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Two-way local cable television transmission

, The development of information superhighway, but also to create opportunities for utilization of cable television. Cable television system in the current information society, not just listening to the radio already watching TV, the cable television network to achieve a two-way transmission, allowing users to pass the signal front-end has become possible,discount mbt shoes, which makes into a CATV system, including communications, computer including integrated information networks. First, the basic principle to achieve the two-way cable TV transmission, front-end benefits of network integrated with the key 47-550MHZ. There are many ways two-way transmission, bidirectional transmission amplifier is not less necessary, as shown in Figure 1. Positive signals (downlink signals) input from the front two-way filter, and then forward amplifier; amplifier output and then by two-way filter to the user. By the user of the reverse signal (uplink signal) by two-way filter to the inverting amplifier, and then by two-way filter to the front, two-way transmission. Two-way transmission only and the information highway to connect and realize the comprehensive utilization of cable television network. Only adjacent transmission structure in order to achieve two-way transmission. Adjacent transmission system and a large number of the current technology is more mature way to enlarge the schematic in Figure 1 using a 300MHz, 450MHz, 550MHz three. A good shielding and testing of the 500MHz bandwidth, power cable, as the system mouse users PAL broadcast system 59 sets 48 sets of TV shows and stereo FM radio. In fact the ground interference by 66 * wave of power may be less than this figure, and because the television receiver on the market today is set by the wireless broadcast band, so in order to receive all the programs installed on the converter also increases (STB). 550MHz leave some part of a 750MHz bandwidth, isolation, will arrange the bandwidth 150MHz digital television broadcast. It is currently considered an ideal way. Currently, the integrated information network using 750MHz uplink adjacent channel carved cutting two-way transmission system, a downlink frequency band 70MHz 75MHz, 87MHz for a 108MHz one for transmitting FM radio, 127MHz a 550MHz analog television transmission for adjacent channel, 550MHz a 750MHz for data transmission and] 1V transmission services. A 50MHz band is 5MHz uplink for transmission system status,p90x workout schedule, monitoring data, and uplink services. Spectrum allocation shown in Figure 2. Figure 2 Schematic drawing down the second spectrum, system design program 1. Front-end system using the 550MHz front-side adjacent channel forward pass with some mix of front-end, user network using 750MHz branch distribution system. System modulator optional multi-function products, the product has intermediate frequency processing, SAW filter and AGC functions for adjacent channel use, the output level of not less than 110dBV, and require adjustable gain, demodulator selection of stable products, use power mixer mixing, independent of frequency channels to expand by simply adding the appropriate equipment can be. 2. Link Design Link Bandwidth 750MHz attenuation of the cable used is less than 5.9dB/100m, the distance between the amplifier stage is not greater than 440m, trunk amplifier with AGC automatic selection of slope compensation, a bi-directional amplification, 750MI - Iz bandwidth, gain work 26dB. Download to noise ratio in the nominal state: N> 50dB floor head amplifier distribution amplifiers, push-pull output, 800MHz bandwidth, maximum output level ll8dB,mac cosmetics, uV. 3. User network design using branch distribution of the users are transmitted,tory burch outlet, the laying of cable in the building, with plastic pipe protection, public support are placed in layers of waterproof box, the user terminal with two holes (TV, FM) with a shield terminal panel, subscriber line high physical foaming cable. Information Superhighway and the organic integration of cable networks,moncler doudoune, cable television network utilization is the trend of development. The user can step the best distribution network, should be returned with a capacity of 750MHz branch distribution system, the national broadcast networks with the same overall planning for future networking with the information superhighway. References [1] Zhang Yan Rong. Satellite television reception and transmission technology. National Defence Industry Press. 1993 [2] Jiaojing Lin. Common type of cable adjacent teaching bidirectional transmission system. TV technology. 1996 (7) * 67 *
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