Technical Standards and Requirements for Television Broadcasting Transmitters

Transcription

1 BETS-4 Issue 1 st November Broadcasting Equipment Technical Standard Technical Standards and Requirements for Television Broadcasting Transmitters Aussi disponible en français - NTMR-4

2 Technical Standards and Requirements for Television Broadcasting Transmitters BETS-4 Purpose This document contains the technical standards and requirements for the issuance of a Technical Acceptance Certificate (TAC) for television broadcasting transmitters. A certificate issued for equipment classified as type approved or as technically acceptable before the coming into force of these technical standards and requirements is considered to be a valid and subsisting TAC. A Technical Acceptance Certificate is not required for equipment manufactured or imported solely for re-export, prototyping, demonstration, exhibition or testing purposes.

3 TECHNICAL STANDARDS AND REQUIREMENTS FOR TELEVISION BROADCASTING TRANSMITTERS TABLE OF CONTENTS 1. GENERAL... 1 PAGE 2. TESTING AND LABELLING STANDARD TEST CONDITIONS Definition Standard Test Voltage Standard Temperature Standard Test Load Standard Test Frequency Standard Test Input Signals Standard Test Equipment Standard Test Set-Up Warm-Up Time TRANSMITTING EQUIPMENT STANDARDS Definitions Type of Emission Power Output Rating Audio-Pre-Emphasis Power Supply Rating Phase-to-Phase Loading... 5

4 PAGE 5. EQUIPMENT REQUIREMENTS Design Protection of Personnel Labelling Equipment Changes and Modifications RF EMISSION STANDARDS Visual Power Output Rating Aural Power Output Rating Carrier Frequency Stability Intermodulation Spurious Emissions Cabinet Radiation Occupied Bandwidth FIGURE 1: AMPLITUDE VS FREQUENCY CHARACTERISTICS FIGURE 2: AMPLITUDE VS FREQUENCY RESPONSE TRANSLATORS. 14 ANNEX A: TECHNICAL STANDARDS VISUAL PERFORMANCE STANDARDS Visual Transmitter Transmitter Input Modulation

5 PAGE 1.4 Signal to Noise Ratio Luminance Non-linearity Differential Gain Distortion Differential Phase Distortion Incidental Carrier Phase Modulation Group Delay Response Linear Waveform Distortion Chrominance\Luminance Relative Amplitude and Delay AURAL PERFORMANCE STANDARDS Aural Transmitter Transmitter Input Modulating Frequency Amplitude Response Modulating Frequency Phase Response Frequency Modulation Signal to Noise Ratio Residual Amplitude Modulation Non-Linear Distortion RF PERFORMANCE STANDARDS RF Input Impedance - Translator Standard Input Noise Figure - Translator Automatic Gain Control Performance - Translator

6 PAGE 3.4 Visual to Aural Cross Modulation - Translator Aural to Visual Cross Modulation - Translator FIGURE A1. Standard Composite Colour Video Signal FIGURE A2A. Staircase Test Signal FIGURE A2B. Staircase Test Signal with Colour Subcarrier FIGURE A3A. Low Pass Filter FIGURE A3B. High Pass Filter FIGURE A4. Group Delay Requirements FIGURE A5(a). Composite Test Signal FIGURE A5(b). Graticule A FIGURE A5(c). Kpb Rating vs 2T Pulse Amplitude FIGURE A5(d). Graticule B FIGURE A6. Application Nomograph for 12.5T Pulses APPENDIX A: Standard Output Signal System M\NTSC APPENDIX B: Standard Pre-emphasis Curve

7 1. GENERAL 1.1 The standards and requirements in this document are the pre-requisite conditions for the issuance of a Technical Acceptance Certificate (TAC) for television broadcasting transmitters. 1.2 Those seeking to obtain a Technical Acceptance Certificate for television transmitters shall, at their own expense, carry out the required tests and send to the Department a certification submission and an engineering brief prepared in accordance with Broadcasting Equipment Standards Procedure 100 (BESP- 100). 1.3 The engineering brief, signed by a professional engineer licensed by a provincial association, shall demonstrate that the equipment meets the technical standards in this document. 1.4 Notwithstanding the fact that a radio apparatus meets all applicable requirements, the Department reserves the right to require that adjustments be made to the equipment should it cause interference. 1.5 Any major design or component changes, other than the replacement of defective components by equivalent parts, will void the approval unless notified to and approved by the Department. 1.6 This document replaces RSS-154, Issue TESTING AND LABELLING 2.1 Section 3 to 6 contain the general equipment standards and the minimum emission standards which relate to the radiated signal of the TV transmitting equipment. Compliance to the standards of these sections shall be supported by an engineering brief stating measurement results in accordance with Broadcasting Standards Procedure 100 (BSP 100). 2.2 Annex A contains the performance standards recognized by the industry to ensure quality operation of TV broadcasting equipment. Compliance to the standards of Annex A shall be supported by a statement certifying that the equipment meets the standards. The submission of test results for performance measurements is not required but the results shall be kept on file by the applicant. 2.3 This document covers the transmitting equipment proper: namely from the video and audio input terminals or the RF input terminal to the output terminals including the filters and the diplexer supplied with the transmitting equipment. 2.4 Equipment considered as low power TV broadcasting transmitting units is classified under one of the following categories: Category A Low power equipment designed to operate in a varying temperature environment. Category B Low power equipment designed to operate in a controlled temperature environment. 1

8 2.5 In the event that the equipment fails to function during the certification tests, all tests affected by the failure shall be repeated after the fault has been corrected. 2.6 The transmitting equipment shall be capable of meeting the standards in this document on each channel at the rated power output for which it is designed to operate. (See also ) 2.7 Each certified broadcasting equipment must display in a conspicuous location: (a) (b) (c) (d) (e) (f) The manufacturer's name, trade or brand name (if different from the manufacturer's name) The model identification The serial number The Technical Acceptance Certificate number The certificate number for low power equipment shall be suffixed with the appropriate category designator (See 2.4). The name of the certification assignee 2.8 The identification label must be indelible, tamper-resistant and affixed permanently or stamped in such a manner as not to be removable except by destruction or defacing. 3. STANDARD TEST CONDITIONS 3.1 Definition Standard test conditions are those conditions which shall apply to a transmitting equipment while it is being tested for minimum requirements. These conditions apply unless otherwise specified. Where no special conditions are called for in the tests, the conditions shall be those specified by the manufacturer for normal operation, and these shall be stated in the engineering brief. 3.2 Standard Test Voltage Shall be one of the rated power supply voltages specified by the manufacturer. 3.3 Standard Temperature Shall be no less than 20E C. Actual temperature shall be recorded in the engineering brief. 3.4 Standard Test Load Shall consist of an impedance of substantially zero reactance and a resistance equal to the surge impedance of the load into which the equipment is designed to operate. The test load impedance shall be essentially constant over the band of frequencies being considered with a return loss of 32 db minimum, 1.05:1 or better voltage standing wave ratio (VSWR) over the operating channel. 3.5 Standard Test Frequency Shall be the visual and aural carrier frequencies of the channel for which the equipment is designed to operate. For equipment capable of operating on one of several channels, tests shall be made on one channel in each band. 2

9 3.6 Standard Test Input Signals The standard video test input signal shall be in accordance with the standard television signal as specified for system M/NTSC (see Appendix A), and shall have a peak-to-peak amplitude of 1.0 volt, (140 IRE units). The polarity of the signal shall be black negative. The voltage shall be measured across the input terminals The standard aural test signal shall be a 400 Hz sine wave The standard RF test signal shall be the standard television signal as specified for system N/NTSC (see Appendix A). The RF input signal for the translator shall be derived from a test modulator and shall occupy a band of spectrum which coincides with a standard designated television channel. The signal shall contain simultaneously a visual carrier modulated with a video waveform consisting of sync, blanking and picture signal as appropriate for the test and an unmodulated aural carrier at a level 10 db below the peak visual carrier. Unless otherwise specified, the level of the RF input signal shall be 1 mvrms (0 dbmv). 3.7 Standard Test Equipment All measurements shall be made with test instruments of accuracy sufficient to ensure that no appreciable error due to test equipment is introduced in the results. 3.8 Standard Test Set-up Internally Diplexed Transmitting Equipment Unless stated otherwise, all visual tests shall be made with the unmodulated aural carrier present at rated power output and all aural tests shall be made with a visual carrier present, at the rated power output and modulated with a staircase video waveform of 50% average picture level (APL). For tests requiring a demodulated video output, a test demodulator with appropriate display devices or metres shall be used Externally Diplexed Transmitting Equipment The standard test load shall be connected to the output of the diplexer and tests carried out with one transmitter on at a time. For tests requiring a demodulated output the same monitoring equipment shall be used as for internally diplexed equipment Unless otherwise stated, all tests shall be performed with the harmonic filters and the external diplexer connected between the transmitters and the sampling point for the test concerned Translating Equipment The standard test load shall be connected to the output of the translator (see definition in 4.1.3) and tests carried out with the test signal supplied from the test modulator unless specified otherwise. For tests requiring an demodulated output, the same monitoring equipment shall be used as for internally diplexed equipment. 3

10 3.9 Warm-up Time The transmitting equipment and test equipment shall be switched on at least 30 minutes before any test is started. 4. TRANSMITTING EQUIPMENT STANDARDS 4.1 Definitions Transmission System Transmitter Translator A television transmitting system consists of the apparatus necessary to convert the input signals to standard output signals as specified in television system M/NTSC. (See Appendix A) A television transmitter consists of the apparatus necessary to convert the standard video and audio input test signals to the standard television output signal as specified for television system M/NTSC. (See Appendix A) A television translator consists of the apparatus necessary to convert a standard RF television input signal to the standard television output signal as specified for television system M/NTSC. (See Appendix A) Low Power Transmitting Equipment A television transmitter or translator having a maximum power output of 50 watts on VHF channels and 500 watts on UHF channels, and is designed to be operated under the requirements for low power television broadcasting stations under one of the following categories of operating conditions: Category A Equipment designed to operate in a varying temperature environment. Category B Equipment designed to operate in a controlled temperature environment. The appropriate category designation will be suffixed to the certificate number. 4.2 Type of Emission Visual transmission shall employ vestigial sideband amplitude modulation and aural transmission shall employ frequency modulation. 4

11 4.3 Power Output Rating The power output rating of a television transmitting equipment is that of the visual transmission section. 4.4 Audio Pre-emphasis The audio signal shall be pre-emphasized in accordance with a 75 microsecond pre-emphasis curve. (See Appendix B) 4.5 Power Supply Rating The preferred AC voltage input ratings are 120/240 V single phase, 120/208 V three phase, or 480 V three-phase, at a frequency of 60 Hz. Voltage, frequency, maximum kva rating, and power factor shall be indicated on the equipment. 4.6 Phase-to-Phase Loading The equipment, if rated above 10 kva input, shall present a balanced load to the AC mains such that the current in each phase shall be balanced within 10% of the average of the three currents. 5. EQUIPMENT REQUIREMENTS 5.1 Design Transmitting equipment shall be designed according to good engineering practice. 5.2 Protection of Personnel 5.3 Labelling The equipment shall be so constructed that all hazardous components are totally enclosed, or protected from accidental contact by personnel. The equipment enclosure shall be sufficient to provide adequate personnel safety during operation. The equipment should be labelled according to the requirements in Equipment Changes and Modifications Any major design or equipment changes outside the replacement of defective components by equivalent parts made to an approved equipment will void the type-approval unless notified to and approved by the Department. The notification shall provide information demonstrating that the modification provides equal or improved equipment performance. 5

12 6. RF EMISSION STANDARDS 6.1 Visual Power Output Rating Definition The visual power output rating of a television transmitting equipment shall be the peak envelope power which is the average power during a synchronizing pulse Method of Measurement Standard The visual carrier shall be modulated with sync and blanking only, such that the sync amplitude at the transmitter output will be 25% of the voltage between peak of sync and zero carrier. For translating equipment, the test modulator shall be modulated as above and the RF test signal set at the manufacturers recommended input value. The output shall be connected to the standard test load. Measure the average power output. The peak envelope power is the measured average power output multiplied by a factor of The standard rating of power output for the visual transmission section shall be as specified by the individual manufacturer. The equipment shall be capable of being adjusted to deliver the rated visual power output when the AC input voltage is 5% above or below rated value The engineering brief shall state the power output limits over which the equipment complies with this specification Power output adjustment of the equipment shall permit operation to at least 3 db below rated power output Standard Low Power The standard rating of power output for the visual transmission section shall be as specified by the individual manufacturer but shall not exceed 50 watts on VHF channels and 500 watts on UHF channels. The equipment shall be capable of maintaining the rated visual power output within 1 db. 6.2 Aural Power Output Rating Definition The aural carrier power output is the power of the aural transmission section available at the output terminals of the equipment when connected to the standard test load Method of Measurement The average power output of the unmodulated aural carrier shall be measured while operating into the standard test load either by using a power measuring device or by a calorimetric method. 6

13 6.2.3 Standard The measured aural carrier output shall not be less than 10% nor more than 20% of the output power of the visual transmission section specified in Power output adjustment shall permit operation to at least 3 db below the level determined in Standard Low Power The measured aural carrier output shall not be less than 5% nor more than 20% of the power output of the visual transmitter. 6.3 Carrier Frequency Stability Definition The carrier frequency stability of the transmitting equipment is a measure of the ability of the equipment to maintain its assigned frequency Method of Measurement Standard After a warm-up period of one hour at rated input voltage, measure the frequency of the visual and aural carriers at one minute intervals during a period of fifteen minutes. From those measurements determine a mean frequency for each carrier. Then measure the operating frequency at ambient temperatures of 5EC and 45EC and at the following three values of power supply voltage for each of these temperatures; 85 %, 100 % and 115 % of nominal supply voltage. For Category "B" low power equipment, the range of the controlled temperature environment shall be specified by the manufacturer but shall not be less than 10EC. The frequency stability of both visual and aural carriers shall remain within ±500 Hz of the mean frequency Standard-Low Power The frequency stability of both the visual and aural carriers shall remain within ±0.003% of the mean frequency. Note that the Category "B" equipment shall be operated in a controlled temperature environment. 6.4 Intermodulation Definition Intermodulation (IM) products are beat signals generated by various combinations of carriers of the nature mf1 ±nf2 ±pf3 where m, n and pare integers. The visual and aural carriers and colour sub-carrier can combine to form IM products. Six predominant products, with respect to picture carrier, are at ±920 khz, ±2.66 MHz, MHz and MHz. 7

14 6.4.2 Method of Measurement Standard The reference level used as 0 db shall correspond to the rated power output of the equipment (visual). The unit shall then be fed with a video test signal consisting of sync, blanking and a 3.58 MHz sinewave on a 50 % APL pedestal. The unmodulated aural carrier shall be present. The level of these carriers shall be adjusted so that their amplitudes with respect to reference level are: visual carrier -8 db 3.58 MHz subcarrier -17 db aural carrier -10 db* * or 7 db if so rated in The instantaneous peak levels of the predominant IM products and the harmonic product of the chrominance carrier shall be measured on a spectrum analyser or other suitable frequency selective voltmeter. The level of the predominant IM products shall be at least 53 db below the reference level Standard-Low Power The level of the predominant IM products shall be at least 50 db below the reference level. 6.5 Spurious Emissions Definition Spurious emissions are unwanted emissions occurring at the output terminals of the transmitting equipment, at frequencies other than those of the predominant intermodulation products described in Section Method of Measurement The transmitting equipment shall be operated into the standard test load at rated power. The aural carrier shall be unmodulated and the visual carrier shall be modulated with normal black level either with or without sync. Both signals shall be present for internally as well as externally diplexed transmitters. Using a sampling device, measure all spurious emissions below 1.8 GHz or up to the third harmonic of the aural carrier frequency, whichever is the higher. The voltage of the emission shall be measured with a frequency selective instrument. The attenuation versus frequency characteristics of the power sampling device and the load used in this test shall be known over the range of frequencies involved. Record all spurious outputs in db relative to peak envelope power except those more than 20 db below the values in

15 6.5.3 Standard Spurious emissions of the transmitting equipment shall not exceed the values given in the following table: Transmitter Power Spurious Emissions Max. Value Any power -4.5 MHz and MHz -40 db* Below 25 watts all others -46 dbw Above 25 watts all other spurious including -60 db* harmonics * Referred to peak envelope power of the equipment 6.6 Cabinet Radiation Definition Cabinet radiation is any emission from the equipment housing or enclosure from sources other than the normal output ports Method of Measurement Standard The visual and aural transmitters shall be operated at rated power output. A receiving dipole (or equivalent), located alternately at a known distance between three and ten metres from at least three sides of the equipment (i.e. front, back, left or right hand side), shall be connected to a calibrated field strength metre or frequency selective voltmeter. Field strength measurements shall be made of all emissions (including the fundamental and harmonics of the visual and aural carrier frequencies) up to 1.8 GHz or the third harmonic of the aural carrier frequency, whichever is the higher frequency. For the measurement, the receiving antenna shall be rotated in all three planes and the maximum received field shall be noted (allowance shall be made for antenna factor and transmission line loss of the measuring equipment). Using the free space formula below, calculate the reference field strength: E = 7 /p / r volts per metre where P is the rated visual output power in watts and r is the distance in metres. Emissions at any frequency shall be at least 54 db below the calculated field strength reference level with the exception that, for UHF equipment at the fundamental frequency, emissions shall be at least 48 db below the reference level. Any radiation weaker than 70 db below the reference level need not be recorded. 9

16 6.7 Occupied Bandwidth Definition The occupied bandwidth is the frequency bandwidth within which the mean power of the radiated emission is confined in accordance with specified limits The visual occupied bandwidth is the amplitude versus frequency characteristic of the visual transmitter including in-band and upper and lower sideband attenuation Method of Measurement Standard For this test the aural carrier shall be turned off and the equipment shall be operated at rated power output with video input consisting of sync, blanking, and a variable pedestal on which is superimposed a 10 MHz video sweep signal of 20 IRE units. Initially set the pedestal to 50 IRE units. Sample the equipment output and feed it to a tracking receiver (sideband analyser or spectrum analyser). Display the frequency range from visual carrier MHz to visual carrier MHz on the oscilloscope. Set the 0 db reference to the output level at visual carrier khz. Measure the output with the pedestal set to 50 units and then change the pedestal to 20 and 80 IRE units and record the results. The amplitude versus frequency characteristic between visual carrier MHz and MHz shall be within the limits shown in Figure 1. In addition, with the variable pedestal changed to 20 IRE units and 80 IRE units, the response shall not vary from that at 50 IRE units by more than ±0.75 db. The response at visual carrier MHz shall not be attenuated by more than the following, (see inset, Figure 1): Aural Occupied Bandwidth Definition - for internally diplexed equipment: -1.5 db - for externally diplexed equipment not provided with a diplexer: -1.5 db - for externally diplexed equipment which include a diplexer: db The occupied bandwidth is the frequency bandwidth such that below its lower and above its upper frequency limits, the mean powers radiated are each equal to 0.5% of the total mean power radiated by a given emission Method of Measurement Test signals applied to the equipment input shall be representative of the system employed and shall result in 85 % of the maximum specified aural carrier deviation. 10

17 6.7.8 Monaural Transmitter The aural transmitter shall be modulated with a 15 khz tone at 85% ( khz). A spectrum analyser shall be connected to the output of the aural transmitter and the energy at 120 khz above and below the aural carrier shall be measured and referenced to the unmodulated carrier M.T.S. Stereo Transmitter The composite input on the aural transmitter shall be modulated by a 15 khz L+R at ±15.25 khz deviation and a 15 khz L-R at ±30.5 khz deviation, a pilot carrier at ±5 khz deviation, a 78.6 khz carrier deviated ±10 khz, and a khz carrier deviated ±3 khz so that total deviation is ±63.75 khz. A spectrum analyser shall be connected to the output of the aural transmitter and the energy at 120 khz above and below the aural carrier shall be measured and referenced to the unmodulated carrier Other Multichannel transmitter Standard The aural transmitter input shall be modulated so as to be representative of the system employed to produce ±63.75 khz deviation. A spectrum analyser shall be connected to the output of the aural transmitter and the energy at 120 khz above and below the aural carrier shall be measured and referenced to the unmodulated carrier. The energy above or below the ±120 khz band may not exceed 0.5% of the total mean power within the band Translator Occupied Bandwidth Definition The occupied bandwidth of translators is the frequency bandwidth given by the amplitude/frequency characteristic measured at the output of the unit Method of Measurement With the AGC inoperative, the unit shall be fed with a sine wave input at the standard level and the frequency of the video carrier of the input channel. The unit shall then be set to deliver rated power output into the dummy load. This output shall be deemed the reference. With the amplitude constant, sweep the frequency of the sine wave between ±8 MHz of the visual carrier at three levels of input 0 dbmv, -16 dbmv and +16 dbmv. 11

18 Standard The occupied bandwidth given by the amplitude versus frequency response of the unit with 0 dbmv input shall be within the limits shown in Figure 2. The amplitude versus frequency response of the unit at ±16 dbmv shall not vary by more than ±l db from the response at 0 dbmv. 12

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21 ANNEX A TECHNICAL STANDARDS 1. VISUAL PERFORMANCE STANDARDS 1.1 VISUAL TRANSMITTERS DEFINITION The visual transmitter shall be that equipment required to convert the standard composite colour video signal (see Figure A1) to a modulated radio frequency signal delivered to the output transmission line. 1.2 TRANSMITTER INPUT DEFINITION The transmitter input is that terminal point that accepts the video signal that will modulate the visual carrier in compliance with this specification and shall be labelled "Video Input" IMPEDANCE AND RETURN LOSS Definition The input impedance is the impedance presented by the transmitter at its video input terminal. The return loss is the measure of dissimilarity between the input impedance and the standard impedance of the transmitter Method of Measurement Standard The input impedance and return loss may be measured with impedance measuring equipment having an error no greater than ±1.0%. The standard impedance shall be 75 ohms unbalanced. The input shall exhibit a return loss of at least 32 db over the frequency range from 0.0 to 4.2 MHz INPUT SIGNAL LEVEL FOR RATED MODULATION Definition The input signal level for rated modulation is that composite video signal amplitude which will drive the transmitter input so as to produce a modulated RF output signal meeting this specification. 15

22 Method of Measurement Standard The input voltage shall be measured by means of a properly calibrated oscilloscope or television waveform monitor, having known deflection sensitivity and at least 4.5 MHz bandwidth, connected across the transmitter input terminals. The transmitter shall be adjusted for proper modulation at rated peak power into a standard test load. The input voltage shall be determined by measuring the peak-to-peak deflection on the display. The amplitude of the composite video signal applied to the input terminal shall nominally be 1.0 volt peak-to-peak when the signal contains reference white. 1.3 MODULATION DEFINITIONS Maximum carrier level, blanking level, and reference white level are as defined for system M/NTSC. (See Appendix A) MODULATION CAPABILITY - METHOD OF MEASUREMENT STANDARD Using the standard test set-up, operate the transmitter at rated output with a standard staircase video input at 50 % APL (see Figure A2). Set the oscilloscope for 100 % at maximum carrier level and zero at zero carrier level. With the blanking level at 75%, the maximum carrier level shall remain between 98% and 102% of the original, and the reference white level shall be at 12.5% ±2.5% MODULATION STABILITY - METHOD OF MEASUREMENT STANDARD With operation as in 1.3.2, vary the staircase APL to 10% and to 90%. At APL between 10% and 90%, the maximum carrier level shall not vary by more than 3% and the blanking level by more than 1.5% of maximum carrier level FIELD TIME DISTORTION - METHOD OF MEASUREMENT STANDARD Retaining the set-up in replace the staircase input signal with a window signal. View the oscilloscope at field rate with DC restoration disabled. The tilt on the window signal shall not exceed 2% of the overall window amplitude between blanking and reference white level. 16

23 1.4 SIGNAL TO NOISE RATIO SIGNAL TO RANDOM NOISE RATIO (10 khz TO 4.2 MHz - UNWEIGHTED) Definition The signal to unweighted random noise ratio of the transmitter is the ratio, stated in decibels, of the peak-to-peak amplitude of the video modulation from blanking to reference white to the RMS amplitude of noise modulation measured at the output of the standard demodulator Method of Measurement The signal to unweighted random noise measurement shall be made using either a waveform monitor or a video noise metre. Connect the signal through the low and high pass filters to confine the noise to the video passband (see Figure A3(a) and A3(b)). The measurement shall be made on a flat field test signal at 10 IRE units Standard-Transmitters The signal to unweighted random noise ratio shall be 50 db or greater Standard-Translators The signal to unweighted random noise ratio for a 0 dbmv RF input level shall be 46 db or greater for translators operating with input on channels 2-13 and 44 db or greater for translators operating with input on channels SIGNAL TO LOW FREQUENCY NOISE RATIO (30 Hz - 15 khz - UNWEIGHTED) Definition The signal to low frequency noise ratio is defined in two ways: (1) Signal to RMS noise or (2) Signal to peak-to-peak noise relative to reference modulation Each ratio, expressed in decibels, is the ratio of the modulation level which would be produced by 100 % modulation of the transmitter with a single frequency sine wave to the noise. 100% modulation is defined as modulation from zero carrier output to peak synchronizing level Method of Measurement The signal to low frequency noise shall be measured at the output of the standard demodulator using a waveform monitor or a video noise metre. The output of the demodulator shall be filtered by a 30 Hz high-pass and a 15 khz low-pass filter. 17

24 Standard The signal to low frequency noise ratio within a band of 30 Hz to 15 khz shall be at least 52 db RMS and 40 db peak-to-peak. NOTE: The reference modulation level for expressing the signal to random noise level modulation from carrier blanking to carrier reference white is different from the reference level used for low frequency noise, 100% modulation. The following relationship exists between the noise ratios so referenced: Signal (100 IRE) to Noise (db) db = Signal (100% modulation) to Noise (db). 1.5 LUMINANCE NON-LINEARITY DEFINITION Luminance non-linearity is a measure of the gain variation of the system for a luminance signal as a function of instantaneous luminance level and APL METHOD OF MEASUREMENT STANDARD The transmitter input terminal shall be fed a staircase test signal of 50% APL (see Figure A2). Using the standard demodulator and a waveform monitor, sample the visual transmitter output. Employ the low pass filter section of the waveform monitor to differentiate the stairsteps. Comparing the amplitudes of the pulses, the pulse with the greatest amplitude is set to 100 IRE. The pulse with the smallest amplitude is read as a percentage of the greatest. The above measurement shall be repeated using 10% APL and 90% APL. (See Figure A2) The luminance non-linearity shall not be greater than 10% for APLs between 10% and 90%. For klystron transmitters using a modulating anode pulser, the non-linearity shall not be greater than 15% STANDARD-LOW POWER The luminance non-linearity shall not be greater than 20% for APLs between 10% and 90% and luminance levels between blanking and reference white. 1.6 DIFFERENTIAL GAIN DISTORTION DEFINITION Differential gain distortion is the change in gain of the system for a small high frequency sine wave (chrominance) signal at two levels of low frequency (luminance) signal upon which it is superimposed. 18

25 1.6.2 METHOD OF MEASUREMENT STANDARD The transmitter shall be fed a standard staircase signal with 3.58 MHz colour subcarrier (see Figure A2(b)). Using a linear demodulator (or a demodulator of known characteristics, and applying appropriate correction factors), the output is sampled and detected and the visual portion passed through a high pass filter to an oscilloscope, or any other suitable means of observing the 3.58 MHz component of the test signal. Any deviation from a constant amplitude display of the 3.58 MHz signal, when viewed at the line rate frequency, is the differential gain variation. The differential gain is the difference between the maximum and minimum 3.58 MHz signal amplitude divided by the maximum amplitude. Observe differential gain at 10%, 50% and 90% APL. The differential gain shall not be greater than 7% STANDARD-LOW POWER The differential gain shall not be greater than 15%. 1.7 DIFFERENTIAL PHASE DISTORTION DEFINITION Differential phase distortion is the change in phase through the system for a small high frequency sine wave (chrominance) signal at two levels of a low frequency (luminance) signal upon which it is superimposed METHOD OF MEASUREMENT STANDARD Using the same set-up as for differential gain and with the same input signal, the output is sampled and detected and passed to any suitable phase measuring equipment. Measurements shall be made at 10%, 50% and 90% APL. The differential phase shall be within ±4E of the colour burst and the overall difference shall not exceed 5E STANDARD-LOW POWER The differential phase shall be within ±7E of the colour burst and the overall difference shall not exceed 10E. 1.8 INCIDENTAL CARRIER PHASE MODULATION DEFINITION Incidental carrier phase modulation (ICPM) is extraneous phase modulation created in the process of visual modulation and amplification (AM to PM conversion). 19

26 1.8.2 METHOD OF MEASUREMENT STANDARD The transmitter input terminal shall be fed a staircase test signal (see Figure A2). A sample of the transmitter output signal shall be detected in the standard demodulator with the sound notch filter out. Synchronous detection referenced to an unmodulated carrier, phase referenced to blanking, shall be employed. The quadrature component of synchronous detection is used to display the luminance incidental carrier phase characteristic on the waveform monitor. Incidental carrier phase modulation by the luminance signal and composite sync shall not exceed ±2E referenced to blanking level. 1.9 GROUP DELAY RESPONSE DEFINITION The group delay response versus frequency of a transmitter is the variation with modulation frequency of the group delay METHOD OF MEASUREMENT Standard The measurement shall be made with the transmitter operating into the standard test load. The measurement shall be made either on the transmitter output signal detected by the standard demodulator, or on the separate sideband signals as detected on a synchronous sweep receiver. The group delay measurement equipment is used under the same operating conditions as in paragraph 6.7, except that the maximum excursion of the modulating signal shall not exceed 25 IRE units. Composite video signals may be used if they are without a vertical interval since it obscures the measurement on some types of delay measuring equipment. A sine wave introduced at the input shall produce an RF signal having a group delay relative to 200 khz of zero nanoseconds up to a frequency of 3.0 MHz and then linearly decreasing to 4.18 MHz intercepting -170 nanoseconds at 3.58 MHz. The tolerance shall increase linearly from 25 nanoseconds at 3.58 MHz to ±50 nanoseconds at 2.0 MHz where the tolerance remains constant down to 0.2 khz and the tolerance shall increase linearly to ±50 nanoseconds at 4.18 MHz from that at 3.58 MHz. (See Figure A4) High rate group delay ripples as a result of saw filter triple transit effect are excluded Standard - Translators The group delay shall be within ±40 nanoseconds of the reference delay characteristic of the test modulator. 20

27 Standard-Low Power The delay characteristic shall be the same as specified in except the permitted tolerance shall be twice that specified in LINEAR WAVEFORM DISTORTION DEFINITION Linear waveform distortion is a measure of the transmitter's ability to faithfully reproduce step functions or pulses. One method of measure is the K factor which describes the transmitter's ability to reproduce the 2T pulse and bar measurement signal K PULSE TO BAR (Kpb) RATING Definition The K pulse to bar rating is a measurement of the peak amplitude of the 2T pulse relative to the amplitude of the mid point of the associated luminance bar waveform. It is expressed as the K pulse to bar rating in percent and is measured with a standard NTSC type A graticule (see Figure A5(b)) Method of Measurement Standard Apply a full field composite test signal [Figure A5(a)] to the video input of the transmitter under test and connect the demodulated video output (using synchronous detection) to a calibrated waveform monitor, equipped with graticule "A". Centre the 2T pulse peak on the Kpb scale. The vertical gain is adjusted to put the bar centre point at 100 IRE and the blanking level at 0 IRE. The K pulse to bar rating is then measured on the graticule using the "Kpb" lines at the top centre of the graticule. To extend the range of the measurement, set the vertical sensitivity of the waveform monitor so that the centre point of the bar waveform has an amplitude of 100 IRE. Measure the peak amplitude of the 2T pulse and read the K pulse to bar rating from the nomogram shown on Figure A5(c). If the 2T pulse is greater than 120 IRE in amplitude, move the display down to put the blanking level at -40 IRE, to keep the 2T pulse "on scale". The K pulse to bar rating (Kpb) shall not exceed 2.5% T PULSE K RATING (K2T) Definition The K rating of the 2T pulse (K2T) is a time weighted measurement of the subjective impairments caused by close-in echoes on the TV signal and is measured with the standard NTSC type B graticule (See Figure A5(d)) and expressed in percentage K. 21

28 Method of Measurement Standard Apply a full field composite test signal [Figure A5(a)] to the video input of the transmitter under test and connect the demodulated video output (using synchronous detection) to a calibrated waveform monitor. To use "Graticule B" to measure K2T, adjust the waveform monitor sweep rate to 0.2 µs/div (or x25 magnifier with a 5 µs/div DISPLAY rate) and use the variable vertical sensitivity to adjust the pulse height to 100 IRE. The lobe that most closely approaches the dotted K2T = 5% outline defines the K2T rating for the transmitter under test. For small values of K2T the vertical sensitivity of the monitor may be increased by a factor of 2 to increase the resolution of the measurement. In this case, the dotted outline becomes K2T = 2.5%. The K2T rating is estimated by subdividing an imaginary vertical line through the lobe peak into convenient units, and expressing the lobe amplitude as a fraction of the distance between the blanking level reference line and the dotted K2T line. The 2T pulse K rating shall not exceed 2.5% K CHROMINANCE-LUMINANCE RELATIVE AMPLITUDE AND DELAY DEFINITION The chrominance-luminance relative amplitude and delay is the relative change in the amplitude and timing of the chrominance and luminance components of a television signal from the output of the transmitter METHOD OF MEASUREMENT STANDARD Feed the transmitter input with the composite test video signal. (See Figure A5(a) Using the standard demodulator in the synchronous detection mode with the sound notch filter out, the test signal bar shall modulate the transmitter to reference white while maintaining rated blanking and peak output power levels. The relative delay change is determined after adjustment of the 12.5T modulated pulse to 100 IRE units by noting the displacement of the baseline by amplitudes Yl and Y2 and referring to the nomograph of Figure A6 or by using the formula: ½ Chrominance-luminance delay = 20(Yl.Y2) nanoseconds Alternately, chrominance amplitude and delay adjustments may be added to the video signal to attain a 12.5T pulse without baseline displacements, recording the magnitude of the corrections required. The magnitudes of the required corrections are equal to the transmitter chrominance-luminance amplitude and delay errors. The chrominance-luminance relative amplitude shall be less than ±3 IRE units. chrominance luminance relative delay shall be less than 50 nanoseconds. The 22

29 2. AURAL PERFORMANCE STANDARDS 2.1 AURAL TRANSMITTER DEFINITION The aural transmitter shall be that equipment required to convert monaural audio, multichannel baseband (including stereo and other subcarriers), and non-program related subcarriers, to a frequency modulated output signal. 2.2 TRANSMITTER INPUT DEFINITION Audio Composite Subcarrier The transmitter input terminals shall be identified as "AUDIO, "COMPOSITE" and "SUBCARRIER." Simultaneous transmitter modulation with both the AUDIO and SUBCARRIER, or alternately COMPOSITE and SUBCARRIER inputs shall be provided. The audio input terminals are those terminals to which signals in the range of 30 Hz to 15 khz are connected to cause frequency modulation of the aural carrier. The composite input terminals are those terminals to which signals in the range of 30 Hz to 120 khz, including BTSC baseband signals as defined in BS 15, are connected to cause frequency modulation of the aural carrier. The subcarrier input terminals are those terminals to which signals in the range of 16 khz to 120 khz are connected to cause frequency modulation of the aural carrier INPUT IMPEDANCE Definition The input impedance is the load presented to circuits supplying signals over the frequency band specified for those terminals Method of Measurement Standard The input impedance shall be measured with a suitably calibrated impedance bridge or network analyser. For audio inputs, the input impedance over the range of frequencies from 30 Hz to 15 khz shall not be less than 10,000 ohms balanced with substantially zero reactance. Provision shall be made to permit the internal connection of a resistor across the input terminals to present a lower input impedance if needed. 23

30 As an example, the audio impedance may be 600/150 ohms balanced. For composite inputs, the impedance over the range of frequencies from 30 Hz to 120 khz shall be 75 ohms unbalanced with a return loss of at least 40 db from 50 Hz to 50 khz and at least 35 db from 30 Hz to 120 khz. For subcarrier inputs, the input impedance over the range of frequencies from 16 khz to 120 khz shall be 75 ohms unbalanced with a return loss of at least 35 db AUDIO INPUT LEVEL Definition The audio input level is the level of the 400 Hz test signal at the audio input terminals necessary for ±25 khz deviation of the aural carrier Method of Measurement Standard Suitable instruments for measuring aural carrier frequency deviation and audio input signal level shall be used. The measurement requires: (1) An AM/FM modulation monitor with an amplitude response of ±0.05 db over the desired frequency range, to be connected to an RF monitoring connection in the aural transmitter output transmission line. (2) An AC signal level metre with a frequency response accuracy of ±0.02 db to measure the voltage applied to the input terminals. The standard sine wave audio input level for ±25 khz deviation at 400 Hz shall be 2.45 volts RMS corresponding to +10 dbm across a 600 ohm impedance. The transmitter shall be capable of adjustment to ±25 khz deviation at 400 Hz at an input level of volt RMS corresponding to 0 dbm across a 600 ohm impedance COMPOSITE INPUT LEVEL Definition The composite input level is the level of a 20 khz test signal at the composite input terminals necessary for ±75 khz deviation of the aural carrier. 24

31 Method of Measurement Standard Suitable instruments for measuring aural carrier frequency deviation and audio input signal level shall be used. The measurement requires: (1) An AM/FM modulation monitor with an amplitude response of ±.05 db over the desired frequency range, to be connected to an RF monitoring connection in the aural transmitter output transmission line. (2) An AC signal level metre with a frequency response accuracy of ±0.02 db to measure the voltage applied to the input terminals. The nominal input level for ±75 khz deviation shall be 20 khz sine wave at 1.0 volt RMS at the 75 ohm input impedance. The transmitter shall be capable of adjustment to ±75 khz deviation with input level of 0.5 volt RMS SUBCARRIER INPUT LEVEL Definition The subcarrier input level is the level of a 20 khz test signal at the subcarrier input terminals necessary for ±15 khz deviation of the aural carrier Method of Measurement Standard Suitable instruments for measuring aural carrier frequency deviation and audio input signal level shall be used. The measurement requires: (1) An AM/FM modulation monitor with an amplitude response of ±0.05 db over the desired frequency range, to be connected to an RF monitoring connection in the aural transmitter output transmission line, (2) An AC signal level metre with a frequency response accuracy of ±0.02 db to measure the voltage applied to the input terminals. The nominal input level for ±15 khz deviation shall be 20 khz sine wave at 1.0 volt RMS across a 75 ohm input impedance. The transmitter shall be capable of adjustment to ±15 khz deviation with an input level of 0.5 volt RMS. 2.3 MODULATING FREQUENCY AMPLITUDE RESPONSE DEFINITION The modulating frequency amplitude response is the ratio of input voltages expressed in db required to obtain a constant frequency deviation over a specified range of input frequencies. 25

32 2.3.2 METHOD OF MEASUREMENT STANDARD Audio Composite Subcarrier The measurement requires equipment with accuracy as specified in paragraph The transmitter is modulated with signals of frequencies in the range of interest. The carrier frequency deviation as read on the modulation monitor is kept constant and the input level is recorded of each modulating frequency. The maximum departure of the amplitude response from the standard 75 µs pre-emphasis curve over the range of 30 Hz to 15 khz shall not exceed ±0.5 db up to ±25 khz deviation. The maximum departure of the amplitude response from 30 Hz to 120 khz shall not exceed ±l db with a deviation of ±15 khz, except in the frequency range of 50 Hz to 50 khz where the amplitude response shall not exceed ±0.1 db with a deviation of ±50 khz. The maximum departure of the amplitude response from 16 khz to 120 khz shall not exceed ±1 db with a deviation of ±15 khz. 2.4 MODULATING FREQUENCY PHASE RESPONSE DEFINITION The modulating frequency phase response is the phase shift of the demodulated signal as referenced to the signal applied to the transmitter input terminals over the specified modulating frequency range. The deviation of phase shift versus frequency from a best fit straight line is a measure of phase non-linearity METHOD OF MEASUREMENT The measurement requires an aural demodulator of known phase response over the desired frequency range. This demodulator is connected to an RF monitoring connection at the aural transmitter output and shall provide a demodulated output from 30 Hz to 120 khz. The transmitter is modulated with signals at the desired frequencies. The transmitter input and demodulator output signals are compared on a suitable dual trace oscilloscope or phase difference metre while the modulating frequency is varied over the range indicated in

33 2.4.3 STANDARD The phase shift at any frequency shall not exceed the values shown below from a best fit straight line drawn through a graph of phase shift versus frequency. TYPE OF INPUT RANGE OF FREQUENCY MAXIMUM PHASE SHIFT (DEGREES) Composite 50 Hz to 50 khz (1) ±0,5 30 Hz to 120 khz (2) ±10,0 Subcarrier 16 khz to 120 khz (2) ±10,0 (1) ±50 khz carrier deviation (2) ±15 khz carrier deviation 2.5 FREQUENCY MODULATION SIGNAL TO NOISE RATIO DEFINITION Frequency modulation signal to noise ratio is the ratio in db of a reference signal modulation level to the residual frequency modulation caused by noise and spurious components without the presence of signal modulation METHOD OF MEASUREMENT STANDARD The measurement requires an aural demodulator. This demodulator is connected to an RF monitoring connection in the aural transmitter output transmission line. The amplitude/frequency response characteristic of the demodulator shall be within ±0.5 db over the frequency range of interest except for audio input signals where it shall be within ±0.5 db of the standard 75 µs de-emphasis curve. The 30 Hz to 120 khz broadband measurement should be made with a demodulator low pass 3 db bandwidth of approximately 150 khz. The transmitter is modulated to ±25 khz deviation with the standard input signal of 400 Hz and the recovered signal from the demodulator is measured with an RMS responding device. This measurement is repeated with no modulating signal and with the input terminals shunted with a resistance equal to the source impedance of the input circuit. The ratio of the two readings expressed in db represents the FM signal to noise ratio RMS noise and spurious levels referenced to ±25 khz deviation. 30 Hz to 15 khz -58 db (with 75 µs de-emphasis)* 30 Hz to 120 khz -30 db or ±800 Hz deviation* * Both conditions shall be met simultaneously. 27