GB/T 4312.1-1984 Technical parameters and measurement methods for FM broadcast transmitters - mono and stereo
Some standard content:
National Standard of the People's Republic of China
GB/T4312.1-—1984
Technical parameters and measuring methodsfor FM broadcasting transmittersmonopnonicand stereopnonic
Published on April 6, 1984
National Standards Supervision Bureau
Implementation on January 1, 1985
National Standard of the People's Republic of China
Technical parameters andmeasuringmethodsfor FM broadcasting transmittersmonopnonic and stereopnonic stereopnonic
UDC621.396.61
：621.317.08
GB/T4312.1—1984
This standard applies to mono and stereo FM broadcast transmitters. Its contents include all technical parameters and measurement methods from the audio input end to the high frequency output end of the transmitter. 1 Explanation of terms
1.1 Separation of left and right signals
The mutual leakage between the left and right signals is called the separation of the left and right signals, which is expressed by the following mathematical formula: Where:
S.=201g B or ED
EL (or Er)
S Separation, expressed in dB,
EL (or ER)
is V,
When the transmitter has only L (or R) channel input audio voltage modulation, the left (or right) output of the demodulator, unit)-When the transmitter has only L (or R) channel input audio voltage modulation, the right (or left) output of the demodulator, unit ER (or EL)
is v.
1.2 Residual wave radiation intensity
refers to the radiation intensity of harmonic radiation, parasitic radiation and mutual modulation other than fundamental wave radiation. 1.3 Phase difference of pilot signal
When the pilot signal intersects with the time axis, the subcarrier signal should also intersect with the time axis with a positive slope. The deviation of their relative positions is based on the pilot scale, that is, the phase difference of the pilot signal. 1.4 Subcarrier suppression
The ratio of the voltage peak of the subchannel signal when it is 100% modulated to the 38kHz leakage voltage amplitude value when it is not modulated. 2 Technical parameters
The technical parameters of the FM broadcast transmitter shall comply with the provisions of Table 1. Among them, 15 to 20 are the indicators added during stereo broadcasting. Issued by the National Bureau of Standards on April 6, 1984
Implemented on January 1, 1985
Band range
Carrier frequency tolerance
Load impedance
Residual wave radiation intensity
Pre-emphasis
Maximum frequency deviation
Maximum modulation capacity
Audio input impedance
Audio input level
Frequency response
Spurious modulation Amplitude noise
GB/T4312.1—1984
Technical indicators of FM broadcast transmitter
87~108MHz
<2000Hz (power>50W)
<3000Hz (power≤50W)wwW.bzxz.Net
<1mW and lower than carrier power 60dB (power>25W)<25μW and lower than carrier power 40dB (power≤25W)50 us
±75kHz
±100kHz
6000 balance
10±2dBm
40~15000Hz:±1dB
≥60dB (1kHz100% modulation)
<-50dB (no modulation)
Output power tolerance
Harmonic distortion
Pilot frequency
Pilot signal phase tolerance
Pilot signal modulation
Subcarrier suppression
Left and right signal level difference
Left and right signal separation
(50 impedance)
40~15 000Hz
75kHz frequency deviation
100kHz frequency deviation
19kHz±2Hz
8%~10%
≤—40dB
40~15000Hz:<1dB
40~15000Hz:>36dB
GB/T 4312.1—1984
3 Test methods for main technical indicators of FM stereo broadcast transmitter 3
Test conditions:
Temperature: 10~40℃;
Relative humidity: 45%~90%;
Voltage: 380V or 220V±5%;
Power frequency: 50±1Hz.
The technical requirements of the test instruments shall comply with the provisions of Table 2. Table 2 Technical requirements for test instruments
3.3 Test precautions:
Lock rate range: 0.02~20kHz
b. Frequency error: <±1%±1Hz
Audio signal generator
Distortion meter
Stereo demodulator
Frequency deviation meter
Digital frequency meter
Oscilloscope
Spectrum analyzer||t t||eAmplitude error: <±0.1dB
d.Harmonic distortion: <0.05%
e.Output impedance: 600Q
Range: 0.05%~100%
Frequency range: 0.02~200kHz
Measurement error: ≤±5%~10%
Voltage range: 100μV~30v
Rate range: 0.0 375kHz
Input impedance: ≥40k2
cLeft and right signal separation: 30~15000Hz≥50dB, right signal distortion: <0.1%
Intermodulation distortion: second-order intermodulation <0.07%
Third-order intermodulation <0.1%
Signal to noise ratio: 30Hz~100kHz>20dB
De-emphasis: 50μs||tt| |Output voltage: ≥2V
Frequency range: covers the entire band
Allowable deviation of oscillator frequency: 10×10-HzFrequency deviation range: 0100kHz
Distortion: 100% modulation 0.04~75kHz<0.25%Signal-to-noise ratio: >65dB
fFrequency response: 40Hz~53kHz<±0.1dBCan meet stereo measurement
h. Can do FM, AM test, output voltage>500mVa.
Accuracy: 1×10-±1 digit
Gate time: 1ms~10s
Axis amplifier sensitivity:
200μV/cm~20V/cmError<3%
3. Z-axis frequency response: <3dB
Scan time: 5s/cm~1μs/cm
Frequency range: upper limit≥1000MHz
Level dynamic range: ≥80dB
GB/T4312.1—1984
Before testing, adjust the transmitter to normal working state, for example, keep the transmitting power, correctly tune at all levels, work stably without self-excitation, and measure without various external interference. In addition, before measuring, check and calibrate the instrument and use it only after it is qualified. 3.4 Test methods for main technical indicators:
3.4.1 Measurement of separation of left and right signals
3.4.1.1 See Figure 1 for the test block diagram.
Sound spot loss L
Sound proof
Modulator
3.4.1.2 Test method:
New bias setting
Transmitter
Slow load
Figure 1 Block diagram of test of separation of left and right signals
Demodulator
a. The pilot signal maintains a modulation degree of 10% (the same below), the modulator does not need to be emphasized, and the demodulator does not need to be de-emphasized. Electric meter
b. The audio oscillator sends 0.04 and 0.1, 1, 3, 5, 7, 10, 12, 15kHz (these test points are the same for the following items) signals to the input of the stereo modulator L (or R), so that the modulation index is 100% (10% of which is the pilot frequency). c. Pick up the signal from the transmitter feeder output port and send it to the frequency deviation meter. At the output of the stereo demodulator, use a level meter to measure the output level of the left (or right) end, and then connect the level meter to the right (or left) end to measure its output level. The ratio of the left and right output levels, expressed in dB, is the separation of the left and right signals at this frequency point. 3.4.2 Measurement of the level difference between the left and right signals 3.4.2.1 The test block diagram is the same as Figure 1.
3.4.2.2 Test method:
a. Same as 3.4.1.2a and b, set the modulation index to 55% (10% is the pilot signal), and use a level meter to measure the output level of the left end of the stereo demodulator;
b. Send the output of the audio oscillator to the R input terminal, and measure the output level of the right end of the demodulator. The difference between the left and right output levels is the level difference between the left and right signals.
3.4.3 Measurement of the phase difference of the pilot signal
3.4.3.1 See Figure 2 (a) for the test block diagram. Product
3.4.3.2 Test method:
Fake price number
Frequency sick leave
(a) Pilot signal phase difference test block diagram Beijing adapter
As shown in Figure 2 (a), when no modulation signal is added, a 19kHz pilot signal is derived from the frequency deviation meter and added to the y-axis of the oscilloscope, and a 19kHz pilot signal is derived from the stereo modulator and added to the axis, see Figure 2 (b), adjust the phase adjuster so that the oscilloscope is a slant line close to 45°, 4
At this time, the phase difference between the two 19kHz signals is zero. GB/T4312.1—1984
Zhefu Night
191.1 from stereo market
Figure 2(b)
Pa-position modulator
b. Turn off the pilot signal output by the modulator to the exciter, and add a 1kHz signal to the input terminals of the stereo modulator L and R (through the inverter, but there should be no amplitude change) at the same time, so that the modulation index is 90% (the pilot is 0). At this time, the signal added to the oscilloscope axis is the "s" signal without a pilot (M=0). The 19kHz pilot signal of the stereo modulator is still sent to the a-axis. The Lissajous figure seen from the oscilloscope is shown in Figure 3 (a, b). Measure the lengths of A and B, and calculate the phase difference of the pilot signal according to the following formula. 180B
(degrees)
(a) Pilot signal has phase shift
(b) Pilot signal has no phase shift
Note: After calibration, if the oscilloscope range is changed (including changing the gain knob), it must be recalibrated at this level, because the distributed capacitance of the oscilloscope is different at different levels, which will cause phase changes, so recalibration is necessary. 3.4.4 Measurement of subcarrier suppression
3.4.4.1 See Figure 4 for the test block diagram.
Figure 4 Subcarrier suppression test block diagram
Small drum leather
3.4.4.2 Test method:
GB/T4312.1—1984
a. Turn off the pilot signal. Use a 1kHz signal to simultaneously add the input terminals of the modulator L and R (via the inverter, but there should be no amplitude change) to make the modulation index 90%. At this time, the signal added to the y-axis of the oscilloscope is the "s" signal (M=0). Measure the amplitude (peak-to-peak) of the "s" signal.
Remove the modulated signal. At this time, the oscilloscope displays the residual subcarrier (i.e., leakage). Measure its size and calculate the subcarrier suppression as follows.
3.4.5 Measurement of pre-emphasis
Subcarrier suppression = 201g (）
E(retard 2(dB)
3.4.5.1The test block diagram is the same as Figure 1.
3.4.5.2Test method:
a. The stereo modulator uses 50us pre-emphasis, the stereo demodulator does not need to be de-emphasized, and the pilot frequency is 10%; b. The audio oscillator sends a 15kHz signal to the input of the stereo demodulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for 10%), and the output levels of the audio oscillator and demodulator are recorded (the 100% modulation index is calibrated at 15kHz to avoid overmodulation at the high frequency end due to emphasis);
According to the above test points, send any frequency of 12kHz.40Hz to the input of L (or R), and keep the input Keeping the level unchanged, read out the output level d of each corresponding frequency at the output end of the demodulator. Make a 50μs pre-emphasis curve with the measured level at each frequency point. 3.4.6 Measurement of frequency response
3.4.6.1 The test block diagram is the same as Figure 1.
3.4.6.2 Test method:
a. The pilot frequency is 10%, no emphasis or de-emphasis is required, the 1kHz signal of the audio oscillator is added to the L (or R) input of the stereo modulator, so that the modulation index is 55% (the pilot frequency accounts for 10%), record the output level value of the left (or right) end of the stereo demodulator as the reference level, and record the output level value of the audio oscillator at this time. b. Keep the output level of the audio oscillator at each test frequency point unchanged, and record the output level of the stereo demodulator at the corresponding Test the output level of the left (or right) end of the frequency point, and make a frequency response curve according to this value. 3.4.7 Harmonic distortion
3.4.7.1 See Figure 5 for the test block diagram.
Audio oscillator installed
Reducer
3.4.7.2 Test method:
Transmitter
People only me
Pre-adjuster
Figure 5 Harmonic distortion test block diagram
De-adjuster
a The audio oscillator sends any signal of the aforementioned test point to the input end of the stereo modulator L (or R), making the modulation degree 100% (the pilot frequency accounts for 10%);
b. Use a distortion meter to measure the distortion of the output signal of the left (or right) end of the stereo demodulator at this frequency point. 3.4. 8 Signal-to-noise ratio
3.4.8.1 The test block diagram is the same as Figure 1.
3.4.8.2 Test method:
The audio oscillator sends a 1kHz signal to the input of the stereo modulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for a.
10%);
GB/T4312.1—1984
Measure the output level of the left (or right) end at the output of the stereo demodulator; remove the 1kHz modulation signal, measure the noise level of the left (or right) output of the stereo demodulator, and calculate the signal-to-noise ratio c according to the following formula.
S/N=ViV2
Where: V1—signal level (with modulation); V2——noise level (without modulation).
3.4.9 Parasitic AM noise
3.4.9.1 See Figure 6 for the test block diagram.
City sound
Modulator
3.4.9.2 Test method
Frequency tracking
Slow load
6 AM noise test block diagram
The transmitter is not modulated, and the parasitic AM noise is measured using the AM linear detector in the frequency deviation meter. 3.4.10 Residual wave radiation intensity
3.4.10.1 The transmitter is not modulated, and the signal is taken out after the transmitter output filter and added to the spectrum analyzer, and the amplitude values of each residual wave are measured. The ratio of each residual wave amplitude to the carrier frequency fundamental wave amplitude value is the residual wave radiation intensity value. When the transmission power is large and the above method is difficult to measure, you can first disconnect the output filter and use a spectrum analyzer to measure the fundamental wave amplitude and the intensity of each residual wave radiation wave, and then measure the output attenuation characteristics of the filter separately, and comprehensively calculate the ratio of the residual wave amplitude to the fundamental wave amplitude. Additional notes:
This standard was proposed by the Ministry of Radio and Television of the People's Republic of China. This standard was drafted by the Guangdong Provincial Broadcasting Bureau. The main drafter of this standard is Zhu Jinxin.2 Test method:
Fake price number
Frequency sick leave
(a) Pilot signal phase difference test block diagram Beijing adapter
As shown in Figure 2 (a), when no modulation signal is added, a 19kHz pilot signal is derived from the frequency deviation meter and added to the y-axis of the oscilloscope, and a 19kHz pilot signal is derived from the stereo modulator and added to the axis, see Figure 2 (b), adjust the phase adjuster to make the oscilloscope a slant line close to 45°, 4
At this time, the phase difference between the two 19kHz signals is zero. GB/T4312.1—1984
Zhefu Night
191.1 from stereo market
Figure 2(b)
Pa-position modulator
b. Turn off the pilot signal output by the modulator to the exciter, and add a 1kHz signal to the input terminals of the stereo modulator L and R (through the inverter, but there should be no amplitude change) at the same time, so that the modulation index is 90% (the pilot is 0). At this time, the signal added to the oscilloscope axis is the "s" signal without a pilot (M=0). The 19kHz pilot signal of the stereo modulator is still sent to the a-axis. The Lissajous figure seen from the oscilloscope is shown in Figure 3 (a, b). Measure the lengths of A and B, and calculate the phase difference of the pilot signal according to the following formula. 180B
(degrees)
(a) Pilot signal has phase shift
(b) Pilot signal has no phase shift
Note: After calibration, if the oscilloscope range is changed (including changing the gain knob), it must be recalibrated at this level, because the distributed capacitance of the oscilloscope is different at different levels, which will cause phase changes, so recalibration is necessary. 3.4.4 Measurement of subcarrier suppression
3.4.4.1 See Figure 4 for the test block diagram.
Figure 4 Subcarrier suppression test block diagram
Small drum leather
3.4.4.2 Test method:
GB/T4312.1—1984
a. Turn off the pilot signal. Use a 1kHz signal to simultaneously add the input terminals of the modulator L and R (via the inverter, but there should be no amplitude change) to make the modulation index 90%. At this time, the signal added to the y-axis of the oscilloscope is the "s" signal (M=0). Measure the amplitude (peak-to-peak) of the "s" signal.
Remove the modulated signal. At this time, the oscilloscope displays the residual subcarrier (i.e., leakage). Measure its size and calculate the subcarrier suppression as follows.
3.4.5 Measurement of pre-emphasis
Subcarrier suppression = 201g (）
E(retard 2(dB)
3.4.5.1The test block diagram is the same as Figure 1.
3.4.5.2Test method:
a. The stereo modulator uses 50us pre-emphasis, the stereo demodulator does not need to be de-emphasized, and the pilot frequency is 10%; b. The audio oscillator sends a 15kHz signal to the input of the stereo demodulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for 10%), and the output levels of the audio oscillator and demodulator are recorded (the 100% modulation index is calibrated at 15kHz to avoid overmodulation at the high frequency end due to emphasis);
According to the above test points, send any frequency of 12kHz.40Hz to the input of L (or R), and keep the input Keeping the level unchanged, read out the output level d of each corresponding frequency at the output end of the demodulator. Make a 50μs pre-emphasis curve with the measured level at each frequency point. 3.4.6 Measurement of frequency response
3.4.6.1 The test block diagram is the same as Figure 1.
3.4.6.2 Test method:
a. The pilot frequency is 10%, no emphasis or de-emphasis is required, the 1kHz signal of the audio oscillator is added to the L (or R) input of the stereo modulator, so that the modulation index is 55% (the pilot frequency accounts for 10%), record the output level value of the left (or right) end of the stereo demodulator as the reference level, and record the output level value of the audio oscillator at this time. b. Keep the output level of the audio oscillator at each test frequency point unchanged, and record the output level of the stereo demodulator at the corresponding Test the output level of the left (or right) end of the frequency point, and make a frequency response curve according to this value. 3.4.7 Harmonic distortion
3.4.7.1 See Figure 5 for the test block diagram.
Audio oscillator installed
Reducer
3.4.7.2 Test method:
Transmitter
People only me
Pre-adjuster
Figure 5 Harmonic distortion test block diagram
De-adjuster
a The audio oscillator sends any signal of the aforementioned test point to the input end of the stereo modulator L (or R), making the modulation degree 100% (the pilot frequency accounts for 10%);
b. Use a distortion meter to measure the distortion of the output signal of the left (or right) end of the stereo demodulator at this frequency point. 3.4. 8 Signal-to-noise ratio
3.4.8.1 The test block diagram is the same as Figure 1.
3.4.8.2 Test method:
The audio oscillator sends a 1kHz signal to the input of the stereo modulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for a.
10%);
GB/T4312.1—1984
Measure the output level of the left (or right) end at the output of the stereo demodulator; remove the 1kHz modulation signal, measure the noise level of the left (or right) output of the stereo demodulator, and calculate the signal-to-noise ratio c according to the following formula.
S/N=ViV2
Where: V1—signal level (with modulation); V2——noise level (without modulation).
3.4.9 Parasitic AM noise
3.4.9.1 See Figure 6 for the test block diagram.
City sound
Modulator
3.4.9.2 Test method
Frequency tracking
Slow load
6 AM noise test block diagram
The transmitter is not modulated, and the parasitic AM noise is measured using the AM linear detector in the frequency deviation meter. 3.4.10 Residual wave radiation intensity
3.4.10.1 The transmitter is not modulated, and the signal is taken out after the transmitter output filter and added to the spectrum analyzer, and the amplitude values of each residual wave are measured. The ratio of each residual wave amplitude to the carrier frequency fundamental wave amplitude value is the residual wave radiation intensity value. When the transmission power is large and the above method is difficult to measure, you can first disconnect the output filter and use a spectrum analyzer to measure the fundamental wave amplitude and the intensity of each residual wave radiation wave, and then measure the output attenuation characteristics of the filter separately, and comprehensively calculate the ratio of the residual wave amplitude to the fundamental wave amplitude. Additional notes:
This standard was proposed by the Ministry of Radio and Television of the People's Republic of China. This standard was drafted by the Guangdong Provincial Broadcasting Bureau. The main drafter of this standard is Zhu Jinxin.2 Test method:
Fake price number
Frequency sick leave
(a) Pilot signal phase difference test block diagram Beijing adapter
As shown in Figure 2 (a), when no modulation signal is added, a 19kHz pilot signal is derived from the frequency deviation meter and added to the y-axis of the oscilloscope, and a 19kHz pilot signal is derived from the stereo modulator and added to the axis, see Figure 2 (b), adjust the phase adjuster to make the oscilloscope a slant line close to 45°, 4
At this time, the phase difference between the two 19kHz signals is zero. GB/T4312.1—1984
Zhefu Night
191.1 from stereo market
Figure 2(b)
Pa-position modulator
b. Turn off the pilot signal output by the modulator to the exciter, and add a 1kHz signal to the input terminals of the stereo modulator L and R (through the inverter, but there should be no amplitude change) at the same time, so that the modulation index is 90% (the pilot is 0). At this time, the signal added to the oscilloscope axis is the "s" signal without a pilot (M=0). The 19kHz pilot signal of the stereo modulator is still sent to the a-axis. The Lissajous figure seen from the oscilloscope is shown in Figure 3 (a, b). Measure the lengths of A and B, and calculate the phase difference of the pilot signal according to the following formula. 180B
(degrees)
(a) Pilot signal has phase shift
(b) Pilot signal has no phase shift
Note: After calibration, if the oscilloscope range is changed (including changing the gain knob), it must be recalibrated at this level, because the distributed capacitance of the oscilloscope is different at different levels, which will cause phase changes, so recalibration is necessary. 3.4.4 Measurement of subcarrier suppression
3.4.4.1 See Figure 4 for the test block diagram.
Figure 4 Subcarrier suppression test block diagram
Small drum leather
3.4.4.2 Test method:
GB/T4312.1—1984
a. Turn off the pilot signal. Use a 1kHz signal to simultaneously add the input terminals of the modulator L and R (via the inverter, but there should be no amplitude change) to make the modulation index 90%. At this time, the signal added to the y-axis of the oscilloscope is the "s" signal (M=0). Measure the amplitude (peak-to-peak) of the "s" signal.
Remove the modulated signal. At this time, the oscilloscope displays the residual subcarrier (i.e., leakage). Measure its size and calculate the subcarrier suppression as follows.
3.4.5 Measurement of pre-emphasis
Subcarrier suppression = 201g (）
E(retard 2(dB)
3.4.5.1The test block diagram is the same as Figure 1.
3.4.5.2Test method:
a. The stereo modulator uses 50us pre-emphasis, the stereo demodulator does not need to be de-emphasized, and the pilot frequency is 10%; b. The audio oscillator sends a 15kHz signal to the input of the stereo demodulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for 10%), and the output levels of the audio oscillator and demodulator are recorded (the 100% modulation index is calibrated at 15kHz to avoid overmodulation at the high frequency end due to emphasis);
According to the above test points, send any frequency of 12kHz.40Hz to the input of L (or R), and keep the input Keeping the level unchanged, read out the output level d of each corresponding frequency at the output end of the demodulator. Make a 50μs pre-emphasis curve with the measured level at each frequency point. 3.4.6 Measurement of frequency response
3.4.6.1 The test block diagram is the same as Figure 1.
3.4.6.2 Test method:
a. The pilot frequency is 10%, no emphasis or de-emphasis is required, the 1kHz signal of the audio oscillator is added to the L (or R) input of the stereo modulator, so that the modulation index is 55% (the pilot frequency accounts for 10%), record the output level value of the left (or right) end of the stereo demodulator as the reference level, and record the output level value of the audio oscillator at this time. b. Keep the output level of the audio oscillator at each test frequency point unchanged, and record the output level of the stereo demodulator at the corresponding Test the output level of the left (or right) end of the frequency point, and make a frequency response curve according to this value. 3.4.7 Harmonic distortion
3.4.7.1 See Figure 5 for the test block diagram.
Audio oscillator installed
Reducer
3.4.7.2 Test method:
Transmitter
People only me
Pre-adjuster
Figure 5 Harmonic distortion test block diagram
De-adjuster
a The audio oscillator sends any signal of the aforementioned test point to the input end of the stereo modulator L (or R), making the modulation degree 100% (the pilot frequency accounts for 10%);
b. Use a distortion meter to measure the distortion of the output signal of the left (or right) end of the stereo demodulator at this frequency point. 3.4. 8 Signal-to-noise ratio
3.4.8.1 The test block diagram is the same as Figure 1.
3.4.8.2 Test method:
The audio oscillator sends a 1kHz signal to the input of the stereo modulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for a.
10%);
GB/T4312.1—1984
Measure the output level of the left (or right) end at the output of the stereo demodulator; remove the 1kHz modulation signal, measure the noise level of the left (or right) output of the stereo demodulator, and calculate the signal-to-noise ratio c according to the following formula.
S/N=ViV2
Where: V1—signal level (with modulation); V2——noise level (without modulation).
3.4.9 Parasitic AM noise
3.4.9.1 See Figure 6 for the test block diagram.
City sound
Modulator
3.4.9.2 Test method
Frequency tracking
Slow load
6 AM noise test block diagram
The transmitter is not modulated, and the parasitic AM noise is measured using the AM linear detector in the frequency deviation meter. 3.4.10 Residual wave radiation intensity
3.4.10.1 The transmitter is not modulated, and the signal is taken out after the transmitter output filter and added to the spectrum analyzer, and the amplitude values of each residual wave are measured. The ratio of each residual wave amplitude to the carrier frequency fundamental wave amplitude value is the residual wave radiation intensity value. When the transmission power is large and the above method is difficult to measure, you can first disconnect the output filter and use a spectrum analyzer to measure the fundamental wave amplitude and the intensity of each residual wave radiation wave, and then measure the output attenuation characteristics of the filter separately, and comprehensively calculate the ratio of the residual wave amplitude to the fundamental wave amplitude. Additional notes:
This standard was proposed by the Ministry of Radio and Television of the People's Republic of China. This standard was drafted by the Guangdong Provincial Broadcasting Bureau. The main drafter of this standard is Zhu Jinxin.1—1984
a. Turn off the pilot signal. Add a 1kHz signal to the input terminals of the modulator L and R (via the inverter, but there should be no amplitude change) at the same time to make the modulation index 90%. At this time, the signal added to the y-axis of the oscilloscope is the "s" signal (M=0), and measure the amplitude (peak-to-peak) of the "s" signal.
Remove the modulated signal. At this time, the oscilloscope displays the residual subcarrier (i.e., leakage). Measure its size and calculate the subcarrier suppression according to the following formula.
3.4.5 Measurement of pre-emphasis
Subcarrier suppression = 201g (）
E(retard 2(dB)
3.4.5.1The test block diagram is the same as Figure 1.
3.4.5.2Test method:
a. The stereo modulator uses 50us pre-emphasis, the stereo demodulator does not need to be de-emphasized, and the pilot frequency is 10%; b. The audio oscillator sends a 15kHz signal to the input of the stereo demodulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for 10%), and the output levels of the audio oscillator and demodulator are recorded (the 100% modulation index is calibrated at 15kHz to avoid overmodulation at the high frequency end due to emphasis);
According to the above test points, send any frequency of 12kHz.40Hz to the input of L (or R), and keep the input Keeping the level unchanged, read out the output level d of each corresponding frequency at the output end of the demodulator. Make a 50μs pre-emphasis curve with the measured level at each frequency point. 3.4.6 Measurement of frequency response
3.4.6.1 The test block diagram is the same as Figure 1.
3.4.6.2 Test method:
a. The pilot frequency is 10%, no emphasis or de-emphasis is required, the 1kHz signal of the audio oscillator is added to the L (or R) input of the stereo modulator, so that the modulation index is 55% (the pilot frequency accounts for 10%), record the output level value of the left (or right) end of the stereo demodulator as the reference level, and record the output level value of the audio oscillator at this time. b. Keep the output level of the audio oscillator at each test frequency point unchanged, and record the output level of the stereo demodulator at the corresponding Test the output level of the left (or right) end of the frequency point, and make a frequency response curve according to this value. 3.4.7 Harmonic distortion
3.4.7.1 See Figure 5 for the test block diagram.
Audio oscillator installed
Reducer
3.4.7.2 Test method:
Transmitter
People only me
Pre-adjuster
Figure 5 Harmonic distortion test block diagram
De-adjuster
a The audio oscillator sends any signal of the aforementioned test point to the input end of the stereo modulator L (or R), making the modulation degree 100% (the pilot frequency accounts for 10%);
b. Use a distortion meter to measure the distortion of the output signal of the left (or right) end of the stereo demodulator at this frequency point. 3.4. 8 Signal-to-noise ratio
3.4.8.1 The test block diagram is the same as Figure 1.
3.4.8.2 Test method:
The audio oscillator sends a 1kHz signal to the input of the stereo modulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for a.
10%);
GB/T4312.1—1984
Measure the output level of the left (or right) end at the output of the stereo demodulator; remove the 1kHz modulation signal, measure the noise level of the left (or right) output of the stereo demodulator, and calculate the signal-to-noise ratio c according to the following formula.
S/N=ViV2
Where: V1—signal level (with modulation); V2——noise level (without modulation).
3.4.9 Parasitic AM noise
3.4.9.1 See Figure 6 for the test block diagram.
City sound
Modulator
3.4.9.2 Test method
Frequency tracking
Slow load
6 AM noise test block diagram
The transmitter is not modulated, and the parasitic AM noise is measured using the AM linear detector in the frequency deviation meter. 3.4.10 Residual wave radiation intensity
3.4.10.1 The transmitter is not modulated, and the signal is taken out after the transmitter output filter and added to the spectrum analyzer, and the amplitude values of each residual wave are measured. The ratio of each residual wave amplitude to the carrier frequency fundamental wave amplitude value is the residual wave radiation intensity value. When the transmission power is large and the above method is difficult to measure, you can first disconnect the output filter and use a spectrum analyzer to measure the fundamental wave amplitude and the intensity of each residual wave radiation wave, and then measure the output attenuation characteristics of the filter separately, and comprehensively calculate the ratio of the residual wave amplitude to the fundamental wave amplitude. Additional notes:
This standard was proposed by the Ministry of Radio and Television of the People's Republic of China. This standard was drafted by the Guangdong Provincial Broadcasting Bureau. The main drafter of this standard is Zhu Jinxin.1—1984
a. Turn off the pilot signal. Add a 1kHz signal to the input terminals of the modulator L and R (via the inverter, but there should be no amplitude change) at the same time to make the modulation index 90%. At this time, the signal added to the y-axis of the oscilloscope is the "s" signal (M=0), and measure the amplitude (peak-to-peak) of the "s" signal.
Remove the modulated signal. At this time, the oscilloscope displays the residual subcarrier (i.e., leakage). Measure its size and calculate the subcarrier suppression according to the following formula.
3.4.5 Measurement of pre-emphasis
Subcarrier suppression = 201g (）
E(retard 2(dB)
3.4.5.1The test block diagram is the same as Figure 1.
3.4.5.2Test method:
a. The stereo modulator uses 50us pre-emphasis, the stereo demodulator does not need to be de-emphasized, and the pilot frequency is 10%; b. The audio oscillator sends a 15kHz signal to the input of the stereo demodulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for 10%), and the output levels of the audio oscillator and demodulator are recorded (the 100% modulation index is calibrated at 15kHz to avoid overmodulation at the high frequency end due to emphasis);
According to the above test points, send any frequency of 12kHz.40Hz to the input of L (or R), and keep the input Keeping the level unchanged, read out the output level d of each corresponding frequency at the output end of the demodulator. Make a 50μs pre-emphasis curve with the measured level at each frequency point. 3.4.6 Measurement of frequency response
3.4.6.1 The test block diagram is the same as Figure 1.
3.4.6.2 Test method:
a. The pilot frequency is 10%, no emphasis or de-emphasis is required, the 1kHz signal of the audio oscillator is added to the L (or R) input of the stereo modulator, so that the modulation index is 55% (the pilot frequency accounts for 10%), record the output level value of the left (or right) end of the stereo demodulator as the reference level, and record the output level value of the audio oscillator at this time. b. Keep the output level of the audio oscillator at each test frequency point unchanged, and record the output level of the stereo demodulator at the corresponding Test the output level of the left (or right) end of the frequency point, and make a frequency response curve according to this value. 3.4.7 Harmonic distortion
3.4.7.1 See Figure 5 for the test block diagram.
Audio oscillator installed
Reducer
3.4.7.2 Test method:
Transmitter
People only me
Pre-adjuster
Figure 5 Harmonic distortion test block diagram
De-adjuster
a The audio oscillator sends any signal of the aforementioned test point to the input end of the stereo modulator L (or R), making the modulation degree 100% (the pilot frequency accounts for 10%);
b. Use a distortion meter to measure the distortion of the output signal of the left (or right) end of the stereo demodulator at this frequency point. 3.4. 8 Signal-to-noise ratio
3.4.8.1 The test block diagram is the same as Figure 1.
3.4.8.2 Test method:
The audio oscillator sends a 1kHz signal to the input of the stereo modulator L (or R), so that the modulation index is 100% (the pilot frequency accounts for a.
10%);
GB/T4312.1—1984
Measure the output level of the left (or right) end at the output of the stereo demodulator; remove the 1kHz modulation signal, measure the noise level of the left (or right) output of the stereo demodulator, and calculate the signal-to-noise ratio c according to the following formula.
S/N=ViV2
Where: V1—signal level (with modulation); V2——noise level (without modulation).
3.4.9 Parasitic AM noise
3.4.9.1 See Figure 6 for the test block diagram.
City sound
Modulator
3.4.9.2 Test method
Frequency tracking
Slow load
6 AM noise test block diagram
The transmitter is not modulated, and the parasitic AM noise is measured using the AM linear detector in the frequency deviation meter. 3.4.10 Residual wave radiation intensity
3.4.10.1 The transmitter is not modulated, and the signal is taken out after the transmitter output filter and added to the spectrum analyzer, and the amplitude values of each residual wave are measured. The ratio of each residual wave amplitude to the carrier frequency fundamental wave amplitude value is the residual wave radiation intensity value. When the transmission power is large and the above method is difficult to measure, you can first disconnect the output filter and use a spectrum analyzer to measure the fundamental wave amplitude and the intensity of each residual wave radiation wave, and then measure the output attenuation characteristics of the filter separately, and comprehensively calculate the ratio of the residual wave amplitude to the fundamental wave amplitude. Additional notes:
This standard was proposed by the Ministry of Radio and Television of the People's Republic of China. This standard was drafted by the Guangdong Provincial Broadcasting Bureau. The main drafter of this standard is Zhu Jinxin.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.