Speech concerns satellite - great antenna gain is required. We consider the parameter to be a double-edged blade: on the one hand, it is good that the signal is received by the weakest, on the other - poorly: the width of the main lobe of the radiation pattern is narrow. Confused? Unravel the knots, see which satellite dish is better.
What are the parabolic antennas
The antenna is composed of at least two standard parts:
- Reflector( reflector).
- The irradiator for a satellite dish plays the role of a radiation receiver( converter).
Often the reflector is an inseparable part of the paraboloid, the antenna is called parabolic. The spatial figure is provided with one curious property known from physics. Parallel rays coming from an arbitrary direction are collected by a plane called the focal. Waves falling perpendicularly open, will gather focus of the paraboloid. They place the feed, the antenna saw each. In everyday life is called a plate.
Now it is clear that if the rays are sent from a higher position of the celestial sphere, they will gather below the focus. Readers of offset saw plates: the irradiator is shifted downwards. Parabolic antennas. The advantage is that from the optical point of view the view of the satellite from the center of the paraboloid is not barred. It is not necessary to lift up the plate, catching a high-lying satellite.
Ask - Is the Earth spinning, how does the satellite hang in one place? Moves in orbit, practicing the angular velocity of rotation of the planet. For a parabolic antenna seems fixed. The position of the satellites is monitored by special ground control stations; periodically, correction of the motion parameters of the spacecraft is required.
To determine the position of a broadcasting satellite, owners post on-screen coordinates of a property in orbit. Traditionally: longitude, most television repeaters hang in the equatorial region. The principle of action of a toroidal antenna is based on this fact.
Toroidal antenna
Toroidal is the best satellite dish for those who want to receive multiple repeaters. Since the orbit of the apparatus is well known, the developers found an original solution to the problem: the parabolic reflector was supplemented with a toroidal one, the irradiators are used according to the number of satellites.
A paraboloid is identical to a typical plate. A toroid is a part of the outer surface of a donut, which is bitten off at once, eating bagels. In fact, science calls a torus a perfect shape torus. The axis of the toroidal reflector runs at an angle to the horizon, discussed below, in a vertical plane parallel to the focal plane of the paraboloid.
Focal plane - the plane passing through the focus of the antenna. The perpendicular emanating from the center of the plate pierces the plane at a right angle( 90 degrees).
Converters are located on a twig guide located at the bottom of the plate between both reflectors.
The idea allowed us to enjoy the transfer of several providers without the need for restructuring the physical position of reflectors and converters. It is more convenient than using rotary devices. Mechanical positioning is wrong, there may be a backlash. In nature, an electronic scan was invented, for this you will need to create an antenna array. We avoid going into details; household items are rarely used.
Terms and Definitions Parabolic antenna pattern - a figure showing the reception sensitivity versus direction. Counting is carried out in two planes, vertical and horizontal. The parabolic antenna has the same curves, showing a pronounced maximum, directed strictly perpendicular to the center of the dish.
Called the central lobe of the pattern. The angular width indicates the position of the points of the celestial sphere, showing the best reception. The top of the peak is called the gain, the number of manufacturers of parabolic antennas boast.
The width of the petal, the gain in constant struggle. I wanted to cover the horizon, the weakest signal to take. At the current level of technological development, a compromise is impossible. There are manufacturers on tricks.
Proper understanding of these terms will allow you to make the choice of satellite dish accurately.
Configuring
Installation is carried out on the support bracket that serves as a support plate. The process is as simple as possible, following a typical pattern, bolts and dowels are embedded in the wall, the installation is carried out with threaded connections. Wide choice of satellite antenna cable. Different types of quality, a set of parameters, price. A trivial statement, but it is worth recalling: for a modest price, palaces are rarely sold( an engineer is able to find).There is no sense in taking gold-plated contacts for a 3-meter-long coaxial segment to connect a personal computer with a satellite dish.
Parabolic antenna
The meaning of creating a dish is to catch the satellite signal. The most difficult begins.
Any geostationary satellite. The provider's website provides a calculator for calculating the exact position of the repeater in the sky. The initial exhibition is performed on a compass, protractor. The next problem is solved with the help of software bundled with a parabolic antenna; other packages are sometimes used.
The standard program for working with a satellite receiver is able to determine the signal level. When moving the antenna with adjusting devices, achieve the best reception. Usually they call in specialists, it is better to work with two people: one moves the plate, the second says the signal level. Especially if the parabolic antenna is mounted on the roof. The professionals bought a small device, based on the connection to a laptop or detached, with a piece of coax and receiver. Make an attempt to collect something similar yourself if there is a laptop. With the device, setup is much easier.
Immediately it should be noted: with a parabolic plate more than one repeater can not be caught. The fact is taken into account when deciding which satellite dish to choose.
Toroidal antenna
Satellite antenna allows you to catch the transmission of several repeaters at once. The usual azimuth angle is 55 degrees. The antenna is designed so that the reception line falls in orbit.
Start should be the choice of satellites. Should not run in azimuth more than the angle covered by the toroidal antenna. The setting can be done in two ways, both of which suggest an approximate elevation angle display. After you need to find the correct azimuth, so that the satellites are captured by the antenna. The tilt angle is regulated last.
- Put the plate almost vertically. The satellite orbit line is clearly above the central direction. One nuance. Coordinates are recorded in a notebook, the central satellite is selected. According to the coordinates to fit in the middle. We aim the design in azimuth. After the toroidal reflector is supposed to adjust the angle of place( move up and down) until the signal of the central satellite reaches a maximum: the center of the reflector is installed. After the azimuth angles, we avoid touching the place. Now we will set the position of converters, first of all one extreme. Now you need to accurately bring the edge to the satellite, tilting the toroidal reflector. The action was successful, we can assume that most of the work was done. Now, each irradiator rotates around the axis of the toroidal antenna, moves along the guide, completing the fine tuning procedure. Switching between converters is performed by software.
- The second method resembles the first, the alignment goes at two ends. You will need to string converters on a guide, as accurately as possible to put the two extreme ones. To begin with, the signal maximum is caught at one, either end. Then the opposite feed is adjusted. In conclusion, each converter rotates around an axis. It will help to ensure the coincidence of the polarization of the signal antenna.
Conclusion
When deciding which satellite dish is better, give preference to the toroidal model if you want to receive several providers. On the contrary, in the absence of a choice to complicate the equipment there is no need.
It is important to know: the larger the plate size, the higher the gain: the
- is more difficult to point to the satellite;
- more interference in windy weather.
Light breeze shakes the house, you can not see with the naked eye, when it comes to catching a small celestial point, the movement will become unacceptable in magnitude. The fact is experienced by people living in open areas, where storms or storms often occur.
