Poor TV shows from the antenna - two reasons. Inconsistency devices, bad equipment. Last touches the antenna, televisions somehow cope with the tasks. However, the problem lies in the amplifier. It should at least be set to the desired frequency. Below we consider the typical situation, methods of solving the simplest methods. A simple way - to buy a satellite dish, put it. Alternatively, finish up watching TV, the Internet is much more fun!
cable problems
It sounds funny, but the first thing is to check the cables. Presented several demands which necessarily follow:
- Firstly, the characteristic impedance of the cable television is 75 ohms. Deviations in value provoke tract reflection part of the power will inevitably lead to losses. Invented methods for matching, using which the cable is allowed to use another wave drag. Wait a little fuss. Devices intended for television broadcast, characteristic impedance of 75 ohms. We consider truism, choosing cable.
- As for the owners of the second council of indoor antennas. A typical pattern: hang wave channel, a half-wave dipole with a mustache and close to Cable Bay lies. The first thing we look, passive or active antenna. You need to turn on the power? If proved to be passive, cut the excess cable, decorate bay storage. Segment feeder introduces irreparable loss of signal. At the receiver antenna sensitivity strongly depends on the attenuation before the first amplifier stage. In our case, such is within the TV cable to the socket brings enormous losses. Another thing is the active antenna. The first amplifier stage is here a cable length becomes uncritical.
- If the passive antenna on the roof, to get hold good, using the internet, cable characteristics. It is logical to see whether the losses per unit exceeds 0.2 dB. Attenuation determines feeder length, electrical characteristics of the product. Three meters of usable cable has a loss equal to the meter cheap. It is recommended to place the antenna amplifying, replace the cable. Fortunately, the television is not expensive. Forget the high cost of high-frequency WiFi!
Why do we need an active antenna
Mentioned that if the antenna is active, it is permissible length of the cable, the loss is not considered a critical element. If you can not get a good conductor, the length can not reduce, the roof away, relies buy an active antenna. Note: for the installation of the equipment will need permission HOA, the owner of the house. There is insanity: harness draw up a special plan for the placement of utilities, by paying a fee to a specialized company, to pay professional artists performing the installation. Should be done according to the rules.
Amplifier antenna will bypass the restrictions imposed on the quality of the cable length. The power cord is often required to pull the roof. The distance to the TV station a small point just blocked by houses - recommend trying to catch a signal room variety. TV will show and without a common antenna. Allowed to place "Cheburashka", decorated with a balcony, even on false ceiling. The path of the reflected beam are inscrutable. However, conditions vary according to weather, the reception will get worse (or better). It is recommended to prefer an omnidirectional antennas having smaller coefficient directional supplying additional external amplifier.
Discover antenna drawback, unrelated to the quality of reception of a single signal. Sources of problems due to the effect of multipath. The omni-directional antenna is receiving from all directions (azimuths). Get a few rays, the image will begin to divide in two. A similar effect is overdrive. Remove the power of electric shock, check the result. Similarly eliminated reddish snow. The reason is the same - overdrive.
Tip! Adjust the equipment, trying to get obtain the required performance. Lower gain. Buy attenuator television. Such would reduce the gain by twenty dB.
The indisputable lack of omnidirectional antennas seen: sources of interference will apply to all parties, sharply reducing the signal / noise ratio. It's not critical digital multiplex broadcasting includes error correction codes. Receiving antenna impossible with analog television amplifier, happen above the level of noise amplify the useful component.
Selection and installation of the antenna
The antenna itself can not respond to the received signal, or improperly installed. Many people know that it is useful to orient the device in space, but not everyone knows how to do it. Television in the Russian built on the SCM for horizontal polarization, so the half-wave vibrator or skewed channels with high wave leads to deterioration of reception. It also shifts the frequency range, whereby the image quality falls further.
Required, using a level to put the antenna in the correct position. In addition, when receiving from the distant televyshek acts simple rule. The higher the antenna, the more chances to catch the broadcast. This rule applies to the DMV, which is why the MF and HF still remains attractive. The waves at these frequencies encircle the earth's surface, so you can catch even without bringing the antenna on the roof.
External barriers are also investing contribution, if spread around the forest, the reception will be degraded. The waves are attenuated by passing through the obstacles. In this case, to recommend to get the antenna to the amplifier. It plays a role and type. Full-wave vibrators better receive the signal, and in the store to get difficult. It helps self-made antenna. Made of copper or aluminum conductors and cables installed by the rules will provide better reception than the store.
More than once described how to produce narrowband antenna, which is tuned to the channel frequency. In this case too, can achieve great results, simple ways. In the end, even the construct quarter-lovers vibrators for digital receivers. It's just a short piece of wire screen which is a quarter wavelength cleaned off at one end. For the first multiplex Moscow, it is 13.5 cm. On the other end is soldered connector that plugs into the receiver. Quarter-vibrator is horizontal. If necessary, you can bend at the base for easy placement. Even such a simple construction gives uncoordinated and results in the reception of television broadcasting.
Alignment Yagi type antennas
Beginners disturbing question how to properly align the antenna type wave channel. The designs are very simple, give a great gain. The design is ideal for UHF, where digital multiplexes lie. First consider balancing signal. The operation will be needed if reducing the cable length of 10 meters. The device is a piece of wire parallel to the feeder, spaced at 3 - 5 cm.
The method is suitable for the wave channel made by standard rules. reduce the cable shield are simply placed on one side of the driven element, but on the other hand and clings balun cable segment. The length depends on the channel, for example, to multiplex the first Moscow is 17.6 cm. In full over a piece parallel to reduce the cable. How to connect:
- Vein balun planted on one side of the driven element parallel conductor drop cable. Here it closed braid segment.
- At a distance of the length of the active balun cable insulation vibrator reduction trimmed. Screens parallel wires are closed, here is attached to a second end of the segment cores.
Much more difficult is the case with the antennas, which are below the characteristic impedance of 75 ohms. Then used a special matching devices. Active vibrator can be T-shaped. The upper part of the loop is incremented additional wire in both directions. The total length is calculated by the formula:
L = (λ / 2) * (1 - 0,225 / ln (λ / 2d)), where
λ - wavelength, m; d - wire diameter, expressed meters. The height of the loop is equal to one-hundredth of λ or less. The width of the loop is chosen experimentally, seek closer to the characteristic impedance of 75 ohms. "Humpbacked" graph of. Maximum observed when the loop width equal to λ / 4.
Through designing own antenna, the method selects an overwhelming number of hams, allow to manufacture the device having a desired characteristic impedance. With the drawing hands, duplicate construction predetermined number of times. Get ready to work, if it is bad TV shows. Find out the broadcast frequency to make a special dish.
signal interference will be minimal in this case. The procedure described by the wave channel design. Shtudiruet portal! Gather strength, consider the construction of log-periodic antenna, just wondering how to do it. Product Feature - catch the broadcast range. Coverage of log-periodic antenna stunning.
