73.807

Part 73, Subpart G, § 73.807 is a core regulation in the Low Power FM radio service. This rule addresses the placement of LPFM stations in respect to other FM broadcast facilities. LPFM stations operating on reserved band FM frequencies (88.1~91.9 MHz) are also required to protect TV facilities on Channel 6 pursuant to § 73.825.

Protections to domestic FM stations

Other LPFM stations

LPFM stations may only be proposed where they are separated by other LPFM stations on the same channel by at least 24 kilometers (14.9 miles) and on first-adjacent channels by 14 kilometers (8.7 miles). LPFM stations are not required to protect other LPFM stations on second adjacent channels.

Full Service FM stations within the United States

In respect to full-service FM stations operating on the same or the first-adjacent channel of the LPFM, the minimum distance separations required are based on the standard interfering contour of the LPFM station and a distance that is 20 kilometers (12.4 miles) past the standard protected service contour of the full-service station. Each full-service FM service class has specific distances required for separation. This additional 20 kilometer "buffer zone" was adopted in the original LPFM Report and Order in order to assure minimal impacts on LPFM stations in the event that a full-service FM station had to make a modification of their facility.

LPFM stations are also required to protect full-service FM stations on second adjacent channels, however that requirement can be waived if a technical showing is made that the proposed LPFM facility does not cause any actual interference to listeners or potential listeners of the short-spaced second adjacent channel station or stations. In addition, LPFM stations must also protect FM stations on third adjacent channels in cases where the other FM station is carrying a Radio Reading Service. Second and third adjacent channel requirements do not include the 20 kilometer "buffer zone".

Waivers of the second-adjacent channel protections are subject to the Second adjacent channel waiver are also subject to the second adjacent channel waiver rule's remediation procedures in the event of interference.

In 2011 with the enactment of the Local Community Radio Act of 2010 (LCRA), the use of minimum distance separation methodology and the actual distances that were codified in this rule at the time when the LCRA was enacted must be used. Because of that statutory requirement, the FCC is unable to give any waiver of the distance separation rules in respect to co-channel (same channel) and first-adjacent channel domestic FM facilities.

Class D stations

LPFM stations are required to protect Class D stations operating on the same channel as well as first and second adjacent channels. Second adjacent channel short-spacing can be waived in a manner similar to full-service FM stations.

Super-powered FM broadcast stations

FM stations operating in the reserved band (88.1~91.9 MHz), including class D stations, that are operating with parameters that exceed the maximum allowed for that service class will be protected at the service class that represents the parameters of the actual facility.

Puerto Rico and the U.S. Virgin Islands

Because of the differences in the maximum parameters of FM broadcast stations within Puerto Rico and the U.S. Virgin Islands, the required minimum distance separations from LPFM stations to full-service FM stations are are larger than those in the mainland United States. In Puerto Rico and the Virgin Islands, only classes A, B1 and B are available to full-service FM stations.

FM Translator Stations

In respect to LPFM stations, FM translator stations are classified into one of three "sub classes". The subclass is based on the translator's maximum effective radiated power (ERP) and overall height above average terrain. The sub-class is based on the average distance to the 60 dBu service contour. LPFM stations must protect FM translators on the same channel, first and second adjacent channels using minimum distance separation. Second adjacent channel spacing can be waived using the same method as waivers in respect to full-service FM stations.

While the FM translator service spacing requirements are not specifically mandated by the LCRA, the FCC has customarily not granted any waivers of distance separation on co-channel and first-adjacent channels, even if a finding of no interference is demonstrated. LPFM stations are required to protect FM translators using directional antennas as if they are using a nondirectional antenna.

Protections to foreign FM stations

Proposals for LPFM facilities located within 320 kilometers (198.8 miles) of the Canadian and Mexican borders will be coordinated with Innovation, Science and Economic Development Canada (ISED) or Mexico's Instituto Federal de Telecomunicaciones (IFT) in accordance with the appropriate international agreements. Normally, those countries will reply with either an acceptance or a objection of the proposed facility. As a result, a grant of an LPFM construction permit in a border zone may take longer than the time it takes for a proposal not involving international coordination. In some cases, the foreign administration may not timely reply to the Commission's proposal. In those cases, the FCC may grant the LPFM construction permit application with a condition that the proposal is still awaiting concurrence from the foreign administration, which can still object to the LPFM proposal. In those cases, the three years allowed to complete construction can be extended under the FCC's tolling policy.

Canada

In 1991, the United States and |Canada reached an international agreement over the use of the FM channels in the border region. This agreement was updated in 1997 to reflect changes in service classes and to improve the lower powered facilities to operate in the region.

Minimum distance separations

LPFM stations are required to protect all Canadian FM facilities, including Canadian low power FM facilities through the use of a distance separation table based on the service class of the Canadian station. Protections are required on the same channel as well as first, second and third-adjacent channels. Unlike the rules for domestic FM facilities, there is no option to waive second (or third) adjacent channel protections. Waivers are not normally given for short-spaced stations where it can be shown that the LPFM station would not interfere with Canadian facilities even though one such waiver was granted to LPFM station WNUC-LP in Detroit.

LPFM stations are also required to protect Canadian facilities on their intermediate frequencies, which are those that are 53 or 54 channels (10.6 and 10.8 MHz) higher or lower than the LPFM's proposed operating channel.

Contour requirements

In addition to the distance separation requirements, LPFM stations operating within 320 kilometers (198.8 miles) of the Canadian border may not extend a 34 dBu interfering contour past 60 kilometers (37.3 miles) in any direction.

Mexico

In 1992, the United States of America reached an agreement with the United Mexican States over the use of the FM channels in the border region. The agreement classifies both LPFM stations and FM translators as "LPFM" stations for the purposes of the agreement.

Minimum distance separations

LPFM stations are required to protect all Mexican FM facilities, including Mexican low power FM facilities through the use of a distance separation table based on the service class of the Mexican station. Protections are required on the same channel as well as first, second and third-adjacent channels. Unlike the rules for domestic FM facilities, there is no option to waive second (or third) adjacent channel protections. Waivers are not normally given for short-spaced stations where it can be shown that the LPFM station would not interfere with Mexican facilities.

Mexico Strip Zone

LPFM stations within 125 kilometers (77.6 miles) of the Mexican border are limited to 50 watts effective radiated power in the directions towards Mexico.

To determine the the area that requires this protection, plot a 125 kilometer radius around the proposed LPFM station and then draws lines from the LPFM station to all points where the 125 km radius intersects with the border. The area between those two or more lines is the area where the Mexico Strip Zone policies apply. In California, applicants need to be aware that Mexican territory extends into the Pacific Ocean to include the Coronado Islands located off the coast of the state of Baja California.

Contour requirements

In addition to the distance separation requirements, LPFM stations within 125 kilometers of Mexico may not extend a 60 dBu contour more than 8.7 kilometers (5.4 miles) towards the other country. In addition, the 34 dBu interfering contour cannot extend more than 32 kilometers (19.9 miles) towards the other country.

LPFM stations more than 125 km from the border may operate up to 100 watts in all directions. For stations exceeding 50 watts, the 60 dBu contour can not extend to any point within 116.3 kilometers (72.3 miles) within the Mexican border.

Caribbean nations

For foreign FM stations in the Caribbean region, the FCC does not have any specific bilateral or multilateral agreements with any other nation's administration. Therefore, there are no specific distance separation requirements to other FM facilities outside of the United States territories.

The assignment of frequencies to LPFM stations in Puerto Rico and the U.S. Virgin Islands are also reported to the International Telecommunications Union's Master International Frequency Register. As a result, LPFM stations, especially those in the U.S. Virgin Islands may receive objections and interference complaints from other nations in the Caribbean region. Such objections and complaints would be lodged through the FCC's International Bureau, which will in turn contact the Media Bureau, which may order the LPFM station to cease operations. LPFM stations in the U.S. Virgin Islands should choose a channel that would not cause interference with FM stations in the British Virgin Islands.

Directional Antennas

Main article: Directional Antennas.

LPFM stations may use a directional antenna in order to achieve a facility that is compliant with an international agreement. LPFM stations that are using directional antennas solely for that purpose are not required to obtain a proof of performance and verifications from an engineer and a surveyor. Such directional antennas will be protected from FM translators as if they are operating with a nondirectional antenna.

Regulatory History

LPFM Report and Order

This rule was first enacted in the original LPFM Report and Order in January, 2000. The original rules included the 10-watt LP-10 service, instituted the 20 kilometer "buffer zone" and did not require the protection of third-adjacent channels.

Order on Reconsideration

In the Order on Reconsideration enacted September 2000, the rule was clarified to state that LPFM applications during a filing window only need to protect other facilities that were filed prior to the public notice announcing the LPFM filing window. Rules were also clarified to clarify that existing stations would be protected based on standard distances based on their service class.

Due to concerns expressed by interests representing audio services for the blind, the FCC imposed third-adjacent channel spacing restrictions by LPFM stations towards full-service FM stations that were operating radio reading services.

The required distance separations were amended to take into consideration low power FM facilities in Mexico, which were inadvertently left out of the original distance table from the Report and Order

Biennial Regulatory Review-Streamlining of Radio Rules

Less than a month later, the Streamlining Order enacted the new C0 class of service. The domestic LPFM distance separation tables were amended to add this new class of service between classes C1 and C.

Second Report and Order

With the enactment of the Radio Broadcast Preservation Act of 2001, a part of an appropriations legislation for the District of Columbia, the Second Report and Order imposed the requirement that LPFM stations must protect domestic FM facilities on third-adjacent channels.

Fifth Report and Order

In March, 2012, with the enactment of the Local Community Radio Act of 2010, the Fifth Report and Order amended the rules to remove the third-adjacent channel protection requirements. Third adjacent channel protections remained in place to radio reading services pursuant to the LCRA.

Sixth Report and Order

In October, 2012, the Sixth Report and Order removed the 10-watt LP-10 service, for which no licenses were ever granted for. LPFM protections towards stations operating on intermediate frequencies were removed. Language was added to implement the new second-adjacent channel waiver aspect of the LCRA.

LPFM Tech Order

In July, 2020, the LPFM Tech Order, which expanded the ability for LPFM stations to use directional antennas resulted in this section being amended to include the international limitations on service contour size and effective radiated power in the border coordination areas.

Text of regulation 47 CFR §73.807

§ 73.807 Minimum distance separation between stations.

Minimum separation requirements for LPFM stations are listed in the following paragraphs. Except as noted below, an LPFM station will not be authorized unless the co-channel, and first- and second-adjacent channel separations are met. An LPFM station need not satisfy the third-adjacent channel separations listed in paragraphs (a) through (c) of this section in order to be authorized. The third-adjacent channel separations are included for use in determining for purposes of § 73.810 which third-adjacent channel interference regime applies to an LPFM station. Minimum distances for co-channel and first-adjacent channel are separated into two columns. The left-hand column lists the required minimum separation to protect other stations and the right-hand column lists (for informational purposes only) the minimum distance necessary for the LPFM station to receive no interference from other stations assumed to be operating at the maximum permitted facilities for the station class. For second-adjacent channel, the required minimum distance separation is sufficient to avoid interference received from other stations.

(a)

(1) An LPFM station will not be authorized initially unless the minimum distance separations in the following table are met with respect to authorized FM stations, applications for new and existing FM stations filed prior to the release of the public notice announcing an LPFM window period, authorized LPFM stations, LPFM station applications that were timely-filed within a previous window, and vacant FM allotments. LPFM modification applications must either meet the distance separations in the following table or, if short-spaced, not lessen the spacing to subsequently authorized stations.

Station class protected by LPFM	Co-channel minimum separation (km)		First-adjacent channel minimum separation (km)		Second and third adjacent channel minimum separation (km)
	Required	For no interference received from max. class facility	Required	For no interference received from max. class facility	Required
LPFM	24	24	14	14	None
D	24	24	13	13	6
A	67	92	56	56	29
B1	87	119	74	74	46
B	112	143	97	97	67
C3	78	119	67	67	40
C2	91	143	80	84	53
C1	111	178	100	111	73
C0	122	193	111	130	84
C	130	203	120	142	93

(2) LPFM stations must satisfy the second-adjacent channel minimum distance separation requirements of paragraph (a)(1) of this section with respect to any third-adjacent channel FM station that, as of September 20, 2000, broadcasts a radio reading service via a subcarrier frequency.

(b) In addition to meeting or exceeding the minimum separations in paragraph (a) of this section, new LPFM stations will not be autorized in Puerto Rico or the Virgin Islands unless the minimum distance separations in the following tables are met with respect to authorized or proposed FM stations:

Station class protected by LPFM	Co-channel minimum separation (km)		First-adjacent channel minimum separation (km)		Second and third adjacent channel minimum separation (km) - required
	Required	For no interference received from max. class facility	Required	For no interference received from max. class facility
A	80	111	70	70	42
B1	95	128	82	82	53
B	138	179	123	123	92

Note to paragraphs (a) and (b):

Minimum distance separations towards “grandfathered” superpowered Reserved Band stations are as specified. Full service FM stations operating within the reserved band (Channels 201-220) with facilities in excess of those permitted in § 73.211(b)(1) or (b)(3) shall be protected by LPFM stations in accordance with the minimum distance separations for the nearest class as determined under § 73.211. For example, a Class B1 station operating with facilities that result in a 60 dBu contour that exceeds 39 kilometers but is less than 52 kilometers would be protected by the Class B minimum distance separations. Class D stations with 60 dBu contours that exceed 5 kilometers will be protected by the Class A minimum distance separations. Class B stations with 60 dBu contours that exceed 52 kilometers will be protected as Class C1 or Class C stations depending upon the distance to the 60 dBu contour. No stations will be protected beyond Class C separations.

(c) In addition to meeting the separations specified in paragraphs (a) and (b), LPFM applications must meet the minimum separation requirements in the following table with respect to authorized FM translator stations, cutoff FM translator applications, and FM translator applications filed prior to the release of the Public Notice announcing the LPFM window period.

Distance to FM translator 60 dBu contour	Co-channel minimum separation (km)		First-adjacent channel minimum separation (km)		Second and third adjacent channel minimum separation (km) - required
	Required	For no interference received	Required	For no interference received
13.3 km or greater	39	67	28	35	21
Greater than 7.3 km, but less than 13.3 km	32	51	21	26	14
7.3 km or less	26	30	15	16	8

(d) Existing LPFM stations which do not meet the separations in paragraphs (a) through (c) of this section may be relocated provided that the separation to any short-spaced station is not reduced.

(e)

(1) Waiver of the second-adjacent channel separations. The Commission will entertain requests to waive the second-adjacent channel separations in paragraphs (a) through (c) of this section on a case-by-case basis. In each case, the LPFM station must establish, using methods of predicting interference taking into account all relevant factors, including terrain-sensitive propagation models, that its proposed operations will not result in interference to any authorized radio service. The LPFM station may do so by demonstrating that no actual interference will occur due to intervening terrain or lack of population. The LPFM station may use an undesired/desired signal strength ratio methodology to define areas of potential interference.

(2) Interference.

(i) Upon receipt of a complaint of interference from an LPFM station operating pursuant to a waiver granted under paragraph (e)(1) of this section, the Commission shall notify the identified LPFM station by telephone or other electronic communication within one business day.

(ii) An LPFM station that receives a waiver under paragraph (e)(1) of this section shall suspend operation immediately upon notification by the Commission that it is causing interference to the reception of an existing or modified full-service FM station without regard to the location of the station receiving interference. The LPFM station shall not resume operation until such interference has been eliminated or it can demonstrate to the Commission that the interference was not due to emissions from the LPFM station. Short test transmissions may be made during the period of suspended operation to check the efficacy of remedial measures.

(f) Commercial and noncommercial educational stations authorized under subparts B and C of this part, as well as new or modified commercial FM allotments, are not required to adhere to the separations specified in this rule section, even where new or increased interference would be created.

(g) International considerations within the border zones.

(1) Within 320 km of the Canadian border, LPFM stations must meet the following minimum separations with respect to any Canadian stations:

Canadian station class	Co-channel (km)	First-adjacent channel (km)	Second- adjacent channel (km)	Third-adjacent channel (km)	Intermediate frequency (IF) channel (km)
A1 & Low Power	45	30	21	20	4
A	66	50	41	40	7
B1	78	62	53	52	9
B	92	76	68	66	12
C1	113	98	89	88	19
C	124	108	99	98	28

(2) Within 320 km of the Mexican border, LPFM stations must meet the following separations with respect to any Mexican stations:

Mexican station class	Co-channel (km)	First-adjacent channel (km)	Second- and third-adjacent channel (km)	Intermediate frequency (IF) channel (km)
Low Power	27	17	9	3
A	43	32	25	5
AA	47	36	29	6
B1	67	54	45	8
B	91	76	66	11
C1	91	80	73	19
C	110	100	92	27

(3) The Commission will notify the International Telecommunications Union (ITU) of any LPFM authorizations in the US Virgin Islands. Any authorization issued for a US Virgin Islands LPFM station will include a condition that permits the Commission to modify, suspend or terminate without right to a hearing if found by the Commission to be necessary to conform to any international regulations or agreements.

(4) The Commission will initiate international coordination of a LPFM proposal even where the above Canadian and Mexican spacing tables are met, if it appears that such coordination is necessary to maintain compliance with international agreements.

(5)

(i) LPFM stations located within 125 kilometers of the Mexican border are limited to 50 watts (0.05 kW) ERP, a 60 dBu service contour of 8.7 kilometers and a 34 dBu interfering contour of 32 kilometers in the direction of the Mexican border. LPFM stations may operate up to 100 watts in all other directions.

(ii) LPFM stations located between 125 kilometers and 320 kilometers from the Mexican border may operate in excess of 50 watts, up to a maximum ERP of 100 watts. However, in no event shall the location of the 60 dBu contour lie within 116.3 kilometers of the Mexican border.

(iii) Applications for LPFM stations within 320 kilometers of the Canadian border may employ an ERP of up to a maximum of 100 watts. The distance to the 34 dBu interfering contour may not exceed 60 kilometers in any direction.