This standard deals with methods of measurement of analogue channels for sound programmes transmitted by radio-relay systems. These measurements concern the audio frequency band only; they are in addition to the baseband requirements for radio-relay systems: television (Part 3, Section 3), frequency division multiplexing telephony (Part 3, Section 4) and mutual interference (Part 3, Section 5). In practice, the sound channel may be obtained by analogue techniques using frequency modulated subcarriers (Annex A A.1) or by digital techniques using time division multiplexing. The methods of measurement described in the following clauses apply to the transmission of sound programmes using subcarriers located above the television channels in the baseband. However, these methods of measurement are also applicable to the transmission of sound programmes using other methods of radio-relay systems. The relevant recommendations and reports of the International Radio Consultative Committee (CCIR) and the International Telegraph and Telephone Consultative Committee (CCITT) are given in Annex A. In general, the methods of measurement described in this standard are consistent with the above recommendations or reports. GB/T 4958.3-1988 Measurement methods for equipment used in terrestrial radio-relay systems Part 3: Measurements on emulation systems Section 6: Measurements on sound programme transmissions GB/T4958.3-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB/T4958.3—1988
idtIEC487-3-6:1984
Methods ofmeasurement for equipment used in terrestrialRadio-relay systems
Part3:Simulated systems
Section Six-Measurementsfor sound-programme transmissionPromulgated on February 10, 1988
Implemented on January 1, 1988
Ministry of Posts and Telecommunications of the People's Republic of China
National Standard of the People's Republic of China
Methods of measurement for equipment used in terrestrialradio-relay systemsPart 3:Simulated systems
Section Six-Measurementsfor sound-programme transmission terrestrialRadio-relay systems
Part3:Simulated systems
Section Six-Measurements for sound-programme transmission621.396
621.317.08
GB/T4958.3—1988
IEC487-—36(1984)
This standard is one of the national standards "Measurement methods for equipment used in terrestrial radio-relay systems" series. This standard is equivalent to the International Electrotechnical Commission (IEC) standard 487-3-6 (1984) "Measurement methods for equipment used in terrestrial radio-relay systems Part 3: Measurement of simulated systems Section 6-1 Scope of application
Measurements for sound-programme transmission".
This standard involves the measurement methods for the simulated channel of sound-programme transmission transmitted by radio-relay systems. These measurements are only related to the audio frequency band and are the measurements required for the baseband of radio-relay systems: including television (Part 3, Section 3). Frequency division multiplexing telephone (Part 3, Section 4) and mutual interference (Part 3, Section 5). In practice, the sound channel can be obtained by analog technology using frequency modulated subcarriers (Annex AA.1) or by digital technology using time division multiplexing. The measurement methods described in the following clauses apply to the transmission of sound programmes using subcarriers located above the television channels in the baseband. However, these measurement methods are also applicable to the self-transmission of sound programs using other methods such as radio-relay systems. The relevant recommendations and reports of the International Radio Consultative Committee (CCIR) and the International Telegraph and Telephone Consultative Committee (CCITT) are given in Annex A. In general, the measurement methods described in this standard are consistent with the above recommendations or reports. 1.1 Test signal levels
Unless otherwise specified, the levels used for measuring any specified characteristic shall comply with the relevant national standards. When pre-emphasis is used on sound programme channels (see A.2 in Annex A), it must be ensured that the channel under test is not overloaded at the higher modulation frequencies. 2 Noise and crosstalk
2.1 Definitions and general considerations
Noise in sound program channels includes random noise and single-tone interference, the latter also known as periodic noise. The noise and crosstalk in the sound program channels of the radio relay system depend on the number of sound program channels transmitted in the same baseband and the presence of television channels. When measuring random noise including crosstalk in a sound program channel, the TV channel and other sound channels are simultaneously loaded with a normal load signal simulating typical program content. The normal load of the TV channel is a color bar signal that complies with the provisions of Part 3, Section 5 of this series of standards: "Measurement of mutual interference" and GB3174-82 "Color television broadcasting". The normal load of the sound program channel is a self-noise signal with voltage period variation appropriately shaped according to the provisions of Section 5.9.2 of GB543885 "Transmission characteristics and measurement methods of mono and stereo programs". These load signals in the interfering channel mainly introduce incomprehensible crosstalk in the interfered sound program channel. When measuring single-tone interference in a sound program channel, no load signal should be applied to other sound channels. When measuring intelligible crosstalk in a sound program channel, other sound channels should be loaded with signals. The definition of intelligible crosstalk is: the difference between the output signal level of the channel with the loaded signal and the decibel number of the output level of the corresponding signal of the interfered channel. Before all measurements are made, a sinusoidal test signal of a specified level and frequency should be connected to the input of the sound program channel under test. And record the output level of the signal as the reference level. The definition of random noise is: the difference between the output level of this test signal and the decibel number of the measured noise. The definition of single-tone interference is: the difference between the output level of this test signal and the decibel number of the measured interference level. The items that need to be measured are summarized in Table 1:
Measurement parameters
Text machine input
Input level
Nominal value
Values ​​equivalent to several fading
Measurement parameters
Nominal value
Values ​​equivalent to several fading
Random noise (including crosstalk)
TV channel plus color bar signalOther sound program channels plus shaped white noise
Unweighted
Single tone interference (periodic noise)
TV channel plus color bar signal
Hearing channel is not as good as negative
Note: In the table, "" means measurement, and "" means no measurement. 2.2 Measurement Methods
2.2.1 Single-tone Interference
Random noise (excluding crosstalk)
TV channel and other sound program channels are not loaded
TV channel is not loaded
Sound channel is not loaded
Unweighted
Intelligible crosstalk
Another sound program channel
Add a sine wave of different frequencies
When measuring single-tone interference, connect the nominal receiver input level at the input of the simulated radio-relay system. Single-tone interference is measured with a suitable narrow-band frequency-selective level meter (or harmonic analyzer) to avoid thermal noise contributions from masking the measured tone. The TV channel is loaded with a color bar signal as specified in 2.1, and other sound program channels are not loaded. Tune the frequency-selective level meter over the entire audio range and record the measured single-tone level. Repeat the measurement without TV loading to evaluate the relative increase in the single-tone level due to TV loading. 2.2.2 Random noise
Random noise is measured using a broadband level meter covering the audio range, preferably a quasi-peak reading meter in accordance with Appendix AA.5. An RMS reading meter may also be used, but the values ​​measured should be approximately 5 dB lower than those obtained using a peak reading meter. In order to assess the subjective interference effect of random noise, the weighting network shown in Figure 1 should be used (see also 5.4 of GB5438). In order to include the crosstalk effect of all other channels, these channels should be appropriately loaded with colour bars for the television channels and suitably shaped white noise for all other sound programme channels, as described in 2.1. The measurements are made initially with the nominal receiver input level connected to the simulated radio-relay system and then repeated at several other levels. Unweighted measurements are made first to assess the effect of any low frequency noise components which, although they may not have a noticeable subjective interference effect on the listener, may still have a loading effect on the sound programme channels. Then, remove all load signals and repeat the measurements under both weighted and unweighted conditions to evaluate the relative increase in noise levels due to the loading of television and other sound program channels. Note: If the single-tone interference level measured in accordance with Article 2.2.1 is low enough, the measured broadband level can be considered to represent true random noise. 2.2.3 Intelligible crosstalk
When making intelligible crosstalk measurements, the simulated radio relay system should be connected to the nominal receiver input level. For other sound program channels, add sinusoidal test signals of different frequencies to each channel at a time. Use a frequency-selective level meter to tune it to each frequency and measure the level of the corresponding signal at the output of each interfered channel.
2.3 Presentation of results
The results of single-tone interference, random noise and intelligible crosstalk measurements shall be tabulated in decibels. For random noise, indicate the type of instrument used (i.e. quasi-peak meter or RMS meter), as well as the weighting network used. For single-tone interference and intelligible crosstalk, the bandwidth of the frequency-selective level meter shall be indicated. In addition, the type and level of the applied load signal and the receiver RF input level used shall be indicated. 2.4 Details to be specified
In the detailed equipment specification, include the following items as required: a. Test tone level and frequency range of the sound program channel being tested; b. Type and level of load signal applied to the television channel and each sound program channel; c. d. The type of instrument used for broadband random noise measurement, i.e. quasi-peak meter or RMS meter, and weighting characteristics; d. The bandwidth of the frequency-selective level meter used for single-tone interference and intelligible crosstalk measurement; e. Receiver RF input level,
f. The maximum single-tone interference level allowed under various given frequency and load conditions, dB; g. The maximum random noise level allowed under various given load weighting and receiver input level conditions, dB; h. The intelligible crosstalk ratio allowed under various given frequency conditions, dB. 3 Linear distortion
To determine the effect of distortion independent of the signal level in the sound program channel, the following items must be measured or checked: a. Input and output characteristics:
Input, output impedance and matching conditions
Terminal balance ratio,
Common mode rejection ratio;
b. Input and output levels;
c. Transfer characteristics:
Amplitude/frequency characteristics,
Group delay/frequency characteristics.
The distortion caused by the baseband, intermediate frequency and radio frequency parts of the simulated radio relay system can generally be ignored compared with the distortion measured in the sound program channel.
3.1 Input, output impedance and matching conditions
3.1.1 Definitions and general considerations
The audio input impedance of the sound program channel equipment is generally 600Ω nominally, balanced to ground. The output impedance is usually also balanced to ground, but the impedance value is generally lower than the nominal load impedance value. When the load is connected, the open circuit transmission level does not decrease by more than a small specified amount (Appendix AA.6 and 1.7).
When measuring the input impedance and output impedance of about 6002, it is compared with a resistive impedance of known precise value, and the result is expressed as the return loss value of the equipment impedance relative to the known impedance. The measurement method is similar to the return loss measurement given in Section 4 of Part 1 of this series of standards: "Measurement within the baseband" and Section 3: "Measurement within the intermediate frequency range" (GB6662-86). For sound program channels with symmetrical input and output impedances, it is necessary to measure the balance of the terminal potential to ground and the influence of the longitudinal current in the connecting cable.
The balance can be expressed by the terminal balance ratio, which can be determined by the ratio of the two measured voltages and is given by the following formula: Terminal balance ratio = 201og10)
1)-6(dB)
The symbols in the formula are shown in Figure 2. The terminal balance ratio determines the external noise picked up by the cable or line connected to the terminal, as well as the intelligible crosstalk between two or more lines connected to the equipment. An ideal symmetrical bipolar circuit has infinite terminal balance. In practice, the impedance imbalance between the two terminals to ground in the center-tapped 3
GB/T4958.3—1988
tap transformer (if used) is inevitable, which will introduce a limited terminal balance, which depends not only on the symmetry but also on the impedance of the terminal to ground. The input and output terminals can be grounded or not. Figure 2 shows that the terminals can be grounded through an impedance of any impedance value. The use of balanced circuits is to reduce the influence of unwanted longitudinal currents in the connecting cables. The magnitude of these currents on the output load depends not only on the terminal balance ratio but also on the asymmetrical stray paths within the device under test. The sensitivity of the device to these unwanted currents is determined by the common-mode rejection ratio (Appendix AA8). The common mode rejection ratio is defined as the ratio of the two voltages at the output of a sound program channel when a specified voltage is first applied symmetrically to the input of the sound program channel and then applied asymmetrically to the input. Symmetrical and asymmetrical connections are shown in Figure 3. The common mode rejection ratio is determined by the ratio of the two voltages shown in the following formula: Common mode rejection ratio = 201og1o)
)(dB)
3.1.2 Impedance measurement method
When the input and output impedances are matched to the nominal source impedance and load impedance respectively, the return loss of the input and output impedances can be measured according to the method specified in Section 4 of Part 1 of this series of standards. It should be noted that the nominal value of the circuit impedance may be 600Q balanced or may be given in the detailed equipment specification. The swept frequency method is preferred, but the point-by-point method can also be used. When the output impedance is lower than the load impedance, the output impedance is not measured directly, but the output level is measured at the output of the measured channel as a function of frequency. During the measurement, the input level is kept constant and the output is alternately open circuited and connected to a load impedance of nominal value. The swept frequency method is preferred, but the point-by-point method may also be used.
When using the swept frequency method, the output of the swept frequency signal generator is connected to the input of the channel under test, with a typical level of -12dBmos, and the output of the channel is periodically connected to a nominal load impedance of B. Care must be taken to ensure that the channel under test is not overloaded, especially for sound program channels using pre-emphasis.
Using a broadband level meter with a suitable frequency range, measure the level variation with frequency at the output of the sound program channel. This level variation is connected to the Y input of an X-Y recorder, and the swept voltage output of the swept frequency signal generator is connected to the X input. The input impedance of the broadband level meter should be high enough to ensure that its load effect on the circuit under test is negligible. Note: The rate at which the nominal load impedance is connected and disconnected should be selected to be proportional to the sweep speed of the test signal to ensure that a sufficient number of samples are recorded.
3.1.3 Measurement method of terminal balance ratio
The measurement method of the terminal balance ratio of the input terminal is shown in Figure 2a. The output terminal is shown in Figure 2b. The precision transformer T in the figure has a turn ratio of 1:1 and a winding with a precise center tap, so that its inherent terminal balance ratio is much larger than the value required during measurement. Before measurement, a preliminary check should be made to prove that the balance ratio of the precision transformer is at least 20dB larger than the balance ratio to be measured. The core size of the precision transformer should be large enough to avoid introducing harmonic levels exceeding a few percent.
The test resistor Zo/4 is a precision resistor. Use a high-impedance unbalanced level meter to measure the voltages V1 and V2 (see Figure 2) to determine the terminal balance ratio. First, connect the level meter to the signal generator, adjust the signal generator output voltage V1 to reach the nominal voltage value suitable for the two ends to be measured, and then connect the level meter to the two ends of the test resistor Z/4 to measure the voltage V2.
If the device under test is not overloaded, it is convenient to adjust V, to +6dBm. The decibel reading V2 relative to 1mW from the level meter will directly give the decibel reading of the terminal balance ratio. For calibration, one end of the terminal under test should be temporarily grounded, which will introduce the maximum imbalance and the level meter will read 0dBm.
Due to various losses in the precision transformer, deviations from 0dBm may occur. In this case, the signal generator level should be readjusted to make the level meter read exactly 0dBm. In systems using pre-emphasis, it is best to use lower signal levels to avoid overloading at higher frequencies. The difference between the calibration level and the measured level then gives the terminal balance ratio. The measurement should be repeated at each frequency point given in the detailed equipment specification. NOTE: The measurement method using a transmission tester is given in Appendix AA.9. 3.1.4 Method for measuring the common-mode rejection ratio
To measure the common-mode rejection ratio, a signal with a voltage of V is applied under the two conditions shown in Figure 3. V under the two conditions. The values ​​are the same, as long as the device under test is not overloaded, V. should be selected as high as possible. A balanced level meter should be used to measure the voltages V1 and V?. Alternatively, an unbalanced level meter can be used, but it must be used in conjunction with the precision transformer required by 3.1.3. The measurement should be repeated at each frequency point given in the detailed equipment specification. 3.1.5 Representation of results
The results of the impedance measurement are best presented as a curve of the return loss value; in the case of low output impedance, it is best presented as a curve of the level versus frequency. When not represented graphically, the measurement results should be given as follows: In the frequency range of 40Hz15kHz, the input return loss value is better than 26dB. In the frequency range of 40Hz~15kHz with 600Q load, the output level changes by less than 0.3dB. The measurement results of the input balance ratio and common mode rejection ratio shall be expressed as follows: Frequency
3.1.6 Details to be specified
Input balance ratio (dB)
In the detailed equipment specification, include the following items as required: a. Nominal input impedance,
b.Nominal output impedance (if applicable);
c. Minimum permissible input return loss;
d. Minimum permissible input balance ratio;
Output balance ratio (dB)
Common mode rejection ratio (dB)
e. Minimum permissible output return loss, or the permissible level change when the sound program channel output is connected to a load of nominal impedance, f. Minimum permissible output balance ratio;
g. Minimum permissible common mode rejection ratio,
h. Frequency at which measurement is required.
3.2 Input and output levels
For measurements within the baseband of a radio-relay system, the method described in Section 4 of Part 1 of this series of standards shall be followed, except that the characteristic impedance of the circuit is 600Ω balanced to ground or is given in the detailed equipment specification. 3.3 Amplitude/Frequency Characteristics
3.3.1 Definitions and General Considerations
The amplitude/frequency characteristics are given by a curve representing the ratio of the output level to a reference level (expressed in decibels) when the input level is held constant and the frequency is the independent variable. The reference level (e.g. -12 dBmos) is the output level of the channel at the reference frequency, preferably 1 kHz.
Quasi-peak reading meters (Appendix A, A, 5) used for noise measurements should not be used to measure the amplitude/frequency characteristics, even if they have a sufficiently wide passband and a uniform frequency response. RMS responding meters should be used to measure the amplitude/frequency characteristics, because they are much less affected by the harmonic distortion of the test signal than quasi-peak reading meters, where the error caused by waveform distortion may be the main source of error when measuring amplitude/frequency characteristics with tighter limits (e.g. ±0.1 dB). 3.3.2 Measurement Methods
The swept frequency method is preferred, but the point-by-point method may also be used. The input and output levels shall be adjusted to the values ​​given in the detailed equipment specification and the test tone levels and frequencies used shall be appropriate.
3.3.3 Representation of results
The results of the swept frequency measurement may be represented by a curve drawn on an X-Y plotter. The reference level and frequency points on the curve shall be marked. When not represented by a curve, the following example shall be given: Amplitude/frequency characteristics are within the following range:
+0.2~0.7dB
40~125Hz
+0.2~-0.7dB
+0.2~1.0 dB
(relative to the level of 1kHz)
3.3.4 Details to be specified
GB/T4958.3—1988
125Hz~10kHz
10~14kHz
14~15kHz
In the detailed equipment specification, include the following items as required: a. Frequency range
b. Reference frequency;
c. Level of reference frequency signal,
d. Permissible amplitude variation range.
3.4 ​​Group Delay/Frequency Characteristics
3.4.1 Definitions and General Considerations
The definitions given in GB6662 apply. However, it should be noted that since the sound program transmission includes low frequencies (e.g. 40 Hz), it is generally more convenient to first measure the phase/frequency characteristics of the sound program channel of the simulated radio relay system and then calculate the group delay/frequency characteristics from the measurement results. Since the input and output connections of the simulation system can be at the same location, the phase/frequency characteristics can be conveniently measured.
3.4.2 Measurement Method
First measure the phase/frequency characteristics of the sound program channel in the typical range of 40 Hz to 15 kHz, and obtain the group delay/frequency characteristics by calculating the rate of change of phase relative to frequency.
Measurement of the phase/frequency characteristics. A sinusoidal test signal of appropriate amplitude and known frequency is added to the input of the channel under test, and the phase of the output signal at each frequency is compared with the phase of the signal applied to the input. A phase meter with appropriate resolution (e.g. 1°) should be used for measurement. Either the swept frequency method or the point-by-point method may be used. For a given test signal level, the phase difference of the signal at the input of the sound programme channel is measured within the specified audio frequency band.
Note: The harmonic content of the sinusoidal test signal should be low enough (e.g. -40 dB relative to the fundamental) to ensure that the measurement accuracy of the phase meter is not affected. 3.4.3 Presentation of results
The results shall be presented as follows:
The difference between the group delay at a given frequency point and the minimum group delay does not exceed the following values:
17 ms, 40 Hz
8 ms, 750 Hz
3 ms, 5 kHz
3 ms, 14 kHz
4 ms, 15 kHz
This presentation also applies to the group delay calculated from the measured phase/frequency characteristic. 3.4.4 Details to be specified
The following items shall be included in the detailed equipment specification as required: a. The frequency of the test signal,
b. Level of the test signal;
c. The allowed group delay limit.
4 Nonlinear distortionbZxz.net
Nonlinear distortion in the sound program channel is related to the amplitude of the added baseband signal and is often frequency-dependent. The input and output impedances of the sound program channel are usually balanced to ground. In this case, input and output transformers are usually used. At lower frequencies, these transformers are often the main source of distortion.
4.1 General considerations
Nonlinear distortion is expressed in decibels as the ratio of the level of harmonics and/or intermodulation products appearing at the output of the device under test to the given reference level at the same point. Two methods can be used for measurement:6
GB/T4958.3—1988
a. Add a signal of a specified frequency and level to the input of the channel, and measure the harmonic distortion at the output of the channel. b. Add two signals of specified frequency and level to the input of the channel, and measure the intermodulation distortion at the output of the channel. It is generally necessary to make measurements at more than one level point. The measurement method used should be clearly stated in the detailed equipment specification. 4.2 Harmonic distortion method
4.2.1 Measurement method
A load signal with a frequency selected in the range of 40Hz to 7.5kHz is added to the measured channel, and its level is various specified values, with typical values ​​in the range of -12 to +12dBmos. It is necessary to verify that the harmonic content of the signal source is small enough that the effect on the measurement accuracy can be ignored. The level of the second, third and (if appropriate) higher harmonics of the selected frequency signal is measured with a harmonic analyzer. The results measured for each signal frequency and level are expressed in decibels relative to the fundamental level. For non-"finalization tests" (see GB4958.1), it is often allowed to measure the total harmonic distortion level of the applied test signal. In this case, the fundamental component of the test signal presented at the output of the channel is suppressed in the measuring instrument, which indicates the total root mean square value of all distortion products. The measurement result is expressed in decibels relative to the output signal level. The test signal used shall generally have a frequency in the range of 40 Hz to 50 kHz and a level within the specified range. 4.2.2 Presentation of results
The level of each harmonic component at each test signal frequency shall be represented by a curve plotted relative to the fundamental component in decibels, or in a table. When measuring total harmonic distortion, for each load level and frequency, the result shall be expressed in decibels relative to the root mean square value of the harmonic level relative to the output signal level.
4.2.3 Details to be specified
In the detailed equipment specification, the following items shall be included as required: a. Channel input (load signal) level; b. Channel output level,
c. Test signal frequency;
d. Required measurement items (harmonic levels and/or total harmonic distortion levels); e. The maximum level of each harmonic (generally the second and third harmonics) allowed in decibels relative to the reference level, or the maximum level of the total harmonic distortion allowed in decibels relative to the output signal level. 4.3 Intermodulation method
4.3.1 Measurement method
For each required input (loading) level, two equal-level signals of specified frequencies are added to the measured channel, and such paired signals are added to the channel input terminal in sequence at the specified level. The intermodulation product level corresponding to each input level is measured at the channel output terminal using a harmonic analyzer. The measurement result is expressed in decibels relative to a signal level. The frequencies f and f2 of the paired signals used. As well as the frequencies of the intermodulation products to be measured are shown in Table 2. The channel output level values ​​used are given in the detailed equipment specifications. Note: Suitable instruments are available on the market, but when using two general-purpose signal generators, there must be sufficient isolation between the two signal generators to prevent the output stage of the signal generator from intermodulating due to the signal from the other signal generator. Table 2
Frequency of test signal (kHz)
4.3.2. Expression of results
“n” order
Intermodulation product to be measured
Frequency (kHz)
The level of the intermodulation product is represented by a curve drawn from the relationship between the decibel number of the two signal levels and the channel output level. Alternatively, the order of the level of each pair of intermodulation products added can be expressed in a table. 4.3.3 Details to be specified
GB/T 4958.3—1988
In the detailed equipment specification, the following items shall be included as required: a. Level applied to the channel input,
b. Channel output level,
c. Frequency of the test signal;
d. Frequency of the intermodulation product to be measured,
e. Maximum permissible level of the intermodulation product.
5. Measurements specifically for stereo transmission
The transmission of stereo program A and B signals generally uses a pair of sound program channels. Therefore, the difference between the characteristics of the two channels should be small enough to ensure that the stereo distribution of the sound is reproduced with the necessary accuracy. In addition to the characteristics given in Chapters 2 to 4, stereo transmission also needs to specify and measure the following characteristics: a. The amplitude/frequency characteristics of one channel relative to the other channel; b. The phase/frequency characteristics of one channel relative to the other channel. These measurements are applicable to systems that transmit A and B signals using independent audio channels, but not to systems that encode A and B signals into one signal, such as those added to broadcast transmitters. 5.1 Amplitude difference between A and B channels
5.1.1 Measurement method
Adjust the levels at the output ends of the two channels to be measured so that they are equal at the reference frequency point of 1kHz. Measure the amplitude/frequency characteristics of each channel according to the method in Section 3.3, and calculate the amplitude difference between the two channels in the specified frequency band by subtraction. 5.1.2 Expression of results
The measurement results shall be expressed as follows:
The amplitude difference between channels A and B shall not exceed the following values:0.5dB, 40~125Hz
0.3dB, 125Hz~10kHz
0.5dB, 10~14kHz
1.0dB, 14~15kHz
5.1.3 Details to be specified
In the detailed equipment specification, the following items shall be included as required:a. Test tone level in channels A and B.
b. Output levels of channels A and B at the reference frequency are adjusted to be equal;c. Frequency range;
d. Maximum permissible amplitude difference between channels A and B within the frequency range. 5.2 Phase difference between A and B channels
5.2.1 Measurement method
Add the same-phase sinusoidal signals of known level and frequency to the A and B channels at the same time, connect a phase meter with appropriate resolution (e.g. 1°) to the output ends of the two channels to be measured, and measure the phase difference value within the specified frequency band and at the specified signal level using the sweep frequency method or the point-by-point method. In actual measurement, use a signal generator and a distribution network to provide two equal-level signals of specified levels (e.g. -12dBm0). The mutual coupling between the two signals should be negligible (e.g. 30dB isolation) to avoid errors caused by the reflection of the input impedance change of one channel to the other channel. The required isolation can be obtained by using a resistive distribution network and feeding it to two separate attenuators.
5.2.2 Expression of results
The results of the measurement shall be expressed as follows:
The phase difference between channels A and B shall not exceed the following values: 0.04kHz, 5%
GB/T4958.3—1988
0.04~0.2kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 0.2~4kHz, 5°
4~14kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 14kHz, 10°
15kHz, 17
5.2.5 Details to be specified
In the detailed equipment specification, the following items shall be included as required: a. Frequency range;
b. Level of the test signal,
c. The phase difference allowed between channels A and B within the specified frequency range. 12-8mH
12.B5n26.82nF
9. 21nF 31,17#F
(a) Weighting network
(b) Frequency response of weighting network
Figure 1 Noise weighting network
Pianxuefa 322
GB/T4958.3—1988
1 Heart pull:
b Output
Figure 2 Configuration of balance ratio at measurement end
Xinzhengqun
Shendiaopiandianpian
Zhucezhenyuan
Zhongwan Production
Figure 3 Configuration for measuring common mode rejection ratio
Channel front
GB/T4958.3—1988
Appendix A
Reference documents
(Reference documents))
A.1CCIR Report 289-4 (Volume X): Preferred characteristics of up to four sound program channels transmitted simultaneously with television in analog radio-relay systems.
A.2CCITT Recommendation J-17 (Volume N-I): Pre-emphasis for use of sound programs in group links. GCIR Recommendation 570 (Volume XI): Standard test signal for normal load of television channels. A.3
CCIR Recommendation 571-1 (Volume XI):
CCIR Report 497-3 (Volume XI): Normal load test signal for analog sound festival signals to measure interference in other channels. CCIR Recommendation 4693 (Volume X): Measurement of audio noise in broadcasting and sound recording and transmission circuits. A.5
A.6CCIR Recommendation 505-2 (Volume XI): 15kHz type sound program characteristics. A.7
CCIR Report 496-3 (Volume XI): Circuits for high-quality mono and stereo transmission. CCIR Recommendation 5041 (Volume XI): Performance characteristics of 10kHz type sound program circuits. A.9CCITT Recommendation 0.121 (Volume I-2): Definition and measurement method of ground balance of transmission testers. Additional notes:
This standard is under the jurisdiction of the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. 112Phase difference between A and B channels
5.2.1 Measurement method
Add the same-phase sinusoidal signals of known level and frequency to the A and B channels at the same time, connect a phase meter with appropriate resolution (e.g. 1°) to the output ends of the two channels to be measured, and measure the phase difference value within the specified frequency band and at the specified signal level using the sweep frequency method or the point-by-point method. In actual measurement, use a signal generator and a distribution network to provide two equal-level signals of specified levels (e.g. -12dBm0). The mutual coupling between the two signals should be negligible (e.g. 30dB isolation) to avoid errors caused by the reflection of the input impedance change of one channel to the other channel. The required isolation can be obtained by using a resistive distribution network and feeding it to two separate attenuators.
5.2.2 Expression of results
The results of the measurement shall be expressed as follows:
The phase difference between channels A and B shall not exceed the following values: 0.04kHz, 5%
GB/T4958.3—1988
0.04~0.2kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 0.2~4kHz, 5°
4~14kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 14kHz, 10°
15kHz, 17
5.2.5 Details to be specified
In the detailed equipment specification, the following items shall be included as required: a. Frequency range;
b. Level of the test signal,
c. The phase difference allowed between channels A and B within the specified frequency range. 12-8mH
12.B5n26.82nF
9. 21nF 31,17#F
(a) Weighting network
(b) Frequency response of weighting network
Figure 1 Noise weighting network
Pianxuefa 322
GB/T4958.3—1988
1 Heart pull:
b Output
Figure 2 Configuration of balance ratio at measurement end
Xinzhengqun
Shendiaopiandianpian
Zhucezhenyuan
Zhongwan Production
Figure 3 Configuration for measuring common mode rejection ratio
Channel front
GB/T4958.3—1988
Appendix A
Reference documents
(Reference documents))
A.1CCIR Report 289-4 (Volume X): Preferred characteristics of up to four sound program channels transmitted simultaneously with television in analog radio-relay systems.
A.2CCITT Recommendation J-17 (Volume N-I): Pre-emphasis for use of sound programs in group links. GCIR Recommendation 570 (Volume XI): Standard test signal for normal load of television channels. A.3
CCIR Recommendation 571-1 (Volume XI):
CCIR Report 497-3 (Volume XI): Normal load test signal for analog sound festival signals to measure interference in other channels. CCIR Recommendation 4693 (Volume X): Measurement of audio noise in broadcasting and sound recording and transmission circuits. A.5
A.6CCIR Recommendation 505-2 (Volume XI): 15kHz type sound program characteristics. A.7
CCIR Report 496-3 (Volume XI): Circuits for high-quality mono and stereo transmission. CCIR Recommendation 5041 (Volume XI): Performance characteristics of 10kHz type sound program circuits. A.9CCITT Recommendation 0.121 (Volume I-2): Definition and measurement method of ground balance of transmission testers. Additional notes:
This standard is under the jurisdiction of the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. 112Phase difference between A and B channels
5.2.1 Measurement method
Add the same-phase sinusoidal signals of known level and frequency to the A and B channels at the same time, connect a phase meter with appropriate resolution (e.g. 1°) to the output ends of the two channels to be measured, and measure the phase difference value within the specified frequency band and at the specified signal level using the sweep frequency method or the point-by-point method. In actual measurement, use a signal generator and a distribution network to provide two equal-level signals of specified levels (e.g. -12dBm0). The mutual coupling between the two signals should be negligible (e.g. 30dB isolation) to avoid errors caused by the reflection of the input impedance change of one channel to the other channel. The required isolation can be obtained by using a resistive distribution network and feeding it to two separate attenuators.
5.2.2 Expression of results
The results of the measurement shall be expressed as follows:
The phase difference between channels A and B shall not exceed the following values: 0.04kHz, 5%
GB/T4958.3—1988
0.04~0.2kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 0.2~4kHz, 5°
4~14kHz, oblique straight line segment on the linearity and logarithmic frequency coordinate diagram 14kHz, 10°
15kHz, 17
5.2.5 Details to be specified
In the detailed equipment specification, the following items shall be included as required: a. Frequency range;
b. Level of the test signal,
c. The phase difference allowed between channels A and B within the specified frequency range. 12-8mH
12.B5n26.82nF
9. 21nF 31,17#F
(a) Weighting network
(b) Frequency response of weighting network
Figure 1 Noise weighting network
Pianxuefa 322
GB/T4958.3—1988
1 Heart pull:
b Output
Figure 2 Configuration of balance ratio at measurement end
Xinzhengqun
Shendiaopiandianpian
Zhucezhenyuan
Zhongwan Production
Figure 3 Configuration for measuring common mode rejection ratio
Channel front
GB/T4958.3—1988
Appendix A
Reference documents
(Reference documents))
A.1CCIR Report 289-4 (Volume X): Preferred characteristics of up to four sound program channels transmitted simultaneously with television in analog radio-relay systems.
A.2CCITT Recommendation J-17 (Volume N-I): Pre-emphasis for use of sound programs in group links. GCIR Recommendation 570 (Volume XI): Standard test signal for normal load of television channels. A.3
CCIR Recommendation 571-1 (Volume XI):
CCIR Report 497-3 (Volume XI): Normal load test signal for analog sound festival signals to measure interference in other channels. CCIR Recommendation 4693 (Volume X): Measurement of audio noise in broadcasting and sound recording and transmission circuits. A.5
A.6CCIR Recommendation 505-2 (Volume XI): 15kHz type sound program characteristics. A.7
CCIR Report 496-3 (Volume XI): Circuits for high-quality mono and stereo transmission. CCIR Recommendation 5041 (Volume XI): Performance characteristics of 10kHz type sound program circuits. A.9CCITT Recommendation 0.121 (Volume I-2): Definition and measurement method of ground balance of transmission testers. Additional notes:
This standard is under the jurisdiction of the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Post and Telecommunications Industry Standardization Institute of the Ministry of Posts and Telecommunications. 11
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