Fundamentals of the basics of satellite reception
Many people do not have a clear idea of how the signal is transmitted from the television company to the final subscriber of satellite TV, so I decided to write a small, light topic for understanding the physics of the process of receiving satellite signals. So, let's go:
1. The earth has the shape of a ball, slightly compressed from the poles.
2. The earth rotates around its axis.
3. Satellites fly around the Earth at different heights and orbits.
4. Any point on the surface of the Earth has its own coordinates: latitude and longitude.
5. Latitudes north of the equator are called north, south of the equator - south.
6. Latitude varies from 0 to 90 degrees (0 at the equator, 90 at the pole).
7. Longitude is eastern and western. It is considered from the city of Greenwich.
8. East of Greenwich - east longitude, west of Greenwich - west longitude.
9. Latitude and longitude are measured in degrees, minutes and seconds. 1 degree = 60 minutes. 1 minute = 60 seconds. Or in degrees with decimal fractions, for example, 3.6 degrees east. longitude
10. Satellites that hang above the equator and rotate synchronously with the Earth are called geostationary.
11. Television and radio broadcasts are usually made from geostationary satellites.
12. Since the geostationary satellite is stationary relative to the earth, in order to catch a signal from it, it is enough to point the antenna at it once, and then there is no need to twist it, because the satellite does not go anywhere (at least while it is in working condition).
13. Since the satellites we need relative to the earth hang motionless and are located above the equator, then in order to accurately indicate their position it is enough to indicate the longitude of the point above which the satellite hangs. For example, Hotbird (13E), Sirius (5.8E), Amos (4W)
14. Each satellite belongs to a large company and is leased to TV companies in whole or in part.
15. The TV company has a large transmitting dish antenna, from which it sends a signal to the satellite. The satellite receives this signal and transmits it back to Earth.
16. Each satellite has several transmitters (transponders). Each transponder transmits a signal at a certain frequency, polarization. If the signal is digital, then you need to know its symbol rate and the position of the error checking byte (FEC).
17. Each transponder can “shine”, that is, transmit a signal to a certain part of the Earth’s surface. Imagine a flashlight hanging on the ceiling and shining on the floor. In the center of the "light spot" the signal will be strong, and further to the edges it is weaker.
18. On satellites, different transponders may shine in different places. Therefore, even if the satellite is geometrically hanging above the horizon and can be seen through a telescope, some transponders may shine not on us, but, for example, on other continents.
19. To catch a signal from a satellite, you need to have a parabolic antenna. The antenna consists of a "basin" - a mirror, a converter, a holder and a bracket.
20. The radio signal from the satellite "shines" in the "basin", is reflected from the surface of the mirror and is focused at some point in front of the mirror. At this point there should be a converter.
1. The earth has the shape of a ball, slightly compressed from the poles.
2. The earth rotates around its axis.
3. Satellites fly around the Earth at different heights and orbits.
4. Any point on the surface of the Earth has its own coordinates: latitude and longitude.
5. Latitudes north of the equator are called north, south of the equator - south.
6. Latitude varies from 0 to 90 degrees (0 at the equator, 90 at the pole).
7. Longitude is eastern and western. It is considered from the city of Greenwich.
8. East of Greenwich - east longitude, west of Greenwich - west longitude.
9. Latitude and longitude are measured in degrees, minutes and seconds. 1 degree = 60 minutes. 1 minute = 60 seconds. Or in degrees with decimal fractions, for example, 3.6 degrees east. longitude
10. Satellites that hang above the equator and rotate synchronously with the Earth are called geostationary.
11. Television and radio broadcasts are usually made from geostationary satellites.
12. Since the geostationary satellite is stationary relative to the earth, in order to catch a signal from it, it is enough to point the antenna at it once, and then there is no need to twist it, because the satellite does not go anywhere (at least while it is in working condition).
13. Since the satellites we need relative to the earth hang motionless and are located above the equator, then in order to accurately indicate their position it is enough to indicate the longitude of the point above which the satellite hangs. For example, Hotbird (13E), Sirius (5.8E), Amos (4W)
14. Each satellite belongs to a large company and is leased to TV companies in whole or in part.
15. The TV company has a large transmitting dish antenna, from which it sends a signal to the satellite. The satellite receives this signal and transmits it back to Earth.
16. Each satellite has several transmitters (transponders). Each transponder transmits a signal at a certain frequency, polarization. If the signal is digital, then you need to know its symbol rate and the position of the error checking byte (FEC).
17. Each transponder can “shine”, that is, transmit a signal to a certain part of the Earth’s surface. Imagine a flashlight hanging on the ceiling and shining on the floor. In the center of the "light spot" the signal will be strong, and further to the edges it is weaker.
18. On satellites, different transponders may shine in different places. Therefore, even if the satellite is geometrically hanging above the horizon and can be seen through a telescope, some transponders may shine not on us, but, for example, on other continents.
19. To catch a signal from a satellite, you need to have a parabolic antenna. The antenna consists of a "basin" - a mirror, a converter, a holder and a bracket.
20. The radio signal from the satellite "shines" in the "basin", is reflected from the surface of the mirror and is focused at some point in front of the mirror. At this point there should be a converter.
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Source: https://habr.com/ru/post/53998/
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