Few people know: the first Simplest Satellite on October 4 came off the carrier, which differed little from an intercontinental ballistic missile. The new product was a derivative of powerful weapons, with the help of which N. Khrushchev wanted to show Kuzkin his mother to the enemies of socialism. The Americans were frightened by the flight of Gagarin, immediately sent an expedition, stalled the moon, where on the reverse side are the bases of the aliens. Jokes jokes, the arms race has gone far, soon the cosmos was stuffed with espionage aircraft. To the satellites do not interfere with each other's work, it was decided to introduce uniform standards, on a territorial basis, purpose. Today we will look at how converters for satellite antennas support the requirements of standards, why it is needed.
Frequency Converter Division
1977 was marked by a meeting of an international conference that adopted the rules for systematizing satellite activity. Naturally, the procedure was preceded by numerous studies by the participants. We studied the passage of waves of different lengths of the atmosphere. Joke, punch the air to the soil from space! Geostationary satellites hover not so low above the Earth. Why soar? The Earth rotates relentlessly, in order to compensate for the motion, the satellite has to move following orbit. The speed is huge, because in 24 hours, it should make a full turn.
The radius of the Earth is approximately 6370 km. The shape of the planet is not round, not even elliptical. Experts say: more like a pear, tapering towards the North Pole, the body is simply devoid of suitable geometry. It is believed that the form of earth is a geoid. Now we give the value of the radius of the orbit, understand, the counting is conducted from the conditional center of the earth, located at the intersection of the equatorial plane and the axis connecting both geographical poles. The center of mass of the planet is in a different place, do not confuse geographic poles with magnetic( indicated by a compass).
In order for a satellite to begin to rotate around the Earth, it is necessary to inform the object of the First Cosmic Speed. In orbit, the device should move, practicing the angular velocity of rotation of the planet. Perform one revolution every 24 hours( 23 hours 56 minutes).Smart heads have calculated: the radius of the orbit should be 42,160 km with an altitude of about 35,790 km. As the Earth rotates around an axis passing through the poles, a single orbit of geostationary satellites is possible. Located strictly above the equator. In order to make a stillness relative to the Earth to a satellite in a different orbit, it will be necessary to constantly exert great efforts, to spend a host of resources.
This does not mean that the spacecraft hanging above the equator at an altitude of 35,790 km are devoid of human attention. Special stations constantly monitor the position and orientation of the satellites, making adjustments to the movement if necessary. The amendments are so small that the fuel lasts for many years of the spacecraft operation. Now we know why the plates of the Northern Hemisphere look south. Not strictly along the meridian, but towards the equator.
Since the zero meridian passes through the axis of the transit device of the Greenwich Observatory, located in the UK, Russia lies in the Eastern Hemisphere. A list of satellites broadcasting in this space is provided by Wikipedia. Not everyone will be visible from an arbitrary point on the earth's surface at the same time; choose a provider with care. Otherwise, the TV will not be able to watch.
Why converter satellite dish
So, the satellite is selected, visible above the horizon at the antenna installation point, it's time to watch TV.A commission that met in 1977 split the broadcasting bands into subranges. We give an incomplete list:
- L: 1.4 - 1.7 GHz.
- S: 1.9 - 2.7 GHz.
- C: 3.4 - 7 GHz.
- X: 7.25 - 8.4 GHz.
- Ku: 10.7 - 14.8 GHz.
- Ka: 15.4 - 30.2 GHz.
- C: 84 - 86 GHz.
Some frequencies are involved by the military. TV broadcasting uses bands C, Ku, and in Europe mainly the second is involved, in the territory of Russia we will meet both. Therefore, the first thing we say about converters satellite antennas - there are different bands. Refers to geometric dimensions. It should be noted: the plates of different ranges have a different diameter( perfect).The wavelength is shorter( higher frequency), more modest is the dimensions of the satellite dish. Caused by the focusing features of electromagnetic waves by paraboloids( dish shape).
Shops sell a complete set: a satellite dish plus a converter; there are quite a few lovers of the immense who are trying to put two non-uniform radio-wave devices nearby. We briefly describe the reason. Two satellites hang, one broadcasts in the C band, the other Ku. Using the experience of using a toroidal antenna, amateurs place two converters as needed so that each receives a signal from one point in the sky, which has arranged the mentioned spacecraft.
The plate is sent to the equator. The criterion is the maximum satellite signal at the output. Each converter adjusts as needed. Moves along the guide in relation to the dish until a steady reception is achieved. If the angle of linear polarization does not coincide( NTV past), the satellite antenna converter is rotated properly. For circular polarization, the orientation of the converter relative to its own axis does not matter.
To perform operations, special devices are used( Satellite Finder), which remove the signal from the dish that evaluate the reception. The received information of both converters is summed up by matching devices and is fed to the input of the detector. The screen displays a table of satellites, you can get information on the received signal of each. If necessary, the base is updated with its own settings.
Satellite Antenna Converter is a device for receiving an electromagnetic signal emitted by a satellite. The plate will serve the purpose of focusing the waves on the converter input. The maximum amplitude of the electromagnetic field in this place is reached. The installation of two converters for a satellite dish on one plate is based on the fact that the rays coming from one direction are collected by the focal plane. The converter for the satellite dish looks directly into the center of the dish contained by the said plane. And if one spacecraft broadcasts in different frequencies? The shelves are crammed with an abundance of combined converters of both ranges.
When tuning the antenna to more than one satellite, remember not only the frequencies. Above casually mentioned: the polarization of the signal is circular or linear, but how is the fact taken into account by the side of the converter? Brilliant is simple. The difference is limited to a small detail design.
Design of satellite dish converters
Any converter, regardless of frequency, type of polarization is characterized by a similar design. Here are the main details:
- is a segment of a circular waveguide, one end is sealed tightly, the second one will serve to receive radio waves;
- waveguide open end of the waveguide to improve the directivity properties, matching all frequencies;
- electronic unit, through whose antennas a signal is received.
Converter is represented by a pipe section, equipped with a socket, a small metal box at the bottom, attached tightly. Antennas - pins sticking out deep in the waveguide. The construction is covered with plastic; the front cover is round, tightly pressed onto the socket. Now polarization.
It turns out that the satellite antenna converter device always takes only linear polarization. If the satellite radiates a circular waveguide, it is supplemented with a plastic plate at an angle of 45 degrees to the pipe axis. Achieved depolarization. Lovers noticed a small detail, began to refine the design according to their needs. Setting the satellite antenna converter to the type of polarization is done by installing / removing the dielectric plate. You can make a plastic card.
It becomes possible to use converters in toroidal antennas. Just the plate is inclined 45 degrees to the other side( rereflection changes the circular polarization of the opposite).To open the airtight plastic cover, scald with boiling water, then an attempt is made to remove it. It is put back on the product without problems. Before checking the converter of the satellite antenna for operability, take the trouble to align the installation angle with an ordinary protractor. In the case of a successful outcome, we fix the result of labor with a small amount of sealant that has adhesion to plastic and metal.
