Antenna amplifier for a TV: the principle of operation and the rules for choosing a TV antenna amplifier

To improve the signal of a television receiver in a city apartment, and even more so in a place remote from the repeater — in a village or in a country house, an antenna amplifier is used for the TV. Small in size and affordable in price, 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 picks up 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 image and sound quality 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 for frequency adjustment.

To set the desired mode, resistors are used. The frequency is regulated 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 feedback section with power and working with 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 are distinguished by strong protection.

Internal amplifiers are located close to the receiver. Their minus is the loss associated with the cable length.

Buying Criteria

The choice of a signal amplifier for a TV antenna depends on both the technical criteria of the device itself and external factors, such as the 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.

By 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 high 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 quality, 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 gain leads to distortion of the signal, 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 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 with improper installation.

Browse Popular Models

Some amplifiers are in demand due to the simple device, low cost and easy installation. If necessary, the devices can be independently installed, replaced or repaired.

When purchasing devices for external use, take care of their tightness. It is noted that external devices have to be changed approximately every 2 years, despite their protection, therefore, if it is possible to install the amplifier under the roof, use it.

Conclusions and useful video on the topic

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 device.