What FCC rule part governs private land mobile radio systems?

47 CFR Part 90 governs the Private Land Mobile Radio Services (PLMRS), covering most non-broadcast, non-carrier radio systems used by businesses, public safety agencies, utilities, and transportation companies. It is subdivided into subparts including Subpart B (Public Safety Radio Pool), Subpart C (Industrial/Business Radio Pool), Subpart S (800 MHz Cellular/SMR), Subpart T (900 MHz), and Subpart Z (700 MHz public safety broadband). Part 90.219 specifically governs signal boosters (BDAs).

Do you need frequency coordination before applying for an FCC Part 90 license?

Yes — before applying for a Part 90 licence on most frequency bands, applicants must obtain frequency coordination from an FCC-certified frequency coordinator such as APCO International, FREQ, or NABER. The coordinator analyses the proposed frequency, location, and technical parameters against its database of existing assignments to identify co-channel and adjacent-channel conflicts, then certifies its recommendation to the FCC with the application.

What is the FCC ULS database used for?

The Universal Licensing System (ULS) is the FCC's online database and application processing system at wireless.fcc.gov/uls, where all licensed radio operations except amateur and CB appear. Engineers use it to search for existing assignments before frequency coordination, look up licensee contacts for interference resolution, verify license validity, and submit new applications and modifications.

What C/I ratio is required for co-channel P25 and analog FM operation?

The carrier-to-interference (C/I) ratio threshold for acceptable P25 operation is approximately 17 dB, versus 12 dB for analog FM. Frequency coordinators use separation distance tables in FCC OET Bulletin 74 and band-specific rules, such as Part 90.621 for 800 MHz, to establish minimum station-to-station separations that maintain these C/I thresholds.

What form is used to apply for a new FCC Part 90 license, and how long does it take?

New Part 90 license applications are filed using FCC Form 601 (main application) with applicable schedules, such as Schedule B for technical parameters; the same form is used for modifications and renewals. Processing time for routine applications is 3–6 weeks, with expedited processing available for public safety applications under FCC Part 1.1235, and stations must be placed in operation within 12 months of grant or the license expires.

Engineering·11 min read·June 17, 2026

📡 FCC Licensing and Spectrum Management for Land Mobile Radio

A comprehensive guide to FCC Part 90 licensing, frequency coordination, spectrum planning, interference analysis, and the licence application process for industrial, commercial, and public safety radio systems.

📖Radio Communications — Illustrated Guide (Full Access)

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The FCC and Spectrum Authority

In the United States, the Federal Communications Commission (FCC) regulates the use of non-federal radio spectrum under the Communications Act of 1934, as amended. The FCC allocates spectrum by service type and geographic area, issues licences to eligible parties, and enforces technical standards to prevent interference. Federal spectrum (military, NASA, NWS, FAA) is managed separately by the National Telecommunications and Information Administration (NTIA). Engineers designing private land mobile radio (LMR) systems, DAS, BDAs, or fixed point-to-point links must ensure their systems comply with the applicable FCC rules and hold valid licences for all licensed operations.

Topics covered

FCC Part 90frequency coordinationFCC ULSspectrum managementland mobile radioco-channel interferenceadjacent channel interferencefrequency reuseFCC Form 601Part 15ISM bandtrunked radio license700 MHz800 MHz