Assimilate those who wish to tune the antenna to television: nature has not created digital things. In the universe, there are analog signals, the power varies according to the quantum states of electrons. Transitions are so small that they seem continuous to a person. The signal may be represented by a certain number multiplied by the elementary energy. We want to make it clear: the nature of the digital signal in the understanding of humanity is devoid of, the digital antenna is not independently constructed. It is possible to manufacture an antenna for receiving an analog signal carrying digital information.
Digital antenna
Digital signal receiving antennas
Today, only digital television. But! Multiplexes, where programs are stamped with frames, contain radio broadcasts. We want to clarify: in the present state of affairs, radio broadcasting has gone astray, capturing the frequencies of the FM band, television has been completely supplanted in UHF.Explained by the features of modern life. The driver wants to listen to the radio, watch TV.Did you see long antennas of radios?34 MHz. Compare: I channel of the USSR was broadcasting 50 MHz. Does everyone on the roof have a two meter long antenna to view the center channel?
Just ridiculous. In contrast to the sticks, FM-UHF antennas are relatively small. Easily fit on the roof. Facilitating the suffering of moviegoers, the channel carries one frequency. The picture is broken by frames, it turns out, quite a few programs are available with a single antenna setup. Conveniently. A lot of the benefits of a technical solution will be seen from the phenomenon called today digital multiplex. The antenna becomes possible to accurately target the frequency of reception( which is a trivial UHF channel) to watch the program, listen to the radio.
To solve the problem, some seemingly “self-made digital antenna” devices are constructed. The antenna is ordinary, add to the interested in type - linear. The design is chosen due to its small size. One problem is highlighted in digital transmission. ..
Television is used to using horizontal polarization. Suffer the fate of digital multiplex. It turns out that the signal is caught then delightfully when the antenna line is perpendicular to the incoming signal beam. Break the rule, power starts to get lost, reception gets worse.
Reception of a digital signal by the antenna
Those who want to receive a digital signal should understand the type of polarization of electromagnetic radiation. To discard satellite television broadcasting personnel, polarization, as Vladimir Volfovich says, is horizontal unequivocally. The type of signal is taken to catch a television on a half-wave vibrator, two types of signal are emitted:
- Symmetric.
- Asymmetrical.
We explain. The first is formed by identical shoulders equal to a quarter of the wavelength. Totally, half the wavelength is obtained. The signal conductor cable is connected to one shoulder, the screen - the opposite. The shoulders in a row form a line, separated by a gap of 20 mm. To reconcile equip the resistance of the antenna and cable, work to balance. The first condition is ideally satisfied, the second at UHF frequencies with decreasing wavelength plays a smaller value.
Do-it-yourself Antenna
To make a digital antenna yourself, it is enough to equip the mast with a carrier plate, horizontally symmetrically attach two wire arms 3 mm thick, each with a quarter wavelength.
The resulting device is soldered to a coaxial with an impedance of 75 Ohms, as indicated above, the cable length is taken as low as possible, each meter consumes a portion of the useful power loss. Only the length up to the first amplifier stage plays a role. By supplying the roof with food, putting the purchase unit at the desired frequency, the bay in the corner, folded behind the TV, makes it impossible to spoil the reception. The effect of over-amplification sometimes introduces unpleasant visual effects, the glorious image is considered the most famous.
Another negative is possible. First you should try the antenna without an amplifier. Reception will not be distorted by extra power. If unpleasant side effects are observed, it is worth trying to fight for quality improvement. It is important to more accurately direct the antenna. Due to the multipath effect in the city, in the village due to the deviation of the direction of wave movement from a straight line, the ray exit point is not where the compass points( according to the map).You should slightly move the antenna, setting the right direction, finding the best position.
Reception of the antenna signal
The half-wave vibrator of the above-described structure on the radiation pattern forms two main lobes.180 degrees apart. The radiation pattern is symmetrical in the horizontal plane. Therefore, we will improve the characteristics by setting the screen. The obvious solution, rarely see for a simple reason: the antenna must catch a wide range, it is difficult to find the right distance. For a half-wave vibrator, the screen will not be a piece of conductive material - a pair of pieces of wire from which shoulders are made. The distance between them is not so important, should not be large. It is quite enough 5 centimeters up and down from the plane of finding the shoulders. The length of the screen exceeds the span of both, electrically located on the braid of the cable.
The importance of finding the distance between the screen and the half-wave vibrator. We are at a loss with the correct answer, which gap separates parts, for zigzag loop antennas the value is 0.175 wavelengths of the signal. We believe that amateurs have the right to try experimentally to find the right distance, professionals have a chance to simulate the MMANA system. The first will get an acceptable result faster, the second will be able to predict the final alignment of an arbitrary wavelength, which is preferable. Antenna modeling is not part of the authors ’interests; enthusiastic people are able to upload a finished file, adding comments to the fruit of technical thought. We believe the alignment will reduce the amount of interference.
Unbalanced Antenna
Unbalanced Digital Antenna
As for an unbalanced half-wave vibrator, is one shoulder. The second is replaced by "earth"( the infinite plane of zero potential), in practice, there is simply nothing in this place. The manufacture of a half-wave asymmetrical vibrator is repeatedly shown by the forums, the VashTehnik portal, and the network. Usually, the antenna serves as a room supplement to a digital receiver, which is afraid to catch on its own. To make an adaptation, the channel wavelength is calculated, divided by four. The screen of the cable is cleared along the length, the internal insulation is preserved - it does not interfere with the reception.
A F-connector is screwed on the end bent by 90 degrees, which is inserted into the receiver, the TV socket( contain the receiving part of the terrestrial digital television the required chip generation).Almost all modern plasma panels have the necessary inside. The setup will take time, the channel frequency is known. We need to find out the number - visit http: // rtrs.rf, look at the region, call the desired phone number. Requests are accepted by e-mail. Of course, if the region is devoid of digital television, no information can be found.
This site is the official resource of the state unitary enterprise, which is entrusted with the task of digitizing the space of the Russian Federation. Ask if a log-periodic digital antenna is being made by yourself? The answer is no need. The log-periodic antenna covers a large range, if you want to watch three Moscow multiplexes, take it. Rejecting caution, use a wave channel antenna, differs from a log-periodic one with somewhat worse band characteristics, simpler design. The method of manufacturing was discussed, the provinces have little sense in wasting time.
Readers understand: the digital antenna device is identical to the usual one. The polarization is linear horizontal, the frequency is determined by the channel. The principle of operation of a digital antenna is similar. Convert electromagnetic wave into current inside the conductor. The feature of digital antennas is precisely tuned to one frequency. The design is simple and efficient. Promising high-quality viewing( without visual, sound interference).Naturally, the TV set-top box must decode the signal.
It remains to say goodbye to readers. Today, the amateur radio industry is a thing of the past, who will predict the expecting humanity tomorrow. ..
