Satellite antennas mass divided into two in the home global type of offset and direct focal. The difference in the arrangement of the illuminators converters. If just the center, direct focal satellite dish in front of us. Newcomers wonder why the plates are very different from other receivers surrounding humanity in everyday life. The point aimed properties. At plates (parabolic antennas) high gain and narrow beam pattern. It takes a tough stabilization of the satellite in orbit, but the power of the radiation is possible to significantly reduce. Spacecraft received from the developers of a wide radiation pattern covers thousands and millions of square kilometers of territory. 99.99% percent of the energy is wasted. Repair his own satellite antennas it comes to most settings, positioning, correct use of converters.
Apparatus satellite antennas
The main types of failures relate to converters. Plate will be able to damage the only purpose. Indeed, what a piece of iron at the break. satellite antenna device is ridiculously simple:
- on the bracket to the wall plate is suspended;
- in the focal plane of the paraboloid placed irradiators.
All! The satellite signal arrives, the subject is far, it is believed that the lines are parallel. As a result, according to the laws of optics going signal at the focal plane. We of offset dish antenna is not perpendicular to the direction of the satellite, the irradiator is far from the center. In contrast, direct focal antennas converter located on the axis, due to which part of the signal is lost. This is an unavoidable disadvantage. In antennas of offset irradiator hanging outside the plate, shown is another factor: the rays capture area is proportional to the cosine of the deviation from the perpendicular. We can not say that the first design is better or worse than the second.
Offset antenna useful where there is no chance to tilt the plate to the axis of looking directly at the satellite. This advantageously equatorial and tropical regions. In practice, the offset antennas meet at least direct focal. Wrong to call irradiator converter and vice versa. The apparatus hanging near the focal plane of the antenna, comprising:
- The irradiator. It looks like a conical opening, protected by a removable plastic cover from the rain.
- Depolarizer. Straight waveguide portion (tubes) where there are dielectric plate and a pair of rods. It serves to convert the circular polarization to linear.
- Converter. It represents an electronic unit, wherein the satellite frequency is reduced to 1 or 2 GHz for transmission over feeder with minimal losses. There is an additional low noise amplifier. In the formula, the sensitivity is dominated by the characteristics of the first active stage. It is important here to reduce noise.
The matter is complicated broadcasting satellites in the frequency range. C and Ku bands accepted. In any dominant own kind of polarization. C - circular, in the Ku - linear. Newcomers wonder. Explains that the C-band, used in Russia, has a circular polarization for several reasons:
- The legacy of the difficult past. In the USSR spacecraft used circular polarization for satellite communication, orbit different from geostationary spy. It is not required to consider the inclination angle of polarization as when using a horizontal type.
- The polarization vector is deflected by magnetic fields. Solar storms and earth fluctuation characteristics influence the tilt angle. Wherein the Faraday effect decreases with increasing frequency. Consequently, in the Ku band is not too terrible.
These features simplify the hardware configuration, there is no need to rotate around the axis of the converter, that's great - angle hard to catch. If C and Ku to broadcast with linear polarization, Faraday effect affected in different ways, as a result you can not adjust the antenna as necessary. This is worse than the loss caused by the hybrid converter. It is difficult to assess, but the closer a subscriber to the pole, the more distortion. RF is in the northern territories.
Add that Ku and C bands are so large that further split portions, otherwise it is impossible to design oscillators for intermediate frequencies (cm. above). Satellites captured not the entire spectrum that is taken into account converters. Keep a piece of advice:
Specify besides subband provider range. When selecting equipment, refer to the wave converter supports.
Converters with similar mean: a steel box section of the pipe, opening, sewn construction in plastic, covered with a cover on the inlet side. In terms of the geometric dimensions of a difference there is for the bands, but more important than filling. Electronics has in any case their own bandwidth without matches will not pass signal. More say - the producers kept secret stuffing equipment, so the individual converters work for full-time outside, it is rather an exception to the rule, rather than a constant surprise for user. Hybrid converters operate at all frequencies (check) within two receivers are.
Setting up satellite dishes
Any converter, regardless of the slope looking to the center. This will provide a hit in the opening of maximum energy. If you deviate slightly, will continue to work even worse. While improving the work situation is possible superposition of fields when a rule is broken, but generally center the opening that looked at the bottom of a dish. Modern equipment works satisfactorily in many situations, but do not neglect the key moments too.
Setting up a satellite dish begins with orientation. The site provider or accessible sought angle calculator. Are aimed at a specific satellite, or the coordinates of the spacecraft will need to enter. Of course, it is necessary to know as precisely as possible geographical location. Easier to find using a smartphone with navigation module. Accuracy is sufficient for the calculation. The calculator will give elevation, azimuth, tilt angle converter. It happens several satellites. Then look at the coordinates of the spacecraft, we find the average, the target plate on the device.
In the latter case, one would be in the middle of the irradiator. For the offset tray elevation different from the issued calculator. Or the robot will ask about the type of antenna. As a rule, the offset feeds just shifted down to consider when targeting. Direct focal differ from, for example, the ratio F / D (focal distance on the antenna diameter). To distinguish about irradiators succeed by their appearance: at the step of offset used a horn in direct focal concentric circles. This is not a rule, but this is the case in reality. Consequently, using inappropriate irradiators not be surprised that the reception quality is below average.
We made it clear what to do when setting up the antenna yourself. We add that the targeting is possible to produce using the receiver. Most sets of satellite antenna embedded program (means) for collecting waves issued quality power. If the first person looks at the screen, and the other is working on the bracket, the result of the joint efforts will be made.
Compass set azimuth, elevation vymeryat level and protractor. After an installation begins positioning indications equipment. After peaking begin experimenting with the converter tilt angle.
Then proceed to install additional irradiators, if any. For a specific angle of inclination is determined separately. If the satellite broadcast in two bands, should be taken Hybrid Converter satellite dish. Depolarization plate angle determines the direction of circular polarization. When receiving no improper installation. Do not repair it sets out satellite dishes, it is recommended to remove the plate, catch the signal without it, then put. This is a complicated process, but doable. In the absence of the plate received power is 3 dB below that corresponds to an equivalent reduction in tray area 1.4 times.
Before removing the antenna make notches in the bracket, it will quickly settle the plate in place. The main causes of failures relate to the failure of the paraboloid focus. By the way, do not forget to put next to the lightning rod, or a lightning burn converters. The electronic part can not be mended. The country has not yet learned how to program the chip.
