provided such transmitter continues to comply with the rules and regulations. (4) A permittee may, without further authority, install a transmitter other than that specifically authorized in its construction permit if such transmitter is listed in the Commission's "Radio Equipment List" as accepted for the power authorized. (5) A licensee may, without further authority, install and utilize a transmitter other than that specifically authorized in its station license if the transmitter so installed and utilized is listed in the Commission's "Radio Equipment List, Part B, Aural Broadcast Equipment" as accepted for the power authorized if the Commission and the Engineer in Charge of the radio district in which the station is located are notified within 3 days after the date of installation of the transmitter. Such notice shall include the make and type number of the transmitter and a certification by the licensee that the transmitter as installed complies with the appropriate technical provisions of this subpart. (b) Additional rules with respect to withdrawal of type-acceptance, modification of type-accepted equipment and limitations on the findings upon which type acceptance is based are set forth in Part 2 of this chapter. [28 F.R. 13574, Dec. 14, 1963, as amended at 33 F.R. 15418, Oct. 17, 1968] § 73.49 Requirements for approval of frequency monitors. (a) General requirements. (1) Any manufacturer desiring to submit a monitor for type approval shall supply the Commission with full specification details (two sworn copies) as well as the test data specified in paragraph (c) of this section. If this information appears to meet the requirements of the rules, shipping instructions will be issued to the manufacturer. The shipping charges to and from the Laboratory at Laurel, Maryland, shall be paid for by the manufacturer. Approval of a monitor will only be given on the basis of the data obtained from the sample monitor submitted to the Commission for test. (2) In approving a monitor upon the basis of the tests conducted by the Laboratory, the Commission merely recognizes that the type of monitor has the inherent capability of functioning in compliance with the rules, if properly constructed, maintained, and operated. The Commission realizes that the fre quency monitor may have limited range over which the visual indicator will determine deviations. Accordingly, it may be necessary that adjunct equipment be used to determine major deviations. NOTE: In addition to the visual indicator, the range of which may be limited in order to obtain the required accuracy, an aural indicator should also be employed to indicate frequency deviations beyond the range of the visual indicator, particularly where the visual indicator is so designed that the indication becomes zero when the deviations become considerably greater than the range of the instrument. (3) Additional rules with respect to withdrawal of type approval, modification of type approval equipment and limitations on the findings upon which type approval is based are set forth in Part 2, Subpart F, of this chapter. (b) General specifications. The general specifications that frequency monitors shall meet before they will be approved by the Commission are as follows: (1) The unit shall have an accuracy of at least five parts per million under ordinary conditions (temperature, humidity, power supply, and other conditions which may affect its accuracy) encountered in standard broadcast stations throughout the United States. (2) The range of the indicating device shall be at least from 20 cycles below to 20 cycles above the assigned frequency. (3) The scale of the indicating device shall be so calibrated as to be accurately read within at least 1 cycle. (4)-(5) [Reserved] (6) The monitor circuit shall be such that it may be continuously operated and the emitted carrier of the station is not heterodyned thereby. (7) Means shall be provided for adjustment of the temperature or other means for correction of the indications of the monitor to agree with the external standard. (c) Tests to be made by the Laboratory Division of the F. C. C. The tests to be made at the Laboratory will include the determination of the following: (1) Accuracy. (i) Oscillator frequency, as received. (ii) Constancy of oscillator frequency, as measured several times in 1 month. (iii) Accuracy of readings of frequency-difference instrument. (iv) Functioning of frequency adjustment device. (v) Effects on frequency of changing tubes and of voltage variations. (2) Temperature control stability. Effect on frequency of variation of room temperature through a range not to exceed 10° to 35° C. (3) Sensitivity. Response of indicating instrument to small changes of frequency. (4) General construction. (1) Inspection to determine ability to stand shipment and service. (ii) Special tests to determine quality of construction, such as effect of tilting or tipping on frequency. (5) Miscellaneous performance. Various, depending on character of apparatus (e. g., changes after stopping and starting, effect of varying coupling with transmitter, etc.). (d) Test operation of equipment. The equipment will be operated in a test in the same way and the same conditions under which it will be used in service as specified by the manufacturer. The manufacturer shall supply to the Laboratory Division all instructions or services which will be supplied to the purchaser of the equipment. The equipment, as submitted, shall be adjusted for operation in connection with broadcast stations operating on 1600 kilocycles. [28 F.R. 13674, Dec. 14, 1963, as amended at 32 F.R. 10306, July 13, 1967] § 73.50 Requirements for approval of modulation monitors. (a) Any manufacturer desiring to submit a monitor for type approval shall supply the Commission with full specification details (two sworn copies) specified in paragraph (b) of this section. If this information appears to meet the requirements of the rules, shipping instructions will be issued to the manufacturer. The shipping charges to and from the Laboratory at Laurel, Maryland, shall be paid for by the manufacturer. Approval of a monitor will only be given on the basis of the data obtained from the sample monitor submitted to the Commission for test. (1) In approving a monitor upon the basis of the tests conducted by the Laboratory, the Commission merely recognizes that the type of monitor has the inherent capability of functioning in compliance with the rules, if properly constructed, maintained, and operated. (2) Additional rules with respect to withdrawal of type approval, modification of type approval equipment and limitations on the findings upon which type approval is based are set forth in Part 2, Subpart F, of this chapter. (b) The specifications that the modulation monitor shall meet before it will be approved by the Commission are as follows: (1) A DC meter for setting the average rectified carrier at a specific value and to indicate changes in carrier intensity during modulation. (2) A peak indicating light or similar device that can be set at any predetermined value from 50 to 120 percent modulation to indicate on positive peaks, and/or from 50 to 100 percent negative modulation. (3) A semi-peak indicator with meter having the characteristics given below shall be used with a circuit such that peaks of modulation of duration between 40 and 90 milliseconds are indicated to 90 percent of full value and the discharge rate adjusted so that the pointer returns from full reading to 10 percent of zero within 500 to 800 milliseconds. A switch shall be provided so that this meter will read either positive or negative modulation and, if desired, in the center position it may read both in a full-wave circuit. The characteristics of the indicating meter are as follows: (i) The damping factor shall be between 16 and 200. The useful scale length shall be at least 2.3 inches. The meter shall be calibrated for modulation from 0 to 110 percent and in decibels below 100 percent with 100 percent being 0 db. (ii) The accuracy of the reading on percentage of modulation shall be ±2 percent for 100 percent modulation, and 4 percent of full scale reading at any other percentage of modulation. (4) The frequency characteristics curve shall not depart from a straight line more than ±1⁄2 db from 30 to 10000 cycles. The amplitude distortion or generation of audio harmonics shall be kept to a minimum. (5) The modulation meter shall be equipped with appropriate terminals so that an external peak counter can be readily connected. (6) Modulation will be tested at 115 volts 5 percent and 60 cycles, and the above accuracies shall be applicable under these conditions. (7) All specifications not already covered above, and the general design, construction, and operation of these units must be in accordance with good engineering practice. (c) The modulation monitor may be a part of the frequency monitor. § 73.51 TECHNICAL OPERATION Antenna input power; how determined. (a) Except in those circumstances described in paragraph (d) of this section, the antenna input power shall be determined by the direct method, i.e., as the product of the antenna resistance at the operating frequency (see § 73.54) and the square of the unmodulated antenna current at that frequency, measured at the point where the antenna resistance has been determined. (b) The authorized antenna input power for each station shall be equal to the nominal power for such station, with the following exceptions: (1) For stations with nominal powers of 5 kilowatts, or less, the authorized antenna input power to directional antennas shall exceed the nominal power by 8 percent. (2) For stations with nominal powers in excess of 5 kilowatts, the authorized antenna input power to directional antennas shall exceed the nominal power by 5.3 percent. (3) In specific cases, it may be necessary to limit the radiated field to a level below that which would result if nominal power were delivered to the antenna. In such cases, excess power may be dissipated in the antenna feed circuit (see § 73.54 (a) and (d)), and/or the transmitter may be operated with power output at a level which is less than the nominal value. (i) Where a dissipative network is employed, the authorized antenna current and resistance, and the authorized antenna input power shall be determined at the input terminals of the dissipative network. (ii) Where the authorized antenna input power is less than the nominal power, subject to the conditions set forth in paragraph (c) of this section, the transmitter may be operated at the reduced power level necessary to supply the authorized antenna input power. (c) Applications for authority to operate with antenna input power which is less than nominal power and/or to employ a dissipative network in the antenna system shall be made on FCC Form 302. The technical information supplied on section II-A of this form shall be that applying to the proposed conditions of operation. In addition, the following in formation shall be furnished, as pertinent: (1) Full details of any network employed for the purpose of dissipating radio frequency energy otherwise delivered to the antenna (see § 73.54). (2) A showing that the transmitter has been type accepted for operation at the proposed power output level, or, in lieu thereof: (i) A full description of the means by which transmitter output power will be reduced. (ii) Where the proposed transmitter power output level is less than 90 percent of nominal power, equipment performance measurements, as specified in § 73.47, conducted at the proposed power output level; in addition, the measurements and observations required by § 73.47(a) (1), (2), (3), and (5) for power output levels 10 percent above, and 10 percent below, the proposed output level, but at a modulation level of 95 to 100 percent only. Such measurements must demonstrate that, operating at the proposed power output level, the transmitter meets the performance requirements of § 73.40. (iii) A showing that, at the proposed power output level, means are provided for varying the transmitter output within a tolerance of 10 percent, to compensate for variations in line voltage or other factors which may affect the power output level. (d) The antenna input power shall be determined on a temporary basis by the indirect method described in paragraphs (e) and (f) of this section in the following circumstances: (1) In an emergency, where the authorized antenna system has been damaged by causes beyond the control of the licensee or permittee (see § 73.45), or (2) pending completion of authorized changes in the antenna system, or (3) if changes occur in the antenna system or its environment which affect or appear likely to affect the value of antenna resistance or (4) if the antenna current meter becomes defective (see § 73.58). Prior authorization for the indirect determination of antenna input power is not required. However, an appropriate notation shall be made in the operating log. (e) (1) Antenna input power is determined indirectly by applying an appropriate factor to the plate input power, in accordance with the following formula: Antenna input power-Ep×Ip>F Where: Ep-Plate voltage of final radio stage. (2) The value of F applicable to each mode of operation shall be entered in the operating log for each day of operation, with a notation as to its derivation. This factor shall be established by one of the methods described in paragraph (f) of this section, which are listed ir. order of preference. The product of the plate current and plate voltage, or, alternatively, the antenna input power, as determined pursuant to subparagraph (1) of this paragraph, shall be entered in the operating log under an appropriate heading for each log entry of plate current and plate voltage. (f) (1) If the transmitter and the antenna input power utilized during the period of indirect power determination are the same as have been authorized and utilized for any period of regular operation, the factor F shall be the ratio of such authorized antenna input power to the corresponding plate input power of the transmitter for regular conditions of operation, computed with values of plate voltage and plate current obtained from the operating logs of the station for the last week of regular operation. (2) If a station has not been previously in regular operation with the power authorized for the period of indirect power determination, if a new transmitter has been installed, or if, for any other reason, the determination of the factor F by the method described in subparagraph (1) of this paragraph is impracticable: (i) The factor F shall be obtaine from the transmitter manufacturer's letter or test report retained in the station's files, if such a letter or test report specifies a unique value of F for the power level and frequency utilized; or (ii) By reference to the following table: (iii) If a station has been authorized to operate with antenna input power which is lower than nominal power, the factor F shall have the value established when such operation was authorized. [37 F.R. 7516, Apr. 15, 1972] § 73.52 Antenna input power; maintenance of. (a) The actual antenna input power of each station shall be maintained as near as is practicable to the authorized antenna input power and shall not be less than 90 percent or greater than 105 percent of the authorized power; except that, if, in an emergency, it becomes technically impossible to operate with the authorized power, the station may be operated with reduced power for a period of 10 days, or less, without further authority from the Commission: Provided, That the Commission and the Engineer in Charge of the radio district in which the station is located shall be immediately notified in writing if the station is unable to maintain the minimum operating schedule, specified in § 73.71, with authorized power, and shall be subsequently notified upon resumption of operation with authorized power. (b) In addition to maintaining antenna input power within the above limitations, each station employing a directional antenna shall maintain the relative amplitudes of the antenna currents in the elements of its array within 5 percent of the ratios specified in its license or other instrument of authorization, unless more stringent limits are specified therein. [37 F.R. 7517, Apr. 15, 1972] § 73.54 Antenna resistance and reactance: how determined. (a) The resistance of an omnidirectional series fed antenna shall be measured at the base of the antenna without intervening coupling networks or components. The resistance of a shunt excited antenna shall be measured at the point the radio frequency energy is transferred to the feed wire circuit, without intervening networks (with the exception that, if the termination of the feed wire is highly reactive a network containing no shunt element may be interposed between the feed wire termination and the point where the resistance is determined). Any network inserted in the antenna circuit for the express purpose of dissipating a portion of the radio frequency energy provided by the transmitter shall be located at the base of the antenna, and the antenna resistance specified in the license or other instrument of authorization shall be the effective resistance at the input terminals of the dissipative network. (b) The resistance and reactance of a directional antenna shall be measured at the point of common radiofrequency input to the directional antenna system The following conditions shall obtain: (1) The antenna shall be finally adjusted for the required radiation pattern. (2) The reactance at the operating frequency and at the point of measurement shall be adjusted to zero, or as near thereto as practicable. (c) (1) The resistance of an antenna shall be determined by the following procedure: A series of discrete measurements shall be made over a band of frequencies extending from approximately 25 kc/s below the operating frequency to approximately 25 kc/s above that frequency, at intervals of approximately 5 kc/s. The measured values shall be plotted on a linear graph, with frequency as the abscissa and resistance as the ordinate. A smooth curve shall be drawn through the plotted values. The resistance value corresponding to the point of intersection of the curve and the ordinate representing the operating frequency of the station shall be the resistance of the antenna. (2) For a directional antenna, the reactance of the antenna shall be determined by a procedure similar to that described in subparagraph (1) of this paragraph. (d) Any element included in the antenna circuit for the express purpose of dissipating a portion of the energy delivered by the transmitter to the directional antenna shall be included at the point of common radio-frequency input, and the authorized common point resistance shall include the effect of the dissipative element. (e) Applications for authority to determine power by the direct method shall specify the antenna or common point resistance, and shall include the following supporting information. (1) A full description of the method used to make measurements. (2) A schematic diagram showing clearly all components of coupling circuits, the point of resistance measurement, location of antenna ammeter, connections to and characteristics of all tower lighting isolation circuits, static drains, and any other fixtures, sampling lines, etc., connected to or supported by the antenna, including other antennas and associated circuits. Any network or circuit component incorporated for the purpose of dissipating radio frequency power shall be specifically identified, and the impedances of all components which control the level of power dissipation, and the effective input resistance of the network shall be indicated. (3) Make and type of each calibrated instrument employed, manufacturer's rated accuracy, together with the date of last calibration of the instrument, the accuracy of the calibration, and the identity of the person or firm making the calibration. (4) A tabulation of all measured data. (5) Graph(s) plotted from this data. (6) The qualifications of the engineer(s) making the measurements. [34 F.R. 18305, Nov. 15, 1969, as amended at 37 F.R. 7517, Apr. 15, 1972] The percentage of modulation shall be maintained at as high a level as is consistent with good quality of transmission and good broadcast service. In no case shall it exceed 100 percent on negative peaks of frequent recurrence, or 125 percent on positive peaks at any time. Generally, modulation shoud not be less than 85 percent on peaks of frequent recurrence, but where such action may be required to avoid objectionable loudness, the degree of modulation may be reduced to whatever level is necessary for this purpose, even though, under such circumstances, the level may be substantially less than that which produces peaks of frequent recurrence at a level of 85 percent. [37 F.R. 7514, Apr. 15, 1972] § 73.56 Modulation monitors. (a) Each station shall have in operation, either at the transmitter or at the place the transmitter is controlled, a modulation monitor of a type approved by the Commission. NOTE: Approved modulation monitors are included on the Commission's "Radio Equipment List, Part B, Aural Broadcast Equipment". Copies of this list are available for inspection at the Commission's office in Washington, D. C. and at each of its field offices. (b) In the event that the modulation monitor becomes defective the station may be operated without the monitor |