The decimeter range refers to the frequency of television broadcasting, including digital. Some segment antennas are simple, others are complex in design. The purpose of the units is to take horizontal polarization from the towers. Today we will consider how the DMV antenna is made by hand.
A simple antenna design with a 500 MHz center frequencyThe partial zigzag scheme is executed. There is a pair with a converter, designed to receive UHF on the meter input of the TV.Those who remember the Soviet technique know: there are two nests on the back of the TV.The decimeter range was not used by the state. Broadcast regional channels. We make a square frame of 75-ohm cable with a side equal to a quarter of the wavelength. We take 500 MHz - we get 12.5 cm. The frame is fastened with one angle down on the basis of the dielectric material:
- The upper corner of the cable is stripped. Isolation is removed, the screen length of 10 mm.
- In the lower corner of the wire is taken with a margin of a couple of centimeters. Isolation is removed from excess areas, then the screens are soldered, forming electrical contact. The inner core just hangs in the air.
- The antenna is fixed to the base using tinned wire 1 mm in diameter. Additionally enhances the contact between the screens in the bottom corner.
- The rest is a square, standing on one corner, which is attached to the base.
The corners of the square are slightly smoothed. Keep the wire clip in place, forming a sturdy construction. You can vary the length of the side of the square according to your needs. Adjust the resonance to the frequency of broadcast television. If necessary, the screen is hung at a distance of 10 cm from the back side of the plate at a distance of 10 cm. In total, the antenna gives almost a side of a square equal to 12.5 cm. Distances are chosen by determining the wavelength.
Reflector screen is mounted in four racks, has a width of 330 mm, a height of 200 mm. The center of symmetry coincides with the construction axis of the antenna. Allows you to receive from one direction, eliminates some of the interference. A step is useful if there is a multipath effect. At the same time, the introduction of the screen approximately doubles the antenna gain. Converter today looks out of place. UHF antenna amplifier is useful, if the signal is weak, the tower is far.
It is easy to notice: the design is bulky.75 Ohm cable is designed for Soviet equipment. The generally accepted standard of television. Today, devices are working, powered by a cable with a wave impedance of 50 ohms. Therefore, before you make the UHF antenna, you need to find. If the amplifier in addition can do well! Get antenna UHF active.
The simplest design of the UHF antenna
It is much easier to use coaxial cable, creating a quarter-wave vibrator. Find the frequency of admission. The Moscow first multiplex uses 559.25 MHz, from here we calculate the wavelength.
So, we will clean by 13.4 cm. The resistance of a quarter-wave vibrator is close to 40 Ohms. We take into account the fact, when coordinating, we simply plug into the receiver of digital television, having attached a pre-f-connector or another necessary connector. We clean only the outer shell, the screen. A quarter-wave vibrator is positioned horizontally for better reception. The design will be collected by schoolchildren who have found 20 rubles for a wire, a knife, a connector. The simplest UHF antenna with their own hands, for comparison, for the purchase they are asking for more wood.
Do not expect great feats, avoid dragging onto the roof. Not external DMV antenna. With a guarantee will strengthen the reception of a conventional receiver. No time to make - try the easy way.
Antenna UHF - 855 MHz
The size of the antenna must correspond to the 69th channel of Eastern Europe, and Russia is included. Video is broadcast at a frequency of 855.25 MHz, sound - 861.75 MHz. As far as can be judged, the loop is tuned to 857 MHz. For the manufacture will need a hefty piece of wire impedance of 75 ohms. From 53 cm we make a ring with a gap, from where we will shoot the signal. Pay attention: the screen is alarm. Attach a 75-ohm U-cable matching half-wavelength of 175 mm.
Is done as follows:
- one end of the inner core of the U-bend is placed on the signal wire, the cable leading to the receiver, also on one side of the antenna screen;
- The second end of the inner core of the U-bend is planted on the opposite end of the antenna screen.
As a result, the added line segment equalizes the resistance of the round loop and the cable leading to the receiver. To get the device from the antenna for digital television UHF, you need to adjust to the frequency of the multiplex. The procedure will clarify:
- The length of the U-knee is equal to half the wavelength of the multiplex.
- The diameter of the frame is equal to a quarter of the multiplex wave.
The wavelength of a multiplex can be found on the Internet, local newspapers. To accept vertical polarization, turn the frame by 90 degrees with a break to the side. You can pick up the radio signal. The simplest outdoor antennas UHF.
All-Wave Antenna UHF-MV
Antenna MV-UHF gives a small gain, covering channels 1-41 with a few exceptions. The design is a parallel connection of the "wave channel" of the decimeter range and the star meter vibrator.
The total length of the device is 64.7 cm. Let's start with the front edge! In the decimeter part 5 directors sheltered, one double reflector. If counted from the front, they have length and distance from each other:
- Length 19.9 cm - the distance from the front edge is zero.
- Length 20.2 cm - removal from the first director of 13.9 cm.
- Length 20.4 cm - removal from the second director of 13.2 cm.
- Length 21.2 cm - removal from the third director of 6.3 cm.
- Length31.4 cm - 2.2 cm distance from the fourth director.
- Reflector length 34.9 cm - 7.7 cm distance from the fifth director.
Note: the reflector consists of two wires, one above the other with a jumper, sitting in the middleThe central axis of the TV antenna UHF.The jumper height is 10 cm. The fifth director is a kind of elongated oval frame, the upper turn of which is attached to the axis of the antenna in the center. The open part of the fifth director will serve for parallel connection of the meter part, mounted vertically at the back of the antenna.
The meter part consists of 6 rays, broken along the vertical axis of symmetry. One is horizontal. Rays are based on three pieces on the elements of a two-wire line width of 5 cm. If you look from above, they are bent forward in a mirror. The angle between the rays is 120 degrees. When viewed from the front, it turns out the correct six-pointed star with an angular distance between the rods of 60 degrees. The length of each 108 cm. To connect the structure, the center of the antenna sitting on the axis is a two-wire line with a total length of 91.5 cm, going straight to the 5th director( lower open coil).
11 cm line goes further up the stars. There is a detail in a semicircle, starting at the 5th director, ending vertically at the star. At a distance of 11 cm, now in the direction of the director there are two wiring points of a 75 Ohm coaxial cable going to the TV.The segments from the point of the two-wire line to the star and the 5th director are chosen so that the waves of the ranges do not mix. Meters easily pass from the star to the cable, do not go to the UHF part, on the contrary, from the 5th director there is little resistance for high frequencies, irresistible for long ones.
Aerials UHF-MV televisions are made of a material that provides the desired strength characteristics. The central conductor of the cable is planted on one wire of a two-wire line, the screen on the other. If necessary, add a matching device. It is difficult to use the U-knee, the ranges are different, the author of the invention writes: there are no particular power reflections.
Other antennas UHF range
The UHF log-periodic antenna is a broadband device. Catching the whole range. It resembles a wave channel configuration, differs in that the directors are located according to a different mathematical law, which gave the name of the design of the UHF antenna. Directors outline a triangle. DMV antenna Delta H111-01 is made in a similar way. Providing broadband.
Antenna for the UHF with their own hands is made of improvised material, you can adjust many metal objects. The indicated constructions are a part of all schemes; narrowly specialized devices work best today. Digital multiplexes do occupy one frequency. Antenna television UHF-MB become unnecessary.
We wish good luck to amateurs, Fortune will need help, given the absurdity of articles on the subject of design. We do not pretend to ideality, but at least we try!
