Menu
homeYandex

Setting up a satellite dish - theory. Selecting a satellite dish. Offset and direct focus antennas

Mirror parabolic antennas come in prime focus and offset. Direct focus antennas are also called axisymmetric. The mirror of a direct-focus antenna is a paraboloid of rotation, the antenna is round, its geometric axis coincides with the electrical axis. The converter is placed on the same axis, which, as a rule, is attached to the edges of the reflector using three or four posts. The offset antenna is a cutout from a paraboloid. As a rule, a notch is formed by the intersection of a paraboloid and a cylinder whose axes are parallel. Thus, the mirror of the offset antenna has the shape of an ellipse, and the direction of the electrical axis of the antenna differs from the direction of the geometric axis of the mirror by a certain angle. As a rule, the electrical axis is 20...30 degrees higher than the geometric axis.

Both antennas have their advantages and disadvantages. A direct-focus antenna uses the mirror area more efficiently. An offset antenna has the same effective area as a direct focus antenna with a diameter equal to the smaller axis size of the offset antenna. In other words, to obtain the effective area of ​​an offset antenna, you need to multiply its physical area by the cosine of the angle between the electrical and geometric axes. U typical antennas physical space is used at 86-90%. On the other hand, with a direct-focus antenna, part of the surface is obscured by the converter and its mounting elements, while with an offset antenna it is not. Therefore, small-diameter antennas, up to 1.5 meters, in which the converter can obscure more than 10% of the area, are usually made offset, and the antennas large sizes are more often direct-focus.

A direct-focus antenna is always raised to a certain positive angle, therefore it represents a “bowl” in which precipitation can accumulate - rain, snow, ice. Offset antennas in our northern latitudes are installed almost vertically, or even “look down” - so they do not have this drawback. On the other hand, on a direct-focus antenna, the converter “looks down”, so you can safely use the feed with a leaky lid or without a lid at all; water and snow will not get inside. On an offset antenna, the converter “looks” up, so it must be sealed, otherwise water will get inside and can damage the electronics of the converter. In addition to water and wind, converter, and other components satellite system, can be ruined by frequent power outages. This issue can be easily resolved, just buy a gas generator for uninterruptible power supply receiving equipment.

There is another feature of using large-diameter offset antennas in northern latitudes - they cannot always be lowered to a sufficiently low elevation angle. For example, if the satellite's elevation angle is 5 degrees, the antenna mirror should be directed 15-25 degrees below the horizon. Offset antennas of large diameters, which are installed on a vertical stand, for example, “Supral” 1.8 m or 2.4 m, cannot be lowered to an angle of less than 11-12 degrees, the lower edge of the antenna rests against the stand. You can get out of this situation by turning the antenna mirror along with the feed mount 180 degrees, then the electrical axis will be 25-27 degrees lower than the geometric one, and the antenna will need to be directed above the satellite. However, this requires serious modification of the fastening parts.

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. Eg, existing standards signals, 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 digital compression MPEG-2 and MPEG-4 video signals. 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 is usually located vertically relative to 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 accuracy focusing. Disadvantages - insufficient protection of the converter from exposure 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

Offset assembly satellite dish— the process is not as complicated as it might seem initially. 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, the user capabilities are quite extensive, but at the same time limited. geostationary orbit 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 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 neighboring countries. 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;
  • geographical coordinates antenna installation location (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 plate in the desired position, and then perform fine tuning, focusing on the quality of the picture on the TV screen. The device is oriented to azimuth using a compass. Then it is set strictly vertical position dishes. The exact vertical of the disk can be obtained by focusing, for example, on installed nearby plumb line We have already obtained the value of the satellite’s elevation angle - using a regular protractor, we must try to bring the antenna to this value as accurately as possible, 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 maximum high-quality picture and then the position of the plate is finally fixed.

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 mode control and control mode for 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 DiSEqC protocol 1.2.

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.

Satellite antenna— a mirror antenna for receiving (or transmitting) a signal from artificial satellite Earth.

The most common satellite antennas are parabolic antennas (they are usually called satellite antennas). Satellite dishes have Various types and sizes. Most often in the world, such antennas are used for receiving and transmitting satellite television and radio programs, as well as connecting to the Internet.

Types of satellite dishes

Mirror parabolic antennas come in prime focus and offset. Direct focus antennas are also called axisymmetric.

Direct focus (axisymmetric) antenna

A direct-focus (axisymmetric) antenna is an antenna with an aperture in the form of a paraboloid of rotation. The mirror of a direct-focus antenna is a paraboloid of revolution, the antenna is round, its geometric axis coincides with the electrical axis. The converter is placed on the same axis, which, as a rule, is attached to the edges of the reflector using three or four posts. The diameter of the antenna determines its gain and, accordingly, the stability of reception satellite signals. Depending on the geostationary satellite used, the diameters receiving antennas can be from 0.55 m to 3.7 m. Typically, such antennas are used to receive signals in the C-band and Ku-band. Parabolic antennas They are also used to transmit signals to satellites. Low noise amplifiers (LNA) with low levels noise and converters, which allows you to amplify high-frequency signals directly after the irradiators and convert them into intermediate-frequency signals. Intermediate frequency signals are transmitted through cables connected to converters for further amplification and detection.

Offset antenna

The offset antenna is the most common in individual satellite television reception, although other principles for constructing terrestrial satellite antennas are currently used. An offset antenna is an asymmetrical cutout from a paraboloid of rotation with a feed at the focus of the paraboloid. As a rule, the cutout is formed by the intersection of a paraboloid and a cylinder, the axes of which are parallel. Thus, the mirror of the offset antenna has the shape of an ellipse, and the direction of the electrical axis of the antenna differs from the direction of the geometric axis of the mirror by a certain angle. Typically, the electrical axis is 20-30 degrees higher than the geometric axis. This eliminates the shading of the useful area of ​​the antenna by the feed and its supports, which increases its coefficient beneficial use with the same mirror area with an axisymmetric antenna. In addition, the feed is installed below the center of gravity of the antenna, thereby increasing its stability under wind loads. The offset antenna mirror is mounted almost vertically. Depending on the geographic latitude, the angle of its inclination varies slightly. This position prevents precipitation from collecting in the antenna bowl, which greatly affects the quality of reception. When viewed through the light, the antenna does not appear as a circle, but as an ellipse, elongated vertically. The dimensions of an offset antenna are usually given in terms of gain equivalent to the direct focus ones. If horizontal given size coincides, then vertically it will be approximately 10% larger.

Usually offset antennas are used to receive C and Ku-band signals (in linear and circular polarization). However, signal reception in the Ka-band, as well as combined, is also possible.

Advantages and disadvantages

Both antennas have their advantages and disadvantages. A direct-focus antenna uses the mirror area more efficiently. An offset antenna has the same effective area as a direct focus antenna with a diameter equal to the smaller axis size of the offset antenna. In other words, to obtain the effective area of ​​an offset antenna, you need to multiply its physical area by the cosine of the angle between the electrical and geometric axes. For typical antennas, the physical area is used at 86-90%. On the other hand, with a direct-focus antenna, part of the surface is obscured by the converter and its mounting elements, while with an offset antenna it is not. Therefore, small-diameter antennas, up to 1.5 meters, in which the converter can obscure more than 10% of the area, are usually made offset, while larger antennas are often direct-focus.

A direct-focus antenna is always raised to a certain positive angle, so it represents a “bowl” in which precipitation can accumulate - rain, snow, ice. Offset antennas in northern latitudes are installed almost vertically, or even “look down” - so they do not have this disadvantage. On the other hand, on a direct-focus antenna, the converter “looks down”, so you can safely use the feed with a leaky lid or without a lid at all; water and snow will not get inside. On an offset antenna, the converter “looks” up, so it must be sealed, otherwise water will get inside and can damage the electronics of the converter.

There is another feature of using large-diameter offset antennas in northern latitudes - they cannot always be lowered to a sufficiently low elevation angle. For example, if the satellite's elevation angle is 5 degrees, the antenna mirror should be directed 15-25 degrees below the horizon. Offset antennas of large diameters, which are installed on a vertical stand, for example, “Supral” 1.8 m or 2.4 m cannot be lowered to an angle of less than 11-12 degrees, the lower edge of the antenna rests on the stand. You can get out of this situation by turning the antenna mirror along with the feed mount 180 degrees, then the electrical axis will be 25-27 degrees lower than the geometric one, and the antenna will need to be directed above the satellite. However, this requires serious modification of the fastening parts.

For the manufacture of satellite antennas, steel and duralumin are mainly used. Satellite TV lovers sometimes install a motor-mount (motor) or a positioner. Using an actuator and a command from the user (or a command from the tuner), it allows you to rotate the antenna to the position of the satellite you need.

Information sources:

  • sattelik.ru - offset and direct focus antennas;

To understand the choice of a satellite dish, you need to have an idea of ​​how it works. And it works very simply. The antenna itself, the dish in our understanding, is nothing more than a reflector - a kind of mirror that concentrates the signal incident on it at the receiver - converter. The converter converts the already received signal into something understandable for the receiver and transmits it via cable. Therefore, no wires fit to the plate itself - they fit to a small box, a converter. The set of reflector and converter is the satellite antenna itself. And depending on the design, antennas are divided into two main types - direct focus and offset.

Direct focus antennas

The antenna mirror has a parabolic shape. Direct focus antennas represent a section of a parabola, its apex and branches. They are located at right angles to the direction of the satellite and reflect the received signal to a point located on the axis of the parabola. The converter is attached to this point. Depending on how far from the center of the antenna the converter is located, they are also divided into short-focus and long-focus. But that doesn't matter anymore.

A direct focus antenna has its disadvantages and advantages. Since the converter is located in the center of the antenna, directly in the path of waves approaching the reflector, it obscures some part of the mirror. Because of this disadvantage, direct focus antennas are initially manufactured with a large diameter. Already for a one and a half meter dish, the area covered by the converter is small enough relative to the area of ​​the mirror so as not to take it into account. Due to the fact that the front-focus dish is absolutely round when viewed from the front, it concentrates the waves into a flat point on the converter. In addition to this advantage, a direct-focus antenna with a large diameter makes the most efficient use of the area of ​​its reflector, because the wave reaches its entire surface and is reflected from each unshaded point into the converter. With an offset plate, approximately 10% of the area is not used due to its shape. For these reasons, direct focus antennas are manufactured in large sizes and are used in professional reception, where quality is most important.

This type of plate also has a lot of disadvantages. First, it is inconvenient to mount such an antenna on the wall of a building, because for this you will have to make a long remote bracket. A straight-focus dish has a larger angle of inclination to the horizon, which means that when tuned to the same satellite, it will stand more “horizontally” than an offset dish. As a result, snow, water, autumn leaves and dirt will accumulate on the reflector and degrade its properties. And this is another reason why home use It is better to have an offset plate.

Offset antennas

If we take a parabola and use only part of its branch, we get an offset antenna. At the same position, the point at which reflection will occur will be shifted relative to the center and the converter installed there will not cover part of the mirror with its shadow. The main disadvantage of direct focus antennas is thus eliminated. The offset antennas themselves have a full face that resembles an ordinary egg for large antennas, or a circle for small ones. Antennas measuring 1.2m and larger are not round or even oval; instead of a diameter, they are usually indicated maximum length and antenna width. Small plates with a diameter of 0.9 m or less are round in shape. Offset plates, reflecting the signal, create an uneven spot on the converter, due to which they are not used for professional television reception.

It is much easier to install an offset plate, because it stands almost vertically, and this makes it easier to place it on the wall of a house or on a balcony. In addition, precipitation does not linger on the offset reflector, and dust is washed off and blown away by the wind. Because of these parameters, offset antennas have become widespread among home satellite TV users and organizations that do not need professional reception quality. For satellite Internet there is not much difference between offset and direct focus dishes.

Antenna material

Today you can find plates made from different materials- made of plastic, steel, aluminum, mesh, or even with holes. It must be accepted as truth that if you need a plate with a diameter of less than 1.8 meters, then it is better to take an aluminum offset plate. Fortunately, this type of antenna is the most common in Russia. You may also be offered a plastic plate, which are common in Europe. But plastic, like other polymers, is affected by temperature: from sun rays the plate can become deformed, even if this deformation is not visible to the eye, it will still negatively affect the reception. With age, a plastic antenna can deform on its own due to the chemical and physical properties of the polymer. In addition, snow sticks to the plastic, it can be fragile and the response quality of such an antenna is worse. A steel antenna is very durable, but it is heavy, making it more difficult to install, and with age it can rust and lose its properties.

Aluminum antennas are used more often than any other today. Aluminum has good reflective properties, it is lightweight, relatively durable and does not rust over time. It has one drawback - it is soft, so if an icicle falls on the antenna from the roof, or someone throws a brick at it, the mirror will most likely have to be replaced.

Large diameter direct focus antennas are often made of mesh. The mesh reduces the overall weight of the plate, reduces windage and is less heated by the sun. Precipitation and dirt do not accumulate on the grid, but this type of antenna has more disadvantages than advantages. These antennas in the Ku band 10.70 ... 12.57 GHz and 12.70 ... 14.80 GHz work even worse than solid ones, because the signal seems to “pass” through the holes in the mesh. This occurs because the holes are too big size, which ideally should not exceed 0.25 of the wavelength (approximately 7 mm in the 11 GHz range). The mesh antenna is prefabricated. Its reflector is assembled from flat segments, which must be bent along two axes during installation. And during assembly it is impossible to bend the segments perfectly. That is, the parabola does not have its own perfect shape. In addition, the segments are attached to the frame with wire staples, which do not provide adequate strength and in strong winds they may not withstand the load, causing the segments to fall off the antenna. As an alternative to mesh antennas, there are regular solid dishes with holes drilled into them. In terms of performance characteristics, they are not inferior to solid ones, but they are not as cheap as mesh ones.

Any satellite antenna must be highly durable. When buying a plate made by the Russian Supral plant, you may not receive mounting rods or brackets included. If this happens, don’t despair - you can order them from some mechanic “for a bottle”, or from antenna sellers for $10-15. Any antenna has a high windage, so when purchasing large antennas, be sure to ensure that there are stiffening ribs at the back. The plate itself must be strong enough so as not to “dance” from gusts of wind. In this case, small 60 cm plates are more suitable for windy places and high floors. They have a smaller area and are unlikely to be blown away by the wind.

What should you pay attention to when buying a plate? First of all, it is better to buy a plate and immediately pay for its installation. In this case, you don’t care about anything, and you just need to indicate the installation location and, while drinking coffee, wait for everything to work. If the kit is missing something, it's not your problem. If you buy a dish and want to install it later, or with the help of a specialist from another company, then strictly ensure that the reflector does not have dents or irregularities in its area, so that the antenna looks smooth and is not misaligned. Look at the delivery contents and ask for assembly instructions. Everyone loves our Supralov plates, but you may not get either instructions or wall mounting. In the case of “foreign cars” this problem does not arise.

Antenna suspensions also vary. Azimuthal suspension is used for antennas aimed at a single satellite. For satellite Internet you don’t need anything else. If you get tired of the provider, call a specialist and he will reconfigure the dish to another satellite. This is the cheapest pendant. The second type of suspension is polar. It allows you to reconfigure the antenna from satellite to satellite by rotating it around a vertical axis. Azimuthal suspension is most often used on inexpensive offset antennas, while polar is the lot of direct-focus antennas, although in Lately everyone got confused and offset plates began to be made with polar suspensions, but it’s up to whoever pays. As additional accessories You can buy yourself an actuator and a positioner - devices that, together, themselves rotate the dish and tune it to a given satellite. They are not cheap, and they are not needed for satellite Internet, so we will not dwell on them.

Converter

Low Noise Blockconvertor, aka LNB, aka Converter, is a device hanging in the focus of a dish onto which a signal from a satellite is projected. The converter converts this signal into an electrical signal, which is transmitted to the receiving device. Converters are available for different ranges. For satellite Internet, you will need a universal one that operates in two bands: 10.7 - 11.7 GHz and 11.7 - 12.75 GHz. The main indicator of the quality of a converter is its noise level. 0.6-0.7 dB is considered normal, but the lower the better. For C-band converters, the noise level is measured in degrees. Modern converters have built-in everything you need - a polarizer, an irradiator. Once you buy it, you don't need any more additional devices for the antenna itself. Please note that different converters must be used for direct focus and offset plates.

If you want to watch TV and access the Internet from the same satellite, you may need a converter with two outputs. Head satellite dish must be hermetically sealed and protected from moisture. Make sure that according to the operating conditions of the converter, it is suitable for your environment, that is, if you have frosts down to -60 o C and heat up to +60 o C, you will need a special converter.

If you need to receive signals from two satellites simultaneously from one antenna, for example Astra 19.2 and HotBird 13E, you will need a special holder for two converters, or a dual converter (in the photo below). To switch between converters, a DiSEqC device is used.

In dual converters, the DiSEqC system is already built-in, but this is more suitable for those for whom one satellite is not enough. Although you may want to simultaneously work with satellite internet, using it for surfing, and then download files via Europe Online without rebuilding the plate. But you never know why? All this costs more, and few people may need it, because when working with the Astra19.2-Hotbird13 pair, it is unlikely that your antenna will work with another pair, at least with Hotbird13-Sirius2.

In general, than better converter, the more expensive it costs. And one tenth of a decibel of noise can cost you tens of dollars. Among inexpensive brands, MTI Blue Line converters have proven themselves well. Judging by the description of the manufacturer, the heads of this series were selected as the highest quality among other converters from this company. They have a noise level of 0.6 dB, are used for offset antennas and are inexpensive. If you install the dish yourself and want to call a specialist who will then set it up, it is better not to install a converter, because its position and rotation also play a role.

Cable

For the satellite dish you will also need coaxial cable, at least two F-connectors (depending on the number of devices to which you will connect the antenna), heat shrink and cable. You can buy the cable yourself; if the installer does not use it, he will deduct its cost. Personally, I saw how RG6 cable, sold at 6 rubles per meter, was considered by honest installers at 15 rubles per meter, and there are those to whom it was sold at 30 rubles per meter. The cable must have characteristic impedance 75 Ohm and length, a little more than that, what you have from the antenna to the equipment. Please note that the cable should not break or bend too much along its path. It is not recommended to extend or stitch the cable, so an extra meter in a turn will not hurt you. There is an opinion that the shorter the cable, the better. This applies when we are talking about 50, or 10 meters, but not when we are talking about 10-12, or even 10-20 meters. The connectors are screwed onto the thread without soldering. Require that the cable connection to the converter be wrapped with electrical tape or sealed with heat shrink. If you bought the entire kit in a store, you can test the device for leaks by pouring water over the converter of the working antenna after installation. But it’s better to check it on the master’s equipment, because your DVB card may not have short circuit protection.

material taken from the site www.hardwareportal.ru

Plan:

1. Satellite dishes.

2. Classification of advantages and disadvantages.

3. Modulation and coding.

There are two types of satellite dishes: direct focus satellite dishes and offset antennas. Direct focus antennas - this is when round form at the antenna, and the focus is where the rays gather, that is, it is in the center. These antennas are large in diameter, that’s how they are produced. They start from 120-150 cm. They are easier to set up, but they require a special converter.

The disadvantage of a direct-focus antenna is that the antenna faces the satellite, and in winter snow accumulates on it. Direct focus antennas became widespread some time ago, with a diameter of 180 cm, made in China, assembled from individual petals. And another disadvantage of a direct-focus antenna is its very poor quality. A direct-focus antenna uses the mirror area most efficiently. The direct focus antenna rises at an angle and looks like a bowl.

Offset satellite dishes are round in shape and their focus is moved away from its center. Offset antennas are available in any size. Another advantage of the antenna is that snow does not accumulate on them in winter; it is located vertically. Inexpensive converters are suitable for it. There are two types of offset antennas: long-focus and short-focus. With long-focus antennas, the focus is further away from the antenna. Converters for offset antennas are designed for long focal lengths. You can only lose efficiency if you install a cone-shaped bell. This happens very often, since short-focus antennas from the Supral plant are very common. The diameters of these satellite antennas are 60, 90 and 120 cm. However, offset antennas are used for C and Ku signal. But it is usually possible to receive a Ka signal in the band.

A satellite antenna is a receiver (or signal transmitter) from an artificial Earth satellite and is a mirror (reflector) to which is attached a device (converter) that receives and converts the received high-frequency signal into a lower intermediate frequency.

There are different types of satellite antennas: mirror, flat, spherical, horn and others. They have many valuable qualities, but due to the high cost and complexity of mass production, they are produced in limited quantities. Therefore, the most common type of satellite antenna is the “dish”.

Since the satellite broadcast signal has a very high frequency and in its physical properties is close to the properties of light, i.e. reflected from the mirror surface and splits at the boundary of different physical environments (air humidity, etc.). Therefore, in order to amplify the signal, it needs to be focused at one point using a large lens - a reflective parabolic antenna. After such amplification, the signal passes for further conversion.

A dish-type satellite antenna has two reflector shapes: long-focus (“shallow”) and short-focus (“deep”).

In systems satellite reception Most often, long-focal reflectors are used (as described above, this form of reflector is described by the term “shallow”).

Parabolic mirror antennas are divided into two types: Direct focus (axisymmetric) and offset (the feed is out of focus).

Direct-focus antennas focus the entire signal in the center of the reflector, representing a classic type of paraboloid of rotation, and this contributes to more accurate orientation to the selected satellite. Typically, such antennas are used to receive signals in the C-band as they are weaker, but this is also possible in the Ku-band, as well as combined.

Offset antennas focus the received signal away from the center of the reflector, i.e. the focal segment is located below the geometric center of the antenna - this eliminates shading of the useful area of ​​the antenna by the feed and its supports, which increases its efficiency with the same mirror area as an axisymmetric antenna.

Each type has its own advantages and disadvantages:

Direct focus antennas.

Advantages:

the manufacturing process is very simple;

low price.

Flaws:

it is impossible to mount it on the walls of houses without a long remote mount (to ensure the required elevation angle), otherwise the edge of the antenna mirror will simply rest against the wall;

complex setup and installation;

the converter is installed in the path of the signal from the satellite, thereby obscuring part of the reflector, and this reduces the overall gain of the received signal;

precipitation accumulates in the antenna: rainwater and snow.

Basically, a direct-focus antenna is used for professional reception of signals from a satellite, and with reflector sizes of more than 1.5...2.0 meters.

Offset antennas.

A toroidal satellite antenna, in addition to two reflectors, can be equipped with several converters. Thanks to this production technology, a toroidal satellite antenna is capable of receiving signals from several satellites simultaneously, and each converter will be located directly in the focus of the satellite to which it is directed - this is a big plus, since there is no need to install rotating devices to catch a signal from the satellite.

The external main mirror of a toroidal antenna differs from a conventional offset parabolic antenna, since it is most likely not an oval, but an egg-shaped one. Due to such a complex profile and reflection from the auxiliary mirror, not a separate point focus is formed in space, but an extended curve, the focus of any visible point of the geostationary orbit.

A toroidal satellite antenna is very difficult to manufacture and configure - this is probably the only disadvantage of this type of satellite antenna.

Note; “dish” is a mirror on which reflection occurs at a certain angle (the angle of reflection is determined by the manufacturer), that is, the offset antenna has a certain angle of signal reflection (19...27?)

Interesting fact.

The main parameter of satellite antennas is gain. The larger the surface of the reflector, the more radiation it will collect in focus. Accordingly, the dimensions of the reflector will be determined by the signal supplied from the satellite to this reflector: if powerful signal from the satellite to the antenna, then you can choose a smaller reflector size, and if the signal is weak, then the reflector should be the largest, accordingly. The main attention should be paid to the fact that for reliable reception in any weather, the size of the reflector must be chosen as large as possible to obtain a power reserve (during precipitation, part of the signal will be absorbed by water droplets, therefore, the signal power is lost and for reliable reception you need to use an antenna with large reflector size).