Under the UHF band implies the frequency of television broadcasting, in this number, and digital television. Some antennas from this group are simple, some can be complex designs. In this article we will explain how to make antenna amplifiers and UHF T2. do it yourself antenna.
- 1 Simple UHF antenna with a frequency of 500 Hertz
- 2 The simplest scheme of UHF antenna
- 3 Antenna at 855 hertz
- 4 All-wave design
- 5 Summarizing
Simple UHF antenna with a frequency of 500 Hertz
This antenna from the publication of Radio Number 3 for 1991 has already been changed several times, and now we want to revive it so that the reader can use it. Made a partial zigzag scheme. It is paired with a converter and is used to set the UHF reception on the meter frequency of the TV. Those who have not forgotten about the Soviet technique, know that here there were two nests, and the state rarely used decimeter frequencies. It showed regional TV channels.
Make square 75 Ohm wire frame with a side that is 1/4 wavelength. For 500 Hertz, this value is 13.5 centimeters. The frame is fixed one angle down on the base of any dielectric material. Here’s how it happens:
- The top corner of the wire is protected. In this area, the screen and insulation are removed for one centimeter.
- In the lower corner the cable is installed with a margin of a few centimeters. Isolation is removed from these excess places, and after the screens are soldered, creating electrical contact. The core wire is just in the air.
- Fixing the antenna to the base is carried out with one-millimeter tinned wire. This reinforces the contact in the lower corner between the screens.
- The rest of the square goes, which stands on one of the corners, fixed to the base.
The corners of the square are slightly rounded, this is normal. Make the fasteners with wire straps in place to get a reliable design. You can change the size of the side of the square to suit your needs in such a way as to adjust the resonance to the television frequency. If necessary, the screen is hung for a length of 10 cm on the other side of the plate for a length of 10 cm. All this in total up to the antenna also forms practically the side of a square, equal to 13.5 cm. This distance is chosen considering the size of the wave.
The screen-reflector is fixed on 4 racks and has a height of 200 millimeters and a width of 330 millimeters. The middle of its symmetry is the same as the middle of the antenna symmetry. This makes it possible to receive only from one direction and removes some of the interference. This step is useful when there is a multipath effect. At the same time setting the screen almost doubles the gain. The converter to the antenna now does not look very appropriate. But the antenna amplifier would, by the way, when the signal is weak, and the tower is far away.
It is easy to understand that the design is rather cumbersome. It should also be noted that the 75 Ohm wire is designed for the post-Soviet equipment, while it was a single standard. Now most devices work 50 ohm wave resistance. Accordingly, the wire, before making the DMV antenna, you need to find a 50 ohm. Well, if you can still do the amplifier yourself, it’s great! We will have an active antenna t2 do it yourself.
The simplest scheme of UHF antenna
It is much easier to make a quarter-wave vibrator from a coaxial wire with your own hands. Why determine the frequency of admission. For example, for the first Moscow multiplex, this amounts to 559.25 MHz, with this in mind, we determine the wavelength, which is equal to 53.6 centimeters.
Respectively, need to clean exactly 13.4 centimeters. The quarter-wave vibrator resistance is close to 40 ohms. We take this into account when coordinating or simply connect to a digital TV receiver by installing a F-connector or another suitable connector before. We clean only the screen and exterior. Directly quarter-wave vibrator set horizontally for better reception. This antenna can be done even by a schoolboy who has 25 rubles for a cable, a connector and a knife. This is the simplest UHF antenna with your own hands.
Do not expect great feats from her and absolutely do not need to put it on the roof. This is not an external UHF antenna and do-it-yourself antenna amplifier. However, it will greatly enhance the reception on a simple receiver. And when there is no time to do something for a long time, try this option.
Antenna at 855 hertz
Estimated antenna size will be match the European 69th channelwhich includes Russia. Television is shown at a frequency of 855.25 Hertz, and the sound - at 861.75 Hertz. According to calculations, your antenna circuit is tuned to 857 Hertz. A large 75 ohm cable will be needed for the design. Of 54 centimeters we make a ring with a gap, we will take a signal from it. Pay special attention that the screen in this version is signal. To him we fix a matching U-bend from a 75 Ohm wire the size of a wave in a floor - 175 millimeters.
It happens like this:
- one end of the core inside the U-bend wire sits on the signal wire connected to the receiver and on one of the screen parts;
- The other end of the U-bend wire strand sits on the other end of the screen.
As a result, the added part of the line equalizes the resistance of the wire supplied to the receiver and the round loop. To make this design a digital UHF antenna, it is necessary adjust to the frequency of the multiplex. How to do this is probably already clear, but we will describe in detail:
- The size of the U-knee is half the size of the multiplex wave.
- The size of the frame is of the multiplex wave.
The size of the multiplex wave can be found on the Internet or in local publications. To obtain vertical polarization, the frame must be rotated at right angles to the side of the gap. In this case, you can catch the signal and radio. These are the simplest external antennas.
This antenna creates a small gain, but covers channels 1 through 41. This design is a parallel connection of the star meter vibrator and the "wave channel" of the decimeter range.
All construction length - 64.7 centimeters. We will consider it from the front edge. In the decimeter part there is 1 double reflector and five directors. If viewed from the front, they have a certain size and removal between them:
- Size 19.9 centimeters - distance from the edge 0.
- Size 20.2 centimeters - removal from 1 director to 12.9 centimeters.
- Size 20.4 centimeters - removal from 2 directors 12.2 centimeters.
- Size 21.2 centimeters - removal from 3 directors 5.3 centimeters.
- Size 31.4 centimeters - removal from 4 directors 1.2 centimeters.
- The size of the reflector is 34.9 centimeters - the distance from the 5th director is 6.7 centimeters.
Important! Reflector has 2 wire construction, one on top of the second with a jumper that is centered on the central axis of the antenna. The height of the partition about 10 centimeters. 5 director in the form of an elongated oval frame, where the upper coil in the middle is fixed to the axis of the antenna. The open part 5 of the director is necessary for parallel connection of the meter part fixed vertically behind the antenna.
The meter part has 6 rays, all rays are broken vertically along the axis. One is horizontal. Rays are set to 3 pieces on the parts of a two-wire line measuring 5 centimeters. If viewed from above, then they all bend mirror anteriorly. The angle between the rays 120 gr. If we look at the front, then a regular six-pointed star comes out with an angle of 60 degrees between the rays. The length of the rays is 108 centimeters.
The line of 11 centimeters goes beyond the star directly upwards. It passes in a semicircle, from the fifth director, and ends vertically near the star. At a distance of 11 centimeters, but in the direction of the director there are 2 points for the soldering of a 75 Ohm coaxial wire going to the TV. Pieces from this place of the two-wire line to the star and the fifth director are chosen so that the waves of these ranges do not intersect.
TV antennas are made of material that provides the necessary strength properties. The central core of the wire sits on one cable of the two-wire line, and the screen on the second. If necessary, matching device is added. In this case, it is difficult to use the U-knee, since the UHF and MV ranges are different, but as the reviews show, there is no big power distortion.