1、 Overview of construction content (1) satellite TV receiving system is composed of uplink transmitting station, satellite body and ground receiving station
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1) The uplink transmitting station can be a fixed large-scale ground station or a mobile ground station
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The directional antenna is used to send program signals and accompanying sound signals, which are processed and amplified and sent to the satellite transponder
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In addition to other uplink stations, the main uplink station has two tasks, one is to provide programs to the stars, the other is to receive the downlink signals of the stars to monitor the quality of programs and the attitude of the satellites
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The main uplink station randomly sends correction instructions to the stars through the uplink station, changes the position and attitude of the satellites, adjusts the antenna and switching equipment to ensure the normal operation of the system
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2) The satellite borne repeater converts the received uplink signal into the downlink FM signal, which is amplified and transmitted to the ground by the directional antenna
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3) The ground receiving station sends the received downlink FM signal transmitted by satellite to CATV system after frequency conversion and demodulation
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The above composition is the basic front-end composition of satellite TV receiving system and CATV receiving system
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(2) CATV system is composed of receiving part, front end part, trunk transmission and distribution network
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1) Receiving part: mainly through the parabolic satellite receiving antenna with high gain to receive the satellite microwave signal
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2) The front part is composed of down converter (LNB) and satellite TV receiver
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The frequency down converter is to reduce the satellite microwave RF signal (C-band, 3.7 ~ 4.2ghz) received by the antenna to intermediate frequency signal (970 ~ 1470mhz)
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The equipment is mainly composed of low noise amplifier and down converter
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The function of satellite TV receiver is to restore satellite TV signal to image and sound with standard TV interface level for general TV viewing
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3) Trunk transmission: the function of trunk transmission part of CATV system is to stably transmit the high frequency TV signal output from the front end part to the input port of system distribution network without distortion, and the output level signal shall meet the requirements of distribution network system
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The common trunk lines are coaxial cable transmission and optical fiber cable transmission
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4) Distribution network: its function is to transmit the high-frequency TV signal provided by the front end to the brancher through the trunk line, and then to the terminal distributor to supply the user’s TV viewing
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2、 Key points of construction site coordination 1
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Key points of construction coordination with civil structure engineering (1) lightning protection of satellite TV receiving antenna: 1) civil construction coordination with reinforced concrete foundation of satellite TV receiving antenna, with a layer of steel mesh connected with the earth at the bottom
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When the measured grounding resistance of steel mesh is less than 4 Ω, it can be used as lightning protection grounding electrode
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The foundation bolt embedded on the foundation is connected with the steel mesh
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Therefore, the lightning rod can be directly connected with the foundation bolt for lightning protection and grounding
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When the grounding resistance of the foundation reinforcement mesh is greater than 4 Ω, an auxiliary grounding electrode should be made
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2) When the satellite TV receiving antenna is installed on the top of the building, it is only necessary to connect the lightning rod of the antenna with the lightning protection grounding grid of the building
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3) According to the dimensions and various technical requirements of the antenna embedded parts and embedded anchor bolts marked in the product manual, the maximum tension, pressure and transverse force of each supporting point of the antenna under different wind speeds are attached
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The roof antenna foundation can be designed only by providing the foundation specification to the building structure engineer
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The designers design a set of reinforced concrete beam system or steel beam system according to the geometric dimensions of each supporting point of the antenna
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The beam system is supported on the column of the building or on the reinforced concrete shear wall or brick wall, the antenna is erected on the beam, and the beam transmits the force to the column and wall through the abutment
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Anchor bars should be set on the abutment to make it bear the tension or pressure from the antenna
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Note: the antenna foundation orientation should be determined before construction
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(2) CATV system antenna lightning protection: 1) the antenna vertical pole can be directly fixed on the building, such as the load-bearing wall of the elevator room or water tank room at the top of the building
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2) The antenna vertical pole is fixed on the embedded steel pipe or channel base, which must be located on the load-bearing wall or beam, and connected with the lightning protection grounding grid of the building
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3) A working platform must be set up on the tower for the self-supporting tower antenna, so as to provide lighting and other technical support during the installation of system components and daily maintenance
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The tower should be able to resist strong wind, and equipped with lightning protection grounding device
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4) The vertical pole of antenna shall be fixed by windproof rope to ensure the position of receiving antenna unchanged
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(3) Cooperate with civil structure construction, carry out indoor buried pipeline, user box and connection box and other reserved holes and embedded iron parts
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2
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Key points of construction cooperation with Earth Building Decoration Engineering (1) cooperate with civil ceiling construction to carry out cable bridge or metal trunking construction
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(2) Cooperate with civil engineering construction for indoor terminal user box threading and panel installation, and at the same time for box installation
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(3) Carry out open distribution pipeline construction indoors, and coordinate the construction with various professional pipelines
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3
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For outdoor overhead (on pole) or trench laying of cable for satellite TV receiving system and cable TV system, the route of trench shall be provided to civil engineering in time, and civil engineering shall assist the construction
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Before the outdoor underground trench is opened, it is necessary to know whether there are other professional pipelines under the route of the cable in advance
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In case of other pipelines and roads crossing the street, it is necessary to pass through steel pipes for protection
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4
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When erecting the wall cable, the wall support and supporting iron should be installed on the wall first, and then the cable should be laid
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3、 Key points of construction site control (1) check whether the system diagram, user level distribution diagram, route layout plan, antenna location and installation diagram of satellite TV receiving system and cable TV system are designed by the design unit with legal person qualification certificate, and confirm that the construction drawing is valid before construction
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(2) After careful review of the construction drawings, the problems found will be collected and provided to the design unit, the design disclosure will be organized, the proposed problems will be formed into solution documents, countersigned for confirmation, and the design change procedures will be handled in time
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(3) Review the construction organization design of satellite TV receiving system and cable TV system
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1) The ordering plan of equipment and materials, labor arrangement plan and construction schedule for the construction of satellite TV receiving system and cable TV system shall correspond to the general construction schedule of civil engineering to ensure the smooth completion of the general construction schedule
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2) Technical disclosure of satellite TV receiving system and cable TV system engineering construction
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Clarify the main contents of the professional construction and installation tasks, and implement them to the operators, clarify the process operation requirements and the quality standards to be achieved, as well as the safety precautions and construction coordination matters of various specialties
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3) Requirements for equipment purchase: equipment purchase should be based on the current task requirements and consider future development
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The selected equipment is the product produced by the designated manufacturer with national certification and approval
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If you choose foreign products, you should choose well-known brands, not inferior quality products
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Note: the antenna can only be purchased after applying to the relevant departments
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4) During the construction of satellite receiving antenna foundation, the buried depth of the foundation should be under the frozen soil layer in the northern region with frozen soil layer in winter
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5) The lightning rod lightning protection grounding protection line shall be connected independently
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It is not allowed to share the lightning protection grounding protection line with the grounding wire of the receiving equipment in the room, otherwise it will be struck back by lightning, causing the equipment to burn down and even personal safety to be injured
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6) The impact grounding resistance of grounding device against direct lightning strike shall be less than 4 Ω
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7) When the antenna pole (tower) is higher than the nearby buildings and structures, and the height is more than 50m, the high altitude obstacle light shall be installed, and the pole (tower) body shall be painted red and white
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The approval of relevant departments should also be obtained for the construction of high towers in the airspace above cities and airports.
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