Introduce
Coaxial cable is divided into thin cable: RG-58 and thick cable RG-11. And use very few semi-rigid coaxial cables and feed tubes.
Thin cable
The thin cable has a diameter of 0.26 cm and a maximum transmission distance of 185 meters. When used, it is connected to a 50 Ω termination resistor, T-connector, BNC connector and a network card. The wire price and connector cost are relatively low, and no equipment such as a hub is required. It is suitable for setting up a small Ethernet network with concentrated terminal equipment. The total cable length should not exceed 185 meters, otherwise the signal will be severely attenuated. The impedance of the thin cable is 50Ω.
Thick cable
The thick cable (RG-11) has a diameter of 1.27 cm and a maximum transmission distance of 500 meters. Due to its relatively large diameter, it is less flexible and is not suitable for installation in a narrow indoor environment. The production method of RG-11 connector is also relatively complicated and cannot be directly connected to a computer. It needs to be passed through a switch. Turn the device into an AUI connector and then connect it to your computer. Due to the strength of the thick cable, the maximum transmission distance is also longer than the thin cable, so the main purpose of the thick cable is to play the role of the backbone of the network to connect several networks formed by thin cables. The thick cable has an impedance of 75Ω.
Semi-rigid coaxial cable
This type of cable is used infrequently and is usually used for the connection of modules inside communication transmitters. Since the transmission loss of this line is small, there are also some disadvantages such as high hardness and difficulty in bending. In addition, most of the transmission frequency of such cables can reach 30Ghz. Model CXJ--50--3 The typical structure of this type of cable is shown in the following table. Diameter of structural material (mm) 1. Inner conductor silver-plated copper wire 0.93 2. Insulator polytetrafluoroethylene (PTFE) 3.00 3. Outer conductor
1 seamlessly annealed copper tube 3.58
2 tin (alloy) seamless copper tube
3 silver-plated seamless copper tube
At present, the technology is gradually improving, and there are also some such wire rods with large bending amplitudes. However, the author recommends using such copper wire as the outer conductor of traditional copper tubes to ensure stability in places where flexibility is not required.
Basic Information
English abbreviation SYV, often have 75-7,75-5, 75-3, 75-1 and other models, the characteristic impedance is 75 ohms, in order to adapt to different transmission distances. It is the main medium for transmitting video signals in asymmetric baseband mode.
The main application area
The main application areas are: bracket connection of equipment, closed-circuit television (CCTV), shared antenna system (MATV) and the transmission of color or monochrome RF monitors. These applications do not require the selection of precision video coaxial cables with particularly strict electrical tolerances. The characteristic resistance of the video coaxial cable is 75 ohms. This value is not optional. Physics has demonstrated that the attenuation characteristic optimized for video signals occurs at 77 ohms. In low-power applications, materials and design determine the cable's optimal impedance of 75 ohms.
Standard video coaxial cables have both solid and multi-strand conductor designs. It is recommended to use a multi-strand conductor design in some applications where the cable is to be bent, such as the internal connection of a CCTV camera to the tray and bracket assembly, or the transmission cable of a remote camera. Also includes monitoring equipment
There are five general body styles of ball Valves: single body, three-piece body, split body, top entry, and welded. The difference is based on how the pieces of the valve-especially the casing that contains the ball itself-are manufactured and assembled. The valve operation is the same in each case.
In addition, there are different styles related to the bore of the ball mechanism itself.
Ball valves in sizes up to 2 inch generally come in single piece, two or three piece designs. One piece ball valves are almost always reduced bore, are relatively inexpensive and generally are throw-away. Two piece ball valves are generally slightly reduced (or standard) bore, they can be either throw-away or repairable. The 3 piece design allows for the center part of the valve containing the ball, stem & seats to be easily removed from the pipeline. This facilitates efficient cleaning of deposited sediments, replacement of seats and gland packings, polishing out of small scratches on the ball, all this without removing the pipes from the valve body. The design concept of a three piece valve is for it to be repairable.
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