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An Overview of the FM Translator Rules

Attorney Gregg Skall dips into the Code of Federal Regulations

This article is part of a series based on the Radio World ebook “What to Know About FM Translators.”

Gregg Skall

The best place to start a discussion of FM translators and boosters is with their FCC description. FM translators and boosters are a low-power service on the FM broadcast band (88 to 108 MHz). Translators retransmit the primary FM or AM service programming on a different frequency and/or amplitude, in order to supplement the originating station’s service in areas that experience poor direct reception due to distance or intervening terrain barriers (for example, a mountain). They also may be used by AM Class D stations to continue operating at night. 

FM boosters share many characteristics as FM translators but operate on the same frequency as the main station. 

Each of these stations can be a useful tool for radio broadcasters serving rural areas or regions with mountains and hills that make reception spotty or nonexistent to many listeners. 

Here is a link to key terms in the Code of Federal Regulations, and most of the links in the text below point to relevant section of those rules.

(Note: As Radio World readers will know, the FCC in November finalized new rules to allow limited program origination on FM boosters, to support “geotargeting.” As that topic is outside the scope of this ebook we do not explore it here.)

Deeper on FM translators

An FM translator may be used for the purpose of retransmitting the signals of a primary AM or FM radio broadcast station or another translator station. The signal must be received over the air, with certain exceptions, for example fill-in translators and some NCEs. See §74.1231(b).

Generally, translators may not originate programming, but they can originate (1) emergency warnings of imminent danger and (2) programming to seek or acknowledge financial support for its operation, limited to 30 seconds per hour. The acknowledgement of financial support may identify the contributor and include the size or nature of the contributions and an advertising message of contributors. An FM translator station rebroadcasting a Class D daytime-only AM radio station may also originate programming during the hours the primary station is not operating. Due to this origination limitation, if the primary station signal is lost, the translator must be set up to also go off the air, unless it is rebroadcasting a Class D daytime-only AM station. 

Commercial translators may be authorized on Channel 221 through 300 (92.1 MHz to 107.9 MHz). Translators rebroadcasting noncommercial-educational stations may be authorized on any FM channel, including the reserved band (Channels 201 to 300, or 88.1 MHz to 107.9 MHz). 

Like full-power stations, translator call signs begin with either a W for those located east of the Mississippi River or a K for those to its west, followed by its channel number and a two-letter suffix (e.g., W285AD or K220AA). 

The maximum effective radiated power (ERP) permitted for any translator station is 250 watts, though the maximum ERP for any particular translator will be dependent upon the antenna height above average terrain, the location of the translator and the surrounding geography. The rules governing translators are found in Part 74, Subpart L, FM Broadcast Translator Stations and FM Broadcast Booster Stations.

The FCC categorizes translators into two types: (1) fill-in and (2) non-fill-in. While there is a lot of overlap in requirements, there are some important variations of which broadcasters need to be aware.

  • Fill-In Translators — Translator stations that provide service within the primary station’s protected service area are classified as “fill-in” stations. Fill-in translators can be owned by the main station or by an independent entity. A commercial fill-in translator may use any terrestrial facilities to receive the primary station signal except satellite delivery. A noncommercial educational FM translator on a reserved channel, i.e. Channels 201–220, and owned and operated by its primary noncommercial educational station may use other delivery methods, including satellite and terrestrial microwave. See Sections §74.1231 (b)(1) and (b)(2).
  • Non-Fill-In Translators — With certain exceptions, commercial non-fill-in translators must be owned by independent entities, while noncommercial educational non-fill-in translator stations are generally owned by the primary station being rebroadcast.
Translator K285BO in Wells, Nev., relays KSOS via another translator in Elko. Courtesy Dan Grimes.
Translator K285BO in Wells, Nev., relays KSOS via another translator in Elko. Courtesy Dan Grimes.

FM booster stations

A booster station is a “fill-in” translator on the same frequency as the main station and must be owned by the licensee of the primary FM station. An FM booster will be assigned to the same channel as its primary station. An FM booster station may use direct reception, satellite and terrestrial microwave services to receive the primary station [47 CFR 74.1231(b)]. Booster call signs use the call sign of the main station with the FM suffix and the booster number, e.g., KBDR-FM1 [47 CFR 74.1283]. A primary FM station may have more than one booster.

The booster service contour may not exceed the protected service contour of the primary station at any azimuth. FM broadcast booster stations include LPFM boosters [47 CFR 74.1201(l)]. The maximum effective radiated power for a booster station is 20% of the main station’s maximum class power.

As noted earlier, new rules were approved in November 2024 to allow limited program origination on FM boosters in support of “geotargeting”; they are not reviewed here.

Permissible service

Fill-in Translators and Boosters — The coverage contour of a fill-in translator or booster must be within the service contour of its primary station as follows:

  • Commercial Class B primary station: The 54 dBu (0.5 mV/m) F(50,50) primary station service contour. 
  • Commercial Class B1 FM primary station: The 57 dBu F(50,50) service contour. 

The distances to the primary station and translator station contours are to be predicted using the standard contour prediction method in 47 CFR Section 73.313, using as many radials as necessary to accurately locate the contours. 

  • AM stations: the fill-in area is defined as the area within the greater of the 2 mV/m daytime contour of the AM station being rebroadcast or a 25-mile (40 km) radius centered at the AM transmitter site.

Non-Fill-In Translators — Non-fill-in translators extend the coverage contour beyond the protected contour of the primary station. In some cases, the service contour of the FM translator may lie entirely outside the primary station’s contour. As noted above, these stations cannot be owned or licensed to the primary station licensee. 

Applications

Generally, a translator applicant is not required to submit a technical need showing with its application for a construction permit. However, an applicant seeking a second translator for the same area must make an appropriate showing of technical need for the additional translator, based on the technical quality of the existing translator signal, not the programming content, format or transmission needs of an area.

Applications for new non-reserved band FM translators or for major modifications of an authorized station, whether for commercial or noncommercial educational broadcast stations, are accepted only during specified auction windows. [See 47 CFR 73.5002 and 74.1233(d)(2)(i).]

Applications for minor modifications in the non-reserved band may be filed at any time, unless restricted by the FCC, and will be processed on a “first come/first served” basis, with the first acceptable application cutting off the filing rights of subsequent, conflicting applicants. 

Applications received on the same day are treated as simultaneously filed. Mutually exclusive applications must be resolved through settlement or technical amendment. 

Minor modification applications for boosters and reserved band FM translators may be filed at any time, unless restricted by the FCC, and are processed on a “first come/first served” basis, with the first acceptable application cutting off the filing rights of subsequent, conflicting applicants. Conflicting applications received on the same day are treated as simultaneously filed and mutually exclusive. Later filed conflicting applications are grouped by filing date, behind the lead application in a queue and “ripen” only upon a final determination that the lead applicant is unacceptable. The queue will remain behind the lead applicant until a construction permit is finally granted and then dissolves.

Applications for reserved band FM translator stations are processed using filing window procedures. The FCC will specify by public notice, a period for filing reserved band FM translator applications for a new station or for major modifications in the facilities of an authorized station. FM translator applications for new facilities or for major modifications will be accepted only during these specified periods. Applications submitted prior to the window opening date identified in the public notice will be returned as premature. Applications submitted after the specified deadline will be dismissed with prejudice as untimely. (See  “Processing FM translator and booster applications.”)

All other applications for booster stations and reserved band FM translator stations are processed in the order in which they are filed.

Power limitations and antenna systems 

Fill-in FM translators are limited to 250 watts effective radiated power. All other translator maximum ERP values are determined in accordance with a chart keyed to antenna height above average terrain (HAAT). The chart is in FCC rule section §74.1235(b). The effective radiated power of an FM booster station is limited such that its predicted service contour may not extend beyond its primary FM station service contour and may not exceed 20% of the maximum allowable ERP for the primary station’s class.

Channel change 

FM translator stations may remediate interference either caused to or received from another broadcast station by changing channels to any available same-band frequency as a minor change upon a simple showing of interference reduction. For FM translators in non-frequency-congested areas, this process is useful for interference complaint remediation and for facility improvements.

Interference 

A translator or booster may not cause predicted or actual interference to the transmission of any authorized broadcast station, reception of the input signal of any TV translator, TV booster, FM translator or FM booster station, or the direct reception by the public of the off-the-air signals of any full-service station or previously authorized secondary station. 

Interference may be demonstrated by the following: 

  1. The required minimum number of valid listener complaints [see Table 1 to § 74.1203(a)(3)];
  2. A map plotting the specific location of the alleged interference in relation to the complaining station’s 45 dBu contour;
  3. A statement that the complaining station is operating within its licensed parameters;
  4. A statement that the complaining station licensee has used commercially reasonable efforts to inform the relevant translator licensee of the claimed interference and attempted private resolution; and
  5. U/D data demonstrating that at each listener location the undesired to desired signal strength exceeds −20 dB for co-channel situations, −6 dB for first-adjacent channel situations or 40 dB for second- or third-adjacent channel situations, calculated using the methodology set out in § 74.1204(b)

Listener complaints — Listener complaints must be signed and dated by the listener and contains the following information:

  1. The complainant’s full name, address and phone number;
  2. A clear, concise and accurate description of the location where interference is alleged or predicted to occur;
  3. A statement that the complainant listens over-the-air to the desired station at least twice a month; and
  4. A statement that the complainant has no legal, financial, employment or familial affiliation or relationship with the desired station.

If actual interference is created, the permittee or licensee is required to resolve all interference complaints by appropriate means. If the interference cannot be resolved, the FM translator or booster station must discontinue operations. A translator construction permit application will not be granted if an objecting party provides convincing evidence that the proposed translator station would likely interfere with off-the-air reception of a full-service FM station, even if there is no predicted prohibited contour overlap. 

Primary station change

An FM translator station licensee may change the primary station being rebroadcast without prior authority of and upon notification to commission. Except when the translator licensee is the same as the new primary station licensee, the translator owner must secure the permission of the new primary station to rebroadcast its programming before commencing operation. This is a statutory requirement.

The translator licensee must notify the commission by electronic filing in the LMS database system of ANY change in the primary AM or FM station rebroadcast, using the “Change of Primary Station Notification” form.

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