---
kind: "range"
citation: "47 C.F.R. §§ 73.21–73.37"
title: "47"
from: "73.21"
to: "73.37"
count: 13
url: "https://uscodex.org/cfr/47/73.21..73.37"
---

# §73.21. Classes of AM broadcast channels and stations.

- (a) **Clear channel.** A clear channel is one on which stations are assigned to serve wide areas. These stations are protected from objectionable interference within their primary service areas and, depending on the class of station, their secondary service areas. Stations operating on these channels are classified as follows:
  - (1) **Class A station.** A Class A station is an unlimited time station that operates on a clear channel and is designed to render primary and secondary service over an extended area and at relatively long distances from its transmitter. Its primary service area is protected from objectionable interference from other stations on the same and adjacent channels, and its secondary service area is protected from interference from other stations on the same channel. (See [§ 73.182](/cfr/47/73.182.md)). The operating power shall not be less than 10 kW nor more than 50 kW. (Also see [§ 73.25(a)](/cfr/47/73.25.md?p=a)).
  - (2) **Class B station.** Class B stations are authorized to operate with a minimum power of 0.25 kW (or, if less than 0.25 kW, an equivalent RMS antenna field of at least 107.5 mV/m at 1 kilometer) and a maximum power of 50 kW, or 10 kW for stations that are authorized to operate in the 1605-1705 kHz band.
  - (3) **Class D station.** A Class D station operates either daytime, limited time or unlimited time with nighttime power less than 0.25 kW and an equivalent RMS antenna field of less than 107.5 mV/m at 1 kilometer. Class D stations shall operate with daytime powers not less than 0.25 kW nor more than 50 kW. Nighttime operations of Class D stations are not afforded protection and must protect all Class A and Class B operations during nighttime hours. New Class D stations that had not been previously licensed as Class B will not be authorized.
- (b) **Regional Channel.** A regional channel is one on which Class B and Class D stations may operate and serve primarily a principal center of population and the rural area contiguous thereto.
- (c) **Local channel.** A local channel is one on which stations operate unlimited time and serve primarily a community and the suburban and rural areas immediately contiguous thereto.
  - (1) **Class C station.** A Class C station is a station operating on a local channel and is designed to render service only over a primary service area that may be reduced as a consequence of interference in accordance with [§ 73.182](/cfr/47/73.182.md). The power shall not be less than 0.25 kW, nor more than 1 kW. Class C stations that are licensed to operate with 0.1 kW may continue to do so.

# §73.23. AM broadcast station applications affected by international agreements.

- (a) Except as provided in [paragraph (b)](#b) of this section, no application for an AM station will be accepted for filing if authorization of the facilities requested would be inconsistent with international commitments of the United States under treaties and other international agreements, arrangements and understandings. (See list of such international instruments in [§ 73.1650(b)](/cfr/47/73.1650.md?p=b)). Any such application that is inadvertently accepted for filing will be dismissed.
- (b) AM applications that involve conflicts only with the North American Regional Broadcasting Agreement (NARBA), but that are in conformity with the remaining treaties and other international agreements listed in [§ 73.1650(b)](/cfr/47/73.1650.md?p=b) and with the other requirements of this part 73, will be granted subject to such modifications as the FCC may subsequently find appropriate, taking international considerations into account.
- (c) In the case of any application designated for hearing on issues other than those related to consistency with international relationships and as to which no final decision has been rendered, whenever action under this section becomes appropriate because of inconsistency with international relationships, the applicant involved shall, notwithstanding the provisions §§ [73.3522](/cfr/47/73.3522.md) and [73.3571](/cfr/47/73.3571.md), be permitted to amend its application to achieve consistency with such relationships. In such cases the provisions of [§ 73.3605(c)](/cfr/47/73.3605.md?p=c) will apply.
- (d) In some circumstances, special international considerations may require that the FCC, in acting on applications, follow procedures different from those established for general use. In such cases, affected applicants will be informed of the procedures to be followed.

# §73.24. Broadcast facilities; showing required.


An authorization for a new AM broadcast station or increase in facilities of an existing station will be issued only after a satisfactory showing has been made in regard to the following, among others:

- (a) That the proposed assignment will tend to effect a fair, efficient, and equitable distribution of radio service among the several states and communities.
- (b) That a proposed new station (or a proposed change in the facilities of an authorized station) complies with the pertinent requirements of [§ 73.37](/cfr/47/73.37.md) of this chapter.
- (c) **That the applicant is financially qualified to construct and operate the proposed station.**
- (d) **That the applicant is legally qualified.** That the applicant (or the person or persons in control of an applicant corporation or other organization) is of good character and possesses other qualifications sufficient to provide a satisfactory public service.
- (e) That the technical equipment proposed, the location of the transmitter, and other technical phases of operation comply with the regulations governing the same, and the requirements of good engineering practice.
- (f) That the facilities sought are subject to assignment as requested under existing international agreements and the rules and regulations of the Commission.
- (g) That the population within the 1 V/m contour does not exceed 1.0 percent of the population within the 25 mV/m contour: Provided, however, That where the number of persons within the 1 V/m contour is 300 or less the provisions of this paragraph are not applicable.
- (h) That, in the case of an application for a Class B or Class D station on a clear channel, the proposed station would radiate, during two hours following local sunrise and two hours preceding local sunset, in any direction toward the 0.1 mV/m groundwave contour of a co-channel United States Class A station, no more than the maximum value permitted under the provisions of [§ 73.187](/cfr/47/73.187.md).
- (i) That, for all proposals for new stations, applications to modify a construction permit for an unlicensed station, and all applications to change a station's community of license, the daytime 5 mV/m contour encompasses the entire principal community to be served. That, for all other applications for modification of licensed stations, the daytime 5 mV/m contour encompasses either 50 percent of the area, or 50 percent of the population, of the principal community to be served. That, for all proposals for new stations in the 535-1605 kHz band, applications to modify a construction permit for an unlicensed station, or applications to change a station's community of license, either 50 percent of the area, or 50 percent of the population of the principal community is encompassed by the nighttime 5 mV/m contour or the nighttime interference-free contour, whichever value is higher. That, for stations in the 1605-1705 kHz band, 50 percent of the principal community is encompassed by the nighttime 5 mV/m contour or the nighttime interference-free contour, whichever value is higher. That Class D stations with nighttime authorizations need not demonstrate such coverage during nighttime operation.
- (j) That the public interest, convenience, and necessity will be served through the operation under the proposed assignment.

# §73.25. Clear channels; Class A, Class B and Class D stations.


The frequencies in the following tabulations are designated as clear channels and assigned for use by the Classes of stations given:

- (a) On each of the following channels, one Class A station may be assigned, operating with power of 50 kW: 640, 650, 660, 670, 700, 720, 750, 760, 770, 780, 820, 830, 840, 870, 880, 890, 1020, 1030, 1040, 1100, 1120, 1160, 1180, 1200, and 1210 kHz. In Alaska, these frequencies can be used by Class A stations subject to the conditions set forth in [§ 73.182(a)(1)(ii)](/cfr/47/73.182.md?p=a-1-ii). On the channels listed in this paragraph, Class B and Class D stations may be assigned.
- (b) To each of the following channels there may be assigned Class A, Class B and Class D stations: 680, 710, 810, 850, 940, 1000, 1060, 1070, 1080, 1090, 1110, 1130, 1140, 1170, 1190, 1500, 1510, 1520, 1530, 1540, 1550, and 1560 kHz.
- (c) Class A, Class B and Class D stations may be assigned on 540, 690, 730, 740, 800, 860, 900, 990, 1010, 1050, 1220, 1540, 1570, and 1580 kHz.

# §73.26. Regional channels; Class B and Class D stations.

- (a) The following frequencies are designated as regional channels and are assigned for use by Class B and Class D stations: 550, 560, 570, 580, 590, 600, 610, 620, 630, 790, 910, 920, 930, 950, 960, 970, 980, 1150, 1250, 1260, 1270, 1280, 1290, 1300, 1310, 1320, 1330, 1350, 1360, 1370, 1380, 1390, 1410, 1420, 1430, 1440, 1460, 1470, 1480, 1590, 1600, 1610, 1620, 1630, 1640, 1650, 1660, 1670, 1680, 1690, and 1700 kHz.
- (b) Additionally, in Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands the frequencies 1230, 1240, 1340, 1400, 1450, and 1490 kHz are designated as Regional channels, and are assigned for use by Class B stations. Stations formerly licensed to these channels in those locations as Class C stations are redesignated as Class B stations.

# §73.27. Local channels; Class C stations.


Within the conterminous 48 states, the following frequencies are designated as local channels, and are assigned for use by Class C stations: 1230, 1240, 1340, 1400, 1450, and 1490 kHz.


# §73.28. Assignment of stations to channels.

- (a) The Commission will not make an AM station assignment that does not conform with international requirements and restrictions on spectrum use that the United States has accepted as a signatory to treaties, conventions, and other international agreements. See [§ 73.1650](/cfr/47/73.1650.md) for a list of pertinent treaties, conventions and agreements, and [§ 73.23](/cfr/47/73.23.md) for procedural provisions relating to compliance with them.
- (b) Engineering standards now in force domestically differ in some respects from those specified for international purposes. The engineering standards specified for international purposes (see [§ 73.1650](/cfr/47/73.1650.md), International Agreements) will be used to determine:
  - (1) The extent to which interference might be caused by a proposed station in the United States to a station in another country; and
  - (2) whether the United States should register an objection to any new or changed assignment notified by another country. The domestic standards in effect in the United States will be used to determine the extent to which interference exists or would exist from a foreign station where the value of such interference enters into a calculation of:
    - (i) The service to be rendered by a proposed operation in the United States; or
    - (ii) the permissible interfering signal from one station in the United States to another United States station.

# §73.29. Class C stations on regional channels.


No license will be granted for the operation of a Class C station on a regional channel.


# §73.30. Petition for authorization of an allotment in the 1605-1705 kHz band.

- (a) Any party interested in operating an AM broadcast station on one of the ten channels in the 1605-1705 kHz band must file a petition for the establishment of an allotment to its community of license. Each petition must include the following information:
  - (1) Name of community for which allotment is sought;
  - (2) Frequency and call letters of the petitioner's existing AM operation; and
  - (3) Statement as to whether or not AM stereo operation is proposed for the operation in the 1605-1705 kHz band.
- (b) **Petitions are to be filed during a filing period to be determined by the Commission.** For each filing period, eligible stations will be allotted channels based on the following steps:
  - (1) **Stations are ranked in descending order according to the calculated improvement factor.**
  - (2) **The station with the highest improvement factor is initially allotted the lowest available channel.**
  - (3) Successively, each station with the next lowest improvement factor, is allotted an available channel taking into account the possible frequency and location combinations and relationship to previously selected allotments. If a channel is not available for the subject station, previous allotments are examined with respect to an alternate channel, the use of which would make a channel available for the subject station.
  - (4) When it has been determined that, in accordance with the above steps, no channel is available for the subject station, that station is no longer considered and the process continues to the station with the next lowest improvement factor.
- (c) If awarded an allotment, a petitioner will have sixty (60) days from the date of public notice of selection to file an application for construction permit on FCC Form 2100, Schedule 301. (See §§ [73.24](/cfr/47/73.24.md) and [73.37(e)](/cfr/47/73.37.md?p=e) for filing requirements). Unless instructed by the Commission to do otherwise, the application shall specify Model I facilities. (See [§ 73.14](/cfr/47/73.14.md)). Upon grant of the application and subsequent construction of the authorized facility, the applicant must file a license application on FCC Form 2100, Schedule 302.

# §73.31. Rounding of nominal power specified on applications.

- (a) An application filed with the FCC for a new station or for an increase in power of an existing station shall specify nominal power rounded to two significant figures as follows:
- (b) In rounding the nominal power in accordance with [paragraph (a)](#a) of this section the RMS shall be adjusted accordingly. If rounding upward to the nearest figure would result in objectionable interference, the nominal power specified on the application is to be rounded downward to the next nearest figure and the RMS adjusted accordingly.

# §73.33. Antenna systems; showing required.

- (a) An application for authority to install a broadcast antenna shall specify a definite site and include full details of the antenna design and expected performance.
- (b) All data necessary to show compliance with the terms and conditions of the construction permit must be filed with the license application. If the station is using a directional antenna, a proof of performance must also be filed.

# §73.35. Calculation of improvement factors.


A petition for an allotment (See [§ 73.30](/cfr/47/73.30.md)) in the 1605-1705 kHz band filed by an existing fulltime AM station licensed in the 535-1605 kHz band will be ranked according to the station's calculated improvement factor. (See [§ 73.30](/cfr/47/73.30.md)). Improvement factors relate to both nighttime and daytime interference conditions and are based on two distinct considerations: (a) Service area lost by other stations due to interference caused by the subject station, and (b) service area of the subject station. These considerations are represented by a ratio. The ratio consists, where applicable, of two separate additive components, one for nighttime and one for daytime. For the nighttime component, to determine the numerator of the ratio (first consideration), calculate the RSS and associated service area of the stations (co- and adjacent channel) to which the subject station causes nighttime interference. Next, repeat the RSS and service area calculations excluding the subject station. The cumulative gain in the above service area is the numerator of the ratio. The denominator (second consideration) is the subject station's interference-free service area. For the daytime component, the composite amount of service lost by co-channel and adjacent channel stations, each taken individually, that are affected by the subject station, excluding the effects of other assignments during each study, will be used as the numerator of the daytime improvement factor. The denominator will consist of the actual daytime service area (0.5 mV/m contour) less any area lost to interference from other assignments. The value of this combined ratio will constitute the petitioner's improvement factor. Notwithstanding the requirements of [§ 73.153](/cfr/47/73.153.md), for uniform comparisons and simplicity, measurement data will not be used for determining improvement factors and FCC figure M-3 ground conductivity values are to be used exclusively in accordance with the pertinent provisions of [§ 73.183(c)(1)](/cfr/47/73.183.md?p=c-1).


# §73.37. Applications for broadcast facilities, showing required.

- (a) No application will be accepted for a new station if the proposed operation would involve overlap of signal strength contours with any other station as set forth below in this paragraph; and no application will be accepted for a change of the facilities of an existing station if the proposed change would involve such overlap where there is not already such overlap between the stations involved:
- (b) In determining overlap received, an application for a new Class C station with daytime power of 250 watts, or greater, shall be considered on the assumption that both the proposed operation and all existing Class C stations operate with 250 watts and utilize non-directional antennas.
- (c) If otherwise consistent with the public interest, an application requesting an increase in the daytime power of an existing Class C station on a local channel from 250 watts to a maximum of 1kW, or from 100 watts to a maximum of 500 watts, may be granted notwithstanding overlap prohibited by [paragraph (a)](#a) of this section. In the case of a 100 watt Class C station increasing daytime power, the provisions of this paragraph shall not be construed to permit an increase in power to more than 500 watts, if prohibited overlap would be involved, even if successive applications should be filed.
- (d) In addition to demonstrating compliance with [paragraphs (a)](#a), and, as appropriate, (b), and (c) of this section, an application for a new AM broadcast station, or for a major change (see [§ 73.3571(a)(1)](/cfr/47/73.3571.md?p=a-1)) in an authorized AM broadcast station, as a condition for its acceptance, shall make a satisfactory showing, if new or modified nighttime operation by a Class B station is proposed, that objectionable interference will not result to an authorized station, as determined pursuant to [§ 73.182(1)](/cfr/47/73.182.md?p=1).
- (e) An application for an authorization in the 1605-1705 kHz band which has been selected through the petition process (See [§ 73.30](/cfr/47/73.30.md)) is not required to demonstrate compliance with paragraph [(a)](#a), [(b)](#b), [(c)](#c), or [(d)](#d) of this section. Instead, the applicant need only comply with the terms of the allotment authorization issued by the Commission in response to the earlier petition for establishment of a station in the 1605-1705 kHz band. Within the allotment authorization, the Commission will specify the assigned frequency and the applicable technical requirements.
- (f) **Stations on 1580, 1590 and 1600 kHz.** In addition to the rules governing the authorization of facilities in the 535-1605 kHz band, stations on these frequencies seeking facilities modifications must protect assignments in the 1610-1700 kHz band. Such protection shall be afforded in a manner which considers the spacings that occur or exist between the subject station and a station within the range 1605-1700 kHz. The spacings are the same as those specified for stations in the frequency band 1610-1700 kHz or the current separation distance, whichever is greater. Modifications that would result in a spacing or spacings that fails to meet any of the separations must include a showing that appropriate adjustment has been made to the radiated signal which effectively results in a site-to-site radiation that is equivalent to the radiation of a station with standard Model I facilities (10 kW-D, 1 kW-N, non-DA, 90 degree antenna ht. & ground system) operating in compliance with all of the above separation distances. In those cases where that radiation equivalence value is already exceeded, a station may continue to maintain, but not increase beyond that level.