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Is there a shielded coaxial cable. Marking of domestic cables RK

Coaxial cable It is an electric cable consisting of a central wire and a metal braid separated by a layer of dielectric (internal insulation) and placed in a common outer shell.

Coaxial cable Until recently, it was common most widely, which is associated with its high noise immunity (due to the metal braid), as well as higher than in the case of a twisted pair, allowed data transfer rates (up to 500 Mbps) and large allowed transmission distances (up to a kilometer and higher). It is more difficult to mechanically connect to unauthorized listening of the network, it also gives noticeably fewer electromagnetic emissions. However, the installation and repair of the coaxial cable is more complicated than the twisted pair, and its value is higher (it is more expensive about 1.5-3 times compared to cable based on twisted par). Comprehensible and installation of connectors at the ends of the cable. Therefore, it is now applied less frequently than twisted a couple.

The main application of the coaxial cable finds in local computer networks with a tire topology. In this case, at the ends of the cable, terminators must be installed to prevent internal reflections of the signal, and one (and only one!) From the terminators must be grounded. Without grounding, the metal braid does not protect the network from external electromagnetic interference and does not reduce the emission transmitted over the network to the external environment. But when grounding braid in two or more locations, not only network equipment, but also computers can exit. Terminators must be necessarily agreed with cable, that is, their resistance should be equal to the wave resistance of the cable. For example, if a 50-ohm cable is used, only 50-ohm terminators are suitable for it.

Less frequently coaxial cables are used in networks with the topology "Star" and "Passive Star" (for example, in the ARCNET network). In this case, the coordination problem is significantly simplified, since external terminators are not required at free ends.

The wave resistance of the cable is indicated in the accompanying documentation. Most often, 50-ohm (for example, RG-58, RG-11) and 93-ohm cables are used in local networks (for example, RG-62). 75-ohm cables common in television techniques are not used in local networks. In general, the brands of the coaxial cable are significantly less than cables based on vital steam. It is not considered particularly promising.

There are two main types of coaxial cable.:

A thin cable having a diameter of about 0.5 cm, more flexible;
Thick cable having a diameter of about 1 cm is significantly more hard. It is a classic variant of a coaxial cable, which is already almost completely displaced by a more modern thin cable.

A thin cable is used to transmit for shorter distances than fat, since the signal will buffer stronger in it. But with a thin cable, it is much more convenient to work: it can be quickly paved to each computer, and thick requires tough fixation on the wall of the room. Connecting to a thin cable (using BNC connections Bayonet type) easier and does not require additional equipment, and to connect to a thick cable it is necessary to use special fairly expensive devices that pierce its shells and install contact with both the central residential and the screen. Thick cable is roughly twice as thin. Therefore, the thin cable is used much more often.

As in the case of twisted pairs, an important parameter of the coaxial cable is the type of its outer shell. In the same way, in this case, both Non-Plenum (PVC) and PLENUM cables are applied. Naturally, the Teflon cable is more expensive than polyvinyl chloride. Usually, the type of shell can be distinguished by its color (for example, for the PVC cable, BELDEN uses yellow color, and for teflon - orange).

The typical values \u200b\u200bof the signal propagation delay in the coaxial cable are for a thin cable of about 5 ns / m, and for thick - about 4.5 ns / m.

There are options for coaxial cable with double screen (One screen is located inside the other and separated from it an additional layer of isolation). Such cables have better noise immunity and listening to listening, but they are a bit more expensive than usual.

Currently it is believed that the coaxial cable is outdated, in most cases it may well be replaced or. New standards on cable systems No longer include it in the list of cable types.

Coaxial cable

Coaxial cable (from lat. co. - together and Axis - the axis, that is, "coaxial"), also known as coaxial (from English. coaxial) - Electric cable consisting of located coaxially central conductor and screen. Usually serves to transfer high-frequency signals. Invented and patented in 1880 by the British physicist Oliver Hevisayd.

RG-59 television coaxial cable

Device

Coaxial cable (see Figure) consists of:

4 (a) - shells (serves for isolation and protection against external influences) from light-stabilized (i.e. resistant to ultraviolet radiation of the Sun) polyethylene, polyvinyl chloride, oops in fluoroplastic tape or other insulating material;
3 (b) - an external conductor (screen) in the form of a braid, foil coated with a layer of film aluminum and their combinations, as well as a corrugated tube, observing metal ribbons and other copper, copper or aluminum alloy;
2 (C) - isolation made in the form of solid (polyethylene, foamed polyethylene, solid fluoroplastic, fluoroplastic tape, etc.) or semi-separated (Caddle-tubular hanging, washers, etc.) of dielectric filling providing constancy of the mutual location (alignment ) internal and external conductors;
1 (d) - an internal conductor in the form of a single straightforward (as in the figure) or a pig in the wire spiral, a multi-moist wire, tubes performed from copper, copper alloy, aluminum alloy, washed steel, copper aluminum, silver plated copper, etc.

Due to the coincidence of the axes of both conductors, the ideal coaxial cable, both components of the electromagnetic field are fully focused on the space between the conductors (in dielectric insulation) and do not go beyond the cable, which eliminates the loss of electromagnetic energy to radiation and protects the cable from external electromagnetic tips. In real cables, the limited output of radiation outwards and sensitivity to the tips are due to the deviations of geometry from ideality.

History of creation

Application

The main purpose of the coaxial cable is the transfer of a high-frequency signal in various fields of technology:

communication systems;
broadcast networks;
antenna feeder systems;
ACS and other manufacturing and research techniques;
systems remote control, measurement and control;
alarm and automation systems;
objective control systems and video surveillance;
communication channels are different radioelectronic devices mobile objects (ships, aircraft, etc.);
intublock and inter-block connections in the composition of radio-electronic equipment;
communication channels in household and amateur technology;
military equipment and other areas of special application.

In addition to the sewage signal, the cable segments can be used for other purposes:

cable delay lines;
symmetrical and matching devices;
filters and pulse formers.

There are coaxial cables to transfer low-frequency signals (in this case, the pole serves as a screen) and for direct current High voltage. For such cables, wave resistance is not normalized.

Classification

By destination - For Systems cable television, for communication systems, aviation, space technology, computer networks, household appliances etc.

International Designations

Systems of the designations in different countries are established by international, national standards, as well as their own standards of manufacturers (the most common series of brands RG, DG, SAT).

Auxiliary elements of the coaxial tract

Coaxial connectors - to connect cables to devices or their joints between themselves, sometimes cables are produced from production with installed connectors.
Coaxial transitions - for the articulation of cables with unpaired connections with each other.
Coaxial tees, directional branches and circulators - for branches and branches in cable networks.
Coaxial transformers - to match the wave resistance when connecting a cable with a device or cables.
Terminal and passing coaxial loads are usually consistent - to establish the right modes Waves in the cable.
Coaxial attenuators - to attenuate the signal level in the cable to the required value.
Ferrite valves - to absorb the reverse wave in the cable.
Graphically distributors based on metal insulators or gas-discharge devices - to protect the cable and equipment from atmospheric discharges.
Coaxial switches, relays and electronic commuting coaxial devices - for switching coaxial lines.
Coaxial-waveguide and coaxial striped transitions, symmetrical devices - for dusting coaxial lines with waveguide, striped and symmetrical two-wires.
Pass and end detector heads - to control the high-frequency signal in the cable by envelope.

Basic normalized characteristics

Ravenly weakening at different frequencies
Running capacity
Running inductance
Diameter of central core
Internal screen diameter
External diameter of the shell
Maximum power transmitted
Maximum allowable voltage
Minimum cable bending radius

Calculation of characteristics

Determination of the rose container, the pattern inductance and the wave resistance of the coaxial cable according to known geometric sizes is carried out as follows.

First you need to measure the inner diameter D. The screen, removing the protective shell from the end of the cable and wrapped the braid (the outer diameter of the internal insulation). Then dimmeter is measured d. Central veins, removing pre-insulation. The third parameter of the cable that needs to be known to determine the wave resistance is the relative dielectric constant ε of the material of internal isolation.

Running capacity C H. (In the SI system, the result is expressed in the Farades per meter) is calculated by the cylindrical capacitor capacity formula:

where ε 0 is electrical constant.

Running inductance L H. (in the SI system, the result is expressed in Henry per meter) is calculated by the formula

where μ 0 is a magnetic constant, μ is the relative magnetic permeability of the insulating material, which in all practically important cases is close to 1.

Wave resistance of the coaxial cable in the SI system:

(Approximate equality is valid in the assumption that μ \u003d 1).

The wave resistance of the coaxial cable can also be determined by the nomogram shown in the figure. To do this, you need to connect the straight line of the point on the scale D / D. (The ratio of the inner diameter of the screen and the diameter of the inner core) and on the scale ε (dielectric permeability of the internal insulation of the cable). Point of intersection spent straight with a scale R. The nomogram corresponds to the desired wave resistance.

The speed of propagation of the signal in the cable is calculated by the formula

where c. - The speed of light. When measuring delays in paths, designing cable lines of delays, etc. It can be useful to express the length of the cable in nanoseconds, for which the reverse signal of the signal is used, expressed in the nanoseconds per meter: 1 / v. = √ ε · 3.33 ns / m.

Limit electrical voltagetransmitted by the coaxial cable is determined by electrical strength S. The insulator (in volts per meter), the diameter of the internal conductor (since the maximum voltage of the electric field in the cylindrical capacitor is achieved near the internal plating) and to a lesser extent with a diameter of the external conductor:

Cables with ruptures in the shielding shell are used as distributed antennas.

Coaxial cable is used to transmit a television signal. With the emergence and development of video surveillance systems of different types And the destination cable began to be used to transmit a signal from video cameras to a centralized surveillance complex. For these purposes, both ordinary and modern digital coaxial cable is used. This article will present a small analysis of the species and features of the use of this cable products for video surveillance purposes.

Cable species and features

This cable was invented in 1880 in the UK. The constructive feature of the coaxial cable is combining on one axis of two conductors separated by a layer of dielectric material in a common outer shell. Initially, the coaxial radio frequency cable was used to transmit a television signal from the antennas of the general use of the public network and individual antenna devices to televisions, as well as in systems of a radio relay, radio transmission, satellite, mobile radio communications. In these areas, it is applied now. Basically, these are powerful cables with a large cross section of the inner conductor and braid in a rigid shell. In video surveillance systems in connection with the features of the gasket in cramped conditions, large number Cable bends are used flexible cables of smaller sections in a softer braid.

Types of cable products

There are two types of cable products that are used for laying in video surveillance systems:

Normal coaxial;
Combined (coaxial + 2 wires for connecting the power supply of video cameras and / or transmission of control signals) Cable. A cable with a carrier steel cable for an outer air gasket between buildings is also manufactured.

The use of a combined cable is preferable to many parameters:

The cost of the cable is lower than the price sum of the conventional coaxial cable and the two-housing electrical wire with the same characteristics by section, the material lived, braid and isolation;
Lighter gasket, convenient installation with a smaller number of fasteners and, accordingly, tidy appearanceThat is especially important when laying in office, shopping and other public spaces and buildings.

Marking

The most famous coaxial cable for video surveillance such labels:

RK - Cables produced in Russia;
RG - imported production.

Brands of a combined video cable - KVK is much larger:

KVK-B - in a polyvinyl chloride outer sheath for the inner laying;
KVK-P - in the outer sheath of light-resistant polyethylene for outdoor gasket;
KVK-PT - similar to the manufacture of KVK-P, but has a steel cable for outdoor gasket between buildings and structures;
KKSP and CSSP - for internal and outdoor gaskets, with a single-core internal conductor;
KKSVG and KKSPG are the same cables, but with a stranded internal conductor;
The SVGG is a universal cable, often erroneous for the designation "NG" non-combustible, does not spread combustion with a group laying.

Types of coaxial cable

The main parameters: the total thickness of the cable, the thickness and density of the braid, the cross section of the inner conductor, the materials used in the production of the cable directly affect the wave resistance of the cable. Wave resistance - this electrical characteristic of the cable measured in OM. It shows the possibility and quality of television signal transmission from the camcorder to the receiving device (video recorder with a monitor or personal computerselected as the operator's workplace). In the security video surveillance system, it is recommended to use a cable with the same wave resistance to ensure the quality of the signal, the lack of additional interference and distortion.

Also conditionally divide coaxial cable for general thickness:

Thin - up to 50 mm, with a single braid and thin outer sheath, for laying in buildings at a distance of no more than 200 to the distance camcorder from the surveillance complex;
Thick - up to 100 mm, double braid, thick outer shell, allowing the transmission of video from the camera without attenuation of the television signal at a distance of up to 650 m, which is very important for video surveillance systems at enterprises and warehouses.

Composition and cable design

The elements of the coax cable are:

Internal electric conductor or central lived;
A shell of dielectric material;
Screen from double-sided foil. It is not used in all types of cable;
Braid of different density of copper;
Outdoor shell.

Internal conductor make:

From single-core aluminum or copper wire;
Coated wire or aluminum wire copper;
Copper strainer;
Copper wire covered with a layer of silver.

Copper and aluminum are used both in purified form and as their alloys. The internal conductor in the coaxial cable is the main element that serves to transmit the signal. The material of the internal conductor or the central core is easily determined by the external inspection of the cable cutoff: silver color - aluminum or steel with copper coating, completely golden - copper. The more section, the better signal can be transmitted. But we should not forget that the price is directly in proportion to the price of 1 cable meter and increase its rigidity, which is not always acceptable.

The shell from the dielectric material isolates the inner conductor from the braid. It is performed from monolithic or foamed polyethylene or polyurethane. The monolithic material is more suitable when laying through rooms with high humidity, it is better protecting from the tip, mechanical damage The central veins during squeezing, due to the rigidity is limited if it is necessary to lay the gasket on corridors and premises with many turns, where the flexible cable with insulation from the foamed porous material is more applied.

The cable braid serves as the second conductor and the grounded screen to protect the central conductor. Sometimes complemented by a metal foil screen. The denser of the braid with a high content of copper wire, the better video signal is provided.

The outer cable shell is protection against external influences. Perched from polyvinyl chloride plastic.

Standard cable products of stamps RK, Rg - coaxial braid cables with insulation from monolithic or porous polyethylene. Single-core or stranded internal copper conductor or copper coated steel wire. External conductor - aluminum foil + copper braid or two silver plated copper braids. The shell is made of plastic that does not spread the burning.

Choosing a coaxial cable

Suitable in all parameters a coaxial cable for video surveillance is selected based on the tasks and conditions when organizing a surveillance system at each specific object of protection. These tasks and conditions are set out in design and estimate documentation, if it is either in the technical task of the customer. In the first case, the cable is selected. In the second variant, which meets much more often, the contractor or the owner, going to mount a video surveillance system on his own, should consider and evaluate several significant parameters:

Distances to selected locations of the camcorder;
The presence of distribution panels, lighting boxes not far from camera installation locations;
Uniformity of the cable laying method to each chamber (internal, outer, air on the cable);
The presence of sources of electrical flooring and electromagnetic interference on the selected cable laying line (power and lighting electrotrassia, electric motors, powerful electrical appliances and other devices that create an electromagnetic field around them), which will lead to loss of video quality;
Requirements for cable products in color, thickness, capabilities of laying ceilings, in cable channels, including existing on the facility, to preserve the integrity of the interior of the premises;
Need to record a beep.

The selected connectors for the coaxial cable are also important, which allow you to correctly connect the cable line to the camcorder.

Having considered all the conditions and options for laying, make the simplest cable magazine with distinction distances, taking into account the geometry of the gasket, the number of bends.

The determining factor is the length of the coaxial cable for video surveillance, because the cable deployed to each chamber must be performed by a solid piece, without any connections to ensure the quality of signal transmission.

It is necessary to take into account the protection of the cable from mechanical damage, humidity in the premises, climatic conditions and air temperature during installation work in the outdoor gasket, the need for transitions between buildings. With this in mind, it is possible to draw conclusions about the possibility and need to apply certain types of cable. Often, various types of cable are used in one system: the usual, combined, on the cable.

In conclusion, it is worth saying that the selection of the cable is very important. But this is only one element of the video surveillance system and achieve the tasks you can only proper selection Total list of necessary equipment, which will serve as other articles.

Coaxial cable is widely used to transfer information signal packages in computer networks, television signals In cable television systems, video surveillance and many other radiotechnical engineering complexes. With the advent of Bluetooth data transmission technologies or more modern and high-speed Wi-Fi, the intensity of the use of the coaxial cable has decreased.

Coaxial cable for transmitting information packages

Disadvantages of new technologies:

a slight range of action;
low noise immunity;
small speed of the information transfer process.

Networks using coaxial cables are still in demand and widely used, especially at military facilities, where noise immunity is of paramount importance.

Cable design

Coaxial cable has two conductive veins:

Central monolithic copper lived. Some standards encounter its multi-divided version of copper alloys and with a silver layer spraying. This lived is a cable core, it is located in a dielectric shell of polyethylene.
An external shielding conductor looks like a wicker grid of copper, copper alloys or aluminum. Some options for the execution of cables allow two shielding layers, between which the dielectric layer. The first is used as the central lived to transmit signals, the other dispels external electromagnetic interference.

General view of the construct of the coaxial cable

In most cases, the external protection of the cable from mechanical effects is performed resistant to ultraviolet rays with a polychlorinide sheath. There are more expensive protection options with teflon coating.

Types of coaxial cables

There are many varieties of coaxial cables, some of them reach several centimeters in diameter. They are used to transmit high-power radiotelevival signals on antenna in 1-5 kW transmitters.

A variety of coaxial cables

To build local computer networks, a cable of two standards are used:

Categories RG-58 / U or 58A / U, 10Base-2 standard. It is called a thin coaxial cable, with a diameter of up to 6 mm, with a wave resistance of 50 ohms, the model RG-58 / U - with a solid copper wire in the center of the cable, in the category 58a / u, the core consists of a twisted stranded copper wire. The cable is capable of transmitting information without significant signal loss, speed up to 10 Mbps, up to 185m, connected cables directly to a network adapter computer board.

Categories RG-11 or RG-8, 10Base-5 standard:

10Base-5 - in everyday life called a thick coaxial cable, with a cross section of 12 mm, central lived, the diameter that is much thicker, allows you to transmit signals with less attenuation.
In the RG-11 category, the resistance is 75 ohms, in the RG-8 - 50 Ohm model. 10 Mbps signal transmission speeds, as in 10Base-2 standards cables, but the distance is significantly more up to 500 m. Very often, this cable is used as a trunk connecting several separate local networksBy connecting it through the transceiver. This device equipped with a vampire tooth connector, which, when connected, pierces the insulating shell and provides electrical contact with the conductor.

One of the advanced manufacturers of coaxial cables is BELDEN its development on improving production, an increase in noise immunity, signal transmission ranges are used by many firms. Some technical solutions are adopted as international standards in production.

BELDEN cable

Cable networks were widespread due to the provision of certain services for consumers in obtaining and processing information. With the transition to digital broadcasting, the quality of the cable TV has improved, high-speed Internet appeared, packets satellite television and IP telephony. The range of up to 2100 MHz and frequency from 5-65 MHz began to be more active for transmitting the reverse channel signals.

BELDEN cable perfectly proven itself in the development of these technologies, the developers realized that the costs of creating interference equipment wireless communication very big. Cheaper and more efficiently exclude electromagnetic interference, creating reliable shielding of coaxial cables.

General view of BELDEN cable

Duobond® Plus shielding technology in BELDEN cables meets the most advanced requirements that consumers put forward.

Features of technical solutions of the DUOBOND® PLUS cable:

The shielding provides sheet aluminum foil and a copper wicker grid, the structure of the outer shielding shell three-layer, aluminum, polyester, and again aluminum. All this is reliably glued around the dielectric layer of foamed, polyethylene nitrogen, which shares the central wire and the multilayer screen. Such a cable manufacturing technology prevents the shielding layer offset, when cutting to fasten the connector and when the stripping process during the gasket. This technical solution developed, Belden specialists is already an industrial standard for all manufacturers.
To increase the mechanical strength of the shielding layer and ensuring the effectiveness of protection against interference at 85 dB, galvanic copper is used 99.99% coated with a layer of tin.
The outer three-layer shielding shell has a unique method of compounding with a closing overlap, which provides electrical contact of the aluminum coating. Thus, a one-piece shielding tube of laminated foil is created.
Cable, Duobond® Plus, are created with shielding, which fully comply with RG 6, RG 11 and RG 59 standards. This greatly simplifies the operation of operators when installed, the same technological techniques, tools and connectors are used in working with other cables of these standards.

The main parameters of the Duobond® Plus cables

Parameters	RG 59.	RG 6.	(PRG 11)
Wave R, in Ohm	75	75	75
Capacity in PF / M	55	56	55
Effect shielding, in dB	>85	>85	>90
Ø central wires, in mm	0.8	1	1.55
Ø dielectric, in mm	3.66	4.75	7.25
Type foil	AL / PE / Al	Cu.	Cu.
Thread density,%	50	50	50
Ø external conductor, in mm	4.2	5.25	7.9
Ø shell, in mm	6	6.9	10.1
Minimum bend radius, in mm	35	35	100
Clock frequency of transmitted signals in MHz		attitude signals in dB / 100m
5	1.8	1.7	0.9
50	4	4.5	2.7
100	5.6	6.4	3.9
200	7.4	9.1	5.7
300	12.6	11	6.9
400	16.2	13.2	8.2
800	23.2	19.2	12
1350	30.7	25.6	16.1
1750	35.3	29.6	18.7
2400	41.9	35.5	22.5

Domestic manufacturers produce coaxial cables with individual labeling, but in compliance with international standards.

Cable RK-75 and RK-50

The shielding mesh of these cables is made of a thin soft copper wire density, which is 90%. There are combined options, lavsan aluminum coating wrapped with a mesh of a tinned copper wire with a 50% density. Combined screen provides greater noise immunity.

The insulation of the central wire consists of a polyethylene foamed with nitrogen, it provides a small attenuation coefficient of the transmitted signal. The central rod is made of solid annealed copper wire or a thin strained structure. This gives greater flexibility to the wire and better conductivity for electrical signals. The structure of the RK-75 coaxial cable is the same with the RK-50, the difference in diameter individual elements and wave resistance. It determines their purpose and scope:

RK-75 is more often used in trunk computer networks between the local branches of the large network;
RK-50 has a large area of \u200b\u200bapplication, it is used on radiotransmitters and radio receivers, for connections of cards for various purposes in separate blocks, transmission of video signals, in local computer networks.

To operate the cable outside the premises, stamps with an outer shell of light stabilizing polyethylene are used, cables with PVC plastic shell are used for laying inside buildings.

Specifications of RK cables

Brand cable	Inner core	Wave resistance w, Ohm	Attenuation, dB / m at frequency		Diameter D, mm
			10 MHz	100 MHz
RK-50-2-11 (RK-119)	Single-resolution	50 ± 2.	0.05	0.18	4.0 ± 0.3.
RK-50-2-13 (RK-19)	"	50 ± 2.	0.05	0.18	4.0 ± 0.3.
RK-50-3-11 (RK-159)	"	50 ± 2.	0.04	0.13	5.3 ± 0.3.
RK-50-3-13 (RK-55)	"	50 ± 2.	0.03	0.13	5.0 ± 0.3.
RK-50-4-11 (RK-129)	"	50 ± 2.	0.03	0.1	9.6 ± 0.6.
RK-50-4-13 (RK-29)	"	50 ± 2.	0.03	0.1	9.6 ± 0.6.
RK-50-7-11 (RK-147)	Multi-breed	50 ± 2.	0.02	0.08	10.3 ± 0.6
RK-50-7-15 (RK-47)	"	50 ± 2.	0.02	0.08	10.3 ± 0.6
RK-50-7-12 (RK-128)	"	50 ± 2.	0.02	0.09	11.2 ± 0.7
RK-50-7-16 (RK-28)	"	50 ± 2.	0.02	0.09	11.2 ± 0.7
RK-50-11-11 (RK-148)	"	50 ± 2.	0.018	0.06	14.0 ± 0.8.
RK-50-11-13 (RK-48)	"	50 ± 2.	0.018	0.06	14.0 ± 0.8.
RK-75-4-11 (RK-101)	Single-resolution	50 ± 2.	0.032	0.1	7.3 ± 0.4.
RK-75-4-15 (RK-1)	"	50 ± 2.	0.032	0.1	7.3 ± 0.4.
Note: The table contains data provided by manufacturers. To estimate the attenuation at a frequency of 27 MHz, linear interpolation can be used.

Combined Cable KVK-B (P) -2

The peculiarity of such a brand is that two copper insulated wires are added to a conventional coaxial cable between the screen and an external insulating sheath. Additional wires stranded with a cross section of 0.5 to control the options of the system and 0.75 mm / kV, for nutrition. TV The signal is transmitted according to the coaxial component of the cable, and the control or power of the camera is carried out using additional wires.

General view of the combined Cable KVK-V (P) -2

Such a cable provides high-quality transmission of the color and black and white video signal, up to 450 m.

Constructions and technical parameters of combined cables

Marking of domestic cables RK

The basis of the marking is the sequence of letters and numbers:

the first number 50 or 75 is the magnitude of the wave resistance of OM;
the second number is the insulation Ø of the central vein;
in the third number, the first digit is insulation material with a category of heat resistance, the second and third digits define the development number.

Example of decoding RK 75-4,9-322A:

P - radio frequency;
To - coaxial cable;
number 75 - wave resistance in OM / M;
4 or 9 - Ø on external insulation;
3 - semi-use, foamed insulation with heat resistance 1250 s;
number 22 - Production Development Room;
the latter in the symbol group of the letter A, denotes the main category of destination "antenna".

Depending on the task and demand, manufacturers make many different brands of coaxial cables. Combined cable models are widespread for video surveillance systems and intercoms.

FEATURES OF MONTAGE

Each described coaxial cable has good flexibility.

The rotation radius during laying should not exceed 12 multiple the magnitude of the cable shell radius. Beginners can over time to put pressure on the central residential dielectric layer and the closure on the screen. It is not desirable to hang the cable for a long time, under its own weight at a distance of more than 15 m, this leads to stretching and breaking of the central core. The correct cutting of the cable ends to attach connections is of great importance.

Sequence and description of the cutting of cable for connecting connector

The cable shell is designed to protect it from moisture and external damage when operating in rooms and on the surface. Do not set the cable under water or under the ground. Capillary water leakage will destroy the shielding shell and the central rod.

It is allowed to operate on the surface in rainy weatherBut in the connecting places it is recommended to use silicone sealants, in extreme cases, isolent and plasticine. There are special moisture-resistant connectors, model SO-239 or PL-259, PL-258.

Connecting connector location PL-259 and PL-258

The compounds are made by soldering, change the magnitude of the wave resistance, are a source of reflected waves, which leads to a distortion of the signal. Use industrial connecting connectors.

Wave resistance

Working with electronic equipment, the signals of which are transmitted along a coaxial cable. It is necessary to understand that the wave resistance cannot be measured on the central dwelling of the usual ohmmeter. It is calculated based on the diameter of the central wire and the diameter of the shielding grid:

Rw \u003d 91lg (DD);
RW - wave resistance in Ohms;
D - Ø Ø internal dielectric layer in mm;
d - Ø internal central rod in mm.

There are calculated graphs of the dependence of the wave resistance from the diameters of the dielectric layer and the central vein.

The graph of the dependence of the wave resistance on the ratio of diameters of the dielectric layer and the central wire

By vertical axis, we note the value of the DD ratio, the horizontal is measured the value of RW (wave resistance). From the graph, it is visible directly proportional to the dependence, with an increase in the ratio increases resistance. Thus, making measurements of diameters and calculations, on schedule you can independently define RW.

Cable selection. Video

How to choose the right cable for TV, tells this video.

Using a coaxial cable when installing radio-electronic equipment, it is recommended to be guided by the installation instructions where the marking is usually indicated. Using the specified brands of cables, modern tools, connectors and other components are easy to perform mounting.

Coaxial cable (coaxial pair) - Couple, conductors of which are located coaxially and separated by insulation.

Coaxial cable (from lat. Co - together and AXIS - axis, that is, "coaxial"), also known as coaxial (from the English COXIAL), - an electric cable consisting of the central conductor and the screen and the screen for transmitting high-frequency signals .

1. Internal conductor in the form of a single straight line (as in the figure) or a pig in a spiral of a wire, stranded wire, tubes performed from copper, copper alloy, aluminum alloy, coched steel, copper ished aluminum, silver plated copper, etc.

Coaxial cable consists of:

Coaxial cable device

2. Insulation made in the form of solid (polyethylene, foamed polyethylene, solid fluoroplast, fluoroplastic tape, etc.) or semi-separated (Caddle-tubular hanging, washers, etc.) of dielectric filling providing the constancy of the mutual location (alignment) of internal and external conductors;

3. External conductor (screen) in the form of a braid, foil coated with a layer of film aluminum and their combinations, as well as a corrugated tube, observing metal tapes, and other copper, copper or aluminum alloy;

4. Shells (serves to isolation and protection against external influences) from light stabilized (that is, resistant to ultraviolet radiation of the Sun) of polyethylene, polyvinyl chloride, octopia of fluoroplastic tape or other insulating material.

History of creation

1929 - Lloyd Espireshid (English Lloyd Espensied) and Herman Effelt from AT & T Bell Telephone Laboratories Patched the first modern coaxial cable.
1936 - AT & T built an experimental television data line on a coaxial cable, between Philadelphia and New York.
1936 - the first television program on a coaxial cable, from the Berlin Olympic Games in Leipzig.
1936 - between London and Birmingham, the postal service (now BT) is laid a cable for 40 phone numbers.
1941 - the first commercial use of the L1 system in the USA, AT & T. Between Minneapolis, (Minnesota) and Stevens Point (Wisconsin) launched a TV channel and 480 telephone numbers.
1956 - the first transatlantic coaxial line, TAT-1 is laid.

Application

communication systems;
broadcast networks;
antenna feeder systems;
ACS and other manufacturing and research techniques;
remote control systems, measurement and control;
alarm and automation systems;
objective control systems and video surveillance;
communication channels of various radio electronic devices of mobile objects (ships, aircraft, etc.);
intublock and inter-block connections in the composition of radio-electronic equipment;
communication channels in household and amateur technology;
military equipment and other areas of special application.

In addition to the sewage signal, the cable segments can be used for other purposes:

cable delay lines;
quarter-wave transformers;
symmetrical and matching devices;
filters and pulse formers.

Classification

By destination - For Systems cable television, for communication systems, aviation, space technology, computer networks, household appliances etc.

On wave resistance (Although the wave resistance of the cable can be any), the standard are five values \u200b\u200bfor Russian standards and three on international:

50 Ohm is the most common type, applied in different areas of electronics. The reason for the choice of this nominal was, first of all, the possibility of transmitting radio signals with minimal losses in the cable, as well as close to the extremely achievable reading of electrical strength and power transmitted (raisin, sviridov, 1975, p. 51-52);
75 ohms - a common type, applied mainly in television and video equipment (was chosen due to a good ratio of mechanical strength and cost and applied where the power is small, and the metrar is large; while losses in the cable are slightly higher than for 50 ohms);
100 ohms - it is rarely applied, in pulse technique and for special purposes;
150 ohms - it is rarely used in impulse techniques and for special purposes, international standards is not provided;
200 ohms - it is urgent rarely, international standards are not provided.

By the insulation diameter:

subminiature - up to 1 mm;
miniature - 1.5-2.95 mm;
mediterranean - 3.7-11.5 mm;
large-sized - more than 11.5 mm.

By flexibility (Resistance to repeated bends and mechanical moment of cable bending):

rigid;
half-west;
flexible;
wORKING.

By shielding degree:

with solid screen:

with a metal tube screen
with the screen of the lugo

with ordinary screen

with one-layer lamp
with two- and multi-layer lamp and with additional shielding layers
Radiant cables having intentionally low (and controlled) degree of shielding

Designations
Designations of Soviet cables

According to GOST 11326.0-78, cable brands should consist of letters meaning the type of cable, and three numbers (separated by defisis).

First number means the value of the nominal wave resistance. The second number means:

for coaxial cables - the value of the nominal diameter on isolation, rounded to the nearest smaller integer for diameters more than 2 mm (with the exception of a diameter of 2.95 mm, which must be rounded up to 3 mm, and the diameter of 3.7 mm, which should not be rounded) :
for cables with spiral internal conductors - the value of the nominal diameter of the core;
for two-wire cables with conductors in individual screens - the value of the insulation diameter, rounded the same as for coaxial cables;
for two-wire cables with conductors in overall insulation or twisted from separately isolated conductors - the value of the greatest size to fill or the diameter by a twist.

Third - two- or three-digit number - Means: The first digit is a group of isolation and a category of the heat resistance of the cable, and the subsequent numbers mean the sequence number of the development. The cables of the corresponding heat resistance assigned the following digital designation:

1 - conventional heat resistance with solid insulation;
2 - increased heat resistance with solid insulation;
3 - conventional heat resistance with semi-insulation;
4 - increased heat resistance with semi-insulation;
5 - ordinary heat resistance with air insulation;
6 - increased heat resistance with air insulation;
7 - high heat resistance.

To the brand of cables of increased homogeneity or elevated stability of parameters at the end through a dash, the letter C.

The presence of the letter A ("Subscriber") at the end of the title denotes the reduced cable quality - the absence of a part of the conductors constituting the screen.

Cables are divided by the Radi Guide scale. The most common cable categories:

RG-8 and RG-11 - "Thick Ethernet" (ThickNet), 50 ohms. 10Base5 standard;
RG-58 - "Thin Ethernet" (Thinnet), 50 ohms. Standard 10Base2:

RG-58 / U - a solid central conductor,
RG-58A / U is a stranded central conductor,
RG-58C / U - Military cable;

RG-59 - Television Cable (Bradband / Cable Televisin), 75 ohms. Russian analogue of the RK-75-X ("Radio Frequency Cable");
RG-6 - television cable (Bradband / Cable Televisin), 75 ohms. Category RG-6 cable has several varieties that characterize its type and material of execution. Russian analogue of RK-75-X-X;
The RG-11-Main Cable, and is almost indispensable if it is required to resolve the issue with long distances. This type of cable can be used even at distances about 600 m. The fortified external insulation allows you to use this cable without any problems in difficult conditions (street, wells). There is an S1160 version with a cable that is used for the reliable brassing of the air cable, for example, between houses;
RG-62 - ArcNet, 93 Ohm

"Thin" Ethernet

It was the most common cable to build local networks. The diameter of about 6 mm and considerable flexibility allowed it to be laid almost in any places. The cables were connected to each other and with a network board in a computer using the BNC T-Connector (BayNet Neill-Cncelman). Between themselves cables could be connected using the BNC i-connector (direct connection). At both ends of the segment, terminators must be installed. Supports data transmission up to 10 Mbps to a distance of up to 185 m.

"Fat" Ethernet

Thirdly, compared to the previous, cable - about 12 mm in diameter, had a thicker central conductor. I was bad and had a significant cost. In addition, when joining a computer there were some difficulties - AUI transceivers (Attachment Unit Interface) were used, connected to a network card using a branch, permerating the cable, so H. "Vampires". Due to the thicker conductor, the data transmission could be carried out at a distance of up to 500 m at a speed of 10 Mbps. However, the complexity and high cost of the installation did not give this cable of such widespread as RG-58. Historically, the RG-8 corporate cable had a yellow color, and therefore sometimes you can meet the name "Yellow Ethernet" (English Yellw Ethernet)

Auxiliary elements of the coaxial tract

Coaxial connectors - to connect cables to devices or their joints between themselves, sometimes cables are produced from production with installed connectors.
Coaxial transitions - for the articulation of cables with unpaired connections with each other.
Coaxial tees, directional branches and circulators - for branches and branches in cable networks.
Coaxial transformers - to match the wave resistance when connecting a cable with a device or cables.
Terminal and passage coaxial loads are usually consistent - to establish the desired wave modes in the cable.
Coaxial attenuators - to attenuate the signal level in the cable to the required value.
Ferrite valves - to absorb the reverse wave in the cable.
Graphically distributors based on metal insulators or gas-discharge devices - to protect the cable and equipment from atmospheric discharges.
Coaxial switches, relays and electronic commuting coaxial devices - for switching coaxial lines.
Coaxial-waveguide and coaxial striped transitions, symmetrical devices - for dusting coaxial lines with waveguide, striped and symmetrical two-wires.
Pass and end detector heads - to control the high-frequency signal in the cable by envelope.