GB/T 4312.2-1984 Technical parameters and measurement methods for FM broadcast transmitters - Stereo with additional channels
Some standard content:
National Standard of the People's Republic of China
GB/T4312.2—1984
Technical parameters and measuring methodsfor FMstereophonic broadcasting transmitterswithsupplementarychannel
Published on April 6, 1984
National Bureau of Standards
Implementation on January 1, 1985
National Standard of the People's Republic of China
Technical parametersandmeasuringmethodsforFMstereophonicbroadcastingtransmitterswithsupplementarychannel channel
1 Explanation of terms
1.1 Explanation of terms for stereo channels
UDC621.396.61
:621.317.08
GB/T4312.2—1984
Same as GB4312.1-84 "Technical parameters and measurement methods for FM broadcast transmitters - mono and stereo" 1.2 Mutual crosstalk attenuation of additional channels in stereo sound band Crosstalk attenuation (dB) = 201gg
Where: U
-Rated audio signal voltage output by the stereo left or right channel (additional channel): U2-The crosstalk voltage output by the stereo left or right channel (additional channel) when there is no input audio signal voltage to the stereo left or right channel (additional channel) and the rated audio signal voltage is input to the additional channel (stereo left or right channel). 2 Technical Parameters
The technical parameters of the stereo FM broadcast transmitter with additional channels shall conform to the requirements of Table 1, Table 2 and Table 1 of Chapter 2 of GB4312.1-84.
Table 1 Technical parameters of FM broadcast additional channel
Subcarrier frequency
Subcarrier frequency tolerance
67kHz subcarrier to main carrier modulation
Modulation mode
Maximum frequency deviation
Audio input impedance
Audio input level
Signal to noise ratio
Harmonic distortion
Frequency response
Pre-emphasis
Compression ratio
Published by the National Bureau of Standards on April 6, 1984
±150Hz
8%~10%
±4kHz (100% modulation)
600Q balance
10±2dBm
>60dB (1kHz, using pre-emphasis and compression expansion technology)<4% (80 Hz~6 kHz)
(80Hz～6kHz), ±2dB
Time constant is 50μs (see GB4311.3——84) 2:1(dB)
Implementation on 1985-01-01
3 Test method
GB/T4312.2—1984
Table 2 Crosstalk index items between stereo and additional channels
Crosstalk attenuation of additional channel to stereo left channel Crosstalk attenuation of additional channel to stereo right channel Crosstalk attenuation of stereo left channel to additional channel Crosstalk attenuation of stereo right channel to additional channel 3.1 Test method for main technical indicators of stereo channel The test method for main technical indicators of stereo channel is the same as GB4312.1-84. Refers to
>65dB (80Hz6kHz)
>65dB (80Hz~6kHz)
>65dB (using compression and expansion technology, 40Hz15kHz)>65dB (using compression and expansion technology, 40Hz15kHz) The modulation index distribution in the stereo band additional channel system should be 80% (stereo) + 10% (pilot) + 10% (67kHz subcarrier) (the same modulation index distribution below).
3.2 Test methods for main technical indicators of additional channels Test methods for main technical indicators of additional channels All pre-emphasis, de-emphasis, compressor and expander are added. 3.2.1 Signal-to-noise ratio
3.2.1.1 See Figure 1 for the test block diagram.
True body
That is, kidney pseudo
3.2.1.2 Test method:
Compressor
Opportunity channel
Additional harmonic test
Control
Expansion band
Promoting negative shoes
Electric semi-meter
Without adding audio signal, adjust the modulation degree of 67kHz subcarrier to the main carrier to reach 10% (the same below). The signal generator outputs a 1kHz audio signal and adds it to the input end of the compressor, so that the modulation degree of the additional channel reaches 100% (the frequency deviation is ±4kHz), and the output audio signal level is measured at the output end of the expander. Then remove the modulation signal of the additional channel, measure the noise level at the output end of the expander, and the difference between the two is the signal-to-noise ratio. 2
3.2.2 Harmonic distortion
3.2.2.1 See Figure 2 for the test block diagram.
Stereo
Preparation
3.2.2.2 Test method:
GB/T4312.2—1984
Compressor
Group amplifier
Amplifier
The signal generator outputs 0.08, 0.2, 0.4, 1, 2, 3, 5, 6kHz audio signals and adds them to the compressor input end, so that the modulation degree reaches 100%, and the distortion value of each frequency is measured at the expander output end (the stereo modulator should be measured separately without adding audio modulation signal and adding rated audio modulation signal in two working states). 3.2.3 Frequency response
3.2.3.1 The test block diagram is shown in Figure 1.
3.2.3.2 Test method:
a Signal generator outputs 1kHz audio signal and adds it to the compressor input end, so that the modulation degree reaches 25%. Measure the 1kHz audio signal value at the expander output as the reference level, keep the signal generator output audio signal level unchanged, measure 0.08, 0.2, 0.4, 1, 2, 3, 4, b.
5, 6kHz signal levels at the expander output, and make a frequency response curve. 3.2.4 Pre-emphasis
3.2.4.1 See Figure 1 for the test block diagram.
3.2.4.2 Test method:
Additional channel modulator adds pre-emphasis, additional channel demodulator does not add de-emphasis, a.
Signal generator outputs 6kHz audio signal and adds it to the compressor input end, so that the modulation degree reaches 100%, and b.
measures the 6kHz audio signal level value at the expander output end;
Keep the signal generator output audio signal level unchanged, and measure 6, 5, 4, 3, 2, 1, 0.2, 0.08c.
kHz corresponding audio signal levels at the expander output end, and make a pre-emphasis curve. 3.3 Test method for mutual crosstalk between stereo and additional channels 3.3.1 Additional channel crosstalk to stereo left channel 3.3.1.1 See Figure 3 for the test block diagram.
Generator 1
3.3.1.2 Test method:
GB/T4312.2—1984
Compression
Transmitter
Stretcher
Equalizer
Level meter
a. Signal generator "1" outputs 1kHz audio signal and adds it to the left channel of the stereo modulator (switch K, set to L position), so that the combined modulation degree of the main and sub-channels to the main carrier is 80%, the pilot signal modulation degree is kept at 10%, and the 67kHz sub-carrier modulation degree is 10%. Measure the voltage u1 of the audio signal at the output end of the left channel of the stereo demodulator (switch K2 is set to L position), and then remove the modulation signal. b. Signal generator "2" outputs 0.08, 0.2, 0.4, 1, 2, 3, 4, 5, 6kHz audio signals which are added to the additional channel modulator through the compressor to make the modulation degree reach 100%; c. Measure the crosstalk voltage u2 of the additional channel to the stereo left channel at the output end of the stereo left channel; crosstalk attenuation (dB) = 201g
3.3.2 Additional channel to stereo right channel crosstalk 3.3.2.1 See Figure 3 for the test block diagram.
3.3.2.2 Test method:
Set switches K1 and K2 to the R position, and the rest is the same as the test method in 3.3.1.2. 3.3.3 Stereo left channel to additional channel crosstalk 3.3.3.1 See Figure 3 for the test block diagram.
3.3.3.2 Test method:
Signal generator "2" outputs 1kHz audio signal and adds it to the additional channel modulator through the compressor to make the modulation degree reach 100%. a.
Measure the audio signal voltage 1 at the output end of the expander, and then remove the modulation signal; b. Signal generator "1" outputs 0.04, 0.1, 0.4, 1, 3, 5, 7, 10, 12, 15kHz audio signals and adds them to the left channel of the stereo modulator (switch K1 is placed in the L position) to make the modulation degree of the main carrier reach 80%, the pilot modulation degree is 10%, and the 67kHz subcarrier modulation degree is 10%;
GB/T4312.2—1984
Measure the crosstalk voltage of each frequency of the stereo left channel to the additional channel at the output end of the expander 2c.
4. Midrange attenuation (a) -20e=
3.3.4 Crosstalk of stereo right channel to additional channel 3.3.4.1 See Figure 3 for the test block diagram.
3.3.4.2 Test method:
Set switch K1 to the R position, and the rest is the same as the test method in 3.3.3.2. 3.4 Instrument requirements
3.4.1 Stereo channel
Same as 3.2 of GB4312.1-84.
3.4.2 Additional channel
Requirements for additional channel demodulator:
Subcarrier frequency: 67kHz±50Hz;
Input impedance ≥2k2;||t t||Input level>0.3V;
Distortion≤0.4%,
SNR>70dB;
Output level+10dB (600α balanced)
+5V (10kQ unbalanced);
De-emphasis: 50μus±1.5us;
Frequency deviation: ±4kHz, ±6kHz;bzxZ.net
Frequency response: ±0.3dB.
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 Heilongjiang Broadcasting Science Research Institute. The main drafters of this standard are Gao Guangliang and Wang Shude. 5
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