What is the difference between analog and digital signal?

TVs receive both analog and digital signals in the same way - in the form of electromagnetic pulses from the local TV tower or via the provider's cable. In both cases, you can watch your favorite TV shows and movies. What, then, is the difference between analogue and digital television and why is there a massive transition from one type of broadcasting to another in 2022? Let's figure out what the difference is and why “digital” is better than “analog”.

Which signal is better

It should be recognized that, despite many improvements implemented in the field of analog representation of information, this method of broadcasting has retained its shortcomings. These include distortion during transmission and noise during playback.

Also, the need to convert an analog signal to a digital one is caused by the unsuitability of the existing recording method for storing information in semiconductor memory.

Unfortunately, existing TV has virtually no obvious advantages over digital, excluding the possibility of receiving a signal with a regular TV antenna and sharing it between TVs.

DSD format

After the widespread use of delta-sigma DACs, it was quite logical for the emergence of a format for recording binary code directly to delta-sigma encoding.
This format is called DSD (Direct Stream Digital). The format was not widely used for several reasons. Editing files in this format turned out to be unnecessarily limited: you cannot mix streams, adjust volume, or apply equalization. This means that without loss of quality, you can only archive analog recordings and produce two-microphone recording of live performances without further processing. In a word, you can’t really make money.

In the fight against piracy, SA-CD format discs were not (and are still not) supported by computers, which makes it impossible to make copies of them. No copies – no wide audience. It was possible to play DSD audio content only from a separate SA-CD player from a proprietary disc. If for the PCM format there is an SPDIF standard for digital data transfer from a source to a separate DAC, then for the DSD format there is no standard and the first pirated copies of SA-CD discs were digitized from the analog outputs of SA-CD players (although the situation seems stupid, but in reality some recordings were released only on SA-CD, or the same recording on Audio-CD was deliberately made of poor quality to promote SA-CD).

The turning point occurred with the release of SONY game consoles, where the SA-CD disc was automatically copied to the console’s hard drive before playback. Fans of the DSD format took advantage of this. The appearance of pirated recordings stimulated the market to release separate DACs for playing DSD streams. Most external DACs with DSD support today support USB data transfer using the DoP format as a separate encoding of the digital signal via SPDIF.

Carrier frequencies for DSD are relatively small, 2.8 and 5.6 MHz, but this audio stream does not require any data reduction conversion and is quite competitive with high-resolution formats such as DVD-Audio.

There is no clear answer to the question of which is better, DSP or PCM. It all depends on the quality of implementation of a particular DAC and the talent of the sound engineer when recording the final file.

Features of analogue and digital television

The philistine judgment about the collapse of terrestrial TV and the transition to broadcasting technologies of the future is somewhat unfair, if only because TV viewers are replacing the concepts: terrestrial and analog TV. After all, terrestrial television is usually understood as any television broadcast over a terrestrial radio channel.

Both “analog” and “digital” are types of terrestrial TV. Despite the fact that analogue television differs from digital television, their general principle of broadcasting is identical - a television tower broadcasts channels and guarantees a high-quality signal only within a limited radius. At the same time, the digital coverage radius is shorter than the range of the unencoded stream, which means that repeaters must be installed closer to each other.

But the opinion that “digital” will ultimately surpass “analog” is true. TV viewers in many countries have already become “witnesses” of the conversion of an analogue signal to a digital one and are thoroughly enjoying watching TV programs in HD quality.

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Features of broadcast television

digital television repeaters

The existing terrestrial television system uses analog signals to transmit television products. They propagate through highly oscillating waves, reaching terrestrial antennas. In order to increase the broadcast coverage area, repeaters are installed. Their function is to concentrate and amplify the signal, transmitting it to remote receivers. Signals are transmitted at a fixed frequency, so each channel corresponds to its own frequency and is assigned to the TV in numerical order.

Advantages and disadvantages of digital television broadcasting

Information transmitted using a digital code contains virtually no errors or distortions. The device that digitizes the original signal is called an analog-to-digital converter (ADC).

To encode pulses, a system of ones and zeros is used. To read and convert BCD code, a device called a digital-to-analog converter (DAC) is built into the receiver. There are no half values ​​for either the ADC or DAC, such as 1.4 or 0.8.

This method of encrypting and transmitting data has given us a new TV format, which has many advantages:

• changing the strength or length of the pulse does not affect its recognition by the decoder;
• uniform broadcast coverage;
• unlike analogue broadcasting, reflections from obstacles of the converted broadcast add up and improve reception;
• broadcast frequencies are used more efficiently;
• It is possible to receive digital TV on an analog TV.

How to understand whether you are watching digital or analog

Old TVs are not capable of receiving DTV on their own. To connect digital, they need an external set-top box. Modern devices are equipped with a special built-in DVB-T2 tuner.

To determine the signal type, you need to look at the TV menu. If ATV is set in the “Source” section, analog video content is viewed.

Other ways to determine the current broadcast type:

• TV channels broadcasting ATV are indicated by the letter A. If it is not there, then the channel shows new TV;
• the antenna plug is pulled out of the socket and retracted 0.5 cm. If the image has become illegible, but has not completely disappeared, analogue television is shown, if the image has completely disappeared - DTV;

  
  Effect of signal attenuation on the picture

• digital television does not show TV channels in the “home” region (it already broadcasts in full in MSC).

What is an antenna radiation pattern

In addition to the sensitivity of the antenna, there is a parameter that determines the extent to which it is able to focus energy. It is called directional gain or directivity, and is the ratio of the radiation density in a given direction to the average radiation density.

A graphical interpretation of this characteristic is the antenna radiation pattern. At its core, it is a three-dimensional figure, but for ease of work it is expressed in two planes located perpendicular to each other. Having such a flat diagram at hand and comparing it with a map of the area, you can plan the antenna reception area for an analog video signal. Also from this graph you can extract a number of useful practical characteristics of the TV antenna, such as the intensity of lateral and reverse radiation and the protective coefficient.

Differences between a digital signal and an analog signal

For most people, the difference between an analog and digital signal can be quite subtle. And yet, their difference is significant and lies not simply in the quality of the television broadcast.

An analog signal is the received data that we see, hear and perceive as the world that surrounds us. This method of generating, processing, transmitting and recording signals is traditional and still very widespread. The data is converted into electromagnetic waves, reflecting the frequency and intensity of the phenomena according to the principle of complete correspondence.

A digital signal is a set of coordinates that describe an electromagnetic wave, which is not inaccessible to direct perception, without decoding, because is a sequence of electromagnetic pulses. Speaking about discreteness and continuity of signals, they mean, respectively, “taking values ​​from a finite set” and “taking values ​​from an infinite set.”

An example of discreteness would be school grades, which take values ​​from the set 1,2,3,4,5. In fact, a digital video signal is often created by digitizing an analog signal.

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Moving away from theory, in reality we can highlight the following key differences between analog and digital signals:

1. analogue television is vulnerable to interference that introduces noise into it, while the digital impulse is either completely blocked by interference and is absent, or arrives in its original form.
2. Any device whose operation is based on the same principle as the transmitter’s broadcast can receive and read an analog signal. The digital wave is intended for a specific “addressee”, and therefore is resistant to interception, because securely encoded.

Image quality

The quality of the TV picture provided by analog TV is largely determined by the TV standard. The frame that carries analog broadcast includes 625 lines with an aspect ratio of 4x3. Thus, the old kinescope displays an image from television lines, while a digital image is made up of pixels.

Picture with analog signal

With poor reception and interference, the TV will “snow” and hiss, not providing the viewer with image and sound. In an attempt to improve this situation, cable TV was implemented at one time.

Picture with digital signal

Other options

Despite the rapid development of electronic technology and the advantages of digital signal over analog, there are still areas in which analog technology is indispensable, such as professional audio processing. But, although the original recording may be no worse than the digital one, after editing and copying it will inevitably be noisy.

Here is a set of basic operations that can be performed with an analog stream:

• strengthening and weakening;
• modulation, aimed at reducing its susceptibility to interference, and demodulation;
• filtering and frequency processing;
• multiplication, summation and logarithm;
• processing and changing the parameters of its physical quantities.

The difference between digital television and analogue

The easiest way to notice the difference between analogue and digital broadcasting is to present the final characteristics of both technologies in the form of a table.

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Satellite TV: how much does it cost and who is it suitable for?

Satellite television has a different broadcasting principle. In this case, the signal comes directly from the satellite, bypassing the TV tower, to a special satellite dish (the same “dish”). The “delivery” of the signal from the satellite to the dish is carried out by the satellite TV operator, who charges a fee for its services.

On the one hand, the benefit seems rather dubious:

• Satellite TV requires special equipment. A set for receiving satellite television costs more than 3.5 thousand rubles, although this is a one-time purchase. It includes the “dish” itself, which also requires external installation, and a set-top box that will transmit the antenna signal to the TV.
• Satellite TV is provided according to tariffs. When purchasing a dish, you must connect at least one channel package, for which a subscription fee is charged. Therefore, not a single satellite operator has a basic package of only twenty federal channels, otherwise they would not have the right to take money from you.
• Satellite TV requires space to receive the signal. In a densely populated area with developed infrastructure, where high-rise buildings and other buildings, wires, trees, poles, as well as various electromagnetic fields may interfere with the antenna’s signal reception, it may arrive weakly or with interference. For reliable reception there should be nothing between the antenna and the sky.

On the other hand, the disadvantages of satellite TV, when looked at in a certain way, turn into advantages:

• Satellite TV broadcasts directly from a satellite. This means that the signal does not depend on how close your house is to the TV tower - you can catch a “satellite” even in the taiga, if only you had an antenna. The coverage of satellite TV is thus greater than that of digital, and much greater than that of cable, which is discussed below. The main thing is that there is no physical interference in the signal path.
• Satellite TV offers cheap rates. In fact, prices from satellite TV operators are quite low, and the conditions are favorable. For a basic package of 20 state and, for example, 160 paid channels, you will be charged about 150 rubles per month - and some operators have special “economical” packages for 50-60 rubles. If desired, you can add additional ones to the basic package.
• Satellite TV allows you to watch foreign channels. After all, TV channels from different countries can broadcast via a common satellite. If, for example, you are a passionate sports fan, and the matches of your favorite team are not broadcast in Russia, an additional package of foreign sports channels will help you. This option is only available from a satellite.

What conclusion can be drawn from this? Satellite TV is an ideal option for those who live far from a TV tower (for example, in a regional village) and for summer residents to whom terrestrial TV “does not reach.” And also for residents of the upper floors of high-rise buildings in cities - they can afford to install a dish and watch more channels for a small fee, and not be content with the “Culture” channel and the “Fashionable Sentence” program. And also for those who don’t like it when the state dictates what to watch.

TV antenna sensitivity

There is no universal recipe for choosing the ideal antenna, but there are mandatory requirements that must be met in order for it to receive analog and digital signals. As the distance from the broadcast object increases, these requirements increase. In particular, to the sensitivity of the receiver - its ability to pick up weak-intensity television signals. Often they are the cause of a blurry image. This problem is solved with the help of an amplifier, which significantly increases the sensitivity of the antenna and removes the question: how to connect it to digital television? The same TV, and the same antenna, only an over-the-air digital tuner will appear near the TV.