Watching TV is one of people's favorite activities. And of course, I want the image on the screen to be of high quality. But this does not always work out. To amplify the signal and picture quality, amplifiers for the antenna are used.
What is it and what is it for?
An antenna amplifier is a device necessary to increase the level of the signal that is fed to the antenna. That is, with an amplifier, the quality of the channels is much higher.
Use an antenna amplifier for television in such cases:
- Weak television signal strength.
- The antenna for the TV is not selected correctly.
- Great distance to the telecentre.
Typically, an antenna television amplifier is used to operate in the decimeter or meter wavelength range. In addition, they can be used to receive channels at a fairly large distance from the transmitter. This is possible in the countryside.
Amplifiers
Devices may differ in appearance and have different parameters. Some of them can work in very remote areas, while others are used only at close range. Install antenna amplifiers for the TV near indoor or outdoor receivers.
Amplifier are:
- Range Such devices include antenna amplifiers SWA and LSA. Quite often they can be found in trellised antennas. Devices allow you to receive signals from stations located at significant distances. They improve picture quality and eliminate noise (noise).
- Multi-range. Amplifiers of the ALCAD and TERRA type belong to this category. They improve the quality of the received picture from receivers that are mounted on high masts. Designed for long and close reception. They can receive several signals from different receivers and combine into one.
- Broadband Distributed in the domestic environment. Since, due to its ability to improve the quality of the resulting image on several devices at once, they are often mounted in apartment buildings. They can work in both the UHF and the MV ranges.
By type, antenna amplifiers can also be divided into:
- Internal That is, those that are installed next to the receiver. Using them is quite convenient, but the signal may be worse due to cable loss.
- Mast. They are installed directly on the mast, and power is supplied using a coaxial cable. They do an excellent job with the main task, but are not durable. Most often they are enough for several years. They can be damaged during a thunderstorm or oxidize when water gets in.
Each type of television antenna amplifier is designed to improve the quality of the received signal.
Amplifier device
The device antenna amplifiers are not complicated. It consists of two boards connected according to a special scheme. Apply such a scheme to reduce the noise level that occurs during operation of the device. To adjust the frequency range, a special capacitor is mounted in the oscillatory circuit.
The input circuit is a high-pass filter. It is placed on special elements. The frequency of the loop in the first range is close to 48.5 MHz, and in the second - about 160 MHz. Thanks to the use of resistors, the operation modes are set.
Using the selection of resistance values, in the end, you can get voltage and current of 5 volts or 5 amperes, respectively. In this way, you can enhance the signal quality to no more than 4.7 dB at a frequency of close to 400 MHz.
The amplifier can operate from a 12 volt power source. This allows you to install it in cars. To ensure the correct operation of the device, it is enough to use a stabilized source, which is a diode bridge and an electrolyte of 1000 ΞΌF.
The amplifier can be connected directly to a power source, using a coaxial antenna cable. In this case, you must not forget about the line power reactor. Connecting the TV to the amplifier through a small capacitor.
The principle of operation of the device
The principle of operation can be given by the example of an antenna amplifier for digital television SWA 36.
The device has two broadband amplification stages. The signal from the antenna passes through a matching transformer, which is located in the antenna box, and a capacitor. Then the signal goes to the first transistor? included in the scheme with a common emitter (OE), where it amplifies and stabilizes the operating point due to the action of negative feedback (OOS) using a resistor. In the first stage, frequency correction is not available.
Now the linear signal passes through the capacitor to the transistor. At the second stage, frequency correction occurs. OOS is performed by voltage through resistors. To avoid large gain losses, one of the resistors is current-shunted by a capacitor with a relatively low capacitance (10 pF) to adjust the frequency response of the device. Next, an already amplified signal is sent to a television receiver.
How to choose an amplifier?
The quality of the device depends on the correct choice of antenna amplifier for digital television . After all, an improperly selected device will not bring the expected result.
So, in order to choose a suitable amplifier, you need to consider the following nuances.
- Type of antenna and model of device for amplification. For example, for a trellis antenna, amplifiers like SWA are suitable. It is important to remember that it is permissible to put a broadband amplifier on a narrow-band receiver. But not the other way around.
- The magnitude of the output signal. The best option is a minimum of 100 dBmkV.
- Working frequency range. These frequencies should be received not only by the antenna, but also by the television receiver. The amplifier must be set to amplify these signals. If either the television receiver or the antenna cannot receive these frequencies, then there will be no sense from a digital antenna amplifier either.
- The choice also depends on the type of terrain and signal quality. If a reliable signal is observed, then a wide-range signal is quite suitable. But the optimal is a device that works in a certain range.
- Gain. The amplifier is selected depending on the distance between the TV and the nearest station that emits the signal. The coefficient should be optimal. But, for example, with a distance of less than 10 km in the amplifier there is no sense, a suitable antenna is enough. Otherwise, the device must be selected according to the distance and not purchased with a gain greater than necessary.
- Current consumption. Experts recommend devices designed for 30-60 A.
- Noise figure. The lower the indicator, the higher the image level. Recommended value - no more than 3 dB.
DIY amplifier
You can make an antenna amplifier with your own hands. To do this, you will need:
- two cans, for example, from beer;
- a pair of screws;
- adhesive tape or electrical tape;
- wooden stick (you can replace it with an old trempel);
- power cable, length is calculated based on needs;
- plug
Production will take 10-15 minutes. The assembly of the device is as follows:
- Tin cans and a stick are connected to each other at a distance of 7-7.5 cm. An electrical tape is used to connect. If there are rings on the banks, then you can fix the power cable on them.
- Screws are screwed into banks. The ends of the cable must first be stripped. This can be done with a stationery knife. Now the ends can be fixed with screws.
- To make the device more stable, the stick is connected to the wire using electrical tape.
- Banks should be covered with a plastic flask. To do this, it is enough to remove the neck and bottom from the bottle.
- Now, in the middle of the container, make a hole through which you need to stretch the cable.
- When the device is assembled, pour boiling water on the bottle. It will change its shape and give tightness to the hole.
- Now you can connect the device and configure the resulting device.
As you can see, making an antenna amplifier with your own hands is a simple matter.
TV connection
Connect the antenna amplifier as follows:
- Install the amplifier as close to the TV as possible. This is true for branded devices and made by hand. An exception would be room amplifiers with short cables.
- Be sure to read the instructions before connecting. Often, the nuances necessary for quality work are indicated there.
- If, after connecting the device, the picture quality leaves much to be desired, then perhaps the problem is in the integrity of the antenna or in the frequency difference.
- Connection should occur only with de-energized devices.
You can connect the device using the coaxial wire of a conventional antenna. But for this, a special choke must be located on the power line. If the amplifier is powerful, then for high-quality operation it is connected through a capacitor element with a low capacity. Adjusting the device is easy. It is enough to transfer the resistor element to the middle and adjust until the picture is of the highest quality.
Summary
There are situations when it is necessary to amplify a television signal. There is a special device for this - an antenna amplifier for the TV. Although this is a simple device, you also need to choose it correctly. But the connection and configuration are quite simple. Such a device can be made from improvised materials, spending a minimum of time on this.