Satellite broadcasts are transmitted by the method of transmitting waves at very short centimeter frequencies. Two levels are used for this purpose: Ku-band (from 10.7 to 12.75 GHz), C-band (3, 5-4.2 GHz). At these values, the electromagnetic wave, which has the ability to overcome more than 35 thousand kilometers from the satellite to the home antenna, instantly fades in the cable. It is to convert the frequency to an intermediate, lower indicator, satellite converters are used. According to international standards, the spectrum of this frequency is in the range of 900-2150 MHz. These frequencies are then fed through a special cable to the microwave input of the receiver.
General principle of work
To reduce the received frequency spectrum, a pair of local oscillators with stabilizers of a high-frequency source are built into the converter. The input indicator is reduced by subtracting the local oscillator frequency from it.
Another nuance is that the signal from the satellite comes with a small endangered power. This is unacceptable in the paths of receiving devices. In this regard, the second important function of satellite converters is the amplification of received pulses. It is worth noting that the device accumulates not only a useful signal, but also incoming parallel noise. The device also 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 low noise level of any device of this type.
The device and equipment
In the receiving part between the antenna and the satellite TV converter, there are two more elements - a polarizer and an irradiator. All parts are mounted in a single design, are located in the focus of the antenna device. The purpose of the irradiator is to more carefully use the surface of the mirror and maintain the maximum gain of the antenna gain. The polarizer serves as a setting for selecting the desired type of polarization.
The configuration of the devices in question may be as follows:
- Release of converters separately.
- Models with integrated polarizer.
- A design that combines an offset irradiator and a polarizer.
In the first version, the satellite converter ends with a rectangular flange, the second model with a round element, and the third version with an irradiator.
When choosing an irradiator, it is necessary to take into account its shape, which should fit along the joints to the antenna used. In addition, you should pay attention 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, an indicator from 0.6 to 0.8 is suitable, and for direct-focus models, it should be 0.3-0.5. The best option would be to buy an antenna complete with an irradiator, which will guarantee their compatibility one hundred percent.
Criterias of choice
There are several factors that influence the choice of satellite dish converter. The main one is the frequency range that is planned to be used. European satellites predominantly broadcast in the Ku band. Some Russian companies operate at the same frequencies.
The second type of device is a C-band converter. These frequencies are oriented to professional reception. Some models are available with converters of the combined type. There are plenty of models aggregating with Ku-bands in the market. It should be noted that the width of this indicator is 2.055 GHz. It does not make it possible to synchronously transfer the signal to 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 range are focused on the reception of certain packages.
Universal Modifications
Most converters are aggregated with a Ku type range. They are equipped with two local oscillators, which convert the upper and lower ranges. The elements are switched by means of a signal that is transmitted from the receiver via a cable, which serves to receive the intermediate frequency from the converter.
Modern devices, in comparison with their predecessors, have a universal design, switching ranges in them is carried out by means of a tone signal. The universal circular satellite converter is distinguished by the number of signals used to switch bands and polarization.
The performance of local oscillators in such devices have values from 9.75 to 10.6 GHz. This design greatly simplifies the configuration of the receiver, up to the automatic configuration after selecting the appropriate menu item.
Satellite Converters for Tricolor
Those wishing to take both ranges at once, you can advise several options. It is realistic to install a pair of converters on the antenna with their own polarizer and irradiator. In this case, one of the irradiators slightly out of focus, which will reduce the directional coefficient. This way is considered quite troublesome.
The second option is to purchase a C / Ku type rotor device containing both band feeds, bifurcating the incoming signal stream. Such elements are equipped with polarizers of the electromechanical type. This design simplifies the installation process, but has several disadvantages. Firstly, there are tangible power losses of the Ku range pulses. Secondly, frequent breakdowns of the 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 much distribution.
Polarizer
This device allows more efficient use of the frequency range of the transmitted waves, which doubles the number of broadcast programs. By adjusting the frequency of the desired channel, the required polarization is simultaneously set. For example, a linear satellite converter with polarization forms vertical and horizontal waves. A circular analog generates right and left pulses of a circular type.
The polarizer filters the waves and passes only pulses of one selected polarity to the converter. It is worth noting that Russian satellites have mainly circular action, while European counterparts have a linear system. For reliable reception of circular waves, another element is mounted - a depolarizer that transforms circular polarity into a linear direction.
The discreteness of the change in polarization is another parameter that distinguishes polarizers. In universal models, the plane discretely changes by 90 degrees. There are also electromagnetic devices that smoothly change the plane of polarization and options with mechanical movement of the probe. Due to the presence of moving parts, electromechanical modifications are less reliable and require three control pulses from the receiver, unlike magnetic counterparts, which have two signals.
Phase modulation
With the advent of digital packages such as “Tricolor” and “NTV Plus,” the European reception scheme based on the use of a polar antenna and a universal converter has gained popularity. This is due to the high signal quality and the digital broadcast method of most programs. Phase modulation is very sensitive to transformations, which can lead to failures when using a magnetic polarizer. In addition, it requires the use of certain materials for the depolarizer plate. As components, dielectric grades are used for working with microwave pulses.
If you decide to mount a magnetic polarizer, you will need to additionally purchase a 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). Usually they are equipped with a built-in polarizer (voltage - 13-18 V). By the type of output pulses, such devices are divided into a variant with 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 outputs outputted by 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.
Two pin converters
This type of device is convenient to operate for those who plan to limit their reception to the upper or lower range. With this scheme, a horizontal type pulse is applied to one receiver input, and a vertical signal to the second. Analogs of this modification with four outputs are used in cable networks or for organizing a small collective reception. In the second case, reception from the converter outputs is carried out through switches for subsequent wiring to subscribers.
In the schemes of collective use increased standards are set for the signal gain. This value is measured in decibels, its allowable indicator varies between 50-70 dB.
Reviews
According to user feedback, it is better to purchase the Tricolor TV satellite converter with two independent outputs, circular polarization 10.7-12.75 GHz, and a noise level of 0.3 dB. Many manufacturers offer similar devices on the market: from Chinese firms to well-known brands. They differ among themselves in price and quality of materials, have an identical principle of action.
In conclusion
When purchasing a converter for an antenna, pay attention to its design features. An airtight model is considered optimal, otherwise condensation may form in the middle of the device due to temperature differences. This leads to a deterioration in performance, up to failure. The negative aspects of this design include the inability to disassemble and repair the converter. However, high build quality and innovative materials minimize breakage.