1. What is satellite live broadcasting?
Recently, several new TV services have appeared in the United States. American households can use small dish-shaped satellite receiving antennas (18 inches to 3 feet in diameter) to receive TV programs directly from satellites. This dish antenna cannot rotate. Fixed pointing to a location in the sky.
The signal is digitally compressed, and a single satellite transponder can broadcast several programs, so the dish antenna pointing to a certain orbital position can receive up to 200 channels. Programs for various services include: most major cable services, sports, pay-per-view (PPV) movies, audio services, and special "niche" programs aimed at a small audience. Although these services are often regarded as direct-to-home (DTH) services, the term direct broadcast satellite (DBS) services is more commonly used.
There are currently five companies providing satellite live broadcast services. Although the number of subscribers is not as large as that of the cable TV service, the number of subscribers to the satellite live broadcast service is growing rapidly, and the growth momentum of this service is very strong. Therefore, many companies intend to develop satellite live broadcast business.
2. What are the satellite live broadcast services now?
At present, there are five companies in the United States that are providing fully digital satellite live broadcasting services. Their business names are: Primestar, DIRECTV, USSB, DISH, Network and Sky Angel. The Primestar service is jointly provided by multiple cable companies. The 27-36-inch dish antenna is used to receive programs from conventional satellites. The Primestar business has achieved great success. Currently, about two million subscribers have live satellite broadcasts. More than 30% of the market, but in recent times, its growth momentum has slowed down.
DIRECTV is a subsidiary of Hughes Communications Corporation. It provides a service called DIRECTV, which uses an 18-inch dish antenna to receive programs from specially designed high-power direct broadcast satellites. The DIRECTV service is considered to be the United States Today's premier live satellite broadcast service has more than three million subscribers since it was launched in 1994, and accounts for more than half of the satellite live broadcast market.
United States Satellite Broadcasting Corporation (USSB) and DIRECTV Company cooperate to send 25 channels of free reward film business. This service uses the same satellite, the same receiving system and the combined program forecast, so these two services seem to be A business. Today the USSB business already has nearly two million subscribers.
Echostar (ECHISTAR0 Communication Company provides the DISH NETWIRK service, which uses an 18-inch dish antenna to receive programs from specially designed high-power direct broadcast satellites. Since the DISH service began in the spring of 1996, its current market share is relatively Smaller, but this kind of business is very popular, and the number of subscribers is growing rapidly. The main reason for its success is that it has entered the market with low-priced hardware and programs, which is very popular with price-conscious subscribers, resulting in Other service providers have lowered the prices of hardware-related programs accordingly. It also promised to broadcast some local channels in major cities in the United States, which will be very popular with viewers.
Domingo Church cooperates with Echostar to broadcast a Catholic religious service of 6 to 10 channels. The name of this service is "SKY ANGEL", using the same contract and a program forecast table. Business looks like a business. It is too early to predict whether the "Sky Angel" will succeed at this time, but this kind of business is indeed aimed at the "niche" gap that other businesses have not considered.
Because some services use the same receiving system and usually work in the same orbital position, the audience may think that there are only three satellite live broadcast services, namely (1) PRIMESTAR, (2) DIRECTV / USSB, (3) ECHOSTAR / SKY ANGEL.
3. What kind of equipment is required?
Each business requires the use of receiving hardware, including dish antennas, decoders and remote controls. A single decoder decodes a single channel and then connects to several TVs and video cassette recorders (VCRs) in the home. If the user wants to watch two satellite channels at the same time, or record a program on another channel while watching one channel, then this family needs two decoders.
Some low-cost satellite direct broadcast systems can only be connected to one decoder, while other systems can be connected to one or two decoders. In general, these systems have two or more decoders. , But in most cases, additional hardware needs to be configured. The system used by the ECHOSTAR / SKY ANGEL business of the DIRECTV / USSB business allows users to install their equipment on their own, but many users still choose to have professionals help with the installation. PRIMESRAR business requires professionals to install the system. The dish antenna can be installed anywhere in the range of the satellite. Be careful not to let trees or high-rise buildings block the crow. The dish antenna generally has a built-in sound signal indicator or a flashing light-emitting diode (LED) indicator to display the signal strength, so that the best installation position can be selected during installation. The self-installation kits for DSSS and SIDH systems cost about $ 70. Kit components generally include: cables, compasses, grounding pieces, telephone T-connectors and all other hardware required to install and connect dish antennas. These installation kits are usually accompanied by a video cassette demonstrating the installation process. All the required cables can be purchased at RADIO SHACK or other similar retail companies. Users who are not convenient for shopping can consider choosing their own installation kits.
Most decoders in the system have built-in copy protection technology, which can determine whether a pay-per-view (PPV) movie can be recorded. The practical scope of this technology is not clear, and some viewers said that they did not encounter protection restrictions when recording programs.
4. Why do I need a decoder?
Satellite live broadcasting has now become a reliable alternative to cable TV. One of the important reasons is that the latest technological advances in real-time digital form video compression technology allow a few channels to be transmitted in the same frequency band. Each satellite live broadcast service uses a recently developed real-time lossy compression system. On average, each satellite transponder can broadcast six channels. In the past, each satellite transponder was able to broadcast only one channel. In business, up to 200 channels can be delivered from a track position in the sky. If you do not use digital compression technology, you can only broadcast up to 32 channels in one orbital position, so that the popularity of satellite live broadcast services will be greatly reduced. The number of channels for various service broadcasts varies greatly.
5. What determines the number of channels for various services?
The number of channels provided by the satellite live broadcast service is determined by the number of transponders the company is authorized to use and the number of channels compressed on each transponder.
The Federal Communications Commission (FCC) authorizes various services to use a certain number of direct broadcast satellite frequencies corresponding to the number of satellite transponders. All these services appear to be licensed to use different numbers of transponders at their designated orbital locations. The number of channels compressed onto a transponder is affected by many factors, such as the required image quality (eg resolution), the frame rate of the source material, the amount of motion in the source material, the degree to which the digitized product is allowed to be visualized, the encoding The complexity of the converter, the closed error control drought formed in the transmitted bit stream, and other factors.
For programs like basketball games, there are many fast-moving small objects in some frames, so each transponder can only compress 3 or 4 channels, otherwise there will be obvious digital products. Most programs with large still images can be compressed in a larger proportion, and each transponder can compress 5 or 6 channels. Movies are 24 frames per second instead of 30 frames per second, so the raw material content is low; in addition, film film is not interlaced, and it is generally a relatively constant frame-to-frame conversion; therefore, the compression ratio of film film can be larger, 7 or 8 channels on each transponder can still achieve satisfactory viewing results. With the continuous advancement of compression technology, these estimates deserve to be somewhat conservative.
6. What kind of compression system is used in the satellite live broadcast service?
Each satellite live broadcast service transmits a bitstream containing compressed audio, compressed video, permission information, program guide information, and other information. The decoder in the subscriber's home decodes this digitized bitstream and converts it into audio and video that can be displayed on a conventional TV. Every business needs a specially designed decoder that can work with its system. The PRIMESTAR business uses the name of the dedicated video compression system developed by General Instruments (GENERAL INSTRUMENTS) as DIGICIPHER-. The format adopted by other services is based on the MPEG-2 compression standard, but also uses a delivery system based on the DVB standard, which seems to be developing into a world broadcast standard. Although DVB uses the standard MPEG-2, it is striving to make the system more standardized.
7. Can the decoder be exchanged between various services?
The answer is no. There is absolutely no decoder standardization in the satellite live broadcast business. DIRECTV and USSB use the same decoder, and Echostar and Sky Angel also use the same decoder, so potential users today have three types of decoders to choose from. These three types of decoders are different and cannot be interchanged. Although many components of these systems are common, their respective broadcast bitstreams contain some unique information that only their decoders can interpret. If you want to change to another service, users must sell their decoders to exchange decoders suitable for new services. When considering what kind of satellite live broadcast business system to buy, what kind of transmission system each service provider uses is irrelevant, because all these systems provide similar quality audio and video, and are unable to interact with other services change. The important thing is to choose a service that can provide your favorite programs at an affordable price.
8. What other information does the PRIMESTAR business need to know?
Many cable system operators (MOS) Lenovo jointly established PRIMESTAR Co., Ltd. to provide 160 channels of digital direct home service to North America. The name of this service is PRIMESTAR. It is the first listening company to provide satellite live broadcast services. In the digital year, it began to provide 30 analog channels. In 1994, it was changed to digital. It claimed to be the first digital service, which was a few weeks ahead of DIRECTV and USSB.
Today PRIMESTAR business has entered nearly two million families, most of which are located in the countryside. The main reason for their success is that this is the only business where users do not need to purchase a decoder or dish antenna. They rent these devices and calculate the rent into the monthly subscription fee. They broadcast from a medium-power conventional satellite at an orbital position of 85 degrees west longitude. The name of this satellite is the GE-2 satellite, so the dish antenna with a diameter of 27 inches is used. To install.
PRIMESTAR's decoder is produced by General Instruments. Its receiving system is called DIGICPHER-1 digital broadcasting system. The decoder is hardware upgradeable, that is, it can be equipped with a hardware upgrade module without replacing any parts. System components have been upgraded. PRIMESTAR has modified the weather forecast channel signal to provide users with local weather information. In this regard, it is the only one. PRIMESTAR hardware and program forecast tables can be purchased at RADIO SHACK stores and NOBODY BEATS THE WIZ stores nationwide.
9. What information do I need to know about the DIRECTV / USSB business? DIRECTV / USSB service is a leading satellite live broadcast service in the world today, which provides nearly 200 video channels. This service uses three specially crafted high-power KU-band satellites in the same orbital position to work. The name of the first satellite is the "Direct Broadcast Satellite One" (DBSI) satellite, which has 16 120-watt transponders; the other two satellites are direct broadcast satellites 2 and 3 (DBS2 and DBS3). The two satellites each have eight 240-watt transponders. There are 32 broadcast transponders in the three satellites. DIRECTV sold five of the 120-watt transponders to the USSB (since federal law requires all direct broadcasters to have their own broadcasting facilities, the USSB actually owns 5/16 of the entire satellite). The two competing companies use the same dish antenna and decoder for program viewing. The hardware used by DIRECTV and USSB is called a digital satellite system, or DSS (TM). Currently Sony, Thomson Consumer Electronics (with PROSCAN, RCA and GE names), Hughes Network Systems, MATSUSHITA (PANASONIC), UNIDEN In addition, there may be other companies that are selling DSS receiving equipment. The decoder is sold by satellite dealers and consumer electronics retailers. Users of DIRECTV and USSB must purchase their own decoders. The price of the decoders is between US $ 100 and US $ 500. The specific price is related to the model type and promotional activities at different times of the year.
Each DSS equipment manufacturer's product has its own unique user interface to make the product different. The difference between these user interfaces is mainly the difference in the look and feel of the networked program forecast table and the difference in the remote control. The information contained in the program forecast table includes the introduction information of the next episode and the planned program introduction. Each manufacturer can also choose whether to add some functions, such as favorite channel list or universal remote control.
10. What are the programs of DIRECTV and USSB services?
DIRECTV and USSB share the right to use all 32 broadcast frequencies located at 110 degrees west longitude. The channel transmitted by each service is unique and will not appear in another service. Except for promotional channels, there are very few two services, or there are no free programs. The USSB broadcasts on five 120-watt satellite transponders, which provide 25 channels. Their business consists of high-quality movie channels, including HBO and Show + ime. DIRECTV has 27 frequencies and 175 program channels. Its programs can be roughly divided into five categories, namely; cable programs, sports programs, music services, pay-per-view (PPV) movies and special interest / niche services. DIRECTV's cable programming is the foundation of its business. DIRECTV allows to order most major professional sports events and a part of college sports events. They use the addressable feature of the decoder to allow only a certain geographic location for program reception, for example, to receive a program outside a local coverage area. An obvious local blanking system has been adopted, which means that many of the events that the audience wishes to watch are not in the area where they are located.
11. What other residences do I need to know about Echo Star / Sky Angel?
Echo Star and Sky Angel are the second high-power satellite live broadcast services launched in the United States. Echostar started work in early March 1996 and has so far signed more than one million subscribers. This business is called the DISH (TM) network, which is sold by the company and Philip. Their program pricing seems to be lower than other satellite live broadcast services. DISH works from two separate orbital locations, it is currently the only company in this regard, and will soon work from three orbital locations. The first orbital position is 119 degrees west longitude. In this orbit, it controls two satellites with a total of 21 broadcast frequencies. The entire United States can receive about 100 channels at this orbital position. The third satellite used by Echostar is in an orbital position of 61.5 degrees. Although the entire United States can receive signals from this satellite, its key coverage area is the eastern half of the United States. Echostar plans to launch the fourth to a 148-degree orbital position in mid-1998 to provide services to the western half of the United States.
Many subscribers may choose to only receive nearly 100 channels at a 119-degree orbital position, while others want to be able to receive programs from more than two orbital positions at the same time.
12. How can I receive DISH programs from two orbital positions by using a dish antenna that can rotate? The answer is no.
To receive programs from two orbital locations, the subscriber must install two independent dish antennas, and one of the price antennas must point to the 119-degree orbital location, and the other antenna must point to the 61.5 long orbital location over the eastern United States or the United States 148-degree orbital position over the west. The price for the second dish antenna upgrade kit is about $ 100, and viewers who want to receive all programs can buy it themselves.
Echostar is equipped with a signal synthesizer in this kit. The signals from the two satellites can be combined together and led to the home by a cable, so no additional cables are laid. All existing and future decoders can receive programs from two track locations. After the installation is completed, users cannot perceive when switching between satellites and orbital positions.
13. What are the DISH programs for different track locations?
Echostar ’s most popular cable programs are included in about 100 channels broadcast from a 119-degree orbital position, so almost all users have a dish antenna that points to a 119-degree orbital position.
The content of services from other orbital locations has not yet been fully determined, but it is likely to be regional channel (see below) data services and some niche programs such as foreign language programs. The viewers who want to watch the purple program need to add another dish antenna.
14. How many satellites does Echostar have in these orbital positions?
The high-power satellites of Echostar are No.1, No.2, No.3, and No.4 respectively. Echostar No.1 and No.2 are currently located at an orbital position of 119 degrees, and Echostar No.3 is located at 61.5 degrees. Orbital position, Echostar No. 4 is located at an orbital position of 148 degrees. However, the company once filed an application for one of the two satellites launched by Echostar 4 to orbit at 119 degrees to drift to an orbit of 148 degrees. The final result can only be proved by time.
15. What is the sky angel business?
Echostar leased a transponder from Echo Yesterday No. 1 at the 61.5 degree orbit position to Domingo Church Satellite Organization. Domingo Church used it to broadcast 8 channels of religious programs and named it "Air "Angel" (Sky Angel). The Sky Angel business uses Echostar ’s receiving hardware and is a free additional service for the DISH business. The relationship between the two is similar to the relationship between DIRECTV and USSB. It should be noted that when receiving Sky Angel and other DISH programs at the same time, a separate dish antenna may be required.
It seems that only the 61.5-degree orbital position has an aerial angel program, so the West Coast region of the United States can only receive this program under extremely low viewing angle conditions in the east.
16. What about watching broadcast networks and local channels?
The lack of local channels is the main reason why people come to the atmosphere to buy satellite live broadcast systems. The direct broadcast satellite company has realized the seriousness of this problem, and is trying to solve this problem in various ways. Echo Star was the first to invest in this effort. It used considerable bandwidth capacity to increase the local branch program of the American Broadcasting Company (ABC) and CBS FOX in several major cities to its Satellite live broadcast service. Only viewers within the terrestrial coverage of this channel are entitled to receive these channels. The total price of this group of channels is $ 5.
When satellite broadcasting these channels, they did not seek the consent of these branches, which caused broadcasters to protest and even filed a legal prosecution. It is unclear if Echostar can continue to do so, it will be the only satellite broadcasting company that uses local channels as a constituent company. It is currently broadcasting in New York, Boston, Washington, DC, Chicago, Atlanta and Dallas, and will soon include several eastern and central cities in this rank. Echostar has no ability to transmit all the local channels of the selected city, and it cannot provide services to a large market with more than 20 in the near future.
Echostar Satellite 3 broadcasts local channels, so a dish antenna is needed for reception. In mid-1998, Echostar Satellite 4 had already begun work, broadcasting local branch channels in the western region.
Among other satellite direct broadcast companies, no company has a plan to carry local channels. They believe that local channels should be received from the air, so they strive to help improve the effectiveness of local ground reception to benefit their users. The decoder manufacturer is developing an additional function to make local channels and satellite-transmitted channels perfectly integrated in the program forecast table, thereby making it easier to switch between the two. USSB is spearheading a research project to determine which best antenna should be selected in each postal code area, so salespeople can buy the most suitable ground antenna. Many users cannot receive local channels from the air due to where they live. For these users, they can choose a branch program aggregation network (the branch is probably not a branch of the subscriber's area) in order to receive the main network program, according to the "Family Watch Satellite Program Law" re-enacted in 1994, using roof-mounted antenna Subscribers of the receiving network cannot receive this set of programs from satellites (but the court has not yet ruled that Echostar is the company ’s local channel business). This is a law made by Congress, not the rules and regulations of the Federal Communications Commission.
17. What kind of satellite direct broadcast system should be used?
What kind of satellite live broadcast system should be used depends on many factors, such as the type of program you want to watch, the size of the antenna you want to use, the amount of capital you plan to invest, and what orbital locations are available in the place where you live Choice, and other factors.
DIRECTV and USSB have the most types of channels, which should be the best choice for subscribers who want to have a large selection of power programs and can withstand multiple services. National Football League (NGL) football fans and other sports enthusiasts can also choose DIRECTV, and users who want to watch a lot of Premium business, pay-per-view movies and events can also choose DIRECTV. Primes + ar requires the least amount of initial investment, and subscribers are not responsible for equipment management. Although the dish antenna used is larger, the initial subscription fee is the lowest, which is very popular with rural users. Primes + ar is also the only company with local weather forecast information in the weather forecast channel.
Echostar is in a leading position in terms of low prices, its hardware and programming costs are the lowest, and it now has a channel capacity with large power. In addition, Echostar has local branches in some major cities, and in this regard, it is the only company that does so. Echo Star also has more super station types of programs that seem to be the only source of S + ar Trek programs. For viewers who want to watch Catholic programs, Echostar ’s associate “Sky Angel†will be the best choice.
Each service provider has a serious debt problem, and all continue to operate in a state of loss. When choosing a satellite live broadcast service provider, users should consider whether this company has sufficient funds to continue operating, otherwise, once this company ceases operation, the hardware purchased by users will become a fee. One of the service providers, Alphas + ar, has declared bankruptcy and the decoder hardware in its subscribers has become useless. It is too early to predict the success of "Sky Angel", but even if it declares bankruptcy, the user's DISH hardware can still be used to receive Echostar's programs. At present, it seems that DIRECTV, USSB and Acoustics will survive And will succeed.
18. How much have these systems been bought? How much is expected to buy?
So far, DIREC and USSB have declared that more than three million licensed decoders have been purchased, and this number is growing at a rate of thousands per day. Primes + ar claims to have nearly 2 million subscribers, but its growth rate has slowed compared to the past. Echostar Nanzai already has more than one million subscribers, and its growth rate is almost as fast as that of DIRECTV. Industry experts predict that by 2000, the total number of satellite live broadcast subscribers will reach about 14 million, but this estimate seems overly optimistic. Since the start of the satellite live broadcast service, the number of subscribers has been growing at a rate of one million per year. In mid-1998, this growth rate has been exceeded. The satellite live broadcast company has not reached their very optimistic subscriber number estimate. The sales rate is also slower than expected, but it is still a growing industry, adding thousands of new subscribers every day.
In order to attract subscribers, the satellite direct broadcast business company began to provide subsidies for equipment purchases in 1997. By doing so, the time to reach the two-point profit and loss far exceeds the originally planned time. DIRECTV and USSB originally expected to achieve a profit-loss balance when they had three million subscribers, but in order to protect the long-term sustained growth rate, it now appears that DIRECTV can achieve a profit-loss balance when it has nearly four million subscribers, and in 1998 Here, the number of its users has reached 400 USSB and achieved a win-loss balance in 1998.
The price of the decoder has been lowered a lot. The price of the first-generation decoder was a few years ago from US $ 700 to US $ 900, but now it has dropped to between US $ 100 and US $ 400. One of the reasons for the price drop is decoder subsidies. Therefore, the price reduction promotion will continue to maintain a high growth rate of the satellite live broadcast business authorization.
What other services do these satellite live broadcast companies provide?
Data services may be the most exciting development direction in satellite live broadcast services. Because the signals are transmitted in digital packets, these systems can deliver any combination of video, audio, and computer data to the decoder. Almost all decoders are equipped with a high-rate data interface, which can be connected to another external decoder of the computer. Each transponder can transmit a large amount of information (at least 23 ratios per second). All satellite live broadcast companies have reserved a certain bandwidth capacity for data services, but the development of data services is extremely slow.
Echostar was the first to launch a data service called AGCAST, which is used to provide services to rural and rural markets. AGCAST is a leaflet-type broadcast news service that displays agricultural news and information on a microcomputer connected to the DISH decoder data interface. The price of the software and cable is $ 70, and the monthly service fee is $ 35. Echostar introduced a microcomputer decoding card in mid-1998. Hard Uncle will be produced by ADAPTEC and will be jointly launched with some user data services announced soon.
DIRECTV company and the computer software company cooperated to produce a WINDOWS95-based microcomputer system, which is difficult to receive DIRECTV programs combined with data services. The hardware is produced by ADAPTEC or other companies and was listed in 1998. DIRECTV said that data services will become an extremely important part of its future business.
19. Can the AC-3 audio system be used?
There is currently no satellite live broadcast service that uses the AC-3 audio system.
Echostar said that they will begin to broadcast AC-3 audio on some channels (probably its PPV channel for each dues) in mid-1998. The company seems to be the only satellite live broadcast company currently owning the AC-3 decoder. DIRECTV has been broadcasting AC-3 on its engineering channel for some time. It has AC-3 broadcasting technology, but said that it is currently unable to carry out this business, because there is currently no AC-3 DSS decoder. However, this company does intend to develop some AC-3 broadcasting services in the near future.
PRIMESTAAR may add AC-3 service to some new high-power services that will be introduced below.
20. What are the disadvantages of the satellite live broadcast service system? Due to the high broadcast frequency used by satellite live broadcast service providers, all satellite live broadcast service systems will experience downtime under severe thunderstorm weather conditions. To solve this problem, satellites provide as much power as possible to rainy areas, but this problem still occurs from time to time. Some viewers feel that the occasional visibility of digital products affects the viewing effect, some people feel very upset, and some people hardly notice these problems. However, digital products are indeed an inherent shortcoming of the direct broadcast satellite service.
Some cable TV users, after connecting their video cassette recorder (VCR) and TV, can watch a channel while recording a program on another channel; or use a video box when going out The VCR records two cable channels. As with all decoders, the satellite live broadcast service can only decode one channel at a time. When all video cassette recorders and televisions are used at the same time, a decoder must be provided for each machine. In addition, some models do not have a program timer, and the video cassette recorder's timer cannot be connected to it, and it cannot record more than one channel at the same time.
Many users living in the West Coast region are disappointed that the broadcast time of the program is too early, because these companies use the broadcast time convention of the East Coast region in most programs.
Although almost all decoders have parental lock protection, occasionally, some violent and pornographic programs that do not give a limited level may still be broadcast, so the audience who set the lock protection limit according to the normal setting mode , May still watch this program, the parental lock protection function will lose its effectiveness.
21. Is there a high-definition television broadcasting plan?
DIRECTV announced that it plans to launch a two-price full-time high-definition television (HDTV) pay-per-view channel at an appropriate time. The premise of this plan is that high-definition TV manufacturers can produce products that meet their requirements before the specified time The high-definition television DIRECTV has demonstrated high-definition television broadcasting in 10801 and received it with RCA ’s prototype projection TV. If this plan is successfully implemented, then by then, the United States will be able to receive at least some high-definition television programs. The terrestrial broadcaster's plan is that each high-definition market should have at least one high-definition TV channel before the launch of high-definition TV. DIRECTV's recent move will also ensure that this plan is realized.
DIRECTV plans to broadcast two high-definition TV channels on one transponder, so that these two high-definition channels will have the same bandwidth as three or four standard-definition channels. If this plan is successful, the satellite replacement business company must carefully consider how to grasp the standard when adding high-definition channels.
A few years later, high-definition broadcasting is expected to form a considerable scale. As for when high-definition television channels can be opened, it is mainly determined by the sales volume of high-definition television in the United States. High-definition TV manufacturers are stepping up their efforts to start selling high-definition TVs as soon as possible, but within a certain period of time, the demand is unlikely to increase significantly. Primes + ar said they currently have plans for high-definition TV channels. Echo Star has no plans for high-definition TV channels. Echo Star has not yet announced their plan for a high-definition TV channel.
22. What hardware do I need to receive high-definition broadcasts?
DIRECTV said that they hope to install the DSS decoder in all high-definition TVs in the next few years. It will cost only about $ 50 to install a DSS decoder for each TV, so it will affect the cost of the TV. Not big. if it is like this. The DSS owner only needs to connect the HDTV and the dish to the satellite receiving antenna, and does not need to connect with the existing decoder. However, doing so also means that additional conditional access and billing cards are required, so let ’s wait and see how DIRECTV has implemented their plan.
Most types of live satellite decoders have extremely high-speed data interfaces. The manufacturer says that it can be directly connected to separately purchased machines and can interpret high-definition TV broadcast data streams. However, no company has announced plans to develop such a separate decoding unit. Most people think that this machine will be quite expensive, and it is not practical to manufacture it. Existing decoders never seem to be used for high-definition television reception. Instead, new decoders and / or TV sets (TVs with built-in direct broadcast decoders) will be used.
23. Can more than one TV be connected to a dish antenna?
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是的，但是在其最终所得的质é‡å¦‚何这一问题上å´é¢‡æœ‰äº›äº‰è®ºã€‚大多数业务所用的压缩比率åé«˜ï¼Œå› æ¤å¶å°”会出现数å—化产物现象。æ¯ä¸ªä¸šåŠ¡æ供商都必须在其系统质é‡ä¸‹é™å’Œç³»ç»Ÿçš„频é“æ•°é‡å¢žåŠ 之间åšå‡ºä¸€ç§æŠ˜ä¸æ€§çš„选择。
很多用户说视频和音频质é‡éžå¸¸å¥½ï¼Œç³»ç»Ÿçš„工作性能也éžå¸¸å¥½ã€‚但是å¦å¤–一些用户则指出至少在æŸäº›é¢‘é“出现了明显的数å—化产物。频é“之间的质é‡å·®åˆ«è¾ƒå¤§ï¼Œåœ¨æŸç§ç¨‹åº¦ä¸Šæ˜¯ç”±äºŽæºæ料有些差别。当所有业务的视频和音频质é‡éƒ½éžå¸¸ä»¤äººæ»¡æ„时，数å—化电视就出现了。
26ã€æœ‰æ¡ä»¶å˜å–系统是如何工件的？
在大多数系统ä¸ã€‚å«æ˜Ÿç›´æ’解ç 器å¯ä»¥æŽ¥æ”¶ä¸€ä¸ªè±¡ä¿¡ç”¨å¡å¤§å°çš„处ç†å™¨æ¿ï¼Œè¿™å—æ¿å称为Smar+Card,该æ¿å¯ä»¥æ’到解ç 器的å‰é¢ï¼Œå…许解ç 器接收授æƒæƒé™å†…的节目。授æƒæƒé™æ•°æ®æµå’Œè§†é¢‘音频信æ¯ä¸€èµ·è¢«é€åˆ°æ¯ä¸ªè½¬å‘器。在需è¦æŠ‘制盗版活动时，户主å¯ä»¥å¾ˆå®¹æ˜“地更æ¢Smar+Cardæ¿ã€‚ 盗版的DSS Smar+Cardæ¿å·²ç»è¢«åˆ¶é€ 出æ¥ï¼Œè€Œä¸”æ£åœ¨è¢«é”€å”®ï¼Œè¿™ç±»ç›—ç‰ˆæ´»åŠ¨å¤§å¤šå‡ºçŽ°åœ¨åŠ æ‹¿å¤§ã€‚å…¶å®ƒçš„ç³»ç»Ÿç›®å‰å¥½è±¡è¿˜æ²¡æœ‰è¢«ç›—版。DIRECTVå…¬å¸é‡‡ç”¨äº†å‡ ç§ç”µå对抗（ECM）手段，暂时压制ä½äº†ç›—版å¡ã€‚该公å¸æŽ§å‘Šäº†å‡ 家盗版商，并æˆåŠŸåœ°å¸®åŠ©èµ·è¯‰äº†å…¶ä¸ä¸€äº›åˆ¶é€ 商。DIRECTVå…¬å¸è¡¨ç¤ºå°†ä¸Žç›—版活动ä»æ—§åœ¨ç»§ç»ã€‚ DIRECTVå…¬å¸ä¸ºäº†å®‰å…¨ã€‚也å¯ä»¥é€‰æ‹©ä½¿ç”¨æ›´æ¢å…¨éƒ¨å¡çš„方法，它曾ç»è¿™ä¹ˆåšè¿‡ä¸€æ¬¡ï¼Œå½“然也å¯èƒ½å†åšä¸€æ¬¡ã€‚
27ã€ç›´æŽ¥å¹¿æ’å«æ˜Ÿä½äºŽå¤©ç©ºä¸çš„什么ä½ç½®ï¼Ÿ
直接广æ’å«æ˜Ÿè¿è¡Œåœ¨èµ¤é“上空22300è‹±é‡Œé«˜ç©ºçš„å‡ ä¸ªè½¨é“ä½ç½®ï¼Œè¿™å‡ 个轨é“ä½äºŽä¸Žç¾Žå›½å…¨å›½ç›¸å¯¹åº”的赤é“上空。碟状å«æ˜ŸæŽ¥æ”¶å¤©çº¿ä»¥é«˜äºŽåœ°å¹³çº¿çš„一定角度指å‘å—方，其角度å–决于秘地ä½ç¦»èµ¤é“有多远的è·ç¦»ã€‚美国北部地区（如明尼è‹è¾¾å·žï¼‰çš„å«æ˜Ÿæ˜¾å¾—更高一些。 DIRECTV/USSBå…¬å¸çš„å«æ˜Ÿå®šä½äºŽè¥¿ç»101度的轨é“ä½ç½®ï¼Œè¿™ä¸€ç»åº¦çº¿ä»Žå—è‡³åŒ—ç©¿è¿‡äº†è¥¿å†…å¸ƒæ‹‰æ–¯åŠ åœ°åŒºã€‚åœ¨ç¾Žå›½ä¸éƒ¨åœ°åŒºçš„居民眼ä¸ï¼Œè¿™é¢—å«æ˜Ÿå¤§çº¦åœ¨æ£å—æ–¹å‘。在东海岸地区，这颗å«æ˜Ÿä½äºŽå西å—æ–¹å‘。在西海地区，则ä½äºŽå东å—æ–¹å‘。
回声星公å¸çš„主å«æ˜Ÿå®šç‚¹äºŽè¥¿ç»119度的轨é“ä½ç½®ï¼Œè¿™ä¸€ç»åº¦çº¿ä»Žå—至北穿过了西内åŽè¾¾åœ°åŒºã€‚在美国西海岸地区的居民眼ä¸ï¼Œè¿™é¢—å«æ˜Ÿå¤§çº¦åœ¨æ£å—æ–¹å‘。在其它地区，这颗å«æ˜Ÿä½äºŽè¥¿å—方呓空ä¸å¤©ä½¿â€å’Œå›žå£°å…¬å¸çš„东海岸å«æ˜Ÿå®šä½äºŽè¥¿ç»61.5度的轨é“ä½ç½®.Primes+arå…¬å¸çš„常规型å«æ˜Ÿå®šä½äºŽè¥¿ç»85度轨é“ä½ç½®ã€‚
28ã€ç›´æŽ¥å¹¿æ’å«æ˜Ÿçš„上行链路设施ä½äºŽä»€ä¹ˆä½ç½®ï¼Ÿ USSBå…¬å¸ä½¿ç”¨ä½äºŽå°¼è‹è¾¾å·žå¥¥å…‹ä»£å°”的全数å—化设施，这一站å€ç¦»åœ£ä¿ç½—很近。它的两个直径为9米的ã€Ka波段上行抛物é¢å¤©çº¿å®‰è£…在特制的罩ä¸ï¼Œè¿™ç§ç‰¹åˆ¶ç½©å…·æœ‰å¾®æ³¢é€æ˜Žæ€§ï¼Œè€Œä¸”能够ä¿æŠ¤å¤©çº¿ä¸å—气候æ¡ä»¶çš„侵扰。
29ã€DSS系统有哪些技术细节情况？
这一系统有三颗工作å«æ˜Ÿï¼Œå®ƒä»¬åˆ†åˆ«æ˜¯ï¼šç›´æ’å«æ˜Ÿä¸€å·ã€ç›´å«æ˜ŸäºŒå·å’Œç›´æ’å«æ˜Ÿä¸‰å·ã€‚æ¯é¢—å«æ˜Ÿæœ‰16个转å‘器，由120瓦行波管放大器（TWTA）æ供功率，能够进行数å—化和模拟å¼ä¼ 输。
这些å«æ˜Ÿå·¥ä½œåœ¨KU波段谱的广æ’å«æ˜Ÿä¸šåŠ¡ï¼ˆBSS）频率（12.2至12.7GHZ）上,采用圆æžåŒ–æ–¹å¼ã€‚它们å¯ä»¥å‘ç¾Žå›½æœ¬åœŸå’ŒåŠ æ‹¿å¤§å—部å‘å°„58至53dBWçš„è¾å°„功率。æ¯é¢—å«æ˜Ÿé‡3800磅，天线和太阳能翼æ¿å±•å¼€æ—¶ï¼Œå«æ˜Ÿé•¿26米，宽7.1米。太阳通用翼æ¿èƒ½å¤Ÿæä¾›4300瓦的电力。
DSS系统采用四相相移键控（QPSK）调制方å¼ï¼Œå¯¹å°„频载波上的数å—化数æ®è¿›è¡Œç¼–ç æ–¹å¼æ˜¯MPEG-1LayerII。在行MPEGç¼–ç 之å‰ï¼Œå¯¹éŸ³é¢‘进行多比环绕声å“的效果。使用MPEG-2è¯æ³•å¯¹è§†é¢‘进行编ç ，å–æ ·é€ŸçŽ‡å¯è¾¾CCIR601-1能够处ç†720×480的图象，但是目å‰é‡‡ç”¨çš„分辨率较低。
这一系统使用一ç§ç»Ÿè®¡å¼å¤šç¨‹åºç¼–ç 器，这一编ç 器的å称是S+a+Mux,它å¯ä»¥æ ¹æ®è§†é¢‘内容，并结åˆè€ƒè™‘到在åŒä¸€è½¬å‘器上å¤ç”¨çš„其它节目，而动æ€åœ°æ”¹å˜æ¯”特速率。æ¯é¢—ç›´æ’å«æ˜Ÿéƒ½å¯ä»¥é…ç½®æˆ16个120瓦转å‘器的é…置方å¼ï¼Œæˆ–是8个240瓦转å‘器的é…置方å¼ï¼Œæˆ–是8个240瓦转å‘器的é…置方å¼ï¼Œè¿™æ˜¯ç”±å«æ˜Ÿå¤ªé˜³èƒ½ç¿¼æ¿æ‰€äº§ç”Ÿçš„ç›´æµç”µé‡å†³å®šçš„。 DSS结构在两ç§å·®é”™æŽ§åˆ¶æ–¹å¼ä¸‹ï¼Œæ¯ä¸ªè½¬å‘器都å¯ä»¥ä»¥æ¯ç§’40兆比的速率分é…给了信æ¯ï¼Œæ¯ç§’10兆比的速率分é…给差错控制；在低差错控制方å¼ä¸‹ï¼Œæ¯ç§’23兆比的速率分é…给了信æ¯ï¼Œæ¯ç§’17兆比的速率分é…给差错控制。实现åŒæ ·çš„端到端å¯ç”¨æ€§ï¼Œé«˜å·®é”™æŽ§åˆ¶æ–¹å¼æ‰€éœ€çš„ä¿¡å·å¼ºåº¦æ¯”低差错控制方å¼çš„高3Db。
ç›´æ’å«æ˜Ÿä¸€å·ä»¥ä½Žå·®æŽ§åˆ¶æ–¹å¼è¿è¡Œï¼Œè€Œç›´æ’å«æ˜ŸäºŒå·å’Œç›´æ’å«æ˜Ÿä¸‰å·åˆ™ä»¥é«˜å·®é”™æŽ§åˆ¶æ–¹å¼å·¥ä½œã€‚å› æ¤DIRECTVå’ŒUSSBå…¬å¸æ‹¥æœ‰16个240瓦ã€ä»¥é«˜å·®é”™æŽ§åˆ¶æ–¹å¼å·¥ä½œçš„转å‘器和16个120瓦ã€ä»¥ä½Žå·®é”™æŽ§åˆ¶æ–¹å¼å·¥ä½œçš„转å‘器。第四颗å«æ˜Ÿå‘å°„å‡ç©ºåŽï¼Œæ‰€æœ‰çš„转å‘器功率都将改å˜ä¸º240瓦，但是DIRECTVå…¬å¸è¯´ä»–们目å‰è¿˜æ²¡æœ‰å‘射第四颗å«æ˜Ÿçš„计划。
30ã€ä»€ä¹ˆæ˜¯é«˜çŽ‡ç›´æ’å«æ˜Ÿï¼Œå®ƒä¸Žä¸€èˆ¬ç›´æ’å«æ˜Ÿæœ‰ä½•åŒºåˆ«ï¼Ÿ
å‡ å¹´å‰ï¼Œè”邦通信委员会为被称为直接广æ’å«æ˜Ÿï¼ˆDSS）的电视业务ä¿ç•™äº†ä¸€éƒ¨å¹¿æ’é¢‘è°±å’Œç¾Žå›½çš„å‡ ä¸ªå«æ˜Ÿè½¨ç–²ä¹ä½ç½®ã€‚这些å«æ˜Ÿç›¸éš”ä¹åº¦ï¼ˆå¸¸è§„å«æ˜Ÿä¹‹é—´çš„间隔为两度）这些å«æ˜Ÿå¯ä»¥ç”¨æ›´ä¸»çš„功率进行广æ’，以便使特别å°çš„å«æ˜ŸæŽ¥æ”¶å¤©çº¿èƒ½å¤Ÿè¿›è¡Œæ— 干扰的接收。这就是è”邦通信委员会对直æ’å«æ˜Ÿçš„å®šä¹‰ï¼Œå®ƒè¿˜ç‰¹åˆ«ä¸ºå‡ å®¶å…¬å¸å‘放了å«æ˜Ÿç›´æ’业务的è¥è®¸å¯è¯ï¼Œè¿™äº›å…¬å¸åˆ†åˆ«æ˜¯DIRECTVå…¬å¸å’Œå›žå£°æ˜Ÿå…¬å¸ã€‚
没有å«æ˜Ÿç›´æ’许å¯è¯çš„其他的其他广æ’å…¬å¸å¯ä»¥ç”¨å¸¸è§„å«æ˜Ÿæ¥æ供直接入户业务。对用户æ¥è¯´ï¼Œç›´æŽ¥å…¥æˆ·ä¸šåŠ¡ä¸Žæœ‰è®¸å¯è¯çš„å«æ˜Ÿç›´æ’ä¸šåŠ¡æ˜¯ä¸€æ ·çš„ï¼Œä¸¤è€…ä¹‹é—´çš„åŒºåˆ«æ˜¯å‰è€…通常需è¦ä½¿ç”¨è¾ƒå¤§çš„碟状接收天线（虽然这ç§å¤©çº¿è¿œæ¯”常规的抛物é¢å¤©çº¿å°ï¼‰è€Œä¸”è¿™ç§å¤©çº¿éœ€è¦ä¸“ä¸šäººå‘˜è¿›è¡Œå®‰è£…ã€‚å› æ¤å«æ˜Ÿç›´æ’的定å˜è‰²é•œä¹Ÿå¸¸å¸¸ç”¨æ¥æŒ‡ç”¨å°åž‹ç¢ŸçŠ¶å¤©çº¿ä»Žå›ºå®šå«æ˜Ÿä½ç½®è€Œæ供的直接入户业务，但是高功率直æ’å«æ˜Ÿä¸€è¯åˆ™æ˜¯è”邦通信委员会用æ¥ä¹‰å«æ˜Ÿç›´æ’业务的专用è¯ã€‚
è”邦通信委员会美国的高功率å«æ˜Ÿç›´æ’业务预留了八个轨é“ä½ç½®ï¼Œå…¶ä¸å››ä¸ªç”¨äºŽå‘东海岸地区æä¾›æœåŠ¡ã€‚å¦å¤–四个轨é“ä½ç½®ç”¨äºŽå‘西海岸地区ææœåŠ¡ã€‚在æ¯ä¸ªè½¨é“ä½ç½®ï¼Œè”邦通信委员会å…许最多å¯ä»¥è®¾ç½®32个广æ’频率（å³è½¬å‘器）。è”邦通信委员会å‘申请者分é…ç›´æ’å«æ˜Ÿé¢‘率时，也为其东海岸å«æ˜Ÿå’Œè¥¿æµ·å²¸å«æ˜Ÿåˆ†é…了相ç‰æ•°ç›®çš„轨é“ä½ç½®ã€‚其指导æ€æƒ³æ˜¯è®©æ¯ä¸ªå…¬å¸åŒæ—¶ä»Žå…¶ä¸œæµ·å²¸å«æ˜Ÿå’Œè¥¿æµ·å²¸å«æ˜Ÿè¿›è¡Œå¹¿æ’，从而å‘整个美国æ供报务。
然而，利用今天的先进技术，四个东部轨é“ä½ç½®ä¸æœ‰ä¸‰ä¸ªè½¨é“ä½ç½®ï¼ˆå³è¥¿ç»101度ã€è¥¿ç»110度和西ç»119度）实际上都å¯ä»¥å¤ç›–整个美国本士。这些轨é“ä½ç½®è¡¥ç§°ä½œæ˜¯Full-Conus（全美本士）轨é“ä½ç½®ï¼Œå½“然也是最佳的轨é“ä½ç½®ã€‚
31ã€åœ¨è¿™äº›å…¨ç¾Žæœ¬å£«è½¨é“ä½ç½®ä¸Šï¼Œæœ‰æ²¡æœ‰å…¶ä»–å«æ˜Ÿç›´æ’业务计划？
ç½—ç€ç‰¹ã€é»˜å¤šå…‹çš„新闻公å¸å·²ç»è´ä¹°äº†è¥¿ç»110度轨é“ä½ç½®çš„28个转å‘器使用æƒã€‚最近该公å¸å®£å¸ƒå°†ä¸ŽPrimes+arå…¬å¸åˆä½œï¼Œåœ¨è¥¿ç»110度的轨é“ä½ç½®ä¸Šæ供一ç§æ–°çš„ã€æ‹¥æœ‰å¾ˆå¤šé¢‘é“的高功率Primes+arå…¬å¸å°±å°†ç”±ä¸€ä¸ªä¸ç‰åŠŸçŽ‡ã€è€Œä¸”大部分是乡æ‘业务公å¸è€Œä¸€è·ƒæˆä¸ºé‡è¦çš„ã€èµ„金雄厚的高功率å«æ˜Ÿç›´æ’业务公å¸ã€‚
由于有线电视集团拥有Primes+arå…¬å¸ï¼ŒåŽé¡¿æ‹…心这一计划ä¸ä¼šæ高有线电视的竞争力，所以对这一计划有些ä¸æ»¡ã€‚然而很多人认ç§å«æ˜Ÿç›´æ’ä¸šåŠ¡ä¸‰å¤§å·¨å¤´çš„æ ¼å±€ä¸å—益，三家都使用高功率，当然所用的碟状天线åˆéƒ½å¾ˆå°ã€‚
Primes+arå…¬å¸è¯´ï¼Œæœ€æ—©å¯ä»¥åœ¨1998å¹´4月开始æ供这ç§åž‹çš„高功率业务。该公å¸åšä¿¡è®¡åˆ’将在1998年年底之å‰å¾—到è”邦通信委员会的批准。他们å¯èƒ½ä¼šå†³å®šæŠŠçŽ°æœ‰çš„用户从ä¸ç‰åŠŸçŽ‡å«æ˜Ÿä¸Šç§»æ¢è€ç¥–å®—æ¥ï¼Œæ–¹æ³•æ˜¯ç§»åŠ¨ç”¨æˆ·çš„天线ã€æ›´æ¢å’Œ/或强化用户的解ç 器；该公å¸ä¹Ÿå¯èƒ½ä¼šæŠŠçŽ°æœ‰ç”¨æˆ·æ— é™æœŸåœ°ç•™åœ¨ä¸ç‰åŠŸçŽ‡ä¸šåŠ¡ä¸Šã€‚è¿™ç§è¿ç§»æ´»åŠ¨å¾ˆè´¹äº‹ï¼Œè€Œä¸”也需è¦å¤§é‡çš„投资。 Primes+arå…¬å¸çš„股份摇拥有者，TCLå…¬å¸ï¼Œæ‹¥æœ‰è¥¿ç»119度轨é“ä½ç½®11个转å‘器（这是回声星公å¸çš„主å«æ˜Ÿè½¨é“ä½ç½®ä½ç½®ï¼‰çš„使用æƒã€‚è”邦通信委员会需è¦å¯¹è¿™ä¸€é—®é¢˜åšå‡ºè£å†³ã€‚Primes+arå…¬å¸è¯´ï¼Œå¦‚æžœå…许它使用西ç»110度的轨é“ä½ç½®ï¼Œå®ƒå¯ä»¥æ‹å–掉西ç»119度的å«æ˜Ÿå®¹é‡ä½¿ç”¨æƒã€‚ USSBå…¬å¸æ‹¥æœ‰è¥¿ç»110度轨é“ä½ç½®ä¸‰ä¸ªè½¬å‘器的使用æƒï¼Œçœ‹èµ·æ¥è¯¥å…¬å¸å‡†å¤‡åœ¨è¿™ä¸€ä½ç½®å¼€å±•æŸäº›ä¸šåŠ¡ã€‚
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工程上常用一些å‚é‡æ¥è¡¨å¾å¤©çº¿ç”¨ä½œå‘射或接收的特性，它们是方å‘图，主瓣电平，增益，æžåŒ–，频带宽度，驻波比，噪声温度ç‰ã€‚这里仅对其ä¸å‡ 个主è¦å‚é‡ä½œç®€å•ä»‹ç»ã€‚
æ–¹å‘图ã€ä¸»ç“£å®½åº¦ä¸Žå‰¯ç“£ç”µå¹³
天线功率è¾å°„击是å¦é›†ä¸ï¼Œå¯ä»¥ç”¨ä¸»ç“£å®½åº¦è¿™ä¸€å‚é‡æ¥è¡¨ç¤ºï¼›ä¸»ç“£ä¸è¾å°„功率为最大值一åŠæ—¶ä¸¤ä¸ªçŸ¢å¾„间的夹角称为主瓣宽度。主瓣宽度越å°ï¼Œæ–¹å‘图越尖é”，表示天线è¾å°„越集ä¸ã€‚ 副瓣的最大值相对主瓣最大值的比，称为副瓣电平，一般用分è´æ¥è¡¨ç¤ºï¼Œå…¶å®šä¹‰ä¸ºï¼š
101g副瓣最大值功率/主瓣最大值功率
如副瓣最大值与主瓣最大值相应功率之比为0.01,则副瓣电平为-20dB。
如果å天线在å„æ–¹å‘è¾å°„击的强度用从原点出å‘的矢é‡é•¿çŸæ¥è¡¨ç¤ºï¼Œåˆ™è¿žæŽ¥å…¨éƒ¨çŸ¢é‡ç«¯ç‚¹æ‰€å½¢æˆçš„包络就是天线的方å‘图。它显示出天线的在ä¸åŒæ–¹å‘è¾å°„的相对大å°ï¼Œè¿™ç§æ–¹å‘图称为立体方å‘图。矢径的方å‘代表è¾å°„çš„æ–¹å‘，矢径的长çŸä»£è¡¨è¾å°„击的强度。方å‘图包å«æœ‰è®¸å¤šæ³¢ç“£ï¼Œå…¶ä¸åŒ…å«æœ€å¤§è¾å°„æ–¹å‘的波瓣称为主瓣。其它ä¾æ¬¡ç§°ä¸ºç¬¬ä¸€å‰¯ç“£ï¼Œç¬¬äºŒå‰¯ç“£ç‰ã€‚ 我们也å¯ç”¨å¢žç›Šæ¥è¡¨ç¤ºå¤©çº¿é›†ä¸è¾å°„的程度。天线在æŸä¸€æ–¹å‘的增益定义为：在相åŒçš„输入功率下，天线在æŸä¸€æ–¹å‘æŸä¸€ä½ç½®äº§ç”Ÿçš„电场强度的平方（E2ï¼‰ä¸Žæ— è€—ç†æƒ³ç‚¹æºå¤©çº¿åœ¨åŒä¸€æ–¹å‘åŒä¸€ä½ç½®äº§ç”Ÿçš„电场强度的平方（E02）的比值，通常以G表示。
G=E2/E02（åŒä¸€è¾“入功率）
åŒæ ·ï¼Œå¢žç›Šä¹Ÿå¯ä»¥è¿™æ ·æ¥ç¡®å®šï¼šåœ¨æŸä¸€æ–¹å‘å‘æŸä¸€ä½ç½®äº§ç”Ÿç›¸åŒç”µåœºå¼ºåº¦çš„æ¡ä»¶ä¸‹ï¼Œæ— 耗ç†æƒ³ç‚¹æºå¤©çº¿çš„输入功率（Pino）与天线的输入功率（Pin）的比值，å³ç§°ä¸ºè¯¥å¤©çº¿åœ¨è¯¥ç‚¹æ–¹å‘的增益。
G=Pino/Pin（åŒä¸€ç”µåœºå¼ºåº¦ï¼‰
通常是以天线在最大è¾å°„æ–¹å‘的增益作为这一天线的增益。增益通常用分è´è¡¨ç¤ºã€‚å³ï¼šG=101gPino/Pin天线增益的计算：G=η4Ï€S/λ2=η（π/λ）2D2å¼ä¸ï¼ŒS-天线å£å¾„é¢ç§¯ï¼ˆå¹³æ–¹ç±³ï¼‰ï¼›Î»-工作波长（米）；D-抛物é¢å£å¾„（å³é¢å£ç›´å¾„）（米）；η-天线效率。
天线的噪声温度：
进入天线的噪声主è¦æ¥é“¶æ²³ç³»çš„宇宙噪声和æ¥è‡ªå¤§åœ°ã€å¤§æ°”çš„çƒå™ªå£°ã€‚ä¸åŒå£å¾„的天线ã€ä¸åŒé¢‘段ã€ä¸åŒä»°è§’å’Œä¸åŒçŽ¯å¢ƒï¼Œå¤©çº¿çš„噪声都ä¸ç›¸åŒã€‚在C波段，宇宙噪声很å°ï¼Œä¸»è¦æ˜¯å¤§åœ°å’Œå¤§æ°”çš„çƒå™ªå£°ã€‚在Ku波段，这些噪声也éšç€é¢‘çŽ‡è€Œå¢žåŠ ã€‚åŒä¸€ä»°è§’时，天线尺寸越大波æŸè¶Šçª„ï¼Œå› æ¤å¤©çº¿çš„噪声温度TA（K）越å°ï¼Œä¸è¿‡éšç€ä»°è§’åŠ å¤§ï¼Œè¿™ç§å·®åˆ«å˜å°ã€‚而åŒä¸€å¤©çº¿å°ºå¯¸æ—¶ï¼Œå¤©çº¿ä»°è§’Φ越大，天线的噪声温度TA（K）越低，å之Φ越å°ï¼ŒTAè¶Šé«˜ã€‚è¿™æ˜¯å› ä¸ºä»°è§’Î¦è¶Šå°ï¼Œä¿¡å·ç©¿è¿‡å¤§æ°”层厚度越大，从而气象噪声ã€å¤§æ°”噪声越强。
电ç£æ³¢çš„æžåŒ–：
电ç£æ³¢çš„æžåŒ–å½¢å¼å¯åˆ†ä¸ºçº¿æžåŒ–波和圆æžåŒ–波，线æžåŒ–æ³¢åˆå¯åˆ†ä¸ºæ°´å¹³æžåŒ–和垂直æžåŒ–波，圆æžåŒ–æ³¢æ ¹æ®ç”µåœºæ—‹è½¬æ–¹å‘ä¸åŒåˆå¯åˆ†ä¸ºå·¦æ—‹å’Œå³æ—‹åœ†æžåŒ–波。我国目å‰å«æ˜Ÿä¿¡å·æ–¹è¦é‡‡ç”¨çº¿æžåŒ–波。
接收天线的æžåŒ–æ–¹å¼åªæœ‰åŒè¢«æŽ¥æ”¶çš„电ç£æ³¢æžåŒ–å½¢å¼ç›¸ä¸€è‡´æ—¶ï¼Œæ‰èƒ½æœ‰æ•ˆåœ°æŽ¥æ”¶åˆ°ä¿¡å·ï¼Œå¦åˆ™å°†ä½¿æŽ¥æ”¶ä¿¡å·è´¨é‡å˜å，甚至完全收ä¸åˆ°ä¿¡å·ï¼Œè¿™ç§çŽ°è±¡ç§°ä¸ºæžåŒ–失é…。当馈æºé‡‡ç”¨çŸ©å½¢æ³¢å¯¼æ—¶ï¼Œå…¶æžåŒ–æ–¹å‘由波导å£çš„æ–¹å‘确定。波导å£çª„边与地平é¢å¹³è¡Œä¸ºæ°´å¹³æžåŒ–，宽边与地平é¢å¹³è¡Œä¸ºåž‚ç›´æžåŒ–。当采用圆波导馈æºæ—¶ï¼Œåˆ™åº”以波导ä¸çš„探针方å‘为准。值得注æ„的是：å«æ˜Ÿè½¬å‘器å‘射的线æžåŒ–波是以å«æ˜Ÿçš„è½´ç³»ä¸ºåŸºå‡†å®šä¹‰çš„ï¼Œå› æ¤åªæœ‰å½“地é¢ç«™å¤©çº¿ä¸Žå«æ˜Ÿæ‰€å¤„çš„ç»åº¦ä¸€è‡´æ—¶ï¼Œåœ°é¢ä¸Šæ³¢çš„æžåŒ–æ–¹å‘æ‰ä¸Žå«æ˜Ÿç›¸åŒï¼Œå…¶å®ƒåœ°åŒºåº”略有åå·®ã€‚å› æ¤åœ¨å®‰è£…时应ç¨å¾®å·¦å³è½¬åŠ¨ä¸€ä¸‹é¦ˆæºï¼Œä½¿æŽ¥æ”¶æœºçš„电平指示最大，以达到æžåŒ–匹é…。
天线æžåŒ–的调整
1ã€çº¿æžåŒ–与圆æžåŒ–å…±å˜æ—¶ï¼ŒæžåŒ–器的调整
对租用的国际通信å«æ˜Ÿå‘å°„æ¥çš„是å³æ—‹åœ†æžåŒ–波，我国å«æ˜Ÿå‘射的是水平æžåŒ–波。从收租星改收我国å«æ˜Ÿæ—¶ï¼Œå°±å¾—转动天线馈æºä¸ç§»ç›¸ä»‹è´¨ç‰‡ï¼Œä½¿ä¹‹ä¸Žæ°´å¹³é¢åž‚直，并调整矩形ä½ç½®ï¼Œä½¿å…¶æ³¢å¯¼è¾“出å£çš„窄边与水平é¢å¹³è¡Œï¼Œè¿™æ—¶å°±å¯ä»¥æŽ¥æ”¶æ°´å¹³æžåŒ–波。
2ã€åªæ”¶çº¿æžåŒ–波时，æžåŒ–器的调整.
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Copper not only has excellent thermal conductivity, but also has good antirust ability. The size of the radiator is generally determined by the size of the fan. Common radiator specifications have a radiator match with one pieces of 120mm fan, people are used to call this radiator 120. The radiator that can match two pieces of 120mm fans is 240. And so on, there are 360 and 480 radiator.
Pure Copper Radiator,Copper Cooling Heatsink,Liquid Cooling Radiators,Computer Water Radiator
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