Powerful DIY antenna amplifier. TV antenna signal amplifier. Electrical circuit diagram of the power supply for the antenna amplifier with adapter

Despite the rapid development of satellite and cable television, the reception of terrestrial television broadcasts still remains relevant, for example, for places of seasonal residence. It is not at all necessary to buy a finished product for this purpose; a home UHF antenna can be assembled with your own hands. Before moving on to considering the designs, we will briefly explain why this particular range of the television signal was chosen.

Why DMV?

There are two good reasons to choose designs of this type:

1. The thing is that most channels are broadcast in this range, since the design of repeaters is simplified, and this makes it possible to install a larger number of unattended low-power transmitters and thereby expand the coverage area.
2. This range is selected for digital broadcasting.

Indoor TV antenna “Rhombus”

This simple, but at the same time, reliable design was one of the most common in the heyday of on-air television broadcasting.

As can be seen from the sketch (B Fig. 1), the device is a simplified version of the classic zigzag (Z-design). To increase sensitivity, it is recommended to equip it with capacitive inserts (“1” and “2”), as well as a reflector (“A” in Fig. 1). If the signal level is quite acceptable, this is not necessary.

The material you can use is aluminum, copper, and brass tubes or strips 10-15 mm wide. If you plan to install the structure outdoors, it is better to abandon aluminum, since it is susceptible to corrosion. Capacitive inserts are made of foil, tin or metal mesh. After installation, they are soldered along the circuit.

The cable is laid as shown in the figure, namely: it did not have sharp bends and did not leave the side insert.

UHF antenna with amplifier

In places where a powerful relay tower is not located in relative proximity, you can raise the signal level to an acceptable value using an amplifier. Below is circuit diagram device that can be used with almost any antenna.

List of elements:

• Resistors: R1 – 150 kOhm; R2 – 1 kOhm; R3 – 680 Ohm; R4 – 75 kOhm.
• Capacitors: C1 – 3.3 pF; C2 – 15 pF; C3 – 6800 pF; C4, C5, C6 – 100 pF.
• Transistors: VT1, VT2 – GT311D (can be replaced with: KT3101, KT3115 and KT3132).

Inductance: L1 – is a frameless coil with a diameter of 4 mm, wound with copper wire Ø 0.8 mm (2.5 turns must be made); L2 and L3 are high-frequency chokes 25 µH and 100 µH, respectively.

If the circuit is assembled correctly, we will get an amplifier with the following characteristics:

• bandwidth from 470 to 790 MHz;
• gain and noise factors – 30 and 3 dB, respectively;
• the value of the output and input resistance of the device corresponds to the RG6 cable – 75 Ohm;
• the device consumes about 12-14 mA.

Let's pay attention to the method of power supply; it is carried out directly through the cable.

This amplifier can work with the most simple designs made from improvised materials.

Indoor antenna made from beer cans

Despite the unusual design, it is quite functional, since it is a classic dipole, especially since the dimensions of a standard can are perfectly suitable for the arms of a decimeter range vibrator. If the device is installed in a room, then in this case it is not even necessary to coordinate with the cable, provided that it is not longer than two meters.

Designations:

• A - two cans with a volume of 500 mg (if you take tin and not aluminum, you can solder the cable instead of using self-tapping screws).
• B – places where the cable shielding is attached.
• C – central vein.
• D – place of attachment of the central core
• E – cable coming from the TV.

The arms of this exotic dipole must be mounted on a holder made of any insulating material. As such, you can use improvised things, for example, a plastic clothes hanger, a mop bar or a piece of wooden beam of appropriate size. The distance between the shoulders is from 1 to 8 cm (selected empirically).

The main advantages of the design are fast production (10 - 20 minutes) and quite acceptable picture quality, provided there is sufficient signal power.

Making an antenna from copper wire

There is a design that is much simpler than the previous version, which only requires a piece of copper wire. We are talking about a narrow band loop antenna. This solution has undoubted advantages, since in addition to its main purpose, the device plays the role of a selective filter that reduces interference, which allows you to confidently receive a signal.

For this design, you need to calculate the length of the loop; to do this, you need to find out the frequency of the “digit” for your region. For example, in St. Petersburg it is broadcast on 586 and 666 MHz. The calculation formula will be as follows: L R = 300/f, where L R is the length of the loop (the result is presented in meters), and f is the average frequency range, for St. Petersburg this value will be 626 (the sum of 586 and 666 divided by 2). Now we calculate L R, 300/626 = 0.48, which means the length of the loop should be 48 centimeters.

If you take a thick RG-6 cable with braided foil, it can be used instead of copper wire to make a loop.

Now let's tell you how the structure is assembled:

• A piece of copper wire (or RG6 cable) with a length equal to L R is measured and cut.
• A loop of suitable diameter is folded, after which a cable leading to the receiver is soldered to its ends. If RG6 is used instead of copper wire, then the insulation from its ends is first removed, approximately 1-1.5 cm (the central core does not need to be cleaned, it is not involved in the process).
• The loop is installed on the stand.
• The F connector (plug) is screwed onto the cable to the receiver.

Note that despite the simplicity of the design, it is most effective for receiving “digits”, provided that the calculations are carried out correctly.

Do-it-yourself MV and UHF indoor antenna

If, in addition to UHF, there is a desire to receive MF, you can assemble a simple multiwave oven, its drawing with dimensions is presented below.

To amplify the signal in this design, a ready-made SWA 9 unit is used; if you have problems purchasing it, you can use homemade device, the diagram of which was given above (see Fig. 2).

It is important to maintain the angle between the petals; going beyond the specified range significantly affects the quality of the “picture”.

Despite the fact that such a device is much simpler than a log-periodic design with a wave channel, it nevertheless shows good results if the signal is of sufficient power.

DIY figure eight antenna for digital TV

Let's consider another common design option for receiving “digits”. It is based on the classic scheme for the UHF range, which, because of its shape, is called “Figure Eight” or “Zigzag”.

Design dimensions:

• outer sides of the diamond (A) – 140 mm;
• internal sides (B) – 130 mm;
• distance to the reflector (C) – from 110 to 130 mm;
• width (D) – 300 mm;
• the pitch between the rods (E) is from 8 to 25 mm.

The cable connection location is at points 1 and 2. The material requirements are the same as for the “Rhombus” design, which was described at the beginning of the article.

Homemade antenna for DBT T2

Actually, all of the examples listed above are capable of receiving DBT T2, but for variety we will present a sketch of another design, popularly called “Butterfly”.

The material can be used as plates made of copper, brass, aluminum or duralumin. If the structure is planned to be installed outdoors, then the last two options are not suitable.

Bottom line: which option to choose?

Oddly enough, the simplest option is the most effective, so the “loop” is best suited for receiving a “digit” (Fig. 4). But, if you need to receive other channels in the UHF range, then it is better to stick with “Zigzag” (Fig. 6).

The antenna for the TV should be directed towards the nearest active repeater, in order to select the desired position, you should rotate the structure until the signal strength is satisfactory.

If, despite the presence of an amplifier and reflector, the quality of the “picture” leaves much to be desired, you can try installing the structure on a mast.

In this case, it is necessary to install lightning protection, but this is a topic for another article.

It was already noted above that installing an antenna amplifier near the TV between the feeder and the antenna input of the television receiver increases the gain of the receiving path, i.e. improves the sensitivity limited by the gain.

It has been shown that when using modern televisions, this method does not lead to improved images in long-distance reception conditions, since it requires an improvement in sensitivity, which is limited not by gain, but by noise. The antenna amplifier, having approximately the same noise level as a television receiver, does not improve noise-limited sensitivity.

Nevertheless, the use of an antenna amplifier in some cases makes it possible to improve reception, but for this it should be installed not near the TV, but near the antenna, on the mast between the antenna and the feeder, or in the feeder gap, in the immediate vicinity of the antenna. What's the difference?

The fact is that the signal, passing to the feeder, undergoes attenuation and its level decreases. Attenuation depends on the brand of cable from which the feeder is made. In addition, the greater the attenuation, the greater the length of the feeder and the greater the frequency of the signal, i.e., the number of the channel through which the transmission is received.

When an antenna amplifier is installed near the TV, its input receives a signal that has already been weakened by passing through the feeder, and the ratio of the signal level to the noise level at the input of the antenna amplifier is less than if the antenna amplifier was installed near the antenna when the signal is not attenuated by the feeder. In this case, of course, passing through the feeder, the signal is also weakened, but by the same amount. noise is also reduced. As a result, the signal to noise ratio does not deteriorate.

Television cables of different brands are characterized by the dependence of specific attenuation on frequency. The specific attenuation of a coaxial cable is usually called the attenuation that a signal of a certain frequency experiences when passing through a cable 1 m long.

Specific attenuation is measured in dB/m and is given in reference books in the form of graphical dependences of specific attenuation on frequency or in the form of tables. In Fig. 1 shows such curves for some brands of 75-ohm coaxial cable.

Using them, you can calculate the signal attenuation in a cable for a certain length, on any frequency channel in the meter or decimeter range. To do this, you need to multiply the specific attenuation value obtained from the figure by the length of the feeder, expressed in meters. The result is signal attenuation in decibels.

Rice. 1. Specific attenuation curves of coaxial cables.

The most common type of cable for the feeder is RK 75-4-11, its specific attenuation is 0.05...0.08 dB/m in the range of channels 1-5, 0.12...0.15 dB/m in the range of 6-12 channels and 0.25...0.37 dB/m in the range of 21-69 channels. Hence, with a feeder length of 20 m, the signal attenuation in the feeder on the 12th channel will be only 3 dB, which corresponds to a decrease in signal voltage by 1.41 times, and with a feeder length of 50 m, the attenuation on the 12th channel will be 7.5 dB (decrease I 2.38 times).

In the decimeter range, with a feeder length of 20 m, the attenuation will be equal to 5.0...7.4 dB V, depending on the channel number, which corresponds to a decrease in signal voltage1 by 3.78...2.34 times^, and with a length feeder 50 m - 12.5... 18.5 dB (signal reduction by 4.22...8.41 times).

Thus, with a feeder length of 50 m, given to channel 12, the signal passing through the feeder is reduced by more than half, and the signal-to-noise ratio at the TV input will also be reduced by more than half. If you install an antenna amplifier before the signal enters the feeder, at the same level of input noise of the antenna amplifier as the TV, the gain in signal-to-noise ratio will be more than doubled.

An even more significant gain will be obtained with a longer feeder length or when receiving a signal in the decimeter range. The necessary and sufficient gain of the antenna amplifier must be equal to the signal attenuation in the feeder. There is no point in using antenna amplifiers with a gain greater than required.

Several types of antenna amplifiers are available. The most widely used antenna amplifiers for the meter range are the UTDI-1-Sh type (individual range television amplifier for frequencies 1-1II ranges).

They are designed for all 12 channels" of the meter range and contain a built-in power supply from the network AC voltage 220 V. The design of the amplifier allows it to be installed on a mast near the antenna with power supply via a feeder without laying additional wires. The gain of the UTDI-1-Sh amplifier is no less than 12 dB (4 times the voltage), and its noise level is slightly lower than the noise level of black-and-white and color television receivers.

If the UTDI-1-III amplifiers are band and are designed to amplify a television signal on any of the 12 channels of the meter range, then antenna amplifiers of the UTKTI type (individual channel transistor television amplifier) ​​are single-channel and are designed to amplify the signal of only one, very specific frequency channel of the meter range.

The channel number is indicated after the amplifier type designation. Thus, UTKTI-1 means that the amplifier is designed to amplify the signal on the first frequency channel, and UTKTI-8 is designed to amplify the signal on the eighth channel. Amplifiers of the UKTI type also have a built-in power supply from an alternating current network with a voltage of 220 V.

The gain of UTKTI-1 - UTKTI-5 is not less than 15 dB, and UTKTI-6 - UTKTI-12 is not less than 12 dB. The self-noise level of amplifiers of this type is somewhat lower than that of the UTDI-1-Sh type. The power consumed from the alternating current network UTDI-1-Sh does not exceed 7 W, and UTKTI - 4 W.

Due to the fact that television broadcasting in the UHF range is now becoming increasingly widespread, and the signal attenuation in the feeder in this range is increased, the use of antenna amplifiers designed for this range is becoming relevant. For example, an amplifier type UTAI-21-41 (individual television antenna amplifier, designed for 21-41 channels) with a gain of at least 14 dB in the frequency range 470...638 MHz.

Previously, despite the release of industrial antenna amplifiers, a large number of descriptions and diagrams of antenna amplifiers for self-made, IN recent years Such publications have become rare. So, in the collection “To help the radio amateur,” issue 101, p. 24-31 provides a very detailed description of a narrowband antenna amplifier with a tunable amplitude-frequency response by O. Prystaiko and Yu.

Pozdnyakova. The amplifier is tuned to one of the channels of the meter range using a tuning capacitor, the amplifier's bandwidth is 8 MHz, and the gain is 22...24 dB. The amplifier is powered constant voltage 12 V. It makes sense to use such an amplifier only in the case when transmissions are received via one specific channel, since it is not possible to rebuild the amplifier installed on the mast.

Wideband antenna amplifier MV

Much more often there is a need for a broadband antenna amplifier that can amplify the signals of all television programs received by the antenna. In Fig. 2 shown circuit diagram of antenna amplifier, designed to amplify all 12 meter channels, developed by I. Nechaev.

Rice. 2. MV antenna amplifier circuit.

At a voltage of 12 V, the gain is 25 dB with a current consumption of 18 mA. The amplifier is assembled using low-noise transistors with a noise figure of about 3 dB. Back-to-back diodes connected at the input protect the amplifier transistors from damage by lightning discharges. Both cascades are assembled according to a common emitter circuit.

Capacitor C6 provides correction of the frequency response of the amplifier in the higher frequencies.

The output of the amplifier is connected to the feeder going to the TV. The central core of this part of the feeder supplies the amplifier with supply voltage through inductor N. Through the same inductor, a voltage of +12 V is supplied to the central conductor of the antenna socket of the TV. The signal from the antenna socket on the TV to the input of the channel selector must be supplied through an isolation capacitor with a capacity of 3000 pF.

The chokes are wound on ferrite cylindrical cores with a diameter of 3 mm and a length of 10 mm using PEL or PEV wire with a diameter of 0.2 mm turn to turn. Each inductor contains 20 turns. Before winding, the core must be wrapped in two layers of lavsan film, and after winding, the turns are secured with polystyrene varnish or enamel.

A more detailed description of the amplifier, a drawing of the printed circuit board and the placement of parts on it are given in the magazine "Radio", 1992, No. 6, p. 38-39.

Another antenna amplifier, designed for the UHF range 470...790 MHz (21...60 channels), was proposed by A. Komok. Its circuit diagram is shown in. rice. 3. The passband gain of this amplifier is 30dB when powered at 12V, and the current consumption does not exceed 12mA.

Rice. 3. UHF antenna amplifier circuit.

The high-pass filter coil L1 is wound with PEV-2 wire with a diameter of 0.8 mm and contains 2.5 turns.

Winding is carried out on a mandrel with a diameter of 4 mm turn to turn, after which the coil is removed from the mandrel. Power, as for the Nechaev amplifier, is supplied through the feeder through the chokes of the design described above. The author used unpackaged transistors in the amplifier, which require careful sealing.

We can also recommend the use of KT399A packaged transistors, which are more affordable and resistant to changes in climatic conditions. Detailed Description of this amplifier was published in the magazine "Radio Amateur 11, 1993, No. 5, p. 2.

As noted, the main purpose of the antenna amplifier is to compensate for signal attenuation in the feeder. When using an antenna amplifier, noise-limited sensitivity, i.e., the ability to receive a weak signal, is determined by the signal-to-noise ratio not at the input of the television receiver, but at the input of the antenna amplifier. Therefore, when installing an antenna amplifier near an antenna, to obtain a certain sensitivity value limited by noise, a lower input signal level will be required than when installing it near a TV. Thus, it is possible to receive a weaker signal with better quality.

Application of antenna amplifier allows the deliberate use of feeders of such great length that, in the absence of an amplifier, would weaken the signal level to an unacceptable level. The need to use a long feeder sometimes arises in closed areas, when the television receiver is located in a hollow and the receiving antenna installed near the house is obscured by hills on the way to the transmitter.

At the same time, television antennas installed at a distance of 100...200 m from this building provide quite reliable reception from good quality images due to the fact that they are not covered by a local barrier. In such conditions, normal reception can be achieved in one of two ways: either by increasing the height of the antenna mast, which is usually a very difficult task, or by installing the antenna in an open area, at a distance of 100...200 m from the house. Then to connect the antenna to the television receiver you will need to use a long feeder.

It is easy to calculate that with a feeder length of 200 m, a cable of the RK 75-4-11 brand at the frequency of the 12th channel creates an attenuation of 30 dB, which corresponds to a decrease in signal voltage by 31.6 times, which, as a rule, is below the sensitivity threshold of a television receiver . Installing an antenna amplifier with at least the same gain at the antenna output will compensate for signal attenuation in a long feeder and provide normal work TV.

If the gain of one amplifier is not enough, you can connect two amplifiers in series one after the other. In this case, the resulting gain will be equal to the sum of the gains of the amplifiers, if they are expressed in decibels.

At very long length feeder and the need to amplify the signal by more than 30 dB, when it is necessary to use two or more antenna amplifiers, in order to avoid overload or self-excitation, all amplifiers should not be installed in one place. Under these conditions, the first amplifier is installed at the antenna output, i.e., at the input of the feeder, and the subsequent ones are installed in the feeder gap at approximately equal distances from one another. These distances are chosen so that the signal attenuation in the feeder section between the two amplifiers is approximately equal to the gain of the amplifier.

From the dependences of specific attenuation on frequency for coaxial cables of different brands (Fig. 1), certain conclusions can be drawn. Cables of brands RK 75-2-13 and RK 75-2-21 have a fairly high specific attenuation even in the meter wavelength range; they should not be used in the decimeter wavelength range. Cables of brands RK 75-7-15, RK 75-9-13, RK 75-13-11 and RK 75-17-17 have lower specific attenuation compared to RK 75-4-11, especially in the decimeter range.

If, with a feeder length of 50 m at a frequency of 620 MHz (channel 39), the RK 75-4-11 cable introduces an attenuation of 16 dB (attenuation of the signal voltage by 6.3 times), then under the same conditions the RK 75-9 cable -13 introduces an attenuation of 9.5 dB (attenuation by 3 times), and RK 75-13-1.1 - 7.25 dB (attenuation by 2.3 times). Thus, a successful choice of cable brand for a feeder in the UHF range can increase the signal level at the TV input several times even without using an antenna amplifier.

We can offer fairly simple advice on cable selection: the larger the cable diameter, the less attenuation it introduces. A coaxial cable with a characteristic impedance of 75 Ohms is always used as a television feeder.

Nikitin V.A., Sokolov B.B., Shcherbakov V.B. - 100 and one antenna designs.

The more I understand the modern element base, the more I am surprised at how easy it is to make such things now electronic devices, which previously could only be dreamed of. For example, the antenna amplifier that will be discussed has an operating frequency range from 50 MHz to 4000 MHz. Yes, almost 4 GHz! In the days of my youth, one could simply dream of such an amplifier, but now even a novice radio amateur can assemble such an amplifier on one tiny microcircuit. Moreover, he has no experience working with ultra-high-frequency circuitry.
The antenna amplifier presented below is extremely simple to manufacture. Has good gain low level noise and low current consumption. Plus a very wide range of work. Yes, it is also miniature in size, thanks to which it can be embedded anywhere.

Where can I use a universal antenna amplifier?

• - As a TV antenna signal amplifier for receiving both digital and analogue channels.
• - As an antenna amplifier for an FM receiver.
• - etc.

Antenna amplifier characteristics

• Operating range: 50 MHz – 4000 MHz.
• Gain: 22.8 dB - 144 MHz, 20.5 dB - 432 MHz, 12.1 dB - 1296 MHz.
• Noise figure: 0.6 dB - 144 MHz, 0.65 dB - 432 MHz, 0.8 dB - 1296 MHz.
• Current consumption is about 25 mA.

Making an antenna amplifier

Scheme

Amplifier board

Setup and testing

Schema addition

Connecting the amplifier to the antenna

An antenna amplifier for a TV is widely used in the CIS. It is the optimal solution for improving the quality of the TV signal. The antenna's own gain does not play a significant role, but its antenna amplifier seriously affects the picture quality.

The best amplifiers that have proven themselves over the years of operation are considered to be SWA-7, 14, 17, 107, 109, 2000. The SWA-2000 is a newer antenna amplifier that has two additional transistors. The amplifier contains two transistors VT1 and VT2, which are connected in accordance with the circuit to the OE. The signal is collected at the collector in transistor VT2 and is fed through capacitor C9 to the cable. The additional transistors VT3 and VT4 are located in active circuits that provide base bias voltage in transistors VT1 and VT2.

Despite the fact that digital television is being actively introduced, there will always be a demand for antennas with active amplification, since the signal to the television tuner is supplied using antennas with a decimeter range.

So, to improve the television signal, they use an antenna amplifier. The best gain is achieved when the antenna amplifier is installed not next to the television input, but in close proximity to the antenna. To reduce attenuation, it is better to use modern coaxial cables. The amplifier is powered using a coaxial cable. The voltage rating of the power supply in the antenna amplifier is most often 12 V, and the cable attenuation value is 0.1 - 0.5 decibels per m, if we take different television channels.

IN rural areas When television centers are located at a great distance, they use amplifiers with a gain of more than 100 dB. If the amplifier was selected incorrectly, or the feeder and antenna are not properly matched, then due to the excitation of the amplifier, the TV screen will display noise and snow.

Although an antenna amplifier for a TV can be purchased at almost any corner, most of them use a standard circuit. That is, they are two-stage aperiodic amplifiers having bipolar high-frequency transistors connected in accordance with the OE circuit. Let's take a closer look at these models: SWA-36 and SWA-49

The SWA-36 amplifier contains broadband amplification stages with transistors VT1 and VT2. The value of the antenna signal, through the matching transformer and capacitor C1, is supplied to the base in transistor VT1, which is included in the circuit with the OE. The operating point in the transistor is determined by the bias voltage, which is determined using resistor R1. At the same time, due to the action of negative feedback(OOS) characteristic in the first stage becomes linear, the position of the operating point stabilizes, however, the gain value decreases.

No frequency correction is applied to the first stage. The second stage is also carried out using a transistor in a circuit with OE and OOS, due to the passage of voltage through resistors R2 and R3. However, there is also a current OOS, through resistor R4, which the emitter circuit has. It stabilizes transistor VT2. To avoid large gain losses, resistor R4 is tongued using capacitor SZ, which has a relatively low capacitance (10 pF).

The result of this is that the lower frequencies in the range of capacitance on the SZ capacitor will be significant and the AC feedback leads to a decrease in gain, due to which the frequency response of the amplifier is corrected. The SWA-36 amplifier has disadvantages, among them the passive loss that the output circuit has.

It implements better isolation of power circuits due to filters L1C6, R5C4 and increased gain thanks to capacitors C5 and C7.

Despite the rapid development of cable and satellite TV, it is too early to write off terrestrial television broadcasting. But for a high-quality signal of the latter, you need to be in the coverage area. As you move away from the TV tower, the quality of the signal decreases and the amount of interference increases. In such cases, an antenna amplifier for a television receiver helps well. We propose to consider what this device is, the principle of operation, various modifications, as well as the possibility of creating a TV signal amplifier for a city apartment, country house or cottage.

What is an antenna amplifier and how does it work?

This is a device that allows you to amplify a certain range of television signals and reduce the level of interference to obtain the highest quality “picture”. In addition, such amplifiers are used to reduce cable losses. Typical block diagrams such devices are shown below.

As can be seen from the presented diagrams, the incoming signal is processed by an external frequency filter, after which it is reduced by an attenuator to required level. Next, the signal enters the unit for adjusting the level of the frequency response slope, the principle of operation of which is in many ways similar to an equalizer. And at the last stage, the signal is amplified, after which it is sent to the television receiver.

Varieties

Despite the variety of equipment of this type, amplifiers can be divided into the following types according to their functionality and range:

How to choose a good antenna with an amplifier?

To get the most out of your purchased equipment, you need to consider the following factors:

• Distance of the nearest television signal repeater. It is generally accepted that the maximum distance is 150 kilometers, but it is a highly averaged value, since much depends on both the type of terrain and the power of the television tower. For example, if you are in a lowland, you may not receive a reliable signal even from a nearby repeater. In this case, installing a mast under the antenna will help correct the situation.
• In what frequency range will the equipment operate? It must be taken into account that the characteristics of wide-band antennas are inferior to narrow-beam antennas. This suggests that for an area of ​​reliable reception, an “all-wave” is quite suitable; accordingly, to receive a signal from a remote repeater, it is better to prefer a design for a certain frequency range (MV, UHF, VHF). But here it is also necessary to take into account the features and nature of the terrain, for example, you can only get rid of the reflected signal with the help of a highly directional antenna.

Having decided on the antenna, we move on to choosing an amplifying device for it. The first thing you need to pay attention to is the gain (indicated in decibels). As a rule, at a distance of up to 10 kilometers from the repeater, there is no need for an amplifier.

It is necessary to pay attention that you should not get too carried away with the high indicator of this parameter, since when high power the device may be “excited”, and as a result, interference will appear, appearing in the form of “white snow” in the picture. Below is a table for SWA equipment, which shows the main characteristics for each model, as well as the relationship between gain and range to the signal source.

The second important characteristic is the noise level (indicated in decibels) produced by the device during operation. The lower this figure, the better.

Naturally, when choosing, it is necessary to take into account the type of antenna; it is allowed to install a broadband device on a narrow-band signal receiver, but not vice versa.

How to make an antenna amplifier with your own hands - step-by-step instructions

Here are a few standard schemes devices for amplifying a television signal, let's start with the simplest one.

Designations:

• VT – chip MAX2633.
• R – 1 kOhm.
• Capacitors C 1, C 2 and C 3 – 1 nF.

Circuit gets tangled from source DC with voltage from 2.8 to 5.2 volts. Distinctive Features: low noise level (about 2 dB) and quite a decent gain, about 13 dB, which, if necessary, should be reduced by increasing the resistance R. Assembled circuit does not require configuration. The above device has proven itself well when working with indoor antennas of television and radio receivers. On the Internet you can find a description of this circuit as broadband, which is not entirely true, based on the datasheet MAX2633 - intended for the VHF range.

Now let's look at typical transistor circuits, which are truly broadband.

Designation:

• Transistor VT1 – KT368.
• Resistances: R1 -100 Ohm; R2 – 470 Ohm; R3 – 51 kOhm; R4 – 100 Ohm.

The scheme is also simple and does not require configuration. Gain and frequency characteristics depend on the transistor used. Devices of this type are characterized by a high gain and low frequency characteristics (which is corrected in emitter-coupled multi-vibrator circuits; if desired, they are not difficult to find, but they are more difficult to configure). Power is supplied from a 9 volt source.

The option with a transistor connected using a “common base” circuit has a lower gain, but a wider frequency range.

Designations:

• Transistor VT1 – KT315.
• Resistances: R1 -51 Ohm; R2 – 10 kOhm; R3 – 15 kOhm; R4 – 1 kOhm.
• Capacitances: C1- 1000 pF; C2 – 33 pF; C3 and C4 – 15 pF.

The inductor is wound on a ferrimagnetic ring, the permeability of which is 600N. For the meter range, it is necessary to make 300 turns; the wire used for this purpose is PEV Ø 0.1 mm.

You can achieve greater gain if you assemble the device on a two-stage circuit, an example of which is given below.

Designations:

• Transistors: VT1 and VT2 – GT311D.
• Resistances: R1 – 680 Ohm; R2 – 75 kOhm; R3 – 1 kOhm; R4 – 150 kOhm.
• Capacitances: C1, C2 and C4 – 100 pF; C3 – 6800 pF; C5 – 15 pF; C6 – 3.3 pF.
• Chokes: L1 – 100 µH; L2 – 25 µH, L3 – is a coil on a frameless base, 4 mm in diameter, 2.5 turns wound, PEV wire used 2 Ø 0.8 mm.

The circuit is powered from a 12-volt source; device configuration is not required.

Step-by-step assembly instructions will be common for all schemes:

• We purchase all the necessary electronic components.
• We prepare tools and consumables.
• We manufacture printed circuit board, hinged assembly and the use of mounting panels is undesirable, since in this case the noise level will significantly increase.
• We solder all the elements.
• We check the assembled structure.
• We connect the antenna and television receiver to the assembled amplifier.

How to connect an antenna amplifier to a TV?

The most important point is that the antenna amplifiers for the TV should be located as close to it as possible. This is due to the fact that cable losses can significantly affect the picture quality. The requirement concerns both homemade designs, so serial models, for example BBK or Terra. The only exception may be indoor antennas, which have a short cable length, but, as a rule, such devices are used in the reception area where there is no need for an amplifier.

Carefully read the connection manual that came with the device.

If connecting an amplifier does not bring results, check the antenna's directivity, as well as its waveform compliance.

All manipulations must be carried out only with de-energized equipment.

Do not connect the amplifier to an external antenna unless it is equipped with lightning protection. Actually, such a signal receiver cannot be used at all.