How to choose satellite converters - overview, features and reviews
Satellite broadcasts are transmitted in a waytransmission of waves at very short centimeter frequencies. For this purpose, two levels are used: Ku-band (10.7 to 12.75 GHz), C-band (3, 5-4.2 GHz). At such magnitudes, the electromagnetic wave, which has the ability to overcome more than 35,000 kilometers from the satellite to the home antenna, in the cable instantly fades. It is for converting the frequency into an intermediate, lower index, satellite converters serve. According to international standards, the spectrum of this frequency is in the range of 900-2150 MHz. These frequencies are then fed via a special cable to the microwave input of the receiver.
General principle of work
To reduce the received frequency spectrum, inconverter are built in a pair of heterodynes with stabilizers of the high-frequency source. A decrease in the input is accomplished by subtracting the local oscillator frequency from it.
Another nuance is that the signalThe satellite arrives with a small disappearing power. This is unacceptable in the paths of the receiving devices. In this connection, the second important function of satellite converters is the amplification of the received pulses. It should be noted that the device accumulates not only a useful signal, but also incoming parallel noises. Also, the device adds its own background, like any other similar device. In the English interpretation, converters are referred to as Low Noise Block (LNB), which emphasizes the peculiarity of any device of this type in terms of low noise level.
Device and equipment
In the receiving part between the antenna and satelliteTV-converter there are two more elements - a polarizer and an irradiator. All parts are mounted in a single structure, located in the focus of the antenna device. The purpose of the irradiator is to more thoroughly use the surface of the mirror and to maintain the limiting gain of the antenna gain. The polarizer serves as an installation for selecting the desired type of polarization.
The components of the devices under consideration can be the following:
- Release of converters separately.
- Models with built-in polarizer.
- A design that combines a blanket irradiator and a polarizer.
In the first variant, the satellite converter ends with a flange of a rectangular type, the second model with a round element, and the third version with an irradiator.
When choosing an irradiator, it is necessary to take it into accountA form that should fit the joints to the antenna used. In addition, attention should be paid to the offset or direct focus type of the receiving element, as well as the ratio of the focal length to the diameter of the antenna. For offset models, the figure is from 0.6 to 0.8, and for straight-focus models it should be 0.3-0.5. Optimal option will be the purchase of an antenna complete with an irradiator, which will guarantee their compatibility by one hundred percent.
Criterias of choice
The choice of a satellite dish converter is affected byseveral factors. The main one is the frequency range that is planned to be used. European satellites mainly broadcast in the Ku band. Some Russian companies work on the same frequencies.
The second type of device is the C-band converter. These frequencies are focused on a professional reception. Some models are produced with converters of a combined type. Models that aggregate with Ku-bands on the market are plenty. It should be noted that the width of this indicator is 2.055 GHz. It does not make it possible to synchronously translate the signal into an intermediate frequency. In this regard, it is divided into three streams (GHz):
- FSS - 10,7 - 11,8.
- DBS - 11.8 - 12.5.
- Telecom - 12.5 - 12.75.
Satellite converters of the second and third bands are oriented to receive certain packets.
Most of the produced converters aggregatewith a range of type Ku. They are equipped with two heterodynamines, which convert the upper and lower ranges. The elements are switched by means of a signal that is broadcast from the receiver via a cable serving to receive the intermediate frequency from the converter.
Modern devices, in comparison withpredecessors, have a universal design, the switching of ranges in them is carried out by means of a tone signal. A universal circular satellite converter is characterized by the number of signals that serve for switching ranges and polarization.
The parameters of heterodynes in such devices arevalues from 9.75 to 10.6 GHz. This design greatly simplifies the setup of the receiver, right up to the automatic configuration after selecting the appropriate menu item.
Satellite converters for Tricolor
If you want to receive both ranges simultaneously, you canadvise several options. It is realistic to install on the antenna a pair of converters with their polarizer and irradiator. In this case, one of the irradiators slightly out of focus, which will reduce the directional coefficient. This way is considered rather troublesome.
The second option is to purchase a C / Ku deviceThe rotor, which contains both band irradiators, splits the input signal stream. Such elements are equipped with electromechanical polarizers. This design simplifies the installation process, but has a number of drawbacks. First, there are perceptible power losses of Ku pulses. Secondly, frequent breakdowns of moving parts of the rotor are observed, especially at subzero temperatures.
Finally, the third option is considered the simplest. You just need to install a combined converter, which has not yet received a special distribution.
This device allows more efficientuse the frequency range of transmitted waves, which doubles the number of broadcast programs. By tuning the frequency of the desired channel, the required polarization is synchronized. For example, a linear satellite converter forms vertical and horizontal waves with polarization. A circular analog generates right and left impulses of circular type.
The polarizer filters the waves and passes toconverter only pulses of one selected polarity. It should be noted that Russian satellites have a predominantly circular action, whereas European analogues have a linear system. To assure reception of circular waves, one more element is mounted - a depolarizer transforming the circular polarity into a linear direction.
The discreteness of the change in polarization is anotherparameter of difference between polarizers. In universal models, the plane discretely changes by 90 degrees. There are also electromagnetic devices that smoothly change the polarization plane and options with mechanical probe movement. Due to the presence of moving parts, electromechanical modifications are less reliable and require three control pulses from the receiver, in contrast to magnetic analogs, which lack two signals.
With the advent of digital packages like "Tricolor" andNTV Plus received a European reception scheme based on the use of a polar antenna and a universal converter. This is due to the high quality of the signal and the digital method of broadcasting most programs. Phase modulation is very sensitive to conversions, which can lead to malfunctions when using a magnetic polarizer. In addition, it requires the use of certain materials for the plate depolarizer. As components, dielectric grades are used, designed to work with pulses of the microwave type.
If it is decided to mount a magnetic polarizer,It will be necessary to purchase an additional converter with a rectangular flange and an irradiator. When distributing the signal to several apartments, it is optimal to use a satellite circular converter (2 outputs or 4 outputs). They are usually equipped with an integrated polarizer (voltage - 13-18 V). By type of output pulses, such devices are divided into one or two pairs of identical outputs with independent switching of polarization and ranges. Such devices are suitable for connecting 2-4 apartments. The second type - with the outputs output on vertical and horizontal polarization plus double division of ranges in the presence of 4 outputs. These devices are designed for a larger number of subscribers.
This type of device is convenient to use,who plans to limit themselves to receiving the upper or lower range. In this scheme, a horizontal pulse type is applied to one input of the receiver, and a vertical signal is applied to the second input. Analogues of this modification with four outputs are used in cable networks or for organizing a small collective reception. In the second case, the reception from the converter outputs is carried out through the swatchers for subsequent wiring by subscribers.
In the schemes of collective use, higher standards are placed on the signal amplification factor. This value is measured in decibels, its permissible value varies within the range of 50-70 dB.
As evidenced by user feedback,satellite converter "Tricolor TV" is better to buy with two independent outputs, circular polarization 10.7-12.75 GHz, noise level 0.3 dB. On the market, such devices are offered by many manufacturers: from Chinese firms to well-known brands. They differ among themselves at the price and quality of materials, they have the same principle of operation.
When purchasing a converter for an antenna,attention to its design features. Optimum is considered a hermetic model, otherwise condensate can form in the middle of the device due to temperature difference. This leads to a deterioration in the performance, up to failure. The negative aspects of this design include the impossibility of dismantling and repairing the converter. However, high quality assembly and innovative materials reduce the possibility of breakage to a minimum.</ p>>