GB/T 5438-1985 Mono and stereo program transmission characteristics and measurement methods
Some standard content:
National Standard of the People's Republic of China
GB/T 5438—1985
Characteristics and measuring methods for monophonic and stereophonic transmissions1985-09-29Promulgated
National Bureau of Standards
Implementation on 1986-06-01
National Standard of the People's Republic of China
Characteristics and measuring methods for monophonic and stereophonic transmissionsUDC 534.86 :681
GB/T 5438—1985
This standard applies to microwave relay, cable and fixed-satellite service systems for the transmission of monophonic and stereophonic programmes dedicated to broadcasting. 1 Explanation of terms
1.1 Hypothetical reference circuit
A system design model of a specified length with a specified number of terminals and intermediate devices. 1.2 Definition of noise voltage
1.2.1 Peak value
peakvalue
The maximum amplitude of a repetitive noise pulse, independent of the repetition frequency of the pulses, or the random intervals between the pulses. 1.2.2 Quasi-peak value
quasi-peak value
A value related to the peak value and the pulse repetition frequency. The quasi-peak meter has a measuring circuit whose time constant allows it to charge quickly and discharge slowly.
2 Definition of measurement unit abbreviations (according to GB3383-82 "Telecommunication Transmission Units - Decibel") 2.10dBms
A 0.775V (effective value) sine wave voltage (equivalent to 1mW of power) applied to a 600Ω load is taken as zero decibel and is defined as the zero level point of sound program transmission.
Take 1mW as the reference value, and the absolute power level expressed in decibels relative to the zero relative level point in sound program transmission. S is the code for sound program transmission.
Relative level of sound program signal expressed in decibels (this abbreviation is only applicable to points in the sound program circuit that can be converted with simple coefficients relative to the input end).
2.4dBqOps
Take 0.775V effective value as the reference voltage, and measure the absolute voltage level in decibels relative to the zero relative level point in sound program transmission using a quasi-peak noise meter (sound program weighting). 3 Technical requirements
This standard sets technical indicators for the transmission characteristics of the sound program circuit based on the assumed reference circuit. 3.1 The main features of the assumed reference circuit (Figure 1) of the sound program transmission system are: Issued by the National Bureau of Standards on September 29, 1985
Implemented on June 1, 1986
GB/T5438—1985
3.1.1 The total length between B and c is 2500km. 3.1.2 The two intermediate audio points (M and M') divide the circuit into three equal length segments. 3.1.3 Each audio segment can be completely independent or can be connected to work together. 3.2 The main features of the hypothetical reference circuit for the transmission of sound programs in the satellite fixed service system are: Window
1-ground station; 2-synchronous satellite, 3
The most basic reference circuit (2500km)
3.2.1 From the ground station to the satellite and then to the ground station is a relay, which is also used as the 2500km hypothetical reference circuit. 3.2.2
A pair of modulation and demodulation equipment converts the baseband to radio frequency, and then converts the radio frequency to baseband. 4 Standard parameters
Mono transmission parameters (see Table 1)
Additional parameters for stereo transmission (see Table 2) Table 1
Item name
Nominal bandwidth
Input impedance
Output impedance?
Level stability
Amplitude-frequency characteristics
Parameter value
0.04~15kHz
60 0Q balanced
Low impedance balanced
Maximum audio level+9dBm
+6dBrs
±0.5dB/d
0.04~0.125kHz+0.5~-2.0dB
0.125~10kHz:+0.5~—0.5dB
Maximum weighted
Noise level||tt ||Non-linear distortion
Project name
Amplitude-frequency characteristics
Group delay difference
No-load channel noise
Program modulation noise
Selected single-tone interference
GB/T5438—1985
Parameter value
10~14kHz: +0.5~-2.0dB
14~15kHz: +0.5~-3.0dB
0.04kHz; the difference with the minimum delay is less than 55ms0.075kHz: the difference with the minimum delay is less than 24ms14kHz: the difference with the minimum delay is less than 8ms15kHz: the difference with the minimum delay is less than 12ms—42dBqOps
—30dBqOps
(—73—)dBmo|| tt||Total distortion
Harmonic distortion
Subharmonic and
Third harmonic selection
0.8 and 1.42kHz
Intermodulation distortion
5.6 and 7.2kHz
4.2 and 6.8kHz
Amplitude/amplitude response error?
Reliable crosstalk
Sound program circuit crosstalk ratio| |tt||Far-end and near-end crosstalk attenuation①
Reconstruction frequency error
0.04~0.125kHz:1%
0.125~7.5kHz:0.5%
0.04~0.125kHZ:0.7%
0.125~7.5kHz:0.35%
Third-order difference frequency
0.18kHz :0.5%
Second-order difference frequency 1.6kHz: 0.5%
Third-order difference frequency
Input amplitude:
1.6kHz:0.5%
-6~+6dBmOs test signal 1kHz
: 0~12dB error±0.5dBbZxz.net
Output amplitude:
0.04kHz:50dB
Continued Table 1
0.04~0.5kHz: The oblique line segment on the linear decibel and logarithmic frequency coordinate graph 0.5~5kHz:74dB
5~15kHz: The oblique line segment on the linear decibel and logarithmic frequency coordinate graph 15kHz:60dB
Not more than 1Hz
Note: ①The output impedance is designed to be connected to the 600Q nominal load impedance. It should be so low that when a 600Q load is connected to the open-circuit output, the output level reduction within the nominal transmission range does not exceed 0.3dB. For the amplifier intended to be directly connected to the sound program line, the maximum value of the series reactance part of the output impedance is 1002 at each frequency within the transmission range. The reactance part of the transmission stereo line pair is required to be as consistent as possible to ensure the phase difference index. 3
GB/T5438—1985
②When a compression expander is used in the transmission sound program channel, this item needs to be measured, and the method is to be determined. ③The ratio of intelligible crosstalk of one sound program circuit interfered by another sound program circuit or telephone circuit. ④The attenuation value of the far-end near-end intelligible crosstalk of the telephone circuit interfered by the sound program circuit. ③The reconstructed frequency error is generally called frequency stability in the multiplexing system. This is mainly due to the deviation of the master frequency, which causes the deviation of the signal frequency at both ends of the channel. Since the frequency deviation tolerance is the final requirement after multiple frequency conversions and multiple transfers in the entire carrier channel, that is, the net change of the audio frequency generated between the receiving end and the transmitting end, the reconstructed frequency error in the transmission channel of a high-quality audio system shall not be greater than 1Hz. Table 2
Item Name
Level Difference between Left and Right Channels
Phase Difference between Left and Right Channels
Understandable Crosstalk Ratio
Crosstalk Ratio between Left and Right Channels
Total Crosstalk Ratio
0.04~0.125kHz: 1.5dB
0.125~10kHz: 0.8dB
10~14kHz: 1.5dB
14~15kHz:3.0dB
0.04kHz:30%
Parameter value
0.04～0.2kHz: oblique line segment on linearity and logarithmic frequency coordinate graph0.2~4kHz:15
4~14kHz: oblique line segment on linearity and logarithmic frequency coordinate graph14kHz:30%
15kHz:40%
0.0415kHz:50dB
Note: The total crosstalk ratio is mainly caused by intermodulation. Intermodulation interference is essentially manifested in the form of noise. The noise interference value caused by intermodulation cannot be greater than -51dBqOps. Because the inherent noise values of the unloaded channel are different, the noise increase tolerance caused by intermodulation is formulated as follows: unloaded channel noise: -60, -57, -54, 51, -48, -45, -42dBqops. Noise tolerance increase: 9.5, 7, 4.8, 3, 1.8, 1.0.5dB. 5 Measurement method for mono and stereo program transmission This measurement method is suitable for testing the various indicators specified in the mono and stereo program transmission standards. 5.1 Level stability
Applicable to the measurement of item No. 5 in Table 1 of this standard. 5.1.1 Test frequency: 1kHz
5.1.2 Test level: -12dBm0
5.1.2 Test connection diagram:
GB/T5438—1985
1-Audio signal generator: output impedance is set to 600α balanced position, 2-Tested equipment (mono or stereo program transmission system); 3-Audio level meter: input impedance is set to 600Q balanced position. External level recorder5.1.4 Test method:
The audio signal generator outputs the test frequency signal to the audio input end of the transmission system, and the audio level meter measures the level value at the audio output end of the equipment, and uses an external level recorder to record the level change for 24 hours. If measuring stereo equipment, the left and right channels are measured once respectively. 5.2 Amplitude-frequency characteristics:
Applicable to the measurement of item No. 6 in Table 1 of this standard. 5.2.1 Reference frequency: 1kHz
5.2.2 Test level: -12dBmOs
5.2.3 Test frequency: Select from the frequency range of 0.04 to 15kHz. 5.2.4 Test connection diagram:
1—Audio signal generator: output impedance is set to 600Q balanced position; 2—Tested equipment (mono or stereo program transmission system) 3 Audio level meter: input impedance is set to 6002 balanced position 5.2.5 Test method:
The audio signal generator outputs the test frequency signal to the audio input end of the transmission system, and the audio level meter is used to measure the amplitude of the corresponding frequency at the output end. If the equipment is a stereo channel, the left and right channels are measured once respectively. 5.3 Non-linear distortion:
Applicable to the measurement of item No. 10 in Table 1 of this standard. 5.3.1 Harmonic distortion measurement:
5.3.1.1 Test frequency: 0.04~7.5kHz5.3.1.2 Test level: +9dBmOs for frequencies less than 4kHz and +6dBmOs for frequencies greater than 4kHz
5.3.1.3 Test connection diagram:
1-Audio signal generator: output impedance is set to 600Ω balanced position; 2-Equipment under test (mono or stereo transmission system, but excluding transmission lines), 3-Distortion tester; frequency selection table (set to narrow band), audio spectrum analyzer5.3.1.4 Test method:
The audio signal generator outputs the test frequency signal to the input end of the equipment under test, and the distortion meter is used to directly measure the total distortion at the output end. The second and third harmonic distortion coefficients are measured by using a frequency selection meter to select the fundamental frequency and the second and third harmonic components at the output end. The second and third harmonic components are compared with the fundamental components, which are the second and third harmonic distortion coefficients. If an audio spectrum analyzer is used, the relative levels of the fundamental wave and each harmonic can be directly viewed. The above test method is not suitable for end-to-end nonlinear distortion measurement in the carrier frequency system to avoid serious interference with other transmission channels. Only local nonlinear distortion measurements are allowed at the end of the modulation and demodulation equipment. If it is necessary to do so under special circumstances (such as checking for faults). The level duration of the transmission signal frequency not higher than 1kHz at +9dBm0 should not exceed 4 seconds. 5.3.2 Intermodulation distortion measurement:
5.3.2.1 Test frequency:
Third order difference frequency between 0.8 and 1.42kHz: 0.18kHzSecond order difference frequency between 5.6 and 7.2kHz: 1.6kHzThird order difference frequency between 4.2 and 6.8kHz: 1.6kHz5.3.2.2 Test level: less than 4kHz+3dBm0 greater than 4kHz0dBm0
5.3.2.3 Test connection diagram:
1, 1° audio signal generator: output impedance is set to 6002 balanced position, 2-audio mixing network Network, 3 Equipment under test (mono or stereo program transmission system) 4-Frequency selector (set to narrow band) or audio spectrum analyzer 5.3.2.4 Test method
Two audio signal generators respectively output equal amplitude test signals of specified frequencies f1 and f2, which are sent to the input end of the equipment under test after passing through the mixing network. At the output end, the amplitude of the fundamental frequency, second-order or third-order difference frequency △f is measured by the frequency selector or audio spectrum analyzer, and the intermodulation distortion value is calculated as follows:
Af amplitude × 100%
Af amplitude
Note: If the stereo equipment is measured, the left and right channels are measured once respectively. 5.4 Noise:
Applicable to the measurement of item 8 in Table 1 of this standard. 5.4.1 Measurement of transmission path noise:
5.4.1.1 Test connection diagram:
1-Device under test: mono or stereo program transmission system; 2-According to CCIR468-2, the recommended sound program circuit and the weighted network for measuring noise (Figure 8); 3-Quasi-peak meter (preferred) or RMS meter 5.4.1.2 Test method:
Apply power to the device under test and terminate it with a 600Ω pure resistor at the input. At the output of the device under test, connect the 468-2 sound program weighted network and measure the noise value with a quasi-peak meter.
GB/T5438—1985
Note: ① If measured with an RMS meter, the measured value is about 5dB lower than that of the quasi-peak meter. ②The measured value of non-weighted noise is inaccurate because it depends on the characteristics of the circuit noise. If the noise measurement is performed without weighting, the worst value should reach -41dBmOs or -36dBqOs. 6AH
Figure 8 CCIR468-2 sound program weighting network 10
Figure 9cCIR468-2 sound program weighting network curve 2 = 6000
Gu (2)
Figure 10 CCIR468-2 sound program weighting network tolerance curve 7
16 000
GB/T5438—1985
Figures 9 and 10 CCIR468-2 sound program weighting network response value and tolerance value. 5.4.2 Measurement of program modulation noise generated after the transmission path uses a compander. 5.4.2.1 Test frequency: 60Hz
Test level: +9dBm0
Test connection diagram:
Recommended tolerance
【±+2.8
1-Audio signal generator: output impedance set to 6002 balanced position; 2-Equipment under test (mono or stereo program transmission system using compandor); 3-High-pass filter (cut-off frequency is less than or equal to 400Hz) attenuation is greater than or equal to 60dB/60Hz; 4-CCIR468-2 sound program weighting network; 5-Quasi-peak meter 5.4.2.4 Test method:
The audio signal generator outputs a 60Hz test signal of +9dBm0 to the input of the equipment under test, and the high-pass filter and sound program weighting network are connected to the output of the equipment under test, and the channel noise is measured with a quasi-peak meter. 8
GB/T5438—1985
Note: If measuring stereo equipment, the left and right channels are measured once respectively. 5.5 Group delay difference:
Applicable to the measurement of item No. 7 in Table 1 of this standard. 5.5.1 Reference frequency: the frequency of minimum group delay. 5.5.2 Test level: -10dBm0s
5.5.3 Test frequency: 40, 75, 14000, 15000Hz. 5.5.4 Test connection diagram:
1-Group delay tester, 2, 21-Audio modulation and demodulation equipment 2
1-Audio signal generator, 2, 21-Audio modulation and demodulation equipment, 3 Low-frequency phase meter 5.5.5 Test method:
The transmitting and receiving loops of the equipment under test are connected to form a loop. 5.5.5.1 Group delay difference test method:
(preferred) (see Figure 12 (a))
The group delay tester provides a reference frequency (the frequency with the minimum group delay) as a reference, sends a test frequency signal to the device under test, and sends the test signal back to the instrument receiving end after loop connection. The group delay difference between the two frequencies is calculated by comparing it with the reference frequency. 5.5.5.2 Calculate the group delay difference from the phase-frequency characteristic: 5.5.5.2.1 Phase-frequency characteristic test method (see Figure 12 (d)) The audio signal generator outputs a pair of test frequency signals with the same frequency, phase, and amplitude to the input end of the circuit under test and the A end of the low-frequency phase meter, and sends the test signal to the B end of the low-frequency phase meter after loop connection. The absolute phase shift of the test signal after passing through the device under test is compared by it. Sequentially test different frequency signals (0.04~15kHz) and record their values to obtain the required phase-frequency characteristics. 5.5.5.2.2 Calculate the group delay difference from the phase-frequency characteristics: Group delay formula:
Where: t is a group delay (s/km);
dq—phase differential (rad/km);
dの——angular frequency differential (rad/s).
Group delay difference formula:
tty-trmin
Where: t——delay of the measured frequency;
delay of the reference frequency.
GB/T5438—1985
Note: If the main sound equipment is measured, the left and right channels are measured once respectively. 5.6 Selected single-tone interference: Applicable to the measurement of item No. 9 in Table 1 of this standard. 5.6.1 Test connection diagram:
1-Device under test (mono or stereo program transmission system); 2-Frequency selector (set to narrow band) 5.6.2 Measurement method:
Terminate the input of the device under test with a 600Ω pure resistor, and use a frequency selector to select the level of the single-tone interference frequency within the range of 815kHz at the output, and then subtract the correction value g@ (the value can be found according to the CCIR468-2 sound program weighted network curve). Note: If measuring a stereo device, measure the left and right channels separately. 5.7 Intelligible crosstalk ratio:
Applicable to the measurement of item 12 in Table 1 of this standard 5.7.1 Sound program circuit crosstalk ratio
5.7.1.1 Test frequency: 0.04~15kHz
5.7.1.2 Test level: -10dBmOs
5.7.1.3 Test connection diagram:
1—Audio signal generator; 2, 2—Equipment under test (2 sound program circuit or telephone circuit, 2 sound program circuit): 3—Frequency selector (set to narrow band) 5.7.1.4 Test method Method:
The audio signal generator outputs the test frequency signal (0.04~15kHz is sent when one sound program signal is serially inserted into another sound program signal. 0.3~3.4kHz is sent when one telephone circuit signal is serially inserted into another sound program circuit) to the input end of one channel (called the interference circuit) of the device under test, and the frequency selection meter measures its fundamental frequency component at the output end and the fundamental frequency component of the test frequency sent to the interference circuit selected at the output end of the other channel (called the interference circuit), and then calculates the difference (the interfered circuit is powered on, and the input end is terminated with a 600Q resistor). 5.7.2 Far-end and near-end crosstalk attenuation;
5.7.2.1 Test frequency: 0.04~15kHz
5.7.2.2 Test level: -10dBm0s
5.7.2.3 Test connection diagram:
GB/T5438-1985
1--Audio signal generator: output impedance set to 600Ω balanced position, 2-sound program transmission system, 2-telephone circuit transmission system, 3-frequency selection table (set to narrow band) 5.7.2.4 Test method;
Figure 15a shows the far-end crosstalk of sound program channel 2 entering telephone channel 2, and the measurement method is the same as 5.7.1.4. Figure 15b shows the near-end crosstalk of sound program channel 2 entering telephone channel 2. Power is applied to the interfering circuit and the interfered circuit, and the output ends are respectively terminated with 600Ω pure resistance. The audio signal generator outputs the test signal to the input of one channel of the device under test (called the interference circuit), and the transmission level (dB) of its fundamental frequency component is measured by a frequency selection meter (set to narrow band). The same frequency level (dB) as the interference circuit is measured at the input of another channel (called the interfered circuit), and then the difference is calculated.
5.8 The level difference and phase difference measurement between the left and right channels is applicable to the measurement of items 1 and 2 in Table 2 of this standard. 5.8.1 Test level: -12dBmOs
5.8.2 Test frequency: 0.04~15kHz
5.8.3 Test connection diagram:
1-Audio signal generator: output impedance is set to 600Q balanced position; 22-DUT (left and right channels of stereo transmission system); 3Low-frequency phase meter (measure phase difference) or audio level meter (measure level difference)5.8.4 Test method:
5.8.4.1 Phase difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the low-frequency phase meter is used to measure the phase difference between the two channels at the output end. 5.8.4.2 Level difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the audio level meter is used to measure the levels of the two channels at the output end, and then calculate the difference. 5.9 Measurement of crosstalk ratio between left and right channels: Applicable to the measurement of item 3 in Table 2 of this standard. 5.9.1 Intelligible crosstalk ratio between left and right channels: The measurement method is the same as that of intelligible crosstalk ratio between two sound programs in 5.7.1. 5.9.2 Total crosstalk ratio:
5.9.2.1 Test signal: White noise with a frequency range of 20Hz to 20kHz. 5.9.2.2 Test level and time:
—4dBmOs
+3dBmOs
No signal1 Test frequency: 0.04~15kHz
5.7.2.2 Test level: -10dBm0s
5.7.2.3 Test connection diagram:
GB/T5438-1985
1--Audio signal generator: output impedance set to 600Ω balanced position, 2-sound program transmission system, 2-telephone circuit transmission system, 3-frequency selection table (set to narrow band) 5.7.2.4 Test method;
Figure 15a shows the far-end crosstalk of the sound program channel 2 into the telephone channel 2, and the measurement method is the same as 5.7.1.4. Figure 15b shows the near-end crosstalk of the sound program channel 2 into the telephone channel 2. Add power to the interference circuit and the interfered circuit, and the output ends are terminated with 600Ω pure resistance respectively. The audio signal generator outputs the test signal to the input of one channel of the device under test (called the interference circuit), and the transmission level (dB) of its fundamental frequency component is measured by a frequency selection meter (set to narrow band). The same frequency level (dB) as the interference circuit is measured at the input of another channel (called the interfered circuit), and then the difference is calculated.
5.8 The level difference and phase difference measurement between the left and right channels is applicable to the measurement of items 1 and 2 in Table 2 of this standard. 5.8.1 Test level: -12dBmOs
5.8.2 Test frequency: 0.04~15kHz
5.8.3 Test connection diagram:
1-Audio signal generator: output impedance is set to 600Q balanced position; 22-DUT (left and right channels of stereo transmission system); 3Low-frequency phase meter (measure phase difference) or audio level meter (measure level difference)5.8.4 Test method:
5.8.4.1 Phase difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the low-frequency phase meter is used to measure the phase difference between the two channels at the output end. 5.8.4.2 Level difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the audio level meter is used to measure the levels of the two channels at the output end, and then calculate the difference. 5.9 Measurement of crosstalk ratio between left and right channels: Applicable to the measurement of item 3 in Table 2 of this standard. 5.9.1 Intelligible crosstalk ratio between left and right channels: The measurement method is the same as that of intelligible crosstalk ratio between two sound programs in 5.7.1. 5.9.2 Total crosstalk ratio:
5.9.2.1 Test signal: White noise with a frequency range of 20Hz to 20kHz. 5.9.2.2 Test level and time:
—4dBmOs
+3dBmOs
No signal1 Test frequency: 0.04~15kHz
5.7.2.2 Test level: -10dBm0s
5.7.2.3 Test connection diagram:
GB/T5438-1985
1--Audio signal generator: output impedance set to 600Ω balanced position, 2-sound program transmission system, 2-telephone circuit transmission system, 3-frequency selection table (set to narrow band) 5.7.2.4 Test method;
Figure 15a shows the far-end crosstalk of the sound program channel 2 into the telephone channel 2, and the measurement method is the same as 5.7.1.4. Figure 15b shows the near-end crosstalk of the sound program channel 2 into the telephone channel 2. Add power to the interference circuit and the interfered circuit, and the output ends are terminated with 600Ω pure resistance respectively. The audio signal generator outputs the test signal to the input of one channel of the device under test (called the interference circuit), and the transmission level (dB) of its fundamental frequency component is measured by a frequency selection meter (set to narrow band). The same frequency level (dB) as the interference circuit is measured at the input of another channel (called the interfered circuit), and then the difference is calculated.
5.8 The level difference and phase difference measurement between the left and right channels is applicable to the measurement of items 1 and 2 in Table 2 of this standard. 5.8.1 Test level: -12dBmOs
5.8.2 Test frequency: 0.04~15kHz
5.8.3 Test connection diagram:
1-Audio signal generator: output impedance is set to 600Q balanced position; 22-DUT (left and right channels of stereo transmission system); 3Low-frequency phase meter (measure phase difference) or audio level meter (measure level difference)5.8.4 Test method:
5.8.4.1 Phase difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the low-frequency phase meter is used to measure the phase difference between the two channels at the output end. 5.8.4.2 Level difference test method: The audio signal generator outputs a pair of test frequency signals with the same frequency, phase and amplitude to the input end of the DUT, and the audio level meter is used to measure the levels of the two channels at the output end, and then calculate the difference. 5.9 Measurement of crosstalk ratio between left and right channels: Applicable to the measurement of item 3 in Table 2 of this standard. 5.9.1 Intelligible crosstalk ratio between left and right channels: The measurement method is the same as that of intelligible crosstalk ratio between two sound programs in 5.7.1. 5.9.2 Total crosstalk ratio:
5.9.2.1 Test signal: White noise with a frequency range of 20Hz to 20kHz. 5.9.2.2 Test level and time:
—4dBmOs
+3dBmOs
No signal
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