Some standard content:
National Standard of the People's Republic of China
GB 20171980
Medium Wave Broadcasting Network Coverage Technology
Published on January 1, 1981
Implemented on January 1, 1981
General Administration of Standards of the People's Republic of China
National Standard of the People's Republic of China
Medium Wave Broadcasting Network Coverage Technology
GB2017—1980
This standard applies to the planning of domestic medium wave broadcasting networks, the estimation of radio station service areas, and the estimation of interference between radio stations. I. Definition of Terms
1. Medium wave frequency band
A section of the radio spectrum allocated for medium wave broadcasting is called the medium wave frequency band. 2. Transmission bandwidth
The frequency bandwidth occupied by each medium wave AM broadcast in the medium wave frequency band is called the transmission bandwidth. 3. Channel
A part of the entire medium wave frequency band, whose width is equal to the transmission bandwidth. The center frequency of each channel is the nominal carrier frequency of the channel. A channel is characterized by its nominal carrier frequency.
4. Channel spacing
The difference between the nominal carrier frequencies of two adjacent channels. 5. RF protection ratio
The minimum ratio of the desired signal strength to the interference signal strength required to ensure satisfactory listening quality, expressed in decibels. 6. Available field strength
The minimum field strength required to obtain satisfactory listening quality in the actual situation where there is natural noise, industrial interference, and interference from co- and adjacent frequency transmitters.
7. Service area
The area around a transmitter, bounded by the available field strength, in which the field strength at each point is greater than or equal to the available field strength. 8. Synchronous broadcasting network
A group of transmitters that broadcast the same program using exactly the same or nearly exactly the same frequency. II. Main technical indicators
9. The main technical indicators should comply with Table 1.
General Administration of Standards
Central Broadcasting Bureau
January 1, 1981
Technical Department of Central Broadcasting Bureau
Medium wave frequency range (kHz)
Channel spacing (kHz)
Nominal carrier frequency of each channel
Emission bandwidth (kHz)
540~1593
RF protection rate (dB):
Co-frequency protection rate
GB 2017—1980
Adjacent frequency protection rate (9kHz interval)
Synchronous broadcast protection rate:
①Ground wave interfered by ground wave
Phase synchronization
Frequency synchronization
②Ground wave interfered by sky wave
Permissible limit of carrier frequency deviation (Hz)
Permissible frequency deviation between adjacent radio stations in frequency synchronization system (Hz)
Note: ①According to needs, it can be less than the value in the table, but it should not be less than 4.5kHz
526.5~1606.5
See Table 2
②When ground wave is interfered by sky wave, the signal strength to be received should be higher than the interference field strength by this value in 50% of the time. When broadcasting programs, the protection rate is reduced to 14 decibels.
③When two co-frequency transmitters (not synchronized) broadcast the same nominal carrier frequency of each channel
Channel number
Channel number
Channel number
10. Radio wave propagation
(1) Calculation method of ground wave propagation
GB2017—1980
Channel number
III. Calculation method and measurement method
Continued Table 2
GB2017—1980
a. Ground wave propagation is calculated according to strict diffraction theory formula. For the convenience of calculation, ground wave propagation curves are drawn for certain specific ground conductivity coefficients as shown in Figures 1 to 9. These curves are all converted to 1 kilowatt power. When the ground conductivity coefficient of a certain area is known, the field strength at the distance (km) can be calculated as follows:
E()=E. ()+P+G
Where: E (r) - field strength at distance r (dB); P - transmitter power (kW);
G - antenna gain,
E. (r) can be found from the corresponding ground wave propagation curve (dB). dB)
For vertical antennas at different heights, the gain G can be found from Figure 10 (dB). b Calculation method of composite propagation path
Assume that the conductivity and dielectric constant are not uniform on the path of radio wave propagation, and assume that the entire path is composed of S1, S2, S3 and other sections. The length of each section is d1, d2, d3...., and its conductivity and dielectric constant are 181, 0282, 0s83... respectively. For example, a three-segment path can be shown as follows:
Si (oi, er)
S2(02, e2)
Sa(o3, 8a)
Assuming that point T is the transmitter and point R is the receiver, the field strength E at point R is calculated as follows: Corresponding to the ground conductivity coefficient of segment S1, mark the field strength E1 (d1) at a distance of d1, in decibels (microvolts/meter). Then, corresponding to the ground conductivity coefficient of segment S2, obtain E2 (a1) and E2 (d1+d2). Then, corresponding to the ground conductivity coefficient of segment S3, obtain the field strength Es (ai+d2) and E (d+d2+ds).
Calculate the field strength at point R as:
Er=Er(d)-E2(d)+E2(d+d2)-E3(dr+d2)+Es(di+d2+d3).......(2) Reverse the above procedure, R is the transmitting point, T is the receiving point, and ET is calculated using the above method: Er=-Es(ds)-E2(ds)+E2(ds+d2)-Ei(ds+d2)+Ei(di+d2+ds).......(3) The field strength value E to be calculated can be calculated as follows: Eo
c. Measuring method of ground conductivity
(ER+Er)
For any area, the ground conductivity is measured by the "ground wave attenuation method", that is, the relationship between ground wave attenuation and distance is measured, and then the measurement results are compared with the ground wave propagation curve (Figures 1 to 9), and the earth conductivity of the measured area can be calculated. This method is applicable to all medium wave frequencies.
(2) Calculation method of sky wave propagation
The field strength calculation of sky wave propagation is also based on formula (1), but E. (r) in the formula should be found according to the sky wave propagation curve in Figure 11. This is an empirical curve made based on actual measurement results, corresponding to 1 watt transmission power: P is the transmitter power (kW);
G is the antenna gain, which should be calculated according to the propagation distance according to Figure 12. (3) Composite field strength of more than two radio waves
When there are two radio waves with the same nominal frequency, and their field strengths are E1, E2, and E. (dB) respectively, their composite field strength should be calculated by adding the power and the following formula:
Etai=101og[10°/10+10°2/10+10/10+]For ease of calculation, Figure 13 can be used. Assuming E≥E2, the composite field strength is: 4
(dB)
GB2017—1980
Etotal=Ei+4R
(dB)
When E1-E2 is known, the 4R value can be found from the curve in Figure 13. If there are more than two radio waves, Figure 13 can be used to add them one by one in the same way as above to obtain the composite field strength. 11. Calculation method of available field strength
Generally speaking, the available field strength during the day is determined by the level of natural noise, internal noise of the radio and industrial interference, while at night, due to the serious interference of the radio station, the available field strength is determined by the interference of the same and adjacent frequency radio stations. Usually, the available field strength value at night is much higher than that during the day. The service area of the radio station will also be reduced. In order to ensure listening during the day and night, the design of the radio network should be based on the available field strength at night. Therefore, the available field strength value of any radio station can be calculated by the following formula: 104B/10
Er=101og2
Where: E is the interference field strength of the same or adjacent frequency radio station (dB), A
is the protection ratio of the same or adjacent frequency radio station, expressed in decibels. The calculation of formula (7) can also be used in Figure 13. 12.Measurement method of frequency deviation between two adjacent radio stations in frequency synchronization system (dB) ·
The field strength recording method is used to test the frequency deviation between two adjacent radio stations in frequency synchronization system. The synthetic field strength of the two transmitters is recorded near the midpoint of the line connecting the two stations, and the synchronous attenuation curve can be obtained. According to the low-band speed of the recorder, the time interval t (seconds) between the two valley points is calculated, and the frequency deviation between the two radio stations is:
GB2017—1980
4S/m, e=80, A——Inverse distance curve
GB20171980
Figure 2 Ground wave propagation curve: land, g=3×10-2S/m, 8=4?A——Inverse distance curve GB2017—1980
Ground wave propagation curve: land, g=10-2S/m, 8=4, A——Inverse distance curve
Figure 4 Ground wave propagation curve
GB2017—1980
3X10-3S/m, 8=4, A
——Inverse distance curve
Wave propagation curve
GB 2017—1980
=10-sS/m，8=4A-
An inverse distance curve
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GB2017—1980
Figure 6 Ground wave propagation curve: land, g=3X10-4S/m, 8=4, A-astno
COKHLI
1EOHSRO N
An inverse distance curve
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