Despite the rapid development of satellite and cable television, the reception of terrestrial television is still relevant, for example, for seasonal residences. It is not at all necessary to buy a finished product for this purpose; a home decimeter (UHF) antenna can be assembled by hand. Before proceeding to the consideration of designs, we will briefly describe why this particular range of the television signal was chosen.
Why DMV?
There are two good reasons to opt for this type of structure:
- The thing is that most channels are broadcast in this range, since the design of repeaters is simplified, and this makes it possible to install a larger number of unattended low-power transmitters and thereby expand the coverage area.
- This range is selected for broadcasting "numbers".
Indoor antenna for TV "Rhombus"
This simple, but at the same time, reliable design was one of the most common in the heyday of on-air television.
Rice. 1. The simplest homemade Z-antenna, known under the names: "Rhombus", "Square" and "People's Zigzag"As can be seen from the sketch (B Fig. 1), the device is a simplified version of the classic zigzag (Z-design). To increase the sensitivity, it is recommended to equip it with capacitive inserts ("1" and "2"), as well as a reflector ("A" in Fig. 1). If the signal level is acceptable, this is not necessary.
As a material, you can use aluminum, copper, as well as brass tubes or strips with a width of 10-15 mm. If you plan to install the structure on the street, then it is better to abandon aluminum, since it is susceptible to corrosion. Capacitive inserts are made of foil, tin or metal mesh. After installation, they are soldered along the contour.
The cable is laid as shown in the figure, namely: it did not have sharp bends and did not leave the limits of the side insert.
Decimeter antenna with amplifier
In places where a powerful relay tower is not located in relative proximity, you can raise the signal level to an acceptable value using an amplifier. Below is a schematic diagram of a device that can be used with almost any antenna.
Rice. 2. Antenna amplifier circuit for the UHF range Item List:
- Resistors: R1 - 150 kOhm; R2 - 1 kOhm; R3 - 680 Ohm; R4 - 75 kOhm.
- Capacitors: C1 - 3.3 pF; C2 - 15 pF; C3 - 6800 pF; C4, C5, C6 - 100 pF.
- Transistors: VT1, VT2 - GT311D (can be replaced with: KT3101, KT3115 and KT3132).
Inductance: L1 - is a frameless coil with a diameter of 4 mm, wound with copper wire Ø 0.8 mm (2.5 turns must be made); L2 and L3 are 25 µH and 100 µH high frequency chokes, respectively.
If the circuit is assembled correctly, we will get an amplifier with the following characteristics:
- bandwidth from 470 to 790 MHz;
- gain and noise coefficients - 30 and 3 dB, respectively;
- the value of the output and input resistance of the device corresponds to the RG6 cable - 75 Ohm;
- the device consumes about 12-14 mA.
Let's pay attention to the way the power is supplied, it is carried out directly through the cable.
This amplifier can work with the simplest designs made from improvised means.
Indoor antenna made from beer cans
Despite the unusual design, it is quite functional, since it is a classic dipole, especially since the dimensions of a standard can are perfect for the arms of a UHF vibrator. If the device is installed in a room, then in this case it is not even necessary to coordinate with the cable, provided that it is not longer than two meters.
Designations:
- A - two cans with a volume of 500 mg (if you take tin, not aluminum, you can solder the cable, and not use self-tapping screws).
- B - places for fastening the shielding braid of the cable.
- C - central vein.
- D - the place of attachment of the central core
- E - cable coming from the TV.
The arms of this exotic dipole must be mounted on a holder made of any insulating material. As such, you can use improvised things, for example, a plastic clothes hanger, a mop bar, or a piece of wooden beam of the appropriate size. The distance between the shoulders is from 1 to 8 cm (selected empirically).
The main advantages of the design are fast production (10 - 20 minutes) and quite acceptable quality of the "picture", provided that the signal strength is sufficient.
Making a copper wire antenna
There is a design that is much simpler than the previous version, which requires only a piece of copper wire. This is a narrow band loop antenna. This solution has undeniable advantages, since in addition to its main purpose, the device plays the role of a selective filter that reduces interference, which allows you to confidently receive a signal.
Fig.4. A simple UHF loop antenna for receiving digital TV For this design, it is necessary to calculate the length of the loop, to do this, you need to find out the frequency of the “numbers” for your region. For example, in St. Petersburg it is broadcast on 586 and 666 MHz. The calculation formula will be: L R = 300/f, where L R is the length of the loop (the result is presented in meters), and f is the average frequency range, for Peter this value will be 626 (the sum of 586 and 666 divided by 2). Now we calculate L R, 300/626 = 0.48, which means that the length of the loop should be 48 centimeters.
If you take a thick RG-6 cable, where there is a braided foil, then it can be used instead of copper wire to make a loop.
Now we will tell you how the structure is assembled:
- A piece of copper wire (or RG6 cable) is measured and cut off with a length equal to L R .
- A loop of a suitable diameter is folded, after which a cable is soldered to its ends, which goes to the receiver. If RG6 is used instead of copper wire, then the insulation is first removed from its ends, by about 1-1.5 cm (the central core does not need to be cleaned, it does not participate in the process).
- The loop is installed on the stand.
- An F connector (plug) is screwed onto the cable to the receiver.
Note that despite the simplicity of the design, it is most effective for receiving "numbers", provided that the calculations are carried out correctly.
Do-it-yourself indoor antenna MV and UHF
If, in addition to UHF, there is a desire to receive MV, you can assemble a simple multiwave oven, its drawing with dimensions is presented below.
To amplify the signal in this design, a ready-made SWA 9 block is used, if there are problems with its acquisition, you can use a home-made device, the circuit of which was given above (see Fig. 2).
It is important to observe the angle between the petals, going beyond the specified range significantly affects the quality of the "picture".
Despite the fact that such a device is much simpler than a log-periodic design with a wave channel, nevertheless, it shows good results if the signal is of sufficient power.
Do-it-yourself figure-eight antenna for digital TV
Consider another common design option for receiving "numbers". It is based on the classic scheme for the UHF range, which, due to its shape, was called the "Eight" or "Zigzag".
Rice. 6. Sketch and implementation of the digital eight Construction dimensions:
- the outer sides of the rhombus (A) - 140 mm;
- inner sides (B) - 130 mm;
- distance to the reflector (C) - from 110 to 130 mm;
- width (D) - 300 mm;
- step between the bars (E) - from 8 to 25 mm.
The cable connection point is at points 1 and 2. The requirements for the material are the same as for the Rhombus design, which was described at the beginning of the article.
Homemade antenna for DBT T2
Actually, all the examples listed above are capable of receiving DBT T2, but for a change, we will give a sketch of another design, popularly called the “Butterfly”.
As a material, you can use plates made of copper, brass, aluminum or duralumin. If the structure is planned to be installed on the street, then the last two options are not suitable.
Outcome: which option to stop?
Oddly enough, but the simplest option is the most effective, so the "loop" is best suited for receiving the "digit" (Fig. 4). But, if you need to receive other channels in the decimeter range, then it is better to stop at the "Zigzag" (Fig. 6).
The antenna for the TV should be directed towards the nearest active repeater, to select the desired position, rotate the structure until the signal strength is satisfactory.
If, despite the presence of an amplifier and a reflector, the quality of the "picture" leaves much to be desired, you can try to install the structure on the mast.
In this case, it is necessary to install lightning protection, but this is a topic for another article.
The era of digital signals has arrived. All broadcasting TV companies began to work in a new format. Analog TVs are dying out. They are still in working condition and are available in almost every family.
In order for the old models to successfully finalize their resource, and for people 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 TV wave signals with a special antenna.
Any home master is able not to buy an antenna in a store, but to make it with his own hands from improvised means for watching digital TV programs at home or in the country. The two most accessible designs are described in this article.
A bit of theory
The principle of operation of the antenna for digital packet television
Any television signal propagates in space from the emitters of the transmitting TV tower to the TV antenna as 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 the sinusoid forms a potential difference with its own sign.
Under the action of an induced voltage applied to a closed receiving circuit of the input signal with resistance R, an electric current flows in the latter. It is amplified and processed by the digital TV circuitry and output to the screen and speakers as picture and sound quality.
For analog models of TV receivers, an intermediate link works between the antenna and the TV - the DVB-T prefix, which decodes the digital information of the electromagnetic wave into a normal form.
Vertical and horizontal polarization of digital TV signal
In television broadcasting, state standards adopted electromagnetic waves to radiate in only two planes:
- horizontal.
In this way, the transmitters direct the radiating signals.
And users simply need to rotate the receiving antenna in the desired plane to maximize the power potential removal.
Requirements for a digital packet television antenna
TV transmitters propagate their signal-waves over short distances, limited by a line-of-sight zone from the top point of the TV tower emitter. Their range rarely exceeds 60 km.
For such distances, it is sufficient to ensure the power of the emitted TV signal of a small value. But, the intensity 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 on the antenna. It creates currents with small amplitudes. This imposes high technical requirements for the installation and workmanship of all parts of digital reception devices.
The design of the antenna must be:
- made carefully, with a good degree of accuracy, eliminating the 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 the antenna
The main parameter affecting the quality of the received digital signal, as can be seen from the explanatory first figure, is the length of the electromagnetic radiation wave. 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.
For this, we will use the Google search and ask it for a list of regional TV communication points for our area.
As an example, a fragment of the data table for the Vitebsk region is shown with a red rectangle highlighting the transmitting center in Ushachi.
The frequency of its wave is 626 megahertz, and the type of polarization is horizontal. These data are sufficient.
We perform the calculation: 300/626 \u003d 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. Under this size, a whip antenna is made. It is usually expressed by the formula λ/4, where λ is the length of the electromagnetic wave.
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 to connect the antenna. I managed to find a ready-made two-meter piece in an old stock.
From the free end with an ordinary knife, I cut off the outer shell. I take the length with a small margin: when adjusting, it is always easier to bite off a small segment.
Then I remove the shielding layer from this section of the cable.
The work is done. It remains 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 windowsill or fixed on the glass, for example, with a piece of adhesive tape or tied to the blinds. Reflected signals and interference can be shielded with a strip of foil located at a small distance from the central core.
Such a design is done literally in ten minutes and does not require special material costs. It's worth trying it out. But, it is able to work in the zone of reliable signal reception. My building is screened by a mountain and a multi-storey building. The transmitting TV 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 watching the video of the owner Edokoff “How to make an antenna for digital TV”
Antenna Kharchenko at 626 MHz
To receive analog broadcasting signals of various wave frequency ranges, 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. The vibrators were made from a flat copper bar, but it is quite possible to get by with a round wire. This will make it easier to bend and align the ends.
How to determine the dimensions of a particular antenna
Online calculator
Let's use the all-knowing Google search. We write on the command line: "Calculation of the Kharchenko antenna" and press Enter.
Choose any site you like and perform an online calculation. I went to the first one that opened. Here's what he gave me.
I presented all his data with a picture with the designation of the name of the size of the Kharchenko antenna.
Manufacture of antenna design details
I took the information provided as a basis, but did not accurately withstand all dimensions. I know from previous practice that the antenna works well in the broadband wave range. Therefore, the dimensions of the parts are just slightly overestimated. The half-wave of each harmonic of the sinusoid of the electromagnetic TV signal will fit into the shoulder of each vibrator and will be accepted by it.
Based on the selected data, I made blanks for the antenna.
Vibrator Design Features
The connection of the ends of the shank for the "eight" was created in the center at the bending stage. Soldered them with a soldering iron.
It was created for me according to the “Moment” principle, made with my own hands from old transformers, it has been working for two decades. I even soldered a copper wire of 2.5 squares to them in a thirty-degree frost. Works with transistors and microcircuits without burning them.
I plan to describe its design in the near future in a separate article on the site for those who also want to make it with their own hands. Follow the publications, subscribe to notifications.
Connecting the Antenna Cable to the Vibrator
I simply soldered the copper core and braid to the figure-eight metal from different sides in its center.
The cable was tied to a copper bar, bending it with a loop in the shape of a semi-square vibrator. In this way, the resistance of the cable and antenna is matched.
Shielding grid design
In fact, the Kharchenko antenna often works fine without signal shielding, but I decided to show its manufacture. For the base, I took a wooden block. I did not paint and impregnate with varnish: the structure will be used indoors.
I drilled holes in the back side of the bar for attaching the screen wires and inserted them, and then wedged them.
The result was a screen for Kharchenko's antenna. In principle, it can also be made of a different design: cut out of a piece of the frontal armor of a tank or cut out of food foil - it will work in about the same way.
On the reverse side of the bar, I fixed the design of the vibrator with the cable.
The antenna is ready. It remains to install it on the window to work in vertical polarization.
When a television receiver is at a great distance from the transmitting generator, then the power of its signal gradually weakens. It can be increased by special electronic devices - amplifiers.
You just need to clearly see the difference between the signals received by the antenna, which can be:
- just weakened;
- contain high-frequency interference that distorts the shape of a digital sinusoid to the shape of some kind of "karyabola".
In both cases, the amplifier will fulfill its role and raise the power. Moreover, the TV will clearly perceive and show a weakened signal, and with an enhanced “karyabola”, playback problems will arise.
To eliminate such wave interference are called upon:
- h/h filters;
- screens.
They must be measured with an oscilloscope, and the ways of using various designs should be analyzed in each specific case individually. The antenna is not to blame.
Digital television broadcasts in the decimeter wave range. Therefore, you can use almost any UHF antenna. But I needed simple, easily repeatable and strong UHF antenna range.
Such that it could be carried with you, and on occasion it was not a pity to give it to people for a small amount.
Based on the well-known eight“, with the difference that I used it without a reflector.
The material for the antenna web can be taken from any conductive, suitable section. It can be copper or aluminum wire with a thickness of 1 to 5 mm, a tube, a strip, a tire, a corner, a profile ... I took a copper wire with a diameter of 3 mm. Easy to solder, easy to bend when assembling, easy to align if bent.
The outer side of the square is 14 cm, the inner side is slightly less - 13 cm due to the fact that the middle of the two squares does not converge, about 2 cm from corner to corner.
So, if you are not making an antenna out of wire, then you measure it - the upper sides are 14 cm each, the sides are 13 cm each.
All sizes are approx. Don't be afraid to miscalculate or make a mistake. Our plans do not include the production of an antenna that meets all standards. We need a simple but workhorse. Surrogate, but reliable. Surrogate because:
1
. Personally, I couldn't stand the dimensions.
2
. The reflector is missing.
3
. I took the cable 50 ohms instead of 75 ohms, but with a thick braid. Friends usually used such a cable for car antennas for 27 MHz radio stations.
Nevertheless, the antenna works and is very good.
A digital signal has a feature, it either exists or it doesn't. When receiving analog television, different channels were shown with different levels of interference, and when removed, the snow level on the screen simply increased until the signal completely disappeared. In digital, the signal is almost the same on all channels, and if there is reception, then there are all channels.
I have tested this antenna on more than a dozen TVs in our region.
So. We measure a piece with a total length of 112 cm and bend the wire. The first section is 13 cm + 1 cm for the loop (for strength). The second and third - 14 cm each, the fourth and heels - 13 cm each, the sixth and seventh - 14 cm each, and the last eighth - 13 cm + 1 cm stiffening loop.
At the two ends, we clean 1.5 - 2 cm each, twist two loops for each other, and then solder the junction. This will be one cable connection pin. After 2 cm another. Where to solder the central core, where the braid is, does not matter.
Distance between solder joints 2cm
I took a cable about three meters. In most cases, it is enough if you are not doing it for yourself personally. Measure out as much as you need.
The cable was stripped from the side of the antenna by two centimeters, to the plug - 1 cm. If the plug is the same as in the photo. You can take any, stronger.
cable stripping
The plug was cleaned with a needle file and a scalpel.
After sealing, both soldering points are filled with glue from a gun. On the plug, first, hot glue is poured into the place of soldering and into a plastic cap, with a margin, the excess can then be removed. Then, while the glue has not cooled down, everything is quickly assembled. You can't gnaw through such a joint with your teeth. Reliable and flexible at the same time.
The soldering on the antenna itself is also filled with glue, but for the rigidity of the structure, a frame is taken - any cover, box, .... I took the cap from a 20 liter water bottle, of which I have accumulated a sufficient amount. If you are making an antenna, like me, for mass production, then it is better to use materials that are common, literally lying under your feet for better antenna repeatability. If the antenna is made in a single copy for quick riveting, then you can not fill anything at all.
It turned out such a design that can be stuck anywhere - on a cornice, on a curtain, on a window frame. To do this, you can carry a piece of wire, a couple of screws, a couple of pins ...
Antenna assembly
If the antenna is wrinkled during transfer, it is easily and without damage aligned. This is perhaps its most important plus.
I do not always carry such a design with me, but only when I receive a specific order for connecting a DVB-T2 digital television tuner. It fits easily with the tool in my backpack.
It is more convenient to make several antennas at once. Takes less time.
This is how my friend fixed the antenna, using it as an external one. The tower is about 9 km. Reception is confident despite the simplicity of the antenna.
Digital TV is sweeping the country, many people are buying TVs that already support this format. And whoever has the previous generation equipment, you can buy a digital set-top box () and connect it to your old TV, which does not support. In general, the standing format allows you to watch television in digital format. BUT, many sellers, along with set-top boxes and TVs, "push" the so-called digital antennas, sometimes the price of the antenna reaches 3,000 rubles. Although you guys can do it yourself, make an antenna for digital television, and very cheaply ...
ADVICE! Guys, by the way, you can watch TV without an antenna at all via the Internet, but for this you need another prefix - read a really cool topic.
We continue the article...
To receive a digital signal, a so-called decimeter antenna is required. You can literally make it from an antenna cable. However, it must be calculated correctly. If you do not want to read the article in full, 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 "father-mother"
3) Tools: a knife, wire cutters, a calculator and a tape measure (well, or a ruler).
Calculation
On the main page, we are looking for a tab - “CETV coverage map” and go to it.
CETV coverage map tab
Before us opened a map of coverage of digital television. We are looking for the nearest station for our city (I have Ulyanovsk, you fill in your city).
As you can see in my city, these are channel 56 - 754 MHz and channel 59 - 778 MHz.
Now we calculate the length of the antenna. I will not go into complex technical formulas and terms, we do not 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 about 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 more than one in the city. In the video under the article, I calculated the antenna for Ulyanovsk, and for Kazan.
Manufacturing
1) We take a piece of antenna wire and first we attach an F-connector at the end. We simply strip the cable and screw on the connector so that the center wire is in the middle, and the screen (wires and foil were 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 these 10 cm, we need to remove the plastic insulator and remove the "screen" (foil and small wires). You don’t need to touch it further, leave the cable in the insulator.
4) All our antenna is ready. You can try to connect.
Connection
You need to get a good reception point in the apartment, and it's not always enough just to 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 already inserted the antenna into the extension cord. So far, all this has not been improvised removed from me, for an example of work (therefore, the cable weighs), and the antenna itself is inserted into it.
Well, as you can see, all channels are working fine, and "first", and "Russia", and NTV, etc.
"The 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 - - MANDATORY! There is a solution to the problem!
That's all, I think my article is very useful and relevant. Read our building site.
The era of broadcasting analog signals on television is over. Modern scientific developments completely replace old technologies.
People, when purchasing new equipment, are forced to make antennas for digital television with their own hands in various ways or buy ready-made industrial designs.
I want to draw your attention to the fact that antennas for DVB T2 digital TV are not at all difficult to make on your own. I specifically tested four schemes that take into account the different living conditions of people. I present them to you for your reference. See my photos and available assembly drawings.
How does a digital TV antenna work: I explain simply
Before you start assembling any of the four models of receiving antennas, you should have a good understanding of the processes that should take place in them.
Electromagnetic waves propagate in all directions of the horizon from the generator of the transmitter of electrical signals installed on the TV tower.
They have coverage for their area, but with increasing distance, their signal weakens. Its magnitude is also affected by the terrain, various electrical and magnetic obstacles, and the state of the atmosphere.
In a vibrator oriented perpendicular to the movement of an electromagnetic wave, according to the laws of induction. The positive and negative half-wave of the harmonic create their own sign.
The voltage reaches its maximum value - the amplitude at the points of time corresponding to ¼ and ¾ of the period or 90 and 270 degrees from the sinusoid of the electromagnetic wave strength.
Any shape and size of active vibrators is created for the most efficient voltage induction with minimal energy loss. Accounting for the position of these points is calculated from the wavelength or harmonic frequency.
The voltage, closed to, generates in the created circuit. Its shape and direction change and proportionally repeat the signals of the transmitter on the active load.
Due to the use of various types of digital modulation on the transmitter side, information signals are received and processed inside the television receiver circuit.
I will not go further to consider the question of how a digital antenna for a TV works when it is created.
What technical characteristics of the antenna determine the quality of TV signal reception
The antenna is classified as a reversible device because it works the same way on the transmitter and receiver sides. When analyzing the characteristics, its inclusion as a generator is used.
For effective reception of a digital signal, it is necessary to take into account that on the side of the generator, the emitter of electromagnetic waves can be placed at any angle to the horizon, but only two directions are legally accepted: horizontal and vertical.
Our task is to repeat this orientation for our own TV.
The polarization direction and other digital signal transmission data can be found on the operator's website through a search engine.
We go to the site, select the necessary information.
We are primarily interested in 3 characteristics:
- channel number and its frequency, for which we will create an antenna according to strict dimensions;
- the radius of the transmitter coverage area, which affects the signal quality and the choice of vibrator design;
- polarization direction.
The distance of the TV from the transmitting TV tower greatly affects the design of the antenna.
The higher the antenna is installed, the better the quality of the received signal will be, but the length of the cable can significantly weaken it. In this regard, residents of the upper floors of multi-storey buildings have a significant advantage over their neighbors below.
For the zone of reliable reception, I tested the simplest Kharchenko models and loop assemblies made of coaxial cable and wire, which have a wide range of reception frequencies.
For long distances, it is better to collect a wave channel or a log-periodic scheme. Of the simple designs, the Turkin antenna, modified by Polyakov, has proven itself well.
For example, in my area, the distance from the TV tower was 25 km, which is included in the zone of reliable reception, and the signal frequency was 626 MHz of vertical polarization.
I calculate the length of the electromagnetic wave through the speed of light in frequency: λ=300/626=0.48 meters. A half wave will be 24 cm, and a quarter - 12.
Under these characteristics, I made 4 test antennas for digital television with my own hands, which I describe below.
Antenna Kharchenko for digital TV: how confident it works
I show a general view of the structure I assembled with a photograph. Given the vertical polarization, it is located in the shape of a figure eight, and for the horizontal orientation it is rotated like a butterfly.
For clarity of consideration, he turned it over with its reverse side: with a screen to the transmitting center, and with an active vibrator made of a copper bar - into the room.
The TV cable is simply taped on one side of the square with electrical tape, fixed on the stand and in my case also serves as a fastener: it is simply thrown over the curtain rod: an antenna hangs on it.
My design has already been repeated by many neighbors. I see it like this window design.
People hang the figure eight even on curtains, they began to make it without a screen and a mounting rail: one active vibrator confidently provides reception. This simplifies assembly. However, in the event of the appearance of extraneous interference, I advise you to collect the screen.
I conclude that the Kharchenko antenna in the zone of reliable reception works quite reliably. Since its calculation and installation is simple, it does not require scarce parts, I recommend it for assembly.
How to calculate the dimensions of an antenna for digital television with your own hands in simple ways
To determine the dimensions of Kharchenko's structure, I found many recommendations that, to put it mildly, do not fit together, but work. In the picture I give only 3 methods of calculation.
There are also online calculators that calculate different sizes. I explain all this by the fact that such a design is not critical to manufacturing accuracy, which I consider to be its advantage.
For verification, I chose the technique where the side of the square is 0.25 of the wavelength of the electromagnetic oscillation λ. Here you need less material, and the working conditions are the most complicated.
I multiply the wavelength 48 by 0.25 and get the side of the square 12 cm.
Then it will capture a slightly larger range of signals due to the fact that such a form of the vibrator processes all the amplitudes of half-waves of tension that fit inside it. Due to this, its broadband is ensured.
How to make a Kharchenko antenna: personal experience of "assembly on the knee" with photos
An active vibrator was made from a copper bar of rectangular section 1x4 mm.
Such a profile is difficult to bend. You have to work under pressure. It is easier to work with a round section. I cleaned the middle part of the varnish and soldered the contact pads with a soldering iron.
On one side of the square, I wound a coaxial cable with electrical tape and soldered its current-carrying wires to the prepared sites.
Due to the created half-loop, an angle of matching of the wave impedances of the cable and antenna is formed. This is the simplest design to implement. But she plays an important role.
I show this connection with additional photos on the finished antenna.
Marked out a wooden rail, drilled thin holes in it.
I inserted pieces of wire into them, the length of which slightly covers the area of \u200b\u200bthe active vibrator, wedged them with matches. You can also add glue.
It turned out such a Kharchenko antenna for digital TV with a cable connected to it.
Here I show its location on the window during work last summer.
And I took this picture recently: I show another view of it.
At this time, I had already abandoned the use of an antenna for digital TV DVB T2 after Beltelecom Yasna.
Antenna for digital TV from cable: how to quickly make
To assemble this circuit, you only need a piece of coaxial TV cable about a meter long, a knife, a soldering iron, although you can do without it.
The loop works in the zone of reliable reception, has good characteristics even inside the dense building of multi-storey buildings made of reinforced concrete slabs. Since a fairly simple assembly took me about 5 minutes of time, it can be checked at least for the sake of curiosity.
I explain the technology of installation.
The size of the circumference of the assembled loop corresponds to the wavelength of the electromagnetic oscillation. I have, as shown above, it is 48 cm.
I cut one end of the coaxial cable at a distance of about 5 centimeters. For clarity, I put a matchbox next to it with standard dimensions 3x5.
From the beginning of the cut, I measured the half-wave distance: 24 centimeters. Next, you need to make a section where the shielding braid will be broken.
We make its distance 2 cm. On this segment, carefully check the absence of wires and electrical connections. Only the polyethylene insulation of the central core should be visible.
Then, along the length of the cable from the created gap, I measure another 24 cm and remove the upper protective sheath made of polyethylene along a ring 1 centimeter wide.
You have to work carefully. The shield braid and its electrical connections must be preserved.
I show this area in close-up.
Now there is just a little left: I check the absence of corrosion on the stripped braids, tightly twist the conductive screen with the central core between my fingers. They need to be short-circuited.
A twisted end is formed about 5 centimeters long. It remains to wrap it tightly around an open section of insulation 1 cm wide. The loop is ready.
On the reverse side of the cable, a plug is soldered for connection to the TV socket. I omit this trivial operation. There are no difficulties in it.
An antenna for digital TV from a cable with its loop plane is oriented perpendicular to the direction of the transmitting station.
Positive moment: the material of the loop is made of the same material as the subsequent feeder for connection to the TV. They have the same wave impedance. Nothing needs to be agreed upon.
Antenna made of wire: the easiest assembly for a TV
You can receive a digital signal on a TV in a zone of up to 30 km on a simple single or double wire ring made of copper wire, taken with a piece of electrical wiring 2.5 mm square.
I show the technology of its assembly from two rings. If you are interested in a simplified version, then do not mount the second element.
The length of the circumference of the ring must correspond to the wavelength of the TV signal of the transmitter. In my example, this is 48 cm. I bite off two pieces of wire: L1 and L2 with a centimeter margin to connect the ends.
I bend future vibrators into rings, and I clean their ends. On a short segment, I make small rings to connect the second workpiece.
I insert one vibrator into another, I crimp the rings with pliers.
I show this process on a larger scale.
I prepare the end of the coaxial cable for connection by removing the insulation.
I twist all the ends.
I solder the joints with a soldering iron.
It turned out such a simple antenna made of wire, consisting of two rings.
Orient it with the side of the long wire to the transmitter. Rings can be bent into a hexagon shape. Then they will take a more stable position.
The photo below simply shows the principle: I did not deal with giving special dimensional accuracy to a geometric figure. Do better for yourself.
The antenna is assembled from wire. We turn it on and check the quality of the received signal on the TV.
Any soft toy will help to give decorative properties to the design. This antenna should be placed near the TV or receiver. It is undesirable to exceed the length of the coaxial cable more than half a meter.
It takes less than 10 minutes to assemble such a design, it does not present any difficulties, like the previous scheme, and its work is due to the assembled loop.
Turkina Antenna: DIY Long-Range Design for DVB T2
Initially, the operation of the receiver of this electrical circuit was developed and practically tested by the radio amateur Turkin.
Its description can be found in an article in the magazine Radio No. 11 for 2000.
Then the engineer Polyakov, using the MMANA computer program, finalized it and published an article in the same Radio. See Issue #1, 2002. A diagram of the improved design is shown in the picture below.
Metal rings of vibrators are located on the dielectric rod due to strictly defined distances in the space of the digital TV signal broadcast zone. Their role:
- D1-D3 - passive elements;
- V1, V2 - active part, assembled by a double Swiss square scheme;
- R is the anti-interference shield function.
All dimensions of the vibrators and the distances between them are tied to the length of the received wave. You can calculate them according to the formulas shown in the picture.
However, I propose an easier way: an online calculator for calculating the Turkin antenna. Enter your channel frequency value in it, expressed in megahertz, and immediately get all the dimensions in millimeters.
DVB-T2 channel numbers (click for reference)
| Channel | Frequency, MHz | Channel | Frequency, MHz |
| 21 | 474 | 46 | 674 |
| 22 | 482 | 47 | 682 |
| 23 | 490 | 48 | 690 |
| 24 | 498 | 49 | 698 |
| 25 | 506 | 50 | 706 |
| 26 | 514 | 51 | 714 |
| 27 | 522 | 52 | 722 |
| 28 | 530 | 53 | 730 |
| 29 | 538 | 54 | 738 |
| 30 | 546 | 55 | 746 |
| 31 | 554 | 56 | 754 |
| 32 | 562 | 57 | 762 |
| 33 | 570 | 58 | 770 |
| 34 | 578 | 59 | 778 |
| 35 | 586 | 60 | 786 |
| 36 | 594 | 61 | 794 |
| 37 | 602 | 62 | 802 |
| 38 | 610 | 63 | 810 |
| 39 | 618 | 64 | 818 |
| 40 | 626 | 65 | 826 |
| 41 | 634 | 66 | 834 |
| 42 | 642 | 67 | 842 |
| 43 | 650 | 68 | 850 |
| 44 | 658 | 69 | 858 |
| 45 | 666 |
They, when viewed from behind, immediately formed concentric circles with a clearly defined axis, which must be directed to the transmitter.
It remains for me to solder the antenna coaxial cable to the active terminals of the Swiss double square.
I pay attention to the method of mounting the feeder. The conclusions of the rings forming the Swiss double square are connected oppositely diagonally, and not in parallel.
Look at the layout of the vibrators in the first picture, which shows the Turkin-Polyakov antenna. An air gap of a few millimeters must be created between the bare connecting wires. It will eliminate the short circuit of the potentials of the output voltage.
I put on a ferrite ring at the cable connection point to match the wave impedances of the cable and antenna.
Its magnetic permeability should be within 400-600. I didn't check mine. It just came up.
The antenna immediately started working right out of the room. True, the distance to the transmitter at the dacha is only 40 kilometers. Haven't tested further.
For horizontal polarization of the signal, the Turkin antenna is rotated from the position indicated in the photo by 90 degrees. Then her cable immediately hangs down vertically from the center of the circles, and not from the side.
Here are 4 do-it-yourself antenna schemes for digital television that you can assemble without spending too much money and time. You can see for yourself that their designs are quite simple.
All four tested circuits worked for me immediately without connecting any amplifiers.
I believe that for residents of rural areas living in the zone of reliable reception of digital signals, the Kharchenko antenna is best suited.
With dense residential buildings in the city, I recommend checking the loop antenna made of cable or wire. It fights well with the interference that the air is saturated with from household equipment.
For those who need to catch a signal weakened by a long distance, it is best to immediately assemble the Turkin-Polyakov antenna. Its technical characteristics are practically in no way inferior to either the wave channel or the log-periodic products.
As you can see, in the article I tried to do without technical terms. He did not give the gain and standing wave, radiation pattern and other characteristics. These options can be discussed in the comments section.
Have questions? Ask, discuss, choose the most affordable and acceptable result for your case.
