Digital television (DTV) uses the formation of a television signal, its transmission and processing in digital form. Information words, images and sound are transmitted as an encoded sequence of "1" (ones) and "0" (zeros). Such a transmission system provides a high degree of protection against external interference, high image quality compared to analog television. In addition, when using DTV, the capabilities of TVs, incorporated in them by the developers and creators of television technology, are fully realized.
Methods of digital television transmission
The transmission method means the option of delivering digital television signals to the subscriber. Based on this, the following types of DTV standards have been developed and adopted by the international organization today:
- DVB-T - digital terrestrial television, for the transmission of signals of which the radio air of a meter orUHF;
- DVB-T2 - an improved type of television signal transmission of the previous standard (2nd generation);
- DVB-C - cable television using MPEG-2 image and audio coding;
- DVB-C2 is the second generation of the previous standard, using methods to improve its noise immunity;
- DVB-S - digital satellite broadcasting;
- DVB-S2 is an improved modification of the previous standard.
In addition to the above options for providing digital television, Internet providers offer users an IPTV service that allows you to receive streaming digital television using fiber-optic cable lines or over the air of cellular operators. You can find out how to connect digital TV in the following sections of the article.
Digital Cable TV
The DTV signal is generated at the operator's base station. It has powerful digital television satellite receivers. The information they receive (image and sound) is coded and compressed, and in this form is transmitted over the cable lines of the regional operator's fiber optic network to switchboards in subscribers' homes. The input to the apartments is carried out by a television coaxial cable RG-6 with a wave impedance of 75 Ohm.
To install digital television, consumer equipment must have a separate decoder. It converts the input signal into a form understandable to the television receiver. The operator provides the subscriber with the opportunity to purchase for a feedecoder.
Digital tuner (decoder) incorporates most modern TVs. For cable TV, it must support the DVB-C/C2 standard. This can be found in the documentation for the TV. In this case, the user will need a special CAM module to view all closed channels. After connecting a paid access smart card to the tuner or CAM-module slot, you can install digital television and tune in to channels provided by the selected operator.
Satellite TV
TV broadcasting satellite receives signals from terrestrial transmitting centers. It moves in a geostationary orbit at an altitude of about 36,000 km from the Earth. A certain area of the territory is constantly in the zone of its visibility. With the help of transponders (responders), the encoded signal is radiated back to the earth's surface, where it hits the narrowly directed antennas of DTV subscribers.
To install digital television, the user is expected to have the appropriate equipment:
- antenna mirror (dish) in the form of a truncated paraboloid with a diameter of 0.6–0.9 meters, focusing the radio waves of the satellite transponders;
- converter - a receiving device located on the bracket at the focus of the antenna;
- tuner (decoder) that converts the signal received by the converter from a DVB-S/2 satellite;
- smart card of selected DTV operator.
If you use a TV with a built-in DVB-S/S2 tuner and a CAM module, you do not need to use an additional set-top box (decoder). The converter is connected to a set-top box or TV set with an RG-6 coaxial cable with high-frequency F-connectors at the ends. Connecting the set-top box to the TV is done with an HDMI cable or "tulips". Installation of an antenna for digital television requires the participation of specialists from the technical service of the DTV operator. The smart card is inserted into the slot of the decoder or CAM module. Which provider has the best digital TV - the answer to this question should already be known to the user of the selected card.
Terrestrial digital television
For the transmission and reception of terrestrial digital television signals, the decimeter wave range is mainly used. In Russia, it corresponds to the frequencies 470-790 MHz or 21-60 TV RF channels. Installation of digital television is possible if the consumer has equipment that includes:
- decimeter antenna providing reception of the signal of the television center;
- DVB-T2 tuner that converts the encoded input signal from the antenna into a form understandable by the television receiver;
- TV for quality picture and sound.
If the consumer uses a TV that has a tuner (decoder) of the DVB-T2 standard, an additional set-top box does not need to be purchased. 20 TV channels are available to a digital television subscriber in high quality. They are combined into 2 multiplexes(10 channels each). Each multiplex is broadcast by its own transmitter on one RF channel. The frequency of the channel depends on the geographic location of the receiving location. There are special maps of digital broadcast coverage areas for the whole country with detailed information.
Starting from January 2019, almost the entire country is being gradually transferred to the "digital" with the disconnection of analog television broadcast transmitters (exceptions are temporarily regional broadcasting centers). Watching digital channels of two multiplexes does not require paying a subscription fee for watching them.
Tuning digital channels
Before tuning, the antenna is connected to the high-frequency jack of the set-top box or TV. In the case of using a decoding set-top box, it is connected by a set of "tulip" cables to the inputs of the television receiver. Using a cable with HDMI connectors is the most preferred. It delivers high-definition multimedia and immersive stereo sound. The control of the set-top box and the TV are provided by different remote controls.
To set up DTV channels using the remote control, select the "Auto search" mode in the device's settings menu. Channels will be determined not one at a time, but dozens at once. The search will take time (up to several minutes). The found channels must be fixed by pressing the corresponding button. If the result of auto-search is unsatisfactory, which may be an insufficient signal level at the receiving point, you must usemanual tuning mode by selecting the appropriate menu item.
Pressing the "Info" button on the remote control allows you to check the intensity and quality of the signal on the screen. Their indicators at the level of more than 60% are considered satisfactory. If these requirements are met, then the digital channel tuning on the TV can be considered complete.
Antennas for digital television
The design of the antenna used does not determine how the television signal is generated. The geometric dimensions of its elements must be commensurate with the wavelength for which it is designed. Therefore, you can see videos about digital antennas and read messages of an exclusively advertising nature. All digital television antennas are designed to receive decimeter radio signals.
Antennas can be omnidirectional. Such devices can be successfully used in the immediate vicinity of the transmitting center at a line-of-sight distance of no more than 3–5 km. They are usually available in indoor version.
Their vibrators are made in the form of telescopic pins that can change their length. Vibrators have the ability to orient in space to obtain the most confident and high-quality reception in urban environments. Vibrators are added in the form of rings of a strictly defined diameter.
What do you need for digital television in the country? The country option involves a significant removal of the TV from the transmitting centers. Therefore, to get a "digital" picture onscreen is possible only through the use of highly directional antennas with a large self-gain.
Often you have to use active antennas or use additional signal amplifiers. It is important not to forget that for digital television in the country, you also need to use a mast that increases the direct visibility of the transmitting television center or repeater.
Factors affecting image quality
The greatest influence is exerted by the quality of the matrix of the television screen and the technology by which it is made. From an old analog TV, to which it was possible to connect a set-top box (decoder) to receive a digital signal, you can only get the very fact of receiving a television broadcast program. The picture quality will remain the same. Reception interference will not appear on the screen as dashes or snow. The image is either present, or it will be replaced by the message "No signal" on the screen.
To date, LCD matrices with LED backlighting, as well as OLED, whose cells are created using organic light emitting diodes, have the highest performance.
Conclusion
After reading the material presented in the article, the reader will understand that the advantages of digital TV over analog are obvious. We must accept the fact that the transition has practically taken place for objective reasons. The choice of equipment the reader will now be able to make with skill, depending on how he intends to receive a digital image.
