Despite the rapid development of satellite and cable TV, the reception of terrestrial television broadcasting is still relevant, for example, for places of seasonal residence. It is not at all necessary to buy for this purpose. ready product, a home decimeter (UHF) antenna can be assembled by hand. Before proceeding to the consideration of the designs, we will briefly tell you why this particular range of the television signal was chosen.
Why exactly UHF?
There are two good reasons to opt for this type of structure:
- The thing is that most of the channels are broadcast in this range, since the design of the repeaters is simplified, and this makes it possible to install more maintenance-free low-power transmitters and thereby expand the coverage area.
- This range is selected for broadcasting "digits".
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 broadcasting.
Rice. 1. The simplest homemade Z antenna, known by the names: "Rhombus", "Square" and "People's Zigzag"As you can see from the sketch (B fig. 1), the device is a simplified version of the classic zigzag (Z-structure). 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 strength 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 outdoors, then it is better to abandon aluminum, since it is prone to corrosion. Capacitive inserts are made of foil, sheet metal or metal mesh. After installation, they are soldered along the circuit.
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 the circuit diagram device that can be used with almost any antenna.
Rice. 2. Scheme antenna amplifier for the UHF range List of elements:
- Resistors: R1 - 150 kOhm; R2 - 1 kΩ; 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 by: KT3101, KT3115 and KT3132).
Inductance: L1 - is a frameless coil with a diameter of 4 mm, wound with a copper wire Ø 0.8 mm (2.5 turns must be made); L2 and L3 are high frequency chokes of 25 μH and 100 μH, respectively.
If the circuit is assembled correctly, we get an amplifier with the following characteristics:
- bandwidth from 470 to 790 MHz;
- gain and noise factors - 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 of supplying power, it is carried out directly through the cable.
This amplifier can work with the most simple constructions made from improvised means.
Indoor antenna made of beer cans
Despite the unusual design, it is quite efficient, since it is a classic dipole, especially since the size of a standard can is excellent for the arms of a decimeter range vibrator. If the device is installed in a room, then in this case it is not even necessary to agree with the cable, provided that it is not longer than two meters.
Legend:
- A - two cans with a volume of 500 mg (if you take tin cans, not aluminum, then you can solder the cable, and not use self-tapping screws).
- B - points of attachment of 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 secured to 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 wood 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 there is sufficient signal power.
Making an antenna from copper wire
There is a design that is much simpler previous version, which only requires a piece of copper wire. It is on the framework loop antenna narrow range. This solution has undoubted advantages, since in addition to its main purpose, the device plays the role of selective filter that reduces interference, which allows you to confidently receive the signal.
Fig. 4. Simple loop UHF loop antenna for digital TV reception For this design, you need to calculate the length of the loop, to do this, you need to know the frequency of the "digit" for your region. For example, in St. Petersburg it is broadcast on 586 and 666 MHz. The calculation formula will be as follows: L R = 300 / f, where L R is the loop length (the result is 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 loop length should be 48 centimeters.
If you take a thick RG-6 cable with braided foil, you can use it instead of copper wire to make a loop.
Now let's tell you how the structure is assembled:
- Measure and cut a piece of copper wire (or RG6 cable) with a length equal to L R.
- A loop of a suitable diameter is folded, after which a cable going to the receiver is soldered to its ends. 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 hinge is installed on a stand.
- An F connector (plug) is screwed onto the cable to the receiver.
Note, in spite of the simplicity of the design, it is the most effective for receiving a "figure", provided that the calculations are carried out correctly.
DIY MV and UHF indoor antenna
If, in addition to the UHF, there is a desire to accept MV, you can assemble a simple multiwave, its drawing with dimensions is presented below.
To amplify the signal in this design, a ready-made SWA 9 block is used, if you have problems with its acquisition, you can use homemade device, the diagram 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 wave channel however, it performs well if the signal is strong enough.
Antenna figure eight for digital TV do it yourself
Consider another common design option for receiving a "digit". It is based on the classic scheme for the UHF range, because of its shape, called the "Eight" or "Zigzag".
Rice. 6. Design and implementation of the digital figure eight Dimensions of the structure:
- 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;
- pitch between rods (E) - from 8 to 25 mm.
The place of cable connection 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 of the above examples are capable of accepting DBT T2, but for a change we give a sketch of another design, popularly called "Butterfly".
As a material, you can use plates of copper, brass, aluminum or duralumin. If the structure is planned to be installed outdoors, then the last two options are not suitable.
Bottom line: which option to choose?
Oddly enough, but the simplest option is the most effective, so the "loop" is best suited for receiving "numbers" (Fig. 4). But, if you want 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, in order 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 imperative to install lightning protection, but this is already a topic for another article.
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). Thus, the antenna is a kind of transmitter (receiver). In this article, we will understand what antenna do you need to receive DVB-T2 signal.
Antenna types:
By type, antennas can be divided into indoor, outdoor and antennas for long-range reception... We are interested in antennas that able receive standard signal DVB-T2... They can be divided into two groups: indoor and outdoor... In turn, they are divided into active and passive.
The signal of digital terrestrial television of the DVB-T2 standard is transmitted in decimeter ( UHF) range. This range (UHF) is within 470-862 MHz... In Russia, these frequencies fill the channels from the 21st to the 69th TV channel(TCEs) inclusive.
We want to make a reservation right away that there are no special antennas for receiving DVB-T2, they are all ordinary decimeter antennas with or without signal amplifier. Select antenna for receiving DVB-T2 is not difficult. There are two main criteria to consider here - distance to the transmitter and relief terrain. Two services will help us with this:
Next, we go directly to the choice of a DVB-T2 decimeter range antenna. If the relief of your area is more or less flat and the distance to the transmitter is no more than ten kilometers, then you the usual UHF antenna without amplifier. Although, if the difference in price is not large, then we advise you to purchase active antenna(with an amplifier), because it can always be turned off.
Indoor antennas DVB-T2:
As an example of a passive room DVB-T2 antenna, let's take the Sirius 2.0 antenna, manufactured by REMO. You can read it on our website.
As an example of an active room DVB-T2 antenna, let us take the MINI DIGITAL antenna by the same manufacturer REMO. You can also find it on our website.
Outdoor antennas DVB-T2:
Outdoor antennas are also classified as active and passive. They must be used when the distance from the transmitter is over 10 kilometers. It is recommended to point these antennas accurately to the transmitting station.
As an example of an outdoor DVB-T2 antenna, let's take the SELENA MINI antenna, manufactured by REMO.
As an example of an outdoor active DVB-T2 antenna, let's take an antenna manufactured by REMO.
Outdoor DVB-T2 antennas for long distance reception:
If the distance to the transmitting equipment is over 30 kilometers then you will need narrow beam antennas With increased sensitivity... These antennas can receive a signal at a distance of up to 100 kilometers. Also, do not forget that such antennas must be installed on an appropriate height.
As an example of an outdoor active DVB-T2 antenna for long-range reception, let's take an antenna manufactured by REMO.
The time has come to divorce the TV cable. I have a lot of TVs planned. To the city 40 km. It's even farther to the translator. The task is to provide TVs with stable reception of DVB-T2 signal. I will use signal dividers, which will further weaken the signal received by the antenna. There is a need to use antenna amplifier DVB-T2... Since the frequencies of both DVB-T2 packets are in the UHF range, the antenna was looked at by a directional, passive UHF range with a gain of 14 dB.
A long distance to the translator and dividing the signal into several TVs will greatly weaken the signal, therefore, you cannot do without the UHF antenna amplifier, which is also a DVB-T2 amplifier. Decided make an antenna amplifier for DVB-T2 with your own hands and see what happens.
Since standard signal dividers, including those that I purchased, do not pass electricity, powering the amplifier through the cable will not work (or the power must be run through the cable up to the divider).
Diagram of a two-stage low-noise antenna amplifier DVB-T2.
Gain from 30dB depending on the selected transistors. Power supply of the amplifier is 12 volts.
I used BFR193 transistors... They are very cheap and have good characteristics... High gain of 50-200. High cutoff frequency works up to 8000MHz. SMD execution. Possess low level own noise.
Can order transistors BFR193 in China, but ours cost a little cheaper.
Ceramic capacitors. We make the conclusions of the capacitors and resistors as short as possible. You can use SMD, I just did what was at hand.
Coil L1 is made from a piece copper wire length 3.5cm diameter 0.8mm. Its diameter is 4mm and contains two and a half turns. I wound it on the smooth part of the 3.3mm drill bit (the coil itself will be about 4mm).
Making an antenna amplifier DVB-T2 (UHF) with your own hands.
The board can be made without etching by simply cutting contact pads... We look at the drawing.
The board is made of double-sided fiberglass. We connect the upper and lower layers with four pins and solder.
I used a transformer power supply to drive less interference, with a voltage stabilization of 12 volts. The amplifier consumes about 12mA.
Everything worked fine for me right away without setting. The setting is reduced in the selection of resistors R1 and R3 so that the currents on the collectors of transistors VT1 and VT2 are 3.5mA and 8mA, respectively.
Tests were carried out at work. In the back of the room. The yard is a well. As an antenna, a piece of SHVVP wire. The result without an amplifier shows nothing at all. I connect an amplifier and as they like to say in advertising, the result exceeded all my expectations, a stable picture without a hint of a breakdown.
List of parts of a homemade antenna amplifier DVB-T2 (UHF).
- Transistors BFR193 - 2 pcs. ().
Capacitors 3.3pF, 10pF, 100pF - 2 pcs., 4700-6800pF.
Resistors 75 KOhm, 150 KOhm, 1 KOhm, 680 Ohm.
Choke 100-125 μH.
Coil L1 is a self-made 2.5 coil with a diameter of 4 mm made of copper wire 3.5 cm long and 0.8 mm in diameter.
Digital television is broadcast in the decimeter wavelength range. Therefore, you can use almost any UHF antenna. But I needed simple, easy to repeat 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.
The well-known “ eight“, With the difference that I used it without a reflector.
Any conductive material of a suitable cross-section can be taken for the antenna web. It can be copper or aluminum wire with a thickness of 1 to 5 mm, a tube, strip, bus, corner, profile ... I took 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 make an antenna not from wire, then you measure it out - the top sides are 14 cm, the side sides are 13.
All sizes are approx. Don't be afraid to cheat or make mistakes. Our plans do not include making an antenna that meets all standards. We need a simple one, but workhorse... Surrogate but reliable. Surrogate because:
1
... I personally could not stand the dimensions.
2
... There is no reflector.
3
... I took the cable 50 ohms instead of 75 ohms, but with a thick sheath. Friends usually used this cable for car antennas for radio stations 27 MHz.
Nevertheless, the antenna works quite well.
Have digital signal there is a feature, it is either there or it is not. When receiving analog television, different channels showed from at different levels interference, and when removed, the snow level on the screen simply increased, until the signal was completely lost. In digital, the signal is practically the same on all channels, and if there is reception, that is, all channels.
This antenna has been tested by me on more than one dozen TV sets 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 stiffness loop.
We clean 1.5 - 2 cm at both ends, twist two loops behind each other, and then seal the joint. This will be one pin of the cable connection. After 2 cm, another. Where to solder the central core, where to braid, does not matter.
Distance between solders 2 cm
I took the cable about three meters. In most cases, it is enough if you do not do it for yourself personally. Measure for yourself how much you need.
Stripped the cable from the antenna side by two centimeters, to the plug - 1 cm. If the plug is the same as in the photo. You can take any stronger one.
Stripping the cable
He cleaned the plug with a file and a scalpel.
After sealing, both soldering points are filled with glue from a pistol. On the plug, first hot glue is poured into the soldering point and into the plastic cap, with a margin, the excess can then be removed. Then, until the glue has cooled down, everything is quickly collected. You cannot gnaw such a joint with your teeth. Reliable and elastic at the same time.
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 lid of a 20-liter water bottle, of which I have accumulated a sufficient number. If you are making an antenna, like me, for mass production, then it is better to immediately use the materials that are widespread, 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.
The result is such a structure that can be stuck anywhere - on a cornice, on a curtain, on a window frame. To do this, you can carry with you a piece of wire, a couple of self-tapping screws, a couple of pins ...
Antenna assembly
If the antenna is wrinkled during transfer, it aligns easily and without damage. This is perhaps its most important plus.
I do not always carry this 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 outdoor one. The tower is about 9 km away. Reception is confident despite the simplicity of the antenna.
