A homemade antenna made from an antenna cable is round. Homemade television antenna: for DVB and analog signal - theory, types, manufacturing

Humanity lives in the digital age. Television is switching to digital signal transmission. The peculiarity of digital broadcasting is that it is conducted in the decimeter range.

Transmitting stations have low power of the transmitted encoded signal. Therefore, to receive the signal and display the image on televisions that are remote from the station, a receiving digital antenna is required. If you don’t know how to make an antenna for a TV, then the answer is simple: you can assemble it with your own hands from scrap materials in literally one hour.

Types of receiving antennas

To reliably receive a signal from a television tower, there are many different television antennas. They differ in shape and range of receiving frequencies.

Antennas can be divided into several main types:

Currently, the vast majority of television signals are transmitted using digital coding. Broadcasting is carried out in the UHF range. The format of such transmission is called DVB - T2.

Theoretically, this signal can be received on some old universal antennas, which is what marketers took advantage of, calling them DVB - T. In order to distinguish the new narrow-profile decimeter antennas from the old classic ones, the number “2” was added at the end of the abbreviation.

Digital TV Basics

Television transmitters transmit a digital signal at a relatively short distances. The transmission range does not exceed sixty kilometers and is limited by the line of sight of the emitter from the television tower.

For these distances, a low-power signal is sufficient. But the design of signal-receiving antennas must meet certain requirements:

The digital signal has its own unique feature. You can either catch him or you can't. He has no middle position.

If a digital signal is one and a half decibels higher than noise, then its reception is always high-quality. The signal may disappear if the cable is damaged or the phase is distorted in the transmitted section. In this case, even if the signal is strong, the image breaks up into small squares.

In order to catch UHF broadcasts, an appropriate antenna is required. According to theory, any antenna will do, but in practice there are nuances.

There are several types of antennas for DMV reception offered by manufacturers:

It’s not at all difficult to make your own antenna for digital TV.

Assembling antennas at home

The shape of the bends should be as smooth as possible. Basic phase distortion appear due to dips and sudden emissions.

Homemade digital antennas turn out to be frequency independent. They don't have the most best characteristics, but are easy to assemble and require little time and money for construction. Suitable for working in noise-free air at a short distance to the repeater.

Reception of signal to beer cans

You can construct a simple all-wave antenna from ordinary beer cans. Of course, it is inferior to industrial designs and is not always able to provide stable signal, but it serves its purpose well. This device receives at least fifteen channels as a minimum.

To assemble this structure, you will need:

After washing and drying the metal cans, DVB - T2, you can begin to assemble the antenna.

Carefully, so as not to deform, pierce the hole in upper parts both cans. A screwdriver is suitable for this procedure. With its help, self-tapping screws are screwed into the prepared holes.

Then take one end of the cable RK75 and at a distance of ten to twelve centimeters, using a knife, it is cleared from the upper shell. In this case, the copper braid should not be damaged. The braid is twisted into a pigtail. The aluminum screen is removed.

Then the polyethylene shell is cut off by six to seven centimeters and the central core is exposed.

The resulting pigtail and central core are screwed to the self-tapping screws. If you have a soldering iron and the skills to use it, then it is best to solder parts of the wire to the cans.

The cans are secured sequentially, using tape, along a plywood board or other base that is at hand. The distance between the banks should be seven and a half centimeters.

To complete the work, a plug is attached to the second end of the cable.

To do this, the end of the cable is stripped and the central core is passed through the hole in one of the plug halves. The cable braid is attached to the plug body. One half is screwed onto the other and as a result we get a plug , ready to go.

All that remains is to connect it to the antenna input of the TV and place the antenna in the right place where the quality of the received signal will be good.

If the created structure is placed outdoors in the open air, it is necessary to protect the device from moisture and dampness. For these purposes, you can use plastic bottles in which the bottom and necks are cut off. The metal parts of the antenna are located inside them.

The resulting model is easy to “customize” by rotating it in space and simply moving around the apartment, balcony or summer cottage.

Zigzag antenna Kharchenko

This zigzag broadband design was invented by engineer K.P. Kharchenko in 1961. For reception digital signal it fit perfectly and received widespread, well-deserved recognition. People call it the “eight” and the complete assembly looks like two diamonds, located one above the other.

When making a figure eight you will need:

• Copper wire with a diameter of 3-5 millimeters.
• Coaxial antenna cable 3-5 meters long and 75 Ohm resistance.
• Soldering iron with solder.
• Scotch tape or tape.
• Plug.
• Bolts for assembly.
• Base: sheet of plywood or plastic.

At the first stage, we assemble the antenna frame. We take a wire 109 centimeters long and bend it into a frame. The frame has the shape of two consecutive rhombuses with sides equal to thirteen and a half centimeters. One centimeter will remain. A loop is made from it that holds the wire together. The ends of the frame are soldered to each other and it thus turns into a closed circuit.

After that coaxial cable is cleared. The cable screen is rolled into a tight rod and soldered to the frame wire at the point where the diamonds meet. The central cable rod is also soldered in the central part of the frame. The core and braid should not touch each other.

The second end of the cable is connected to the plug. The plug at the soldering points is first wiped with alcohol and treated with sandpaper. The monocore is soldered to the central output of the plug, and the twisted braid is soldered to the side.

If the frame will be used outdoors, the future plywood base can be painted or varnished. Soldering points can be wrapped with tape or tape. But this is not the most the best option, as the adhesive tape may become unraveled over time. If you put plastic tubes of a suitable diameter on the wire before soldering, then at the end of the work the tubes are pulled over the soldered areas and reliably protect the frame. After which the frame is installed on the prepared base.

The digital antenna is assembled with your own hands and is ready for use.

If desired, you can assemble an antenna tuned to a specific wavelength. To do this, you need to calculate the length of the square. This is not difficult: the wavelength of the desired signal is divided by four. In the end it turns out desired value length of the diamond frame.

The simplest cable antenna

She needs one tv cable with a resistance of 75 Ohms. The required cable length is calculated based on the required digital broadcast frequency. Its value in megahertz is divided by 7500 and the resulting amount is rounded.

The resulting value is the required cable length.

After this, one end of the cable is cleared of external insulation and inserted into the antenna connector of the TV. A mark is made on the cable from two centimeters after the connector.

It is from this mark that the required cable length is measured. Use pliers to pinch off the excess part.

After this, you need to return to the mark on the cable. Only the insulated rod is left in this place, and the outer braid is removed. The cleaned part is bent at an angle of ninety degrees.

All is ready. The TV can be tuned with a new antenna.

Installation safety precautions

For reliable operation of such antennas, it is necessary to place them above the ground at a level of 7-10 meters. Therefore, during installation it is necessary to strictly observe safety regulations:

• Do not install the structure in heavy rain or heavy fog.
• It is not advisable to go upstairs alone, especially in icy, cold, or snowy conditions.
• If it is necessary to climb a shaky structure or high-altitude work is carried out in dangerous places, then a fixed mounting belt is required.

After correct installation homemade antennas They work no worse than factory ones with significant budget savings.

The era of digital signals has arrived. All broadcast television companies began to work in a new format. Analog TVs are reaching their end. They are still in working order and are found in almost every family.

In order for older models to successfully complete their service life, and for people to be able to use them when watching digital broadcasting, it is enough to connect the DVB-T set-top box to the TV receiver and pick up the TV wave signals with a special antenna.

Any home craftsman can not buy an antenna in a store, but make it with his own hands from available materials for watching digital TV programs at home or in the country. The two most accessible designs are described in this article.

A little theory

Operating principle of an antenna for digital packet television

Any television signal propagates in space from the emitters of the transmitting television tower to the TV antenna by an electromagnetic wave of a sinusoidal shape with a high frequency, measured in megahertz.

When an electromagnetic wave passes through the surface of the receiving beams of the antenna, a voltage V is induced in it. Each half-wave of a sinusoid forms a potential difference with its own sign.

Under the influence of an induced voltage applied to a closed receiving circuit of the input signal with resistance R, electricity. It is amplified and processed by the digital TV circuit and output to the screen and speakers as image and sound.

For analog models of TV receivers, an intermediate link works between the antenna and the TV - a DVB-T set-top box, which decodes digital information of an electromagnetic wave into a normal form.

Vertical and horizontal polarization of digital TV signal

In television broadcasting, state standards require electromagnetic waves to be emitted in only two planes:

1. horizontal.

In this way, transmitters send emitting signals.

And users simply need to rotate the receiving antenna in the desired plane to maximize the power potential.

Requirements for a digital packet television antenna

TV transmitters propagate their signal waves over short distances, limited by the line of sight from the top point of the TV tower emitter. Their range rarely exceeds 60 km.

For such distances, it is enough to provide a small power of the emitted TV signal. But, the strength of the electromagnetic wave at the end of the coverage area should form a normal voltage level at the receiving end.

A small potential difference, measured in fractions of a volt, is induced at the antenna. It creates currents with small amplitudes. This imposes high technical requirements on the installation and quality of manufacturing of all parts of digital reception devices.

The antenna design should be:

• manufactured carefully, with a good degree of accuracy, eliminating loss of electrical signal power;
• directed strictly along the axis of the electromagnetic wave coming from the transmitting center;
• oriented according to the type of polarization;
• protected from extraneous interference signals of the same frequency coming from any sources: generators, radio transmitters, electric motors and other similar devices.

How to find out the initial data for calculating an antenna

The main parameter influencing the quality of the received digital signal, as can be seen from the explanatory first figure, is the length of the electromagnetic wave of radiation. Under it, symmetrical arms of vibrators of various shapes are created, and the overall dimensions of the antenna are determined.

The wavelength λ in centimeters can be easily calculated using a simplified formula: λ=300/F. It is enough just to find the frequency of the received signal F in megahertz.

To do this, we will use a Google search and ask it for a list of regional TV communication points for our area.

As an example, a fragment of a data table for the Vitebsk region is shown with the transmitting center in Ushachi highlighted in red.

Its wave frequency is 626 megahertz, and its polarization type is horizontal. This data is quite sufficient.

We carry out the calculation: 300/626=0.48 m. This is the length of the electromagnetic wave for the antenna being created.

We divide it in half and get 24 cm - the desired half-wave length.

The tension reaches its maximum value in the middle of this section - 12 cm. It is also called amplitude. It is made to this size whip antenna. It is usually expressed by the formula λ/4, where λ is the electromagnetic wavelength.

The simplest TV antenna for digital television

It will require a piece of coaxial cable with a characteristic impedance of 75 Ohms and a plug for connecting the antenna. I managed to find a ready-made two-meter piece in the old stock.

I cut off the outer shell from the free end with a regular knife. I take the length with a small margin: when setting up it is always easier to bite off a small piece.

Then I remove the shielding layer from this section of the cable.

The work is done. All that remains is to insert the plug socket into the connector on the TV signal set-top box and direct the bare wire of the inner core across the incoming electromagnetic wave, taking into account horizontal polarization.

The antenna should be placed directly on the window sill or secured to the glass, for example, with a piece of tape, or tied to the blind mount. Reflected signals and interference can be shielded with a strip of foil located a short distance from the central core.

Such a design can be done in literally ten minutes and does not require any special material costs. It's worth trying. But, it is capable of working in an area of ​​reliable signal reception. My building is screened by a mountain and a multi-story building. The transmitting television tower is located at a distance of 25 km. Under these conditions, the digital electromagnetic wave is reflected many times and is poorly received. I had to look for another technical solution.

And for you on the topic of this design, I suggest you watch the video by the owner of Edokoff “How to make an antenna for digital TV”

Kharchenko antenna at 626 MHz

To receive analogue television signals of various wave frequencies, the design of a zigzag broadband antenna, which does not require complex manufacturing, worked well for me before.

I immediately remembered one of their effective varieties - the Kharchenko antenna. I decided to use its design for digital reception. I made the vibrators from a flat copper bar, but it’s quite possible to get by with round wire. This will make it easier to bend and straighten the ends.

How to determine the dimensions of a specific antenna

Online calculator

Let's use the all-knowing Google search. We write to command line: “Calculation of the Kharchenko antenna” and press Enter.

We choose any site you like and perform online calculations. I went into the first one that opened. This is what he calculated for me.

I presented all his data with a picture indicating the size of the Kharchenko antenna.

Manufacturing of antenna design parts

I took the information provided as a basis, but did not accurately maintain all the dimensions. I know from previous practice that the antenna works well in the broadband wavelength range. Therefore, the dimensions of the parts were simply slightly increased. The half-wave of each harmonic of the sine wave of the electromagnetic TV signal will fit into the arm of each vibrator and will be received by it.

Based on the selected data, I made blanks for the antenna.

Vibrator design features

The connection of the ends of the figure eight busbar is created in the center at the bending stage. I soldered them with a soldering iron.

I created it according to the “Moment” principle, made it with my own hands from old transformers, and has been working for two decades. I even soldered 2.5 square copper wire with it in thirty-degree frost. Works with transistors and microcircuits without burning them out.

In the near future I plan to describe its design in a separate article on the website for those who also want to make it themselves. Follow publications, subscribe to notifications.

Connecting the antenna cable to the vibrator

I simply soldered the copper core and braid to the metal of the figure eight from different sides in its center.

The cable was tied to a copper bar, bent into a loop in the shape of a semi-square vibrator. This method matches the resistance of the cable and antenna.

Screening grid design

In fact, the Kharchenko antenna often works normally without signal shielding, but I decided to show its manufacture. For the base I took a wooden block. I did not paint or varnish: the structure will be used indoors.

In the back side of the block I drilled holes for attaching the screen wires and inserted them, and then wedged them.

The result was a screen for the Kharchenko antenna. In principle, it can be made of a different design: cut from a piece of frontal armor of a tank or cut from food foil - it will work approximately the same.

On the back side of the bar I secured the vibrator structure with a cable.

The antenna is ready. All that remains is to install it on a window to work in vertical polarization.

When a television receiver is located at a great distance from the transmitting generator, the power of its signal gradually weakens. It can be increased with special electronic devices- amplifiers.

You just need to clearly see the difference between the signals received by the antenna, which can be:

1. simply weakened;
2. contain high-frequency interference that distorts the shape of the digital sinusoid into the shape of some kind of “doodleball”.

In both cases, the amplifier will fulfill its role and increase the power. Moreover, the TV will clearly perceive and display a weakened signal, but with an amplified signal, playback problems will arise.

The waves are designed to eliminate such interference:

• high-pressure filters;
• screens.

They must be measured with an oscilloscope, and the methods of using various designs must be analyzed individually in each specific case. The antenna is not to blame here.

Digital television is sweeping the country; many people are buying TVs that already support this format. And who has previous generation equipment, you can buy digital set-top box() and connect it to your old TV, which does not support . In general, a worthwhile format allows you to watch television in digital format. BUT many sellers, along with set-top boxes and TVs, “sell” so-called digital antennas, sometimes the price of an antenna reaches 3,000 rubles. Although guys, you can make an antenna for yourself with your own hands. digital television, and very cheap...

ADVICE! Guys, by the way, you can watch television without an antenna at all via the Internet, but for this you need another set-top box - read this really cool topic.

We continue the article...

To receive a digital signal, a so-called decimeter antenna is required. It can be made literally from antenna cable. However, it needs to be calculated correctly. If you do not want to read the entire article, you can find the desired item in the table of contents

What you need to make an antenna

1) We need a piece of antenna cable, about 30 cm long.

2) Antenna connectors, the so-called F - connector and male - female connector.

F - connector and male-female

3) Tools: a knife, wire cutters, a calculator and, of course, a tape measure (or a ruler).

Calculation

On home page We look for the tab - “CETV coverage map” and go to it.

“CETV coverage map” tab

A map of digital television coverage opened before us. We are looking for the nearest station for our city (I have Ulyanovsk, you are forgetting your city).

As you can see in my city, this is channel 56 - 754 MHz and channel 59 - 778 MHz.

Now we calculate the length of the antenna. I won’t go into complex technical formulas and terms; we don’t really need them. But to calculate the antenna, you need to divide 7500 by our frequencies.

THAT is: 7500/754=9.94 cm, this is for channel 56.

7500/778=9.64 cm, this is for channel 59.

Our antenna should be approximately 10 cm, and exactly - ((9.94 + 9.64)/2 = 9.79 cm)

For your city, you also need to display the average length for your stations, if you have several of them in the city. In the video below the article I calculated the antenna for Ulyanovsk and for Kazan.

Manufacturing

1) Take a piece of antenna wire and first attach an F-connector to the end. We simply strip the cable and screw on the connector so that the central wire is in the middle, and the screen (the wires and foil are in the mount), detailed (useful).

2) Set aside a couple of centimeters from our connector (this will be a kind of indent), then measure 10 cm and cut off the unnecessary cable.

3) Now from this 10 cm, we need to remove the plastic insulator and remove the “screen” (foil and small wires). There is no need to touch it further; we leave the cable in the insulator.

4) Our antenna is ready. You can try to connect.

Connection

You need to get a good reception point in your apartment, and it’s not always enough to just insert it into a TV or set-top box. I have such a place near the window, so I inserted an extension cord into the console and inserted the antenna into the extension cord. So far, I have not removed all this improvisedly, for an example of work (that’s why the cable weighs), and the antenna itself is inserted into it.

Well, as you can see, all channels are working normally, “first”, and “Russia”, and NTV, etc.

"First"

Thus, if you have 80 - 100 rubles, you can make an antenna for digital television (DVB-T2 standard) with your own hands, easily and simply.

Now video version

For those who do not show it - - MANDATORY! There's a solution to the problem!

That's all, I think my article is very useful and relevant. Read our construction site.

Digital signals are already known to everyone for a long time. All television organizations switched to new format. Analogue television devices have moved aside. But despite this, quite a few are in working condition and can last for more than one year. In order to outdated equipment completed the allotted operational life, while there was the possibility of viewing digital broadcasting, you will need to connect DVB-T to the TV receiver and catch the wave signals with a zigzag antenna.

For those who want to save their family budget and at the same time receive high-quality television broadcasting, you need to pay attention to the Kharchenko antenna for digital TV with your own hands.

This unique design has been known for a long time, but found itself relatively recently.

Operating principle of an antenna for digital television

After radio communications appeared, the relevance of using an antenna device increased. Since the 60s of the twentieth century, the then recognizable engineer Kharchenko flaunted a design of 2 rhombuses. This device allowed him to catch US airwaves.

This double square from thick copper wire. The squares are connected through open corners; this is where the cable from the TV is connected. To increase directivity, a grid made of material capable of conducting current is mounted at the rear.

The perimeter of the squares is equal to the wavelength to which the reception is tuned. The diameter of the wire should be about 12 mm for broadcasting from 1 to 5 TV channels. The design turns out to be far from compact, in the case of assembly for radio communications and meter-wave TV with up to 12 channels.

To make the device lighter, 3 wires of a smaller cross-section were used. Despite this, the size and weight remained impressive.

The antenna in question received its second wind when broadcasting appeared in the UHF range. Most people know rhombuses, triangles and other homemade figures in the form of antenna devices for receiving a signal of decimeter waves. Antennas of this type can be found on balconies and windows of both private houses and multi-storey buildings.

At the beginning of the 2000s, American professor Trevor Marshall came up with a proposal to use this design in Bluetooth and Wi-Fi networks.

The biquad antenna is also an antenna device of a Soviet engineer. This option is created according to the same principles as a regular biquadrat. A distinctive feature is that at the tops of the squares, instead of the corners, there are additional squares.

As for the sizes of these squares, they are identical to the usual ones. This avoids additional calculations. It is enough to use the standard biquadrat calculation.

Let us remind you that the wires in the place where they intersect require insulation from each other.

Required materials and tools

Kharchenko's DIY television antenna for DVB T2 is quite economical. In order to assemble the structure, you will need the following parts:

• Wire;
• Coaxial cable;
• Wooden slats.

As for tools: pliers, hammer, sharp knife. If you plan to attach the antenna device to a wall or other surface, you will most likely need a drill for mounting.

Antenna calculation

Before you start creating the design, you will need to calculate the Kharchenko antenna. This will allow you to assemble an effective device with maximum accuracy. The dimensions of the DVB T2 zigzag antenna play a significant role in increasing signal reception.

Since technology has stepped forward, there is now no need to leaf through reference books or look for formulas for calculating dimensions. And even more so, carry out complex mathematical calculations in order to correctly develop a sketch or future drawing.

After this you receive information: about the required length copper wire, its sides, diameter.

Assembly of Kharchenko antenna for digital TV

Step-by-step instructions that will allow you to quickly assemble a Kharchenko antenna for digital television with your own hands:

1. Determine the polarization and frequency of the wave. The device must be linear.
2. The biquad type zigzag antenna device is made of copper. All elements are located at the corners, with one of them touching. For horizontal type polarization, the figure eight must stand upright. If you do vertical polarization, the structure lies on its side.

1. The side of the square is calculated using a special formula - wavelength, which is divided by four.
2. Imagine the design, it should be oval in shape, and pulled across the center larger side. The sides do not touch, but are in close proximity to each other.
3. We connect the antenna cable to the approach points on both sides. It will be necessary to block one direction of the diagram; for this, a fetal screen made of copper is mounted; it will be located at a distance of 0.175 from the working wavelength. It should be placed on the cable braid.

As for the reflector, previously it was made of textolite boards that were coated with copper. Today, this component is made from metal plates. It is on this principle that the design for receiving digital television is made. Nothing complicated. Everything you need is at hand.

Antenna testing

The device has been created, it’s time to check the effectiveness of the work done. To test the reception quality of the wave channel, you need to connect the antenna to the receiver. Turn on the TV and receiver.

Open the main menu of the console, select automatic search channels. On average, this process will only take a few minutes. You can find channels manually, but to do this you will have to enter their frequency. To test Kharchenko’s design for a TV, it’s enough to simply evaluate the quality of the broadcast. If the channels show well, then the job was done correctly.

What to do if interference is visible? Rotate the TV antenna and see if the picture quality improves. Once the optimal location is determined, simply secure the device. Naturally, it should be directed towards the TV tower.

Note.

The modern market offers a huge range of antennas for reception terrestrial television. There are two main types of these products that allow you to receive meter and decimeter radio waves. They can also be divided according to the place of use into outdoor and indoor. Fundamentally, they are not much different. Here, first of all, the emphasis is on size and maintaining the necessary parameters under the influence of weather conditions. In this article we will discuss existing species of these products, let’s look at what parameters they have and how to conduct testing. And for those who like to tinker, we’ll tell you how to make a decimeter antenna with your own hands.

What's the difference?

Let's try to explain in a nutshell how to determine what type of product is in front of you. The UHF antenna looks like a ladder. Install them parallel to the ground. Meter ones are crossed aluminum tubes. Appearance both types are shown in the photo below. There are also combined antennas, when both the “ladder” and cross tubes are combined.

Problem of choice

It would seem that everything is simple. However, the buyer is faced with the question of how to choose the right device and what parameters to pay attention to. In general, it is best to test TV antennas directly in the conditions in which they will operate. The passage of a radio signal is often individual for a particular area. Thus, a product shows the same results in laboratory conditions, but completely different results in the field. There are certain tactics that allow you to test both meter and decimeter TV antennas. However, when choosing such a product in a store, we do not have the opportunity to conduct full testing. Not a single seller will agree to give us several different antennas to test. In this case, you have to trust the characteristics of these products. And hope that the selected antenna will perform its functions according to the passport data, and not real conditions.

Main settings

A decimeter antenna is characterized primarily by its radiation pattern. The main parameters of this characteristic are the level of the side (auxiliary) lobes and the width of the main lobe. The width of the diagram is determined in the horizontal and vertical planes at a level of 0.707 from the largest value. So, according to this parameter (the width of the main lobe), diagrams are usually divided into non-directional and directional. What does this mean? If the main lobe has a narrow shape, then the antenna (decimeter) is directional. The next important parameter is noise immunity. This characteristic primarily depends on the level of the back and side lobes of the diagram. It is determined by the ratio of the power released by the antenna, subject to a consistent load at the time of receiving a signal from the main direction, to the power (with the same load) when receiving from the side and rear directions. First of all, the shape of the diagram depends on the number of directors and the design of the antenna.

What does the term “wave channel” mean?

TV antennas of this type are very effective directional receivers of radio signals. They are widely used in areas of clearly weak television airwaves. The antenna (decimeter) of the “wave channel” type has high gain and has good directivity. In addition, these products have relatively small dimensions, which (on par with high level reinforcement) makes it very popular among residents of holiday villages and other settlements remote from the center. This antenna also has a second name - Uda-Yagi (named after the Japanese inventors who patented this device).

Principle of operation

A decimeter antenna of the “wave channel” type is a set of elements: passive (reflector) and active (vibrator), as well as several directors, which are installed on a common boom. The principle of its operation is as follows. The vibrator has a certain length, it is located in the electromagnetic field of the radio signal and resonates at the frequency of the received signal. In it, an electromagnetic field is induced on each passive element, which also leads to the occurrence of EMF. As a result, they re-emit secondary electromagnetic fields. In turn, these fields induce additional EMF on the vibrator. Therefore, the dimensions of the passive elements, as well as their distances to the active vibrator, are chosen such that the EMF induced by them due to secondary fields is in phase with the main EMF, which is induced in it by the primary electromagnetic field. In this case, all EMFs are summed up, which increases the efficiency of the design compared to a single vibrator. Thus, even an ordinary room can provide stable signal reception.

The reflector (passive element) is installed behind the vibrator 0.15-0.2 λ 0. Its length must exceed the length active element by 5-15 percent. Such an antenna produces a one-way directional pattern in the vertical and horizontal planes. As a result, the reception of reflected signals and fields that come from the back of the antenna is significantly reduced. If necessary, receive a television signal over long distances, as well as in difficult conditions, in the presence of large quantity interference, it is recommended to use a three or more element antenna, which consists of an active vibrator, one or more directors and a reflector.

Direct and reflected signals

In an article devoted to a wave receiving device (“Tele-Sputnik” No. 11 for 1998), it was noted that in the case when the signal source is not a standard (that is, not a laboratory) generator and emitting antenna, and the signal is broadcast by a television tower, a significant Weather conditions play a role, as does the location where the receiver is installed. This especially affects the operation of UHF products. This is explained by the fact that in the decimeter range there is less, and accordingly, obstacle avoidance is much worse, and any signal reflections play an important role in the quality of the received picture. In particular, even the wall of a house can be a wave reflector. So, in conditions where there is no direct visibility, this property can be used - to receive the reflected signal. However, its quality will be lower than that of the direct one. If the level of the transmitted signal is high, but there is no line of sight, then you can use the reflected wave. In fact, an indoor decimeter antenna works precisely on this principle. After all, it is difficult to catch a direct wave in a room if the windows face the opposite direction. Therefore, if you try, you can always find a point where the received signal will be higher. But in the case of direct visibility, any reflected interference will spoil the received picture.

A technique that allows you to compare antenna parameters

In order to test receiving devices, they need to create the same conditions:

1. Select the installation location where your antenna will operate. You can use a balcony, roof or mast. The main thing is that both the height and the location are the same for all products.

2. The direction to the source of the broadcast signal should be maintained with an accuracy of three degrees. To do this, you can make a special mark on the mounting pipe.

3. Measurements should be carried out under the same weather conditions.

4. The cable connecting the antenna and the TV must have the same resistance and length. It is best to use one wire, changing only the receivers.

Testing should only be carried out on products of one type. For example, an indoor UHF antenna should not be compared with an outdoor one or with meter receivers. It should be understood that field tests may produce results that differ significantly from laboratory tests.

UHF antenna for digital television

Recently, the media have been increasingly talking about the need to switch to digital television. Many have already done this, and some are still thinking about it. So far, the signal is broadcast in both modes. However, the quality leaves much to be desired. In this regard, people are interested in what decimeter antennas can be used for T2. Let's look at this issue. Essentially, digital television broadcasts on a UHF channel. So a standard UHF antenna may be suitable for receiving it. You can often see receivers in stores that indicate that they are intended for digital television. However, this is a marketing ploy that allows you to sell a standard decimeter antenna for more than it costs. When purchasing such a product, you will not have a guarantee that it will provide better reception than what you already have in your home and has been working for more than one year. As we said earlier, the quality depends mainly on the level of the broadcast signal and line of sight conditions. However, it should be borne in mind that in most cities, significantly more powerful generators are used for transmitting digital television than for analogue. This is done in order to speed up the transition to new standard. After all, viewers want to see a clear image, and not “snow” on the screens. Therefore, if there is a receiver in the window that says “UHF antenna for DVB T2”, know: this does not mean that this is some kind of special product. It’s just that a not entirely honest seller wants to profit from an uninformed buyer. You should also know that the transition program to the new standard provides for the creation of advisory centers. In them you can get comprehensive information on any issue related to digital television. All consultations are provided free of charge. In some cities, this equipment is in test mode, so the signal may be unstable or weakened. Don’t worry, the center staff will always tell you how to solve the problem with signal reception quality.

DIY decimeter antenna

The length of UHF waves falls within the range from 10 cm to 1 m. Their name comes from this feature. At this frequency they propagate predominantly in a straight line. They practically do not bend around obstacles and are only partially reflected by the troposphere. In this regard, long-distance communication in the UHF range is very difficult. Its radius does not exceed one hundred kilometers. Let's look at a couple of examples of how to make a decimeter antenna at home.

The first version of a homemade television broadcast receiver will, so to speak, be assembled on the knee from scrap materials. UHF channels are located in the range from 300 MHz to 3 GHz. Our task is to produce an antenna that will operate precisely at these frequencies. For this we need two 0.5 liter beer cans. If you use a larger capacity, the received frequency will decrease. For installation you will need some kind of frame; you can use a board 10 cm wide. You can also use a regular wooden hanger, in which case the resulting antenna can be hung on a nail in any convenient place in the room. In addition to the frame and cans, you need to prepare a pair of self-tapping screws, tools, a coaxial cable, a connector, terminals, and insulating tape. We put a television connector on one end of the cable and solder it. We insert the second end into the terminal block. Next, we attach the terminals to the necks of the cans with screws. The wires should fit snugly to the metal. Now let's start assembling the antenna itself. To do this, we secure the jars on a horizontal crossbar with their necks facing towards each other. The distance between them should be 75 mm. You can use insulating tape to secure the cans. That's it, the antenna is ready! Now we need to find a place for stable reception of a television signal and hang our “hanger” in this place.

Receiver for digital television

This section is intended for people who do not want to use a regular (analog) product, but want a special UHF antenna to be used for the new format. It is also easy to assemble such a receiving device with your own hands. To do this, we will need a square wooden (or plexiglass) frame with a diagonal of 200 mm and a regular RK-75 cable. The option presented to your attention is a zigzag antenna. It has proven itself to be excellent when working in the digital television reception range. Moreover, it can be used in places where there is no direct visibility to the signal source. If your broadcast is weak, you can connect an amplifier to it. So let's get to work. We strip the end of the cable by 20 mm. Next, we bend the wire into a square shape with a diagonal of 175 mm. We bend the end outward at an angle of 45 degrees, and bend the second stripped end to it. We connect the screens tightly. The stripped central core hangs freely in the air. On the opposite corner of the square, carefully remove the insulation and screen over a 200 mm area. This will be the top of our antenna. Now we connect the resulting square with a wooden frame. At the bottom, where the two ends are connected, copper staples made from thick wire should be used. This will ensure better electrical contact. That's all, the decimeter antenna for digital television is ready. If it will be installed outside, you can make a plastic case for it, which will protect the device from precipitation.