To improve the signal of the television receiver in a city apartment, and even more so in a place remote from the repeater - in the village or in the country, an antenna amplifier is used for the TV. Small in size and affordable at the cost of the device can be installed independently, if you correctly approach the choice of model.
Consider the technical features of the devices and analyze the criteria for choosing an amplifier for home use.
What is a signal amplifier necessary for?
If the TV does not work from a cable or satellite dish, it means that it catches a signal using a conventional antenna - indoor or outdoor. The transmission process is as follows: at a certain distance from each other, towers are installed that relay transmissions.
Household receivers - televisions - use the antenna to pick up signals and convert them into video, accompanied by sound.
A good signal is created in line of sight. If there are obstacles in its way in the form of, for example, reinforced concrete structures, then the quality of the image and sound drops sharply
To stabilize and improve the TV signal, an amplifier is used for a home television antenna. Its importance grows where a common powerful receiver is not installed on the roof, that is, outside the city. The device helps to achieve the maximum clear picture on the screen and sound purity due to the fact that it reduces interference.
Some antennas cope with the transmission of the signal themselves, without connecting additional devices. Therefore, before buying, study the technical characteristics of the antenna and make sure that its capabilities are limited, and it is not possible to configure it to receive high-quality image and sound without connecting a special device.
The principle of operation of the antenna adapter
Amplifiers for TVs are simple in device and can have a different design. Some consist of a pair of boards on which a circuit is implemented to reduce noise. One of the circuits performs the function of a high-pass filter, the second is equipped with a capacitor to adjust the frequencies.
To set the desired mode, resistors are used. The frequency is adjustable in two ranges: in the first - about 48.5 MHz, in the second - 160 MHz
Thanks to the adjustment, a maximum signal gain of 4.7 dB can be achieved at an operating frequency of 400 MHz.
Some types of amplifiers are designed to be powered from a 12 V source, that is, they can be connected to a car battery. To achieve stability, a stabilizer is used, the circuit of which includes an electrolyte and a diode bridge.
A number of devices are connected with a coaxial cable, but using a choke. They are connected to the TV via a capacitor.
Consider the example of one of the transformer amplifier circuits, how the device works. The module is powered by a signal cable.
The antenna is connected directly to the transformer winding. Amplifier element VT1 is matched with a common emitter. Feedback is carried out by elements C1, R3, L1
C1 - a capacitor connecting the power feedback section and operating at low frequencies. R3 - a resistor that determines the stable operation of the amplifier in various frequency ranges. L1 - inductance equalizing the amplitude of the frequencies.
Flow feedback organized by loop C3, R4which together with R1 and R2 include cascade mode of operation. C2 - a capacitor for connecting a transformer.
The signal from the antenna enters the matching transformer, then is transmitted through the transistor, amplified and stabilized in the emitter. Then there is a frequency correction at the second stage of cascade transistors, after which the signal enters the TV.
If several TVs are used in the house, then a splitter for 3-6 connectors is used to connect the cable and signal amplifier
Thus, thanks to the television amplifier, the sensitivity limited by noise is increased, and the losses of the received signal in the coaxial cable are also compensated.
Types of television amplifiers
The division of devices into categories is most often carried out according to two parameters: the installation location and the frequency range. This applies both specifically to antenna amplifiers, and to related analogs - television and satellite.
In the frequency range there are three types:
- range;
- multi-range;
- Broadband
Range the device amplifies the signal only in a certain, predetermined frequency range - meter or decimeter. One of its functions is to reduce the noise that appears when the cable length is increased.
Multiband devices work with the same efficiency in different frequency ranges, can also receive signals from several sources.
Broadband the amplifier operates in the meter and decimeter ranges, used for digital television.
Sample broadband device - model GAL AMP-101. Connection is via a coaxial cable and a separator. Gain - 20 dB
At the installation site, all devices are divided into external (mast) and internal. External mount at the installation site of the television antenna - on a pole or mast, mounted on a balcony or roof. They have strong protection.
Internal amplifiers are located near the receiver. Their minus is the loss associated with the cable length.
Buying Criteria
The choice of signal amplifier for the TV antenna depends both on the technical criteria of the device itself and on external factors, for example, location and installation conditions. However, in the first place - always characteristics that affect the quality of the signal - this is what additional devices usually acquire for the sake of.
Criterion # 1 - operating frequency range
The frequency range connects three devices - the television receiver itself, the antenna and the amplifier. First pick up the antenna. It should be remembered that wide-range ones lose out to narrowly focused ones, i.e. the signal will be weaker.
An antenna amplifier operating in the range 470-862 MHz and having a gain of at least 30 dB. Providing additional protection against moisture, can be installed outdoors
If the reception area is not far from the repeater, then you can buy a "Vsevolovka", covering a wider range. However, it is better to catch a signal from a remote tower for a limited frequency range - for example, MV or UHF.
According to the frequency response of the antenna, an amplifier is also chosen. If it does not match the range, then it will not work.
Criterion # 2 - noise figure
The antenna amplifier should adjust the signal-to-noise ratio upwards. However, each device in the process of transmitting data receives its own noise - and the stronger the signal, the more pronounced.
With a large noise figure, only intense noise interference, known as “snow,” will be visible on TV screens. The image disappears completely, the sound also disappears
It is believed that the noise figure should not exceed 3 dB - this is the only way to guarantee good signal transmission, but the latest generation devices have lower values - less than 2 dB.
Criterion # 3 - gain
Do not assume that the higher the signal gain, the better the transmission quality. In fact, excessive amplification leads to signal distortion, in which the opposite effect occurs - clipping or overload.
The parameter is measured in dB and has average values:
- decimeter - 30-40 dB;
- meter - 10 dB.
Thus, decimeter channels can cover both 22 and 60 channels, and meter channels - no more than 12. If the amplifier increases the coefficient by 15-20 dB, this is considered a good result.
When choosing an amplifier by coefficient, it is necessary to take into account real conditions and the level of reception. Usually they are guided by the distance to the tower, that is, the repeater.
An amplifier is usually used if the distance from the repeater to the receiver is at least 9 km. If the tower is 150 km or further, using even a powerful device is useless - this is the maximum for which household models are designed
In order not to get into trouble, you can choose a device with the ability to adjust, additional adjustment. There are many universal models, while they are designed for different distances.
If the tower is in direct line of sight, an amplifier is not needed.
Criterion # 4 - active or passive
If we consider the principle of operation of the device, then we must take into account the division into active and passive. Passive works offline, while the active one needs additional power from the network. Most often, the device is connected through an adapter - an adapter for 9 V or 12 V.
The closer the installation location of the active device to the TV, the better the signal. A long cable increases the risk of interference that cannot be eliminated by the adjustment.
If the device is located outdoors, it is necessary to provide protection against moisture and precipitation. Sometimes they implement the following option: an antenna with an amplifier is installed outside, and the adapter is left inside the room.
But it is better to follow the instructions of the manufacturer, who usually warns about the occurrence of interference during improper installation.
Browse Popular Models
Some amplifiers are in demand due to the simple device, low cost and easy installation. If necessary, devices can be independently installed, replaced or repaired.
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When purchasing devices for external use, take care of their tightness. It is noted that external devices have to be changed about once every 2 years, despite their protection, so if you can install the amplifier under the roof, use it.
The main thing about popular amplifiers:
Overview of Universal Broadband Devices:
If the image “snows” on the TV screen or is completely scattered into pixels, we recommend improving the quality of signal reception with the help of a home TV antenna amplifier. Difficulties with independent connection usually do not arise if you follow the manufacturer’s advice and take into account the characteristics of the antenna and the device.