More often the antenna amplifier for the TV is necessary for the lower floors of high-rises. Powerless to penetrate the signal, even reflected. If you lay the cable to the roof, you need a signal amplifier for the TV antenna. Low power easily attenuates in the area preceding the entrance of the socket. Cable loss is 0.2 - 0.7 dB / m. Until the signal comes from the roof, it will decrease many times. Below we consider the theoretical, practical aspects, why we need antenna amplifiers for the TV.
Sensitivity, communication with the antenna of the TV
Sensitivity is the minimum threshold of the useful signal on the air, which the device receives, reproduces with a given level of distortion.
The signal is eclipsed by interference from adjacent channels. To better understand the moment, let's look around. The stars, the sun, the moon, the planets, the earth are sources of radiation. Occurs because the temperature of the bodies is above absolute zero( - 273 ºС).By law, Wines natural object demonstrates a certain maximum of the emission spectrum. Higher body temperature, more frequency, which accounts for the peak. The sun appears yellow, the hottest stars of blue. It is easy to remember, using the help of one proverb, given to children by the school teacher:
- Every Hunter Wants to Know Where the Pheasant Is Sitting.
Encrypted formula for the visible spectrum. Starting in red to purple, the frequency of the radio waves increases. Received:
- Red, Orange, Yellow, Green, Blue, Blue, Purple.
Now readers will understand what the expression of the red dwarf means. A small, relatively cold star, warms the planets with difficulty. The maximum radiation of the sun falls on the yellow light. High frequency, the figure is now calculated. The wavelength of the yellow color falls on 570 nm. We find the frequency using the well-known formula:
с - the speed of light in a vacuum.
We see that the maximum frequency of the solar radiation falls on the range that is ten thousand times higher on the scale than the usual 5 GHz Wi-Fi. The spectra of bodies have a stretched character, the stars of the galaxy, the Sun, are noisy in the radio range. There are cosmic radiations originating from various physical processes, the background is nothing in comparison with anthropogenic interference. This includes cell phone towers, a television tower, and household appliances. A welding machine, an asynchronous motor, a car ignition system are examples of artificial noise, the time of occurrence of which is difficult to predict.
Methods for ensuring reliable reception
Not surprisingly, they are unable to catch the useful signal. There are special methods to counter the interference of natural, anthropogenic origin. The signal is encoded by pseudo-random sequences. For reception use the phenomenon of the world of mathematics - the correlation function. Serves to assess the similarity of two random processes. When scientists need to understand whether there is a common between signals, graphs, they find a correlation function for this case. If on the receiving side know the form of a pseudo-random sequence, confidently conduct reception.
A pseudo-random sequence is called so by the form: an incomprehensible set of pulses filled with a carrier frequency( we immediately switch to digital signals).No matter how long, the parameters are strictly defined. Zero is encoded by one pseudo-random sequence, one by another. On the receiving side, both sets are known, it becomes possible to find an autocorrelation function representing the time integral of the signal brought by the ether, of the pattern present on the receiving side. If there is a coincidence, a peak is so high that the noise level may exceed the level of the incoming wave, we will correctly receive packets.
Digital technology is so popular today. The techniques will allow to reduce the transmitter power several times, to establish a stable reception, to correct errors as they occur. This solves the problem of transmitting useful information in terms of signal structure. This technique is called the scientific environment code redundancy.
By limiting the amount of interference, the excess is cut off by two or three ways antenna:
- Resonant frequency.
The first factor will allow you to take a small part of the spectrum. Heard, each channel is separated by a band, we are talking about this. TV antenna amplifier is configured to take a certain range. Helps to spend electrical energy in a rational way.
Antenna for TV helps to receive the signal of only one azimuth. The higher the passive gain of the fixture, already the reception sector. The unshakable rule today. Being outside, together with interference from the field of view of the antenna for the TV disappears.
Polarization is associated with the form of transmission of the signal by the ether. There are many ways, the characteristics of the receiving and transmitting antennas should be the same. Communication, broadcasting are conducted on vertical polarization, television is used horizontal. Neighboring channels less interfere with each other.
devices When a signal propagates, the usual active resistance of the line, the wave properties of the channel, take effect. The screen is necessary for the conductor, so that it does not radiate, does not turn into an antenna.
To ensure that the signal power is no longer reflected, the devices are coordinated. Achieved by the fact that the impedance of the antenna for the TV coincides with the cable, receiver. The scatter is visible, it is necessary to use special matching devices.
On the receiver side, the task is to ensure maximum sensitivity for the signal that is received with such difficulty. The problem solves the antenna amplifier for the TV.The sensitivity factor directly includes the factor: cable length up to the first amplification stage. If on the roof there is a “wave channel” with a long wire, devoid of an antenna amplifier for a TV, the losses level the gain created by the directivity. The effect is small. If the antenna amplifier for the TV increases the signal power before transmitting to the cable, the result will exceed the expectations.
The composition of the antenna amplifier for the TV
If in olden days the design of the antenna amplifier for the TV began with the choice of a transistor, today it is preferable to find a ready-made hybrid chip that performs the functions. It will remain the operating mode set. When installing an antenna amplifier for a TV on the street, give preference to the element base used at temperatures below zero to minus 60 ºС.Household chips enclosed in a plastic case are not suitable.
The main characteristics of the transistor, the antenna amplifier chips for the antenna are:
- Noise figure.
- Frequency Band.
Of course, other characteristics can not be cast aside, the two mentioned dominate. Not every transistor( microcircuit) is suitable for designing an antenna amplifier for a TV.Special element base is called low noise. Using this, a signal amplifier for a television antenna is constructed. We lead the narration in a simplified manner; in reality, the sensitivity formula contains noise; if the transistor is noisy, the effect of the cascade operation may be zero, negative. Such an antenna amplifier for a TV will make reception worse.
As a result,
Now we know how to amplify the signal of a television antenna, why it is done. The store has a billion broadband devices available for each broadcast band. Those who have no idea what harmonization, design, tuning of radio equipment is, it is strongly recommended to buy an amplifier for a TV antenna. There is a chance to make your own device, more powerful and more economical. Traditionally, the antenna amplifier for a TV has no frequency settings, it just works across the whole spectrum. If you only need the first multiplex of digital television, you will be able to assemble an economical device with a resonance on the carrier channel. It will be better than buying an amplifier for a television antenna in a store.
The moment needs to be clearly understood. The best quality is achieved by a specialized device. It is impossible to kill two birds with one stone at a time, unless they take a hunter in packs. Usually animals do not do that. In the process of designing, it is required to understand how to amplify the signal of the TV antenna, this concerns the range, coordination with all devices and selection of the necessary element base.
Numerous schemes are easy to find on the Internet and literature. Having the skills to handle a soldering iron, readers construct their own antenna amplifier for the TV.Check back often at the portal Your Technician, which counts with readers and cares about them. You can not be sad, having such an assistant. And when life is fun - the work goes on!