What is a passive and active antenna. Active antenna. Active television antenna

Passive and active external antenna

At a great distance from the television center, the collective antenna produces 3–4 channels, so to receive other channels, an external antenna is required that is suitable in terms of gain and received frequency band. It must be installed correctly to ensure the best signal reception conditions: it should not be located behind reinforced concrete barriers, but should be directed towards the television tower.

An external antenna can be either active or passive.

They come in a variety of shapes. Some are similar to collective ones and are its distant descendants, others are decimeter antennas in the form of loop vibrators or lines with connected dipoles of various lengths, to which, if necessary, meter range antennas are attached, and there are multi-story flat ones. Most antennas have a design that combines different kinds antennas

With the required transmitter power, the signal received by the passive antenna has a gain (the difference between the output signal level and the sensitivity of the TV) sufficient to obtain good image quality. If necessary, you can buy a signal amplifier for an external passive antenna.

An active outdoor antenna has a built-in amplifier for meter and decimeter waves, which is powered from the network adapter via a coaxial cable through a special device called a separator.

When choosing an antenna, you should take into account the dimensions, as well as the strength of the structure, since it may simply not withstand strong winds and snow. You should also pay attention to the labor intensity of the upcoming installation.

When purchasing an antenna, you should pay attention to the gain (measured in dB). An active room must be able to adjust the signal gain.

You should also pay attention to the antenna radiation pattern, which is measured as twice the angle between the directions corresponding to the maximum of the received signal and its attenuation by half. The smaller it is, the clearer the signal, but the more difficult it is to align the antenna with the TV tower.

Important has an APR (front-to-back ratio), which is measured in dB and represents the difference between the voltages received by the antenna from opposite sides. PZO reflects the degree of attenuation of extraneous signals. For example, when using antennas with PZO in the city, dB leads to the image being split into two.

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Surely everyone who has had to choose one or another antenna - be it television or radio - has come across such concepts as active and passive antenna. And many were at a dead end: how do they differ from each other and which, in fact, is better to choose?..

A feature of any passive antenna is that it picks up and receives a signal solely due to its geometry (shape). Accordingly, the larger the area of ​​such an antenna, the more reliable the signal will be.

The advantages of such an antenna can be considered:

• The absence of its own interference and interference due to the fact that in such an antenna, in fact, there is nothing to be aimed at. After all, its design does not contain any elements that could generate electromagnetic radiation.
• Exceptional ease of installation and operation. All that is required is to correctly orient the passive antenna on the terrain.
• You can even make a passive antenna yourself from scrap materials. As a rule, the entire structure of such an antenna is a metal frame with a transmitting cable or wire.
• A passive antenna does not require a separate power source.
• Finally, it is worth noting the low cost of a passive type antenna.

However, a passive antenna also has disadvantages:

1. It is susceptible to various types of interference, and the signal quality greatly depends on its location;
2. When installing a passive antenna, you have to carefully select a location and carry out careful orientation, especially if the installation takes place in an area of ​​poor reception.
3. Typically, a passive type antenna is installed at a fairly high altitude - up to 10 meters, which requires the installation of a special mast, additional reinforcements for it, etc.
4. Passive antennas must provide a sufficiently large reception area, which makes them bulky and inconvenient, for example, indoors.
5. The quality of the signal can be influenced by a huge number of factors: buildings, trees and terrain, as well as weather conditions.

Thus, it is recommended to install a passive antenna only where there is a fairly strong signal area and there is no need for additional amplification. Passive antennas come in both indoor and outdoor types. As a rule, it is installed in apartments located within the city, where the signal level is usually quite high. However, in suburban areas, on highways, etc. Active antennas are usually used.

A feature of the active type antenna is that the captured signal passes through special converting devices and only then directly to the receiving equipment. All kinds of amplifiers, noise suppressors, decoders, etc. can act as converting devices.

Such devices can be mounted either directly on the antenna itself or outside it. They are usually fed through household electrical network, but in some cases an autonomous power source in the form of rechargeable batteries or batteries can be organized.

Advantages of active antennas:

• They can be made in almost any size and shape.
• Active antennas can be installed almost anywhere - indoors or outdoors. The quality of work is little influenced by both the terrain and interference from trees, buildings, etc.
• Even a low signal level is not a hindrance for an active antenna: it is amplified by additional equipment.
• Many active antennas have adjustable gain and noise reduction levels.
• Interference that may be present when using an active antenna is also removed by special noise reduction devices.

At the same time, the disadvantages of active antennas can be considered:

1. Their relative high cost.
2. Technical complexity: after all, an active antenna uses a large amount of electronic equipment.
3. For correct operation of the active antenna, a constant power source is required.
4. In some cases, the cause of electromagnetic interference may be the antenna's own equipment. However, they are also eliminated with special “noise suppressors”.
5. Sometimes an active antenna is quite difficult to install and configure.
6. Due to the large amount of electronics, an active antenna has a lower degree of reliability compared to a passive one, in which, strictly speaking, there is practically nothing to break.

The main differences between active and passive antennas

The main difference between active and passive antennas can be considered presence or absence of additional electronic equipment, which amplifies the signal and suppresses noise.

As a result, active and passive antennas differ in the installation method, requirements for the presence of a power source, as well as the qualifications of the technician who installs the antenna. If almost any person can install a passive one, then in most cases only a qualified specialist can be involved in the correct installation, configuration and debugging of an active type antenna.

What are active and passive antennas used for and how do they differ?

Thanks to the dynamic development of television broadcasting in the modern world, there is probably no person who has not encountered antennas. In order to watch their favorite TV programs in the best quality, the user needs to connect an antenna to their receiving equipment. And here the question arises: Which antenna to choose, active or passive? In this article we will consider in as much detail as possible the features of each antenna, as well as their scope of application. But first of all, it is necessary to give a detailed definition of the term “antenna” itself and briefly describe the history of its creation.

A special device whose main task is to receive or emit radio waves. It converts electrical current fluctuations into radio waves or vice versa. As can be seen from the definition, antennas can operate for reception, transmission, or reception-transmission. The simplest antenna operation diagram looks like this: a television or radio device produces a signal, which is amplified and transmitted to the transmitting antenna. The antenna, in turn, distributes this signal in the form of radio waves. During the propagation process, the waves reach receiving antennas, which record them and transmit them for processing with subsequent output to end devices in the format of the original signal. Each stage of antenna operation may be accompanied by certain interference arising from other radiation sources or terrain features.

The creator of the antennas was a famous German physicist. It was he who, in 1888, made the first such device to confirm the presence of electromagnetic waves. Of course, since that time, antennas have changed significantly both externally and functionally. Today we will only touch on the classification according to the level of antenna activity, although there are quite a large number of different types and types of antennas.

A passive antenna receives all signals only due to the features of its shape. It does not contain any additional amplification devices or other electrical equipment. Based on this, we can conclude that the reception strength directly depends on the area of ​​the device. has the following advantages:

• does not interfere, since it does not contain any devices capable of producing an electromagnetic field;
• cheapness;
• easy to install and subsequent use, the only thing that is necessary is to make the correct orientation on the ground;
• does not require a special power source;
• minimal probability of failure (by and large there is nothing to break);
• If desired, the PA can be assembled independently, since the design is extremely simple and includes only a few elements (frame and wire).

If you are already inspired and started making a passive antenna, don’t rush. It also has a number of disadvantages:

• dependence of the level and quality of the received signal on location;
• exposure to various types of interference (climatic conditions, terrain, nearby objects, electromagnetic radiation, etc.);
• the need to create a large canvas for good reception.

Passive antenna: conclusions

It should be remembered that passive antenna can be installed both at home (indoors) and outdoors. Naturally, when choosing an antenna, you should immediately take into account the installation location.

To summarize, we can say that a passive antenna justifies its installation in an area with a good signal, where additional gain is not required. The most common passive antenna is used in city apartments.

Active antenna

In the design of an active antenna There must be an additional device that amplifies the received signal and supplies it to the receiver. These can be various kinds of decoders, suppressors, amplifiers, etc. This device may already be integrated into the antenna or mounted on its surface. For its operation, a standard 220V power supply is required, obtained either from an outlet or from a battery.

Active antenna boasts the following advantages:

• wide selection of different shapes and sizes;
• installation in almost any territory, since terrain features (and weather) do not significantly affect the operation of the active antenna;
• signal amplification of any power and compensation for emerging interference and noise;
• ability to catch a wide range of signals;
• adjusting reception settings.

It would seem that an active antenna is the best option for a receiving device. We don’t argue, she really was far ahead of her “passive” sister. But along with the undeniable advantages there are also several disadvantages:

• high cost; in this case, you should not chase cheap options, otherwise you risk getting a model with a low-quality amplifier, which makes the purchase absolutely useless;
• complexity of execution (it’s unlikely to be possible to fix it yourself);
• the need for a constant power source;
• an active antenna can create interference for itself (in fairness, it is worth noting that it also suppresses them itself);
• for high-quality installation you need to hire a qualified specialist, who, unfortunately, does not work for free;
• the probability of failure is higher than that of a passive antenna.

Active antenna: conclusions

Active antenna - the right solution for areas with weak signals, such as rural or forested areas.

The quality of playback of radio broadcasts by a car radio is largely determined by the correct selection and installation of the receiving antenna.

General information

Receiving antenna- a device that receives the energy of the electromagnetic field of radio waves and converts it into an electrical signal, which is then amplified by a radio receiver.

Currently, they are mainly used in cars active internal and passive external antennas.

Active antenna operates together with an amplifier included in its design, which compensates for signal attenuation due to the small size of the antenna. The amplifier requires power to operate.

Basic dignity active antennas - small in size and easy to install. Antennas of this type are installed inside the cabin, so they are protected from atmospheric and mechanical influences. Their flaws- lower sensitivity compared to passive antennas, as a result of which, along with the amplification of the radio signal, other radio noise increases, deteriorating the sound quality.

Passive antenna Connects directly to the radio and does not require electrical power.

Advantages Passive antennas are highly sensitive and simple in design. TO shortcomings This may include lack of protection from external influences, large dimensions, and, for retractable (telescopic) antennas, low reliability.

When making a choice in favor of an active or passive antenna, it is necessary to take into account the conditions of their operation in a particular area (signal level, reflections, interference), as well as the range in which it is primarily intended to operate, and the characteristics of the propagation of radio waves in it.

Features of radio reception in various bands

VHF band (FM). The signal strength of ultra-short wave (VHF) transmitters is low, and reception is only possible in the line of sight. Taking into account the height of the transmitting antennas, this distance rarely exceeds 40-50 km from the transmitter, and signal repeaters are not used in local VHF radio broadcasting. The zone of reliable reception, free from noise and interference, is noticeably smaller and amounts to 15-20 km. Significant changes in the level and 1 Signal interference due to reflections and the shielding effect of buildings (“dead zones”) can cause poor reception in urban environments. The terrain has a similar effect - in the lowlands the signal level is noticeably lower than in the hills. This range is more often used by residents of large cities, so recently more and more “city” radios have appeared that have only the VHF range.

Ranges LW, MW, HF. Transmitters in the long-wave (LW), medium-wave (MV) and short-wave (HF) ranges have high power, and the reliable reception zone is hundreds and even thousands of kilometers. Therefore, these ranges become the only ones available for long-distance radio broadcasting. Reception of local radio stations on medium waves during the daytime is always stable. Reception of long-distance radio stations on MF and HF improves noticeably soon after sunset. However, due to the technical features of amplitude modulation, the signal quality is noticeably lower than on the VHF band. The influence of interference, especially noticeable in industrial centers, also plays a role here.

Types of antennas

Telescopic with automatic drive(external). The automatic drive allows you to extend the antenna without leaving the car. Some models of such antennas allow you to adjust the length of the telescopic element and the angle of inclination to achieve optimal reception quality.

Telescopic (external). It differs from automatic in the absence of an electric drive.

Pin, fixed length(external). It has various designs: pin with a coil spring at the base; twisted spiral in a casing; ordinary pin.

In-cabin. They differ in operating ranges, gain, size and shape of the antenna housing and its receiving elements, as well as in the installation method. Some antenna models, thanks to the built-in converter, allow you to receive VHF radio stations on receivers operating in the FM range.

Antenna types

Passive and active antennas are divided into the following types:

• symmetrical vibrator,
• rolled up (shortened) symmetrical vibrator,
• asymmetrical vibrator,
• helix antenna
.

Symmetrical vibrator(Fig. 1, a) and symmetrical coiled vibrator(Fig. 1, b). Majority in-cabin active antennas belong to these types. For maximum efficiency of a symmetrical vibrator, its electrical length must be half the wavelength, hence its other name - half-wave. However, due to the fact that the wavelength in the frequency range 88-108 MHz and 66-74 MHz, allocated for VHF radio broadcasting, is 3-4 m, the antenna dimensions will be 1.5-2 m, respectively. Therefore, in a car, instead of a half-wave vibrator, a rolled-up symmetrical vibrator is used. Almost all types of car antennas are shortened.

Asymmetrical vibrator(Fig. 1, c) is obtained from a symmetrical one if one of its halves is replaced with grounding, the role of which is played by the car body. Antennas of this type include pin and telescopic, which are currently most widespread. For greater efficiency, the electrical length of these antennas should be a quarter wave or 75-80 cm for the 88-108 MHz range and 100-110 cm for the 66-74 MHz range. An arbitrary change in these dimensions worsens the matching of the antenna with the receiver and reduces its efficiency. Quarter-wave vibrators are too long, and they are not very convenient to operate, so shortened vibrators in the form of a pin 30-50 cm long are more often used. For better coordination with the receiver, the design of such an antenna may include a matching device - a coil. The remaining differences are decorative.

Helix antenna(Fig. 1,d) - a type of shortened asymmetrical vibrator. Structurally, it is a flexible rod made of dielectric material, onto which several dozen turns of wire are wound with a fairly large pitch. The top of the structure is also covered with a layer of dielectric. The only advantage of this antenna over others is flexibility.

Antenna installation locations

Correct installation of the antenna will allow you to fully realize its capabilities. According to the installation location, all antennas can be divided into interior and exterior.

In-cabin antenna It works most effectively if it is placed in or near a window opening. Her receiving elements should be no closer than 2-3 cm from the body. Typically the windshield or rear parcel shelf is used for installation. It should be remembered that the antenna elements on the windshield should not impair visibility in the upper and middle parts or in one of the upper corners.

Many motorists are convinced that the best place for outdoor antenna- this is the roof. However, it is not. Indeed, the efficiency of an antenna is determined by its height, but the height above conductive surface. In our case, the entire car is a conductive surface, so it makes no difference whether the antenna is installed on the roof or on the fender. For example, a bumper can be considered a bad place, since most of the antenna is in close proximity to the electrically conductive body, which reduces its effectiveness.

Depending on the method of mounting the antenna, there are:

• mortise - installed in a through hole pre-drilled in the body;
• on a magnetic basis (various diameters);
• pins, attached to the drain;
• stick-on
.

Antenna selection. Apart from design features, passive antennas are in most cases preferable to active ones, since they provide a better signal-to-noise ratio and, as a result, cleaner reception. However, due to their impressive dimensions, they are not always convenient to use.

Some antenna manufacturers specify the gain and noise level for their products. When comparing antennas based on these indicators, you need to remember The main thing: Higher reception quality will be ensured by an antenna with a higher gain and a lower amplifier noise level.

Universal all-wave antennas optimized primarily for the VHF band. When traveling within the city or at a short distance from it (10-20 km), you can use any type of antenna - the reception quality will be approximately the same. To receive radio transmissions at a distance of 30-70 km, “full-size” passive antennas are preferable, providing better reception of weak signals by eliminating the noise of the antenna amplifier and the minimum level of interference outside the city. The DV, MF and HF bands are mainly “in demand” among those who make long trips, while a passive antenna will also provide better reception.

Reception quality of weak signals active antenna largely depends on the noise level of its amplifier and the receiving path of the car radio tuner. At a short distance from the transmitting station, a strong signal causes overload of the antenna amplifier and receiver, which can lead to noticeable distortion. Therefore, some active antenna designs have a manual “city-highway” gain level switch, which allows you to limit the gain of powerful signals and avoid overload.

When choosing an antenna, you should pay attention to cable: it must be shielded. Many active antennas, instead of a separate shielded cable (to save money), are equipped with a regular one, through which both the signal received by the receiver and the supply voltage are supplied. This solution is not always successful. This “antenna” sometimes works better with the power turned off.

The length of the antenna's own cable is usually short and sufficient only for windshield-mounted antennas. In all other installation options you have to use extension cables and adapters, commercially available. When choosing them, the main attention should be paid to the clear fixation of the connectors and the quality of the cable. It is not advisable to lengthen and splice the antenna cable by twisting or soldering without special skills, since an improperly made connection can cause additional interference during radio signal reception. In addition, it should be borne in mind that excessive cable length (more than 4 m) can also lead to poor reception quality due to strong capacitive losses.

Antenna installation. When installing a flush-mounted antenna, you may have to drill a hole in the vehicle body. To prevent the occurrence of pockets of corrosion, it is advisable to treat the edges of the hole with an anti-corrosion compound, for example “Movil” or similar.

Installation diameter The longer the pin itself, the more mortise antennas there should be. Long whip antennas have a large mass and therefore are equipped with additional stands that ensure the reliability and stability of the antenna when the vehicle is moving in difficult conditions.

Best antenna efficiency for the VHF range can be achieved by installing it in the vertical plane, and for the SW range - in the horizontal plane. For external whip antennas operating simultaneously in the VHF and CB bands, a compromise solution is usually used - installing the antenna at an angle.

When installing active interior antennas The attached instructions must be strictly followed. Before gluing the receiving elements - “whiskers”, you need to thoroughly degrease the glass at the place of the sticker, and separate the protective film from the adhesive layer immediately before gluing. In order for the reception efficiency on the VHF (FM), MW and LW bands to be maximum (taking into account the peculiarities of wave polarization in these ranges), one of the elements (“whiskers”) can be directed horizontally, and the second vertically.

You should try to lay the antenna cable so that there are no kinks. If the cable is passed through a hole in the bulkhead, it must be protected with a rubber grommet.

Table: Consumer characteristics of the main types of antennas

Antenna type	Design features and installation method	Advantages	Flaws
Active	“Tablet” - a small round antenna body resembles a tablet. The antenna body and its receiving elements (“whiskers”) are glued to the windshield.	Compactness. Reliability.	It is difficult to dismantle glued antenna elements.
	A small box with two short receiving elements in the form of strips (left and right), with tracks of conductive material applied to them. Installed under the central mirror.	Compactness. Reliability.	Low sensitivity.
	“Book” - the antenna resembles a book, since its receiving element (in the form of a plate) is connected to the body through an axis and can be manually lowered and raised, like the cover of a book. The housing is rigidly mounted on the rear parcel shelf of the car.	Good sensitivity. Low cost.	Takes up space on the shelf. Need a long cable.
Passive	Long pin. Mounts on the rear or front fender and other body elements.	High sensitivity.	Large dimensions. Difficult to install.
	Long pin. Attaches to the drain.	High sensitivity. Easy to install.	Large dimensions. Risk of damage to the cable by the door.
	Helix antenna (flexible). Mounts on the rear or front fender and other body elements.	Flexibility. Small dimensions.	Low sensitivity.
	Telescopic antenna. Installed on the rear or front fender.	High sensitivity.	Low joint strength. Must be pulled out manually.
	Automatic (semi-automatic). Installed on the rear or front fender.	Compact when folded. High sensitivity.	Difficult to install. Low reliability, requires additional maintenance, especially in cold weather.

Today, one of the sources of information is television. Of course, it is not as popular as the Internet, but many people use it. Every home has a TV, not always just one. With it, everyone can watch news, exciting movies or exciting TV shows. To view them you need to get a good signal. An active television antenna is suitable for this.

Kinds

They are divided into three types:

1. Radio antenna. Designed for car receivers only.
2. Television. Used to view analogue or digital television.
3. Combined. Such models receive all types of signals, from radios to navigators.

There is also another type of active antennas - satellite. This type is not very common among car enthusiasts due to the difficult setup and high cost of the equipment.

In addition, active automotive elements are divided according to their installation location. It can be both external and internal. The first type is installed on the roof, trunk or side doors. The main advantage is a high-quality signal. However, there are also disadvantages: they have big sizes, low service life, as they are subject to mechanical and climatic influences. They are also difficult to install. To do this, it is necessary to make additional holes in the car body, which spoils its appearance. Internal models are installed on the rear or windshield. They can have different designs and shapes. The antennas are characterized by small overall dimensions. They are not exposed to external mechanical influences, as well as climatic conditions. Therefore, the car retains its pleasant appearance for a long time.

Installation locations

An active antenna can be outdoor or indoor. The first type is installed on the roof of houses so that the quality of the television picture is at the highest level. An active indoor antenna is used in a specific range, that is, the device will not work the same in all places. Most users note this drawback: the part picks up the signal unevenly, that is, the TV will not show outside the other room. Before installing it, you need to make sure that the apartment is located in an area where there is a good TV signal.

What is the difference between passive and active?

So, all indoor antennas are divided into two types: passive and active. Representatives of the first species pick up the signal using their design. Their main advantage is that they do not need to be connected to the mains, nor do they need to be equipped with additional amplification equipment. Many users note that when using passive elements there is no signal interference.

But such models cannot always cope with their task. In this case, an indoor active antenna is installed. Better signal reception is achieved with the help of an additional device. This device can be installed in the element body or come separately. In this case, the active antenna is powered using the electrical network.

Like every device, the active part has its drawbacks. One of the main negative aspects is the poor quality signal. It occurs due to a low-quality amplifier. Such cheap Chinese models are widespread on the market. The signal can also be distorted from a very sensitive amplifier. Distortion occurs in the area of ​​reliable reception, where the use of an additional amplifier is not required.

Range of action

An active antenna can perceive both special bands and capture any types of signals. All-wave devices are widely used among consumers, as they are convenient and capable of picking up a fairly large number of channels.

When using an indoor antenna for digital television, it is necessary to purchase those models that pick up special bands. In this case, each person will save significantly.

When purchasing active TV antennas, you need to pay attention to the following criteria:

• Before choosing a model, you should evaluate the signal level in the apartment. You should not buy a device just because of its beautiful appearance.
• If the windows in the apartment overlook the television center, then you can install the antenna on the glass. In this case, the signal will be much better. Although these models are mounted on glass, they perform the same work as external devices.
• If the distance to the repeater is more than ten kilometers, then using active antennas is not recommended. The signal will be weak and the picture and sound will be noisy. In this case, it is better to purchase an external structure.

Active car antenna

Standard built-in car antennas have low sensitivity.

It decreases when exposed to mechanical damage. Such processes can disable its antenna. At first, every driver does not pay attention to the antenna, as he listens to music that is recorded on different media. However, she is also starting to get bored. Therefore, there is a need to purchase a new part.

An active car antenna is used not only for a radio.

Many drivers use it to watch movies or TV shows. In this case, you should also purchase a special TV antenna for the car.

Peculiarities

This type of parts is used for those vehicles that make long trips. In large cities the signal is good. It will get worse the further you get from the radio tower. Even if the distance is small, the signal may be distorted due to uneven terrain, that is, mountains, hills, etc. Therefore, a device such as a TV active antenna will definitely come in handy.

When a vehicle moves over uneven terrain, the radio receiver picks up a signal not from the radio tower, but from the distorted terrain. He's not strong enough. To capture it, an additional amplifier is required, which is already built into the active part.

To counteract interference both in the city and outside it, such antennas can operate in two modes:

• for urban areas;
• for country roads.

In the first case, they can work without an amplifier, since its presence will interfere with the signal.

Connecting an active antenna

As mentioned earlier, for the mechanism to function, it must be connected to an electrical outlet. This is one of the disadvantages. So, first you need to decide on the connection location. Some car enthusiasts connect the device to the battery.

However, this is unjustified. In this case, the structure is constantly on. That is, when the car is idle, a certain amount of energy from the car battery will be consumed. Accordingly, it will take longer to recharge than usual.

How do you still make the connection? There is a special connector for the car radio for this. This is the best option since the antenna will function together with the receiver. In this case, the consumption of electric current will be moderate.

There is another option. The antenna is connected to the ignition switch. Voltage is supplied when the ignition key is turned. The device is turned off when the owner leaves his vehicle.

It is worth noting that installation methods and procedures may be indicated in the instructions. In order for the fastening to be reliable, it is necessary to check the structural details.

Manufacturers

After making the connection, you need to check the operation of the antenna. Both options are suitable for all types of devices. The most popular manufacturers of active antennas are Alpine, Supra, and Bosch. Thanks to its affordable price, any car enthusiast can purchase it. The cost of an active antenna ranges from three hundred to one and a half thousand rubles.

Purchasing this part is a rather troublesome process. The wrong model will not pick up the signal and the sound or picture quality will suffer. Therefore, the choice of this element should be taken responsibly.

So, we found out what an active television antenna is.