes of this section, the authorized operating area of a station or proposed station with no associated base station shall be used as both the station's service contour and its interference contour.

(D) After January 1, 2013, licensees with an authorized bandwidth exceeding 12.5 kHz will not be deemed affected licensees, unless the licensee meets the efficiency standard set forth in [§ 90.203(j)(3)](/on/2024-09-20/title-47/section-90.203#p-90.203(j)(3)) or the licensee was granted a waiver of [§ 90.209(b)](/on/2024-09-20/title-47/section-90.209#p-90.209(b)).

(2) The written consent from an affected licensee shall state all terms agreed to by the parties and shall be signed by the parties. The written consent shall be maintained by the operator of the centralized trunked station and be made available to the Commission upon request. An application for a centralized trunked station shall include either a certification from the applicant that written consent has been obtained from all affected licensees, or a certification from the frequency coordinator that there are no affected licensees.

(3) In addition, the service contour for proposed centralized trunked stations on Industrial/Business Pool frequencies shall not be overlapped by an incumbent licensee's interference contour. An application filed for Public Safety Pool frequencies, see [§ 90.20](/on/2024-09-20/title-47/section-90.20), for a proposed centralized trunked station in which the service contour of the proposed station is overlapped by the interference contour of the incumbent station(s) is allowed, but the applicant must accept any resultant interference.

(e) The exclusive service area of a station that has been authorized for centralized trunked operation will be protected from proposed centralized trunked, decentralized trunked or conventional operations in accordance with the standards of [paragraph (d)](/on/2024-09-20/title-47/section-90.187#p-90.187(d)) of this section.

(f) Trunking of systems licensed on paging-only channels or licensed in the Radiolocation Service (subpart F) is not permitted.

(g) *Channel limits.*

(1) No more than 10 channels for new centralized trunked operation in the Industrial/Business Pool may be applied for at a single transmitter location or at locations with overlapping service contours as specified in [paragraph (d)](/on/2024-09-20/title-47/section-90.187#p-90.187(d)) of this section. Subsequent applications for centralized trunked operation are limited to no more than an additional 10 channels, and must be accompanied by a certification, submitted to the certified frequency coordinator coordinating the application, that all of the applicant's existing channels authorized for centralized trunked operation at that location or at locations with overlapping service contours have been constructed and placed in operation. Certified frequency coordinators are authorized to require documentation in support of the applicant's certification that existing channels have been constructed and placed in operation.

(2) Applicants for Public Safety Pool channels may request more than 10 centralized trunked channels at a single location or at locations with overlapping service contours if accompanied by a showing of sufficient need. The requirement for such a showing may be satisfied by submission of loading studies demonstrating that requested channels in excess of 10 will be loaded with 50 mobiles per channel within a five year period commencing with the grant of the application.

(h) If a licensee authorized for centralized trunked operation discontinues trunked operation for a period of 30 consecutive days, the licensee, within 7 days thereafter, shall file a conforming application for modification of license with the Commission.

[[78 FR 28754](https://www.federalregister.gov/citation/78-FR-28754), May 16, 2013, as amended at [80 FR 18146](https://www.federalregister.gov/citation/80-FR-18146), Apr. 3, 2015]