The most common mistake in installing a TV cable: laying in a wall without corrugation (explains a TV systems specialist)

  • Dec 11, 2020
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A source: https://www.emctestlab.ru/news
A source: https://www.emctestlab.ru/news

Good afternoon, dear guests and subscribers of the "Build for Myself" channel!

I had a dispute with an employee of the office that is engaged in the installation of cable equipment. I confess that I have never seen UTP and coax cables get plastered in corrugation. Laying under the screed - yes, under the ceiling - sometimes, on the walls - I've met how many construction projects I've met, I've never seen a TV cable in a corrugation!

Today, the market offers a very large selection of antenna cables such as SAT 50, RG 6, DG 113 and many others. They all have an identical design with the main conductor in the middle, followed by insulation, shield and solid external insulation. In this article, in order not to overload it, I will not touch on the materials used in production, as well as high-quality and cheap products, - the principle is the same for everyone, but correct installation, including laying in a corrugation - this is my topic articles!

Photo source: https://blogvp.ru
Photo source: https://blogvp.ru
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And the point here is not a quick replacement of the cable after aging or its failure.

In fact, it is not enough to choose a high-quality cable, it still needs to be properly and properly laid, knowing the purpose and specifics of the product.

One of the main parameters of the cable is characteristic impedance (50 Ohm or 75 Ohm), which must be consistent with the device receiving the signal. When the resistance in the cable fluctuates, ripples and blurring of the picture on the television screen are formed. If the characteristic impedance does not match the receiver, part of the signal does not reach it, but is reflected by a backward wave, creating distortion.

Photo source: https://myguru.ru/services/remont-televizorov

Cable cross-section geometry

This is where a common mistake lies, which the master mentioned. This category also includes a cable hall. So, in any plaster, cement or gypsum, when it hardens, stresses inevitably arise when the mixture shrinks (cobwebs on the plaster, cracks are the result of stresses). The cable undergoes micro-deformation along its entire length and from all sides, somewhere it is stretched, somewhere it is flattened, and somewhere cracks - that's why the masters strongly recommend laying the "coaxial" only in the corrugation or after rough work in cable channels. In addition, the master plasterer will definitely hit him with the rule a couple of dozen times :-)

To understand why the wave resistance changes, it is enough to look at its formula:

If there is a shift between the central core and the screen (whether it is a hall when turning, stretching or flattening), this the section immediately changes the value of the wave resistance, since it depends on the distance between the central core and braid. Deformation is not always noticeable by eye, and special devices show serious deviations.

And, secondly, the sheath of such products does not provide for contact with aggressive cement, at the slightest exposure of the cable, the braid will short out with the wall, and this will inevitably lead to signal interference.

Therefore, the professional told me: " Now you will know that a TV cable in the wall without corrugation gives interference - after all, this is a very common problem that we are worried about, thinking that it is the equipment. This is not a warranty case. Corrugation costs a penny in comparison with a good cable, it is better to play it safe than to collective farms and pull the cable repeatedly along the walls, hiding it behind the baseboards and in cable channels. "

I think the article has become useful for you! Thanks for attention!

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