Active antennas differ from passive ones by the presence inside the amplifier, which requires adapter power supply of 9 or 12 V. Other voltage ratings are possible. The first amplifying cascade is tried to be positioned closer to the reception point, this dramatically increases the sensitivity. The loss in the feeder( 75 ohm cable) does not affect the quality here. A special element base of low-noise transistors and microcircuits is chosen for the amplifier, but there is no need to make it today. An antenna for a television with an amplifier is not so expensive to create it yourself.
Remember, the final gain of the active antenna consists of two parts:
- The gain of the amplifier.
- The gain achieved by forming the main lobe of the antenna pattern.
The first item is clear, but it’s worth talking about the second one in more detail. First, this component can be zero if the antenna is omnidirectional. They are rare, but equipped with an amplifier. What are the pros and cons.
- We are receiving from all sides, do not bother with aiming the antenna for the TV.However, we accept interference in full, the excess is also amplified and goes to the screen. In digital television, this factor loses its value - the package structure is set a priori. The new version of digital broadcasting focuses on tracking and correcting errors. However, a strong interference prevents reception. Just instead of snow on the screen will appear colored squares.
- We accept several TV towers at the same time, and also reflected rays, which is why the image is split. A similar sign is present when over-amplifying a signal.
- A directional antenna has a high gain, eliminates unnecessary interference, the design is more difficult to direct to the target. If the direction of arrival of the beam changes, the broadcast will not be caught.
Antenna takes better from one or two directions. This is ensured by the design features. An example of an antenna with two lobes - a framework. The main thing is to arrange perpendicular to the source of the broadcast, no matter which side. An example of a unidirectional antenna is called a wave channel and a log-periodic - a long horizontal pin studded with transverse crossbars.
Now let's talk about the form. The directivity pattern is the dependence of the signal reception level on the azimuth. Looks like an inverted parabola. It turns out such a high and narrow pulse in the region of zero azimuth. On either side of it, pulses of different shapes and widths, side lobes, diverge; they usually do not participate in useful signal reception. The best is a parabolic antenna( dish).The ratio between the height of the main lobe and the first side is expressed in relative values of dB.The parameter is called the level of the first side lobe. The higher the negative, the better.
The width of the main lobe of the radiation pattern is measured in degrees at the level of 0.707 maximum, if field strength is measured. Moreover, the area of the figure is equal to that even circle, which is a characteristic of an omnidirectional antenna. This is derived from the law of conservation of energy. The higher the lobe( and the gain), the narrower it is, and the harder it is to catch the signal. Recall a satellite dish with 38 dB.How difficult it is to catch a point in the sky. For this purpose, special instruments were invented, estimating the signal level from each spacecraft.
With an omnidirectional antenna is simpler, and the wave channel is something average. The design should be directed in the direction of reception. Which antenna is better, with a narrow or wide main lobe? If the reception point is far away, a high gain directional antenna is needed. It is necessary to choose the active, it increases the chances of catching the signal. A television antenna with an amplifier will allow you to catch weak broadcasts over hundreds of kilometers.
There are stories about mercury antennas. This is nonsense, or the material is not mercury. After all, microwave radiation is only on the surface. It makes no sense to pour liquid metal into thick flasks and make an accessory. In addition, mercury vapor is poisonous, there is an opportunity to really get poisoned.
Finally, it is permissible to buy an amplifier for a television antenna separately, but it is better to take everything together. However, in the first case, we get the opportunity to design the desired device with our own hands, which you additionally read about on our website. It is more difficult to assemble the amplifier yourself, it will also have to be configured.
Manufacturers of antennas for TV with amplifier
Active antennas are produced by many companies. From the Russian at the hearing Delta. This is another round of Russian production, its quality should be trusted. We have already written on the portal how to choose an antenna for a TV, we recall that it should be aimed at our tower:
- For digital broadcasting, you need a UHF antenna with reception above 470 MHz;
- For radio, there must be an FM or VHF mark( less often HF or HF);
- All-wave antennas are more complicated, the room antennas have a pair of vibrator mustaches and a frame, and the street ones will also be surprised with an unusual shape.
Here are some examples:
- All-Wave Active Antenna The Delta K331A has a different gain over the ranges. For HF - 6 dB, for VHF - 14-15 dB, for the decimeter range - 22-25 dB.The best reception is on digital broadcasting, commercial and regional channels. Separate amplifiers were used to cover such a large range for MF and UHF.This will get the maximum quality. The overall gain depends on the directional properties of the antenna over ranges. On meter waves below. Please note that in order to receive the radio, the antennas will have to be tilted to the side, but due to different polarization, the television broadcast will disappear. By default, the antenna for the TV does not accept the radio signal. Of course, the device is designed to use a standard cable with a characteristic impedance of 75 Ohms.
- Active Antenna The Delta K331A.03 is not named active in the catalog. Although its capabilities are clearly higher than the previous one. This antenna is log periodic and costs 1000 rubles. The previous model also belongs to this class, but the configuration of the vibrators resembles a wave channel. In Delta K331A.03 it is in the form of triangles arranged in a specific order. For the range of MV added telescopic "antennae."Both varieties are indoor antennas. The advantage is that the antennae are oriented independently of the vibrators, which means that it is possible to receive broadcasting from two directions, or from one tower. Vibrators of the log-periodic antenna are regulated on a corner of a place( to look up or down).This is done to provide reception in difficult urban environments where the signal comes from any direction.
- The external antenna H3311A is made according to a log-periodic scheme, but the antennae are tightly fixed for the MW range. On the mast, the device will be swinging with the wind with might and main, and broadcasting failures are unacceptable. H3311A - a combined antenna of two, a log-periodic and symmetrical vibrator. There is a US on HF and VHF, and a pair of log-periodic antennas for UHF, going on two parallel crossbars.
As a result,
Manufacturers of television antennas are trying with might and main. Add broadcasting reception, but soon everything will switch to multiplex. Choose antennas without receiving the SCM today is no longer fashionable. However, broadcasting in the figure is promised in the HF and HF bands.
Antenna amplifier manufacturers are the same. Lying on the shelves and Delta. There may be a situation that the signal MW does not have to be strengthened, as it relates to local broadcasting, and the UHF comes from far away. In this case, a broadband device is not required, but stock up on a pair of tees to create a junction.
We hope we helped determine the choice of antenna with an amplifier for the TV.