Subsystems like satellite offset dish. Satellite antenna


That's all today more people purchase satellite antennas, which are usually called satellite dishes. So let's look at what it is and what they are.

What it is
The “dish” itself is a reflector, something similar to a mirror, which concentrates the waves falling on its surface on a receiver called a converter, and the converter converts the signal and transmits it to the receiver. And from the receiver the signal goes to the receiver, TV or computer. This is the principle.

What types of satellite dishes are there?
Satellite antennas come in direct focus and offset.

Direct focus is when the antenna mirror has the shape of a parabola cut, the satellite signal is reflected to a point on the axis of the parabola, where the converter is attached. Depending on the mounting distance of the converter, antennas can be short-focus and long-focus, but we won’t go into that much depth. Direct focus antennas have their advantages and disadvantages.

Advantages
Since the shadow from the converter covers the area of ​​the dish, worsening the quality of the signal, they are made larger to get rid of this disadvantage. And since they are large and the converter is located on the axis, the signal is focused at a point with good quality. Therefore, such antennas are usually used for professional work.

Flaws
The disadvantages include problems with mounting; such antennas have a large angle of inclination to the horizon, as a result, water, snow, and dirt accumulate in the antenna, deteriorating the quality.

Offset antennas
Such antennas seem to use part of a parabola; as a result, the point at which the rays are reflected is shifted and the installed converter does not cover the antenna mirror. Offset antennas do not reflect an even spot onto the converter, which is why the signal quality is worse than that of direct-focus antennas.

The advantages include the fact that they are easy to install and are placed almost vertically, as a result, precipitation and dirt do not accumulate in them.

Material
Today, antennas are made from steel, aluminum, plastic, even mesh.
Aluminum
In our region, as a rule, antennas made of aluminum are common; they are lightweight, do not corrode, and reflect the signal well. But they have one drawback: they are not very durable.

Steel
Steel antennas are durable, but they are heavy and susceptible to corrosion, which degrades the quality of the received signal.

Plastic
Antennas made of plastic reflect the signal well, they are lightweight, but in regions with large temperature differences they become unusable. The plastic loses its shape and cracks, which leads to a decrease in signal quality.

Fastenings
Satellite antenna hangers are divided into two types.
The first is an azimuth suspension and is used for antennas aimed at one satellite.

The second is polar, it allows you to tune the antenna from one satellite to another.

Converter
This is a device in the center of the dish that converts the signal and transmits it to receiving device. Converters come in different ranges and the main indicator of their quality is the noise level, which should be within 0.6-0.7 dB. If you expect to watch TV and surf the Internet from one satellite, then you will need a converter with two outputs.

Conclusion
In conclusion, I would like to note that when buying a satellite dish, the most the best option It will happen if you immediately conclude an agreement with this company for the installation of all equipment, which will avoid many problems and, most importantly, complications in the operation of the system.

In this article we will look in detail different kinds satellite antennas, we will tell you about the rules of their installation, features of equipment configuration and operation. After reading the article, you will be able to do everything yourself - from purchasing to calculating the position of the “plate”.

Basics of Satellite TV Reception

For future users satellite television no need to go into detail technical details, but it doesn’t hurt to know some basics. For example, existing signal standards, frequency ranges and some other details.

Common standards for transmitted signals:

  • DVB-S Mpeg-2 - television broadcast, plus the Internet. Almost all satellites existing today support this standard, just like anyone satellite receiver, commercially available.
  • DVB-S Mpeg-4 - the standard is similar to the first, with the exception of one point - it requires a receiver that supports the Mpeg4 format.
  • DVB-S2 Mpeg-4 (DVB-S2) - relatively new standard TV signal, Internet signal. Requires appropriate receivers.

Frequency ranges

Broadcasting of TV signals and reception/transmission of Internet signals using satellites is carried out in two frequency ranges:

  • Band C - to receive signals in this frequency range, a parabolic antenna with a large diameter dish of 2.0-4.5 meters is required.
  • Ku band - reception of signals in this frequency range is possible using parabolic antennas with a dish diameter of 0.5-1.5 meters.

Parabolic antennas

Reception of a television signal from satellites is possible using two types of antennas - offset and direct focus. These are parabolic antennas with three main components:

  1. Reflecting and focusing mirror (parabolic dish).
  2. The feed unit is assembled with a low-noise amplifier and signal converter.
  3. Rotary support adjustment mechanism.

Irradiator(low-noise block converter) - also known as a converter (popularly called simply “head”), receives a focused signal, amplifies it and converts it into an intermediate frequency signal suitable for processing by the receiver.

Receiver- a special electronic set-top receiver, where the intermediate signal is decoded and converted into a signal suitable for processing by a television receiver. There are many models of satellite television receivers, including those that support MPEG-2 and MPEG-4 digital video compression technologies. Typically, receivers are sold complete with parabolic antennas.

Typical receiver design:

  • conditionally coded (paid) access;
  • access via smart cards (receivers with a card reader);
  • access via CI module (receivers with TV signal decoding);
  • free public TV (FTA series receivers).

Types of parabolic antennas

Offset satellite dish- a design that has a slightly shifted focus relative to the central point of the dish, so the actual direction of the offset antennas is usually slightly below the satellite horizon. The antenna disk, as a rule, is located vertically relative to the earth's surface. The “offset” is usually installed on the wall of the house. Offset designs are designed to receive a Ku-band signal, but can also operate in the C-band if the dish mirror has a diameter of more than 1.2 meters. Advantages: high focusing accuracy. Disadvantages: insufficient protection of the converter from the external environment. This is the most common version of “plates” in the private residential sector.

Direct focus satellite dish- here the focus is located exactly in the center. The diameter of the mirror of such designs varies in the range of 0.9-4.7 meters. Installation usually requires the creation of a horizontal support. Advantages - the collapsible design of the mirror, which is of no small importance for large sizes. However, for the same reason, disadvantages appear in the form of poor focusing and, as a result, losses of up to 10% efficiency. This type of antenna can be considered universal - it is designed to receive both C and Ku-band signals.

Attention! Satellite antennas are narrowly focused devices. Regardless of the design, installation is carried out taking into account the mandatory orientation of the device to the southeast, south or southwest (depending on the specific satellite). In other words, the antenna must be installed in a place where coverage of the indicated directions is ensured (optimally, all three).

Offset antennas. Assembly and installation

Assembling an offset satellite dish is not as complicated a process as it might initially seem. Usually included with the purchased device is detailed instructions on assembly. The task is to connect the dish to the bracket, assemble the rotating mechanism and install the antenna converter holder. After assembly, the rotating mechanism should ensure that the mirror moves with some force, both vertically and horizontally.

The structure is delivered to the installation site and installed on the wall of the house. You first need to mark and make several holes on the wall for anchor bolts. Anchor bolts are installed and the antenna bracket is attached. Next, all that remains is to attach the converter itself to the converter holder and connect everything with a signal cable according to the diagram: antenna converter - receiver - TV.

Direct focus antennas. Assembly and installation

The procedure for assembling a direct-focus antenna is somewhat more complicated than an offset antenna, but many people can also do this kind of work. The mirror of direct-focus antennas, as a rule, is collapsible, consists of several segments that form a dish as a whole. In the case of a private house, the plate is collected on the ground and then raised to the roof. Since the roofs of private houses are mostly pitched, you will need to make a special stand.

An antenna stand is an option, a prototype of a stair step with a riser, given that direct-focus satellite antennas are mounted on a horizontal surface. The stand is mounted on the roof slope and the antenna mirror is mounted on the stand along with the support “leg” and the adjustment mechanism. Mounting options on a rod or on the wall of a house are also not excluded if they ensure unhindered direction of the antenna to the satellite.

Setting up a satellite TV antenna

You can start setting up under the following conditions:

  • a satellite is selected - a television signal translator;
  • the space in front of the antenna mirror is free for signal passage;
  • The TV screen is accessible for viewing by the tuner or the tuner’s assistant.

Selecting a satellite

The list of operating satellites is quite wide. Naturally, and user capabilities quite extensive, but at the same time limited by the geostationary orbit of satellites. All satellites are located in the sky region: southeast - south - southwest. In this case, the greatest angle of elevation of the satellite relative to the horizon line is located exactly in the south direction. That is, the greater the deviation to the southeast or southwest, the lower the satellites are located above the horizon.

Interesting TV satellites:

  • YAMAL 201/300K, orbital position - 90° east. d. Coverage: the entire territory of Russia, plus Near Abroad. Open access to popular central channels in the C and Ku bands.
  • EUTELSAT 36A/36B, orbital position - 36° east. d. More than 150 channels from well-known operators NTV-Plus and Tricolor-TV, including channels broadcast in HDTV format. Most channels are paid, but there are also free access channels.
  • HOT-BIRD 13B/13C, orbital position - 13° east. d. An impressive range of channels, including European ones. There are paid and free channels.
  • HORIZONS-2/IS-15, orbital position - 85.2° E. d. Basis of broadcasting - paid packages"Continent TV" and "Telekarta TV".

The list goes on. If desired, satellite information is always available online.

Obtaining data to direct the antenna to the satellite

To set up a satellite dish, you will need the following data:

  • value of the satellite's orbital position;
  • geographic coordinates of the antenna installation site (terrain coordinates);
  • satellite elevation angle relative to the antenna installation location;
  • azimuth value.

At first glance, it’s quite difficult. But only at first glance. Essentially, all marked data can be calculated using formulas.

Calculation of the elevation angle:

  • F = arctg( / sqrt(1 - Cos2(g2 - g1) x Cos2(v)])

Calculation of azimuth value:

  • Ф = 180° + arctg(tg(g2 - g1) / sin(v))

Where: g2— the value of the longitude of the area, v— the value of the latitude of the area, g1— satellite longitude value.

However, if you have difficulties with higher mathematics, then it is better to use a special software(for example, a program Satellite Antenna Alignment), or obtain calculation data on specialized sites.

Installing the antenna in the desired position

So, the data has been received. You can begin to install the dish in the desired position, and then make fine adjustments, focusing on the quality of the picture on the TV screen. The device is oriented to azimuth using a compass. Then the strictly vertical position of the plate is set. The exact vertical of the disk can be obtained by focusing, for example, on a plumb line installed nearby. We have already obtained the value of the satellite’s elevation angle - using a regular protractor, we need to try to bring the antenna as accurately as possible to this value, starting from an imaginary horizontal straight line formed between the central point of the converter head and the central point of the antenna mirror.

Next, slowly turn the plate to the right and left, while simultaneously monitoring the appearance of the signal on the TV screen. If the signal does not appear, change the elevation angle by one or two degrees and repeat the process. When a signal appears, they strive to obtain the highest quality picture and then finally fix the position of the plate.

Some features of installing satellite dishes

Modern satellite dishes can be equipped with various accessories, the presence of which greatly simplifies the setup process, and sometimes the user does not have to configure the equipment at all. Among these accessories:

  • actuators
  • motorcycle suspensions
  • positioners

For example, the SuperJack V-BOX II positioner provides full control of the satellite dish via a rotating mechanism. The device's memory chips contain about one hundred satellite orbital positions. Supports both local control mode and control mode with commands coming directly from the satellite.

STRONG SRT DM2100 DiSEqC

Motor suspension or rotary motor. An example of such a device is the Strong DM2100 DiSEqC system, capable of tracking satellites located from 30° west longitude to 90° east longitude. The system also has pre-programmed installation data for over twenty popular satellites. However, this motorized suspension can only be used with parabolic antennas with a diameter of no more than 1.2 meters. Works with receivers using the DiSEqC 1.2 protocol.

Lightning protection Dr.HD

Like any antenna system, satellite also needs lightning protection. Everything is quite simple here. There are special compact inexpensive devices, like Dr.HD/Prof GC-862BL, that reliably protect not only the antenna, but all equipment as a whole.

Before choosing a satellite antenna (dish), you need to get an idea of ​​how it works. In principle, the operation of the plate is not complicated. The antenna itself, the dish in our understanding, is a reflector electromagnetic waves, like an ordinary mirror, which she focuses on a converter rigidly mounted on a plate. The converter converts the signal received from the satellite into the first intermediate frequency and transmits it to the receiver via cable. The set, consisting of a reflector, a converter, is the receiving antenna itself.
Antennas according to their design are divided into two main types - direct focus (round) and offset (elliptical).
Satellite signals are broadcast mainly in the Ku bands (~11 GHz) and less often in the C bands (~4 GHz), that is, the signals have a wavelength of 27 and 75 mm, respectively.
All Russian operators satellite television: NTV plus, Tricolor TV, Continent TV, Raduga TV, etc. operate in the Ku (~11 GHz) band!

Satellite dish parameters

Effective antenna area A(effective antenna surface) - a value that characterizes the ability of the receiving antenna to concentrate incident incident on it electromagnetic radiation. A is defined as the ratio of the maximum power that can be delivered by the receiving antenna (without loss) to the matched load to the power P, plane wave (not distorted by the antenna) per unit area of ​​the antenna.

Antenna noise temperature. Noise increases the response threshold digital devices from the useful signal. The antennas themselves do not make noise; the noise is created by the surface of the earth, the structures on it, the airwaves, and deep and near space. Obviously, for a given antenna size, the noise will be less for antennas with a narrow radiation pattern and small side lobes.

The receiving and transmitting antennas use the same principle of operation, because In almost any linear systems, the field conversion coefficients are mutual. However, the technical and operational features of receiving and transmitting antennas may differ significantly due to differences in the requirements placed on them (power limits, frequency bandwidth, noise, etc.).

Selecting a satellite dish

How to choose an antenna by size. When choosing an antenna, very important parameter is her size. The size is directly related to the gain of the dish, the larger the size, the higher the gain. If the size of the dish is smaller than that allowed for receiving the required transponder, then the message “no signal” will appear on the TV screen; if we have a threshold signal level, then the image will crumble into squares, the same will happen if the dish is not accurately aligned with the satellite and when shielding satellite signal foreign objects.
For different satellite signal powers, different dish diameters are required: 53dbW - 0.6m, 48dbW - 0.8m, 45dbW - 1.0m, 40dbW - 1.5m.
Usually installers know what size dish can be used to “catch” the desired satellite, and how to determine it yourself right size We'll tell you about the plates at the end of the article.

How to choose an antenna by type. Next you need to decide on the type of antenna: direct focus (round) or offset (elliptical)?
Up to a size of 1.6m, for domestic needs in the Ku (~11 GHz) range, offset antennas are mainly used, why?

It follows from the figure that the converter and its mounting hardware create a radio shadow on the dish, which reduces the efficiency of signal reception. In addition, during precipitation, water accumulates in the dish, especially at a high elevation angle, closer to the equator, as well as snow, which also reduces the efficiency of satellite signal reception.
Already for satellite antennas with a size of 1.5 m, the radio shadow from the converter and its mounting is a relatively small part of the mirror area to be taken into account. A round direct-focus antenna focuses radio waves more evenly on the converter feed. In addition, for a round antenna it is easier to calculate and coordinate the converter feed with the antenna, due to which the entire surface of the antenna is effectively used. With an offset plate, up to 10% of the area is not used due to its shape, especially for large plates.
For these reasons, antennas larger than 1.5 m in size are manufactured mainly as direct focus antennas and are intended for professional reception.

Offset antenna - with a shifted focus, has the shape of an ellipse, elongated vertically. The converter is mounted on a special bracket; due to the shifted focus of the antenna, the converter and its mounting unit do not fall into the irradiation zone. The reception efficiency of such an antenna is higher than that of a direct-focus antenna. The plane of such antennas is located almost perpendicular to the plane of the earth and precipitation does not accumulate on its surface. The mounting design of an offset antenna is simpler than that of a round antenna and its cost is lower. Choose offset antenna!

How to choose an antenna based on design, material and stamping quality. Antennas vary in designs- solid (one-piece stamped), mesh and prefabricated (sectional). Solid antennas are preferred as they provide better reception quality. Mesh plates, for example Lance, have a reduced windage, but their reception efficiency is lower than that of solid ones. Some believe that the holes in the mesh themselves reduce the efficiency of the antenna, that the signal “leaks” through them. In fact, the holes have nothing to do with it. The fact is that the mesh is soft and in the spaces between the rigid elements of the plate it stretches, trying to accept flat shape, as a result of which the surface of the mesh plate is not a paraboloid, but consists of flat segments that form a surface close to a paraboloid. The antenna paraboloid is considered smooth if the average size of the irregularities on the surface of the dish does not exceed one quarter of the wavelength. In the Ku range, the length is 2.5 cm, while the permissible deviation of the surface from the paraboloid will be approximately 6 mm. In the C band, the wavelength is 7.5 cm, and the size of the irregularities can therefore reach 19 mm. Because of this, in the C-band, to lighten the weight, antennas are made of mesh, and to reduce dimensions during transportation, they are made of petals, because C-band antennas are usually larger than 1.6m.
Material, from which the antenna mirror is made, can also be different: plastic, due to Bad quality antennas, due to warping in the sun, are practically not used, steel is a durable material, therefore it provides good quality mirrors, but the dishes are heavy and susceptible to corrosion, aluminum is a light but soft material, subject to deformation and does not rust.
Stamping quality, is directly related to the antenna gain. The quality can be easily checked by placing the antenna on thick glass, good quality the plate will fit tightly around the entire circumference of the glass. The warping of the antenna with a “screw” has a particularly bad effect on the antenna gain.

How to choose an antenna based on the type of suspension. There are antennas with azimuthal and polar suspensions. With an azimuth mounting, the antenna is aligned to the satellite and is rigidly mounted on the bracket. Polar - suspension rotating with a special actuator. With the help of a polar gimbal you can tune in to everything “visible” in the data geographical coordinates satellites.
The polar suspension is designed in such a way that, by rotating around a vertical axis (i.e. changing the azimuth of the setting to the satellites), the antenna also tracks the elevation angle, that is, it describes the arc on which the satellites are located.
For household antennas, polar suspensions are no longer relevant; they have been replaced by motorized suspensions; regular antennas with azimuth suspension.

Mirrors of different depths: 1- shallow (long-focus); 2 - average in depth (mid-focus); 3 - deep (short throw)

Directional pattern parabolic antenna completely determines the distribution of the field in its aperture, as well as the relationship between the wavelength and the aperture radius of the mirror.
At a certain value of the antenna mirror aperture, the main lobe of the radiation pattern will be the narrowest if the distribution of the field amplitude in the mirror aperture is uniform, but in this case the side lobes will also be large. If the field amplitude decreases from the center to the edges of the mirror, then the main lobe of the radiation pattern becomes wider and the levels of the side lobes decrease.
To reduce the level of side lobes, the antenna mirror is irradiated in such a way that the field amplitude decreases when moving from the center of the aperture to its edges, but at the same time the coefficient of utilization of the aperture surface also decreases. In practice, a compromise solution is sought for rational irradiation of the mirror.
If one strives to obtain the highest gain from a parabolic antenna, then the mirror is irradiated in such a way that the field amplitude at its edges is 10 dB lower than in the center of the aperture.
If they want to reduce the side lobes and thereby reduce the noise temperature of the antenna, then the mirror is irradiated in such a way that the field amplitude at its edges is 15 - 20 dB lower than in the center of the aperture.
By selecting the feed, the size of the paraboloid and the focal length, the required radiation pattern of the satellite antenna is obtained. The radiation patterns of antennas of different mirror depths are also different, because they have different distributions of field amplitudes in the mirror aperture. Less deep mirrors are irradiated more evenly, so their main lobe is narrower and the side lobes are larger. You can obtain a given amplitude distribution in the antenna aperture different ways:

  • Selecting an irradiator.
  • Using two-mirror antennas.
  • The shape of the mirror and its modifications.

In conclusion, we give advice, how to choose your plate size. The smartest thing to do is look at the coverage map the right companion and determine from the irradiation power what minimum antenna diameter is required.
For example, on the sites http://www.flysat.com or http://www.lyngsat.com.

How to choose an antenna (dish) for Russian satellite operators

Based on the above information when considering satellite irradiation zones, you can choose the size of the satellite dish for viewing TV channels of each of the Russian satellite operators. The irradiation zones and the distribution power of the satellite signal in the irradiation zones can be viewed on the website pages:
Transponders and irradiation zone of Tricolor TV >>
Transponders and irradiation zone NTV Plus >>
Transponders and irradiation zone Continent TV (Telecard) >>

Today satellite TV subscribers are offered several types of dish antennas. They are different in shape, size, materials of manufacture and, of course, functionality.

Actually, the difference in functionality is due to the difference in shapes and sizes. If, for example, an antenna with a small diameter of up to 1 m is suitable for Tricolor TV, then it may not be suitable for receiving signals from other operators, especially if a person lives in the Asian part of Russia or in the north. The secret is that the satellite signal power may be too weak to be received by a small diameter antenna. Those. The weaker the received signal, the larger the diameter of the “dish” should be. A special convector is placed in its center, which collects radio waves reflected from the surface of the antenna and transforms them into electrical signals transmitted through cables to the receiver. The size and diameter of the installed antenna must correspond to the geographic location of the subscriber relative to the satellite.

There are several types of satellite dishes. As was said, they differ in many respects, but the main difference is in the capabilities of receiving and broadcasting radio waves.

Offset (asymmetric) antenna

It is made in the form of a plate and has a shifted center for installing the converter. Thanks to this, the antenna can be installed at a different angle to the satellite (vertically), which prevents the appearance of a shadow on the mirror reflecting radio waves. If the subscriber lives in the European part of Russia, diameters less than 1 m will be suitable for him.

Direct focus (symmetrical) antenna

It focuses strictly in the center, which ensures a clear signal from the satellite. The converter is located outside the antenna, i.e. It is attached to three holders located around the perimeter, which creates a shadow on the useful area of ​​the mirror. It has a parabolic appearance and is popularly called a “plate”, but in Russia on the European part it is almost never used due to its too large diameter. In other words, if the subscriber is in an area of ​​stable signal reception, then there is no need for a large diameter.

Toroidal antenna

This model with two mirrors appeared quite recently, but immediately won love large number subscribers. Thanks to a special device in which two mirrors are located opposite each other at a certain angle, it is capable of tuning into several satellites scattered in orbit and receiving several radio waves. Those. the number of broadcast channels increases sharply.

Mobile antenna

This model is rarely larger than 40 cm in diameter. The use of a portable satellite dish is justified on tourist trips, in the country and in places where it is impossible to install a standard one. With its help, you can receive signals from satellites anywhere on the planet where their activity is recorded.

The benefits that a satellite dish brings to its owner have led to the great popularity of satellite television. After all, thanks widest choice channels, you can not only get access to a huge number of films, favorite sports and cultural programs, but also keep abreast of all important events, improve your knowledge of a foreign language, that is, combine a pleasant pastime with useful self-education. And if we add here the excellent image and sound quality, it becomes clear why the satellite dish is of such interest to those who are just wondering what TV to install on new apartment or who is tired of constant interference when receiving a signal.

How does a satellite dish work?

The principle of operation of all plates is approximately the same. First, the signal hits the mirror surface. Then it is reflected and sent to the converter, from where it, in turn, hits the receiver, and from it it is sent directly to the TV itself.

A satellite dish can be one of two types: offset or direct focus. is not directed exactly to the satellite, but slightly below it, since the signal that is reflected from its surface enters the converter at a certain angle. This type of receiving device is mounted almost vertically, which avoids the accumulation of substances that greatly degrade the quality of reception. This is the type of antenna that can most often be seen near the windows of apartment buildings, since it is convenient to install along the walls. Optimal size of this plate is 1.5-1.8 m.

In a direct-focus device, part of the mirror surface is covered by a converter, but as the diagonal increases, this becomes less noticeable. The quality of reception directly depends on the size. Good characteristics start from 1.5 m. With such dish sizes, the irradiator no longer “shades” the surface of the mirror. This type The antenna is used for professional reception.

It should be noted that the satellite dish is very “picky” about the terrain. Any interference in the signal path, be it a tree or a wall, can completely or partially block the reception. Therefore, before a possible purchase, you need to check whether there is interference in the direction from the intended installation location to the selected satellite.

Satellite Is it worth a try?

If you dial in Google search“homemade satellite dish”, the Internet will give you the most bizarre pictures with images of such amazing designs that sometimes you admire the boundless imagination of a person. There are beer cans, umbrellas, cut-up frames, etc. Will any of this work? Maybe. However, it is unlikely that such a design can compare with a regular plate, which can be easily purchased at any specialized store. Considering the fact that average price satellite dishes are quite democratic, there is no need to waste your time on the construction of a dubious design, except, perhaps, in the case if a person is an inventor by nature or has deep knowledge in this field.


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