REC Open Letter to existing FM broadcast stations re: interference from LPFM applications in the 2023 Filing Window

REC Networks is the national regulatory advocacy supporting small radio broadcast stations, such as those in the noncommercial educational (NCE) sector with a very strong focus on the Low Power FM (LPFM) broadcast service.

In December, 2023, the FCC had conducted a filing window for new LPFM construction permits. On December 17, 2023, the FCC released the details of the applications filed in that window. A total of 1,336 applications were filed.

LPFM stations must meet specific licensing requirements such as being a local organization that does not have any attributable interests in any other broadcast service (there are some very limited carve outs to this rule).  LPFM station must also meet specific minimum distance separation requirements to other FM broadcast facilities (full-service, FM translator and other LPFM) stations on co-channel, first-adjacent and second-adjacent channels.  LPFM stations that to not meet the minimum distance separation requirements on second-adjacent channels to full-service and FM translator facilities may include a technical showing that there will not be any interference to listeners of the affected second-adjacent channel station(s) in the immediate area surrounding the proposed LPFM stations.  Second-adjacent channel protection is not required between two LPFM stations.  LPFM stations are also not required to protect any domestic FM facility on third-adjacent channel nor intermediate frequency (+/- 10.6 or 10.8 MHz) channel.

REC Networks has been receiving reports from applicants in the 2023 filing window that they have been receiving correspondence from representatives of incumbent broadcast stations claiming that the proposed LPFM station will cause interference within the existing station’s “45 dBu area” and that they plan to file an objection. 

In respect to LPFM stations, complaints like this are mistaken and inappropriate. 

The translator interference rules

In 2019, the FCC issued a Report and Order in MB Docket 18-119 (34 FCC Rcd. 3457 (2019)) ("R&O").  In this R&O, the Commission amended 47 CFR §§ 74.1203 and 74.1204 in respect to interference received to broadcast facilities (including full-service, LPFM and FM translators) from subsequently authorized FM translators.  The R&O established an evaluation area of the 45 dBu from the incumbent site as to where if in the event that the undesired to desired (U/D) ratio exceeds -20 dB for co-channel situations at a particular listener's location, that listener's information can be included as part of an interference complaint "package".  A threshold of such listener interference complaints, based on the population that is served by the incumbent station is required prior to the interference complaint being accepted.  The rule does require that the proponent for the subsequent station be contacted first.

As such, the interference redress policy that involves the use of the “45 dBu contour” only applies if the interfering or potentially interfering subsequent facility is an FM translator.  This rule does not apply if the proposed/new/modified facility is an LPFM station.

FCC rules related to new LPFM interference to full-service FM stations

The applicable rule in this case is 47 CFR §73.209(c), which states:

Permittees and licensees of FM stations are not protected from interference which may be caused by the grant of a new LPFM station or of authority to modify an existing LPFM station, except as provided in subpart G of this part.

Further, 47 CFR §73.809(a) states:

If a full service commercial or NCE FM facility application is filed subsequent to the filing of an LPFM station facility application, such full service station is protected against any condition of interference to the direct reception of its signal caused by such LPFM station that operates on the same channel or first-adjacent channel provided that the interference is predicted to occur and actually occurs within:
(1) The 3.16 mV/m (70 dBu) contour of such full service station;

(2) The community of license of such full service station; or

(3) Any area of the community of license of such full service station that is predicted to receive at least a 1 mV/ m (60 dBu) signal. Predicted interference shall be calculated in accordance with the ratios set forth in § 73.215 paragraphs (a)(1) and (a)(2). Intermediate frequency (IF) channel interference overlap will be determined based upon overlap of the 91 dBu F(50,50) contours of the FM and LPFM stations. Actual interference will be considered to occur whenever reception of a regularly used signal is impaired by the signal radiated by the LPFM station.

The provisions of §73.809(a) are only in force if a full-service station files an application to modify their licensed facility in a manner that would cause the relevant interfering contour of the LPFM station to overlap into the proposed full-service 70 dBu community coverage contour.  Since these are new stations and the full-service FM station is not making a modification, §73.809(a) is not applicable.

FCC policy related to new LPFM interference to FM translator and other LPFM stations

When the FCC created the LPFM service, they decided to use distance separation requirements to establish interference protections in order to “preserve the integrity and technical excellence of the existing FM radio service.” (Creation of a Low Power Radio Service, Report and Order 15 FCC Rcd. 2205, 2223-33 (2000)). 

In the 2016 Packinghouse case where an existing LPFM station claimed interference from a new LPFM station, the FCC had denied the complaint because the two stations do meet the minimum distance separation requirements. (Calvary Chapel of Redlands d/b/a Packinghouse Christian Fwp., Letter, 31 FCC Rcd. 12694 (2016)). 

Neither the LPFM service nor the FM translator service have any specific rules to redress potential or actual interference caused by a subsequently authorized LPFM facility as long as that subsequent LPFM is operating their authorized facilities.

It is important to note that since FM translators use contour overlap instead of distance separation to protect the LPFM service, existing LPFM stations can seek redress from subsequently filed FM translator facilities using §§ 74.1203 and 74.1204. 


All LPFM proposals must meet the minimum §73.807 distance separation requirements to all existing full-service FM (commercial and noncommercial) facilities as well as to existing FM translators and LPFM stations. 

Because distance separation is used, the protections afforded to existing stations pursuant to §§ 74.1203 and 74.1204 do not apply when the new or modified facility is an LPFM.  It only applies when such station is an FM translator.

If you have any further questions, please let us know.


Michelle Bradley, CBT
REC Networks
January 10, 2024