1. What is satellite live broadcast?
Recently, several new TV services have appeared in the United States. American households can use small satellite dish antennas (18 inches to 3 feet in diameter) to receive TV programs directly from satellites. This dish antenna cannot be rotated. Fixed point to a certain position in the sky.
The signal is digitally compressed, and a single satellite transponder can broadcast several programs, so a dish antenna pointed at 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-style" programs aimed at a small audience. Although these services are often referred to 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 are interested in developing satellite live broadcast services.
2. Which satellite live broadcast services are there now?
There are currently five companies in the United States that are providing fully digital satellite live broadcast 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. Primestar has achieved great success. At present, there are about 2 million subscribers occupying satellite live broadcasts. More than 30% of the market, but its growth momentum has slowed down in recent times.
DIRECTV is a subsidiary of Hughes Communications. It provides a service called DIRECTV that uses an 18-inch dish antenna to receive programs from specially designed high-power direct broadcast satellites. DIRECTV service is considered to be the United States Today's primary satellite live broadcast service has more than 3 million subscribers since its inception in 1994, which accounts for more than half of the satellite live broadcast market.
The United States Satellite Broadcasting Corporation (USSB) cooperated with DIRECTV to send 25 channels of free bonus movie services. This service uses the same satellite, the same receiving system and combined program forecasts, so the two services seem to be A business. Today the USSB business has nearly two million subscribers.
Echistar (ECHISTAR0 Communications Company) provides DISH NETWIRK service. It uses an 18-inch dish antenna to receive programs from a specially designed high-power direct broadcasting satellite. Since the DISH service started in the spring of 1996, its current market share is relatively Small, 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 enters the market with low-priced hardware and programs. This move is popular with price-conscious subscribers, resulting in Other service providers have also lowered the prices of hardware programs accordingly. It also promised to broadcast some local channels in major cities in the United States, which will be very popular with viewers.
The Dominican Church cooperated with Echostar to broadcast a Catholic religious service with 6 to 10 channels. The name of this service is "Sky Angel" (SKY ANGEL). The same contract and program schedule are used. Both Business appears to be a business. At this time, it is too early to predict whether the "air angel" will succeed, but this kind of business is indeed aimed at the "niche" blank that other businesses have not taken into account.
Because some services use the same receiving system and usually work in the same orbital position, viewers 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 needed?
Each service 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 televisions and video cassette recorders (VCRs) in the home. If the user wants to watch two satellite channels at the same time, or while watching one channel while recording another channel's program, then this family needs two decoders.
The dish antennas of some low-cost satellite live broadcast systems can only connect to one decoder, while other systems can connect to one or two decoders. Generally, these systems have two or more decoders that can be connected , But in most cases, additional hardware needs to be configured. The ECHOSTAR/SKY ANGEL service of DIRECTV/USSB service uses a system that allows users to install their equipment by themselves, 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 within the range of the satellite, and be careful not to block the falcons from trees or high-rise buildings. Dish antennas generally have a built-in installation audible signal indicator or flashing light-emitting diode (LED) indicator to display the signal strength, so that the best installation location can be selected during installation. Self-installation kits for DSSS and SIDH systems are priced at around $70. The kit components generally include: cables, compasses, grounding pieces, telephone T-connectors, and all other hardware required to install and connect the dish antenna. These installation kits usually come with a video tape that demonstrates the installation process. All required cables can be purchased from RADIO SHACK or other similar retail companies. Users who are not very convenient for shopping can consider installing their own kits.
The decoders in most systems 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 television. One important reason is that the latest technological advances in real-time digital video compression technology allow the transmission of a few channels in the same frequency band. Each satellite broadcast service uses the recently developed real-time lossy compression system. On average, each satellite transponder can broadcast six channels. In the past, each satellite transponder could only broadcast one channel. In business, up to 200 channels can be transmitted from one orbital position in the sky. If digital compression technology is not used, only 32 channels can be broadcast in one orbital position, so the popularity of satellite live broadcast services will be greatly reduced. The number of channels broadcast by various services 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 authorized to use the company and the number of compressed channels 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 seem to be licensed to use different numbers of transponders at their designated orbital positions. The number of channels compressed to a transponder is affected by many factors, such as the required image quality (such as resolution), the frame rate of the source material, the amount of motion in the source material, the degree to which the digital product is allowed to be visualized, and the encoding The complexity of the device, the closed error control formed in the transmitted bit stream, and other factors.
For programs like basketball games, because there are many fast moving small objects in some of the frames, only 3 or 4 channels can be compressed on each transponder, otherwise obvious digital products will appear. Most programs that are large-scale still images can be compressed at a larger ratio, and 5 or 6 channels can be compressed on each transponder. The film is 24 frames per second instead of 30 frames per second video, so the raw material content is low; in addition, the film film is not interlaced, generally a relatively constant frame-to-frame conversion; therefore, the compression ratio of the film film can be larger, Satisfactory viewing effects can still be achieved when 7 or 8 channels are compressed on each transponder. With the continuous advancement of compression technology, these estimates deserve to be somewhat conservative.
6. What kind of compression system does the satellite live broadcast service use?
Each satellite live broadcast service transmits a bit stream containing compressed audio, compressed video, authority 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 regular TV. Every business needs a decoder specially designed to work with its system. The PRIMESTAR business uses a dedicated video compression system developed by General Instruments (GENERAL INSTRUMENTS). The name is DIGICIPHER-. The format used by other services is based on the MPEG-2 compression standard, but it 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 decoders be interchanged between various services?
The answer is no. There is absolutely no decoder standardization in the satellite live broadcast service sector. DIRECTV and USSB use the same decoder, Echostar and Air 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 bit streams contain some unique information that only their own decoders can interpret. If you want to switch to another service, users must sell their decoders in exchange for decoders suitable for the new service. When considering what kind of satellite broadcast service system to purchase, what kind of transmission system each service provider uses is irrelevant, because all these systems provide audio and video of similar quality, and they cannot interact with other services. change. The important thing is to choose a service that can provide your favorite programs at a reasonable price.
8. What other information do I need to know about the PRIMESTAR business?
Many cable system operators (MOS) Lenovo jointly established PRIMESTAR Co., Ltd. to provide 160 channels of digital direct-to-home services to North America. The name of this service is PRIMESTAR. It is the first company to provide satellite live broadcast services. It began to provide 30 analog channels during the digital years. It was changed to digital in 1994. It claims to be the first digital service, which is a few weeks ahead of DIRECTV and USSB.
Today, the PRIMESTAR business has entered nearly two million households, most of which are located in rural areas. The main reason for their success is that this is the only business where users do not need to buy a decoder or dish antenna. They rent out the equipment and calculate the rent into the monthly subscription fee. They broadcast from a medium-power conventional satellite located at an orbital position of 85 degrees west longitude. The name of this satellite is GE-2 satellite. Therefore, they use a dish antenna with a diameter of 27 inches. This antenna requires professionals. Install it.
PRIMESTAR’s decoder is produced by General Instrument Company. Its receiving system is called DIGICPHER-1 digital broadcasting system. The decoder has hardware upgradeability, that is, it can be equipped with a hardware upgrade module without replacing any parts. System components are upgraded. PRIMESTAR modified the signal of the weather forecast channel to provide users with local weather information. In this respect, it is the only one. At RADIO SHACK stores and NOBODY BEATS THE WIZ stores nationwide in the United States, PRIMESTAR hardware and program forecast tables can be purchased.
9. What other information do I need to know about DIRECTV/USSB business?
The DIRECTV/USSB service is the leading satellite live broadcast service in the world today. It provides nearly 200 video channels. This service uses three specially made high-power KU-band satellites located in the same orbit for work. The name of the first satellite is the "Direct Broadcast Satellite One" (DBSI) satellite, this satellite has 16 120 watt transponders; the other two satellites are Direct Broadcast Satellite 2 and 3 (DBS2 and DBS3) satellites , The two satellites each have 8 240-watt transponders. There are a total of 32 broadcast transponders on the three satellites. DIRECTV sold five of the 120-watt transponders to the USSB (because federal law requires all direct broadcasters to have their own broadcasting facilities, in fact, USSB owns 5/16 of the entire satellite). These two competing companies use the same dish antennas and decoders 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 decoders ranges from US$100 to US$500. The specific price is related to the model variety and promotion activities at different times throughout the year.
Every DSS equipment manufacturer has its own unique user interface for its products to differentiate the products. The difference between these user interfaces is mainly the difference in the appearance and tactility of the networked program forecast and the difference in the remote control. The information contained in the program forecast table includes the introduction of the next episode and the introduction of the program scheduled to be broadcast. 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 broadcasting frequencies located at the 110 degree west longitude orbital position. The channels transmitted by each service are 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, and the five transponders provide 25 channels. Their business consists of high-quality movie channels, including family box channel (HBO) and show time channel (Show+ime). DIRECTV scored 27There are 175 program channels on each frequency, and 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 program is the foundation of its business. DIRECTV allows subscription to most major professional sports events and some college student sports events. They use the addressable feature of the decoder to only allow program reception in a certain geographic location, such as receiving a program somewhere outside the local coverage area. An obvious local blanking system is adopted, which means that many of the events that viewers want to watch are not in their area.
11. What other places do you need to know about Echo Star/Sky Angel?
Echostar and Sky Angels are the second high-power satellite live broadcast services launched in the United States. Echostar started work in early March 1996 and has signed more than one million subscribers so far. This business is called the DISH(TM) network and is sold by the company and Philips. The pricing of their programs seems to be lower than that of other satellite live broadcast services. DISH works from two separate orbital positions. It is currently the only company in this regard and will soon be working from three orbital positions. The first orbital position is 119 degrees west longitude. In this orbit, it controls two satellites with a total of 21 broadcasting frequencies. The entire United States can receive about 100 channels at this orbital position. The third satellite used by Echostar is located at an orbital position of 61.5 degrees. Although the entire United States can receive the satellite's signal, its key coverage area is the eastern half of the United States. Echostar plans to launch the fourth one to an orbital position of 148 degrees in mid-1998 to provide service to the western half of the United States.
Many subscribers may choose to only receive nearly 100 channels at a 119-degree track position, and some subscribers want to be able to receive programs from more than two track positions at the same time.
12. Using a rotating dish antenna, how can I receive DISH programs from two orbital positions?
The answer is no.
If you want to receive programs from two orbital locations, the subscriber must install two independent dish antennas, and one of the antennas must point to the 119-degree orbital position, and the other antenna must point to the 61.5-long orbital position over the eastern United States or the United States. Orbital position of 148 degrees over the west. The purchase price of the second dish antenna upgrade kit is about $100, and viewers who hope to receive all programs can buy it themselves.
Echostar company 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 one cable, so no additional cables are laid. All existing and future decoders can receive programs from two track positions. After the installation is completed, the user will not feel it when switching between satellites and orbital positions.
13. Which DISH programs are there for different track positions?
Echostar’s most popular cable program is included in about 100 channels broadcast from a 119-degree orbital position, so almost all users have a dish antenna pointing to a 119-degree orbital position.
The content of services from other track locations has not yet been fully determined, but it is likely that it will be regional channel (see the introduction below) data services and some niche programs such as foreign language programs. Viewers who wish to watch the purple program need to add another dish antenna.
14. How many satellites does Echostar have in these orbital positions?
Echostar’s high-power satellites are Soundstar 1, 2, 3, and 4. Echostar 1 and 2 are currently located at an orbital position of 119 degrees, and Echostar 3 is located at 61.5 degrees. Orbital position, Echostar 4 is located at an orbital position of 148 degrees. However, the company once filed an application requesting that one of the two satellites launched by Echostar 4 to an orbital position of 119 degrees drifts to an orbital position of 148 degrees. The final result can only be proved by time.
15. What is the air angel business?
The Echostar Company leased a transponder from the Echo No. 1 yesterday, located in the 61.5 degree orbit, to the Dominican Church Satellite Organization. The Dominican Church used it to broadcast religious programs on 8 channels and named it "Aerial "Sky Angel". Air Angel business uses Echostar’s receiving hardware, which is a free additional service for DISH business. The relationship between the two is similar to that between DIRECTV and USSB. It should be noted that to receive 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 the air angel program, so the west coast area of the United States can only receive this program under the conditions of extremely low viewing angles in the east.
16. What about when watching broadcast networks and local channels?
The lack of local channels is the main reason why people come to Taiyang and are willing to buy satellite live broadcast systems. Satellite broadcasting companies have realized the seriousness of this problem, and are trying to solve this problem in a variety of ways. Echostar is the first company to invest in this effort. It uses a considerable amount of bandwidth capacity to add local branch programs of American Broadcasting Corporation (ABC) and CBS (CBS) FOX in several large cities to its Satellite live broadcast service. Only viewers within the terrestrial coverage area of this channel have the right to receive these channels. The total price of this group of channels is $5.
When broadcasting these channels via satellite, they did not seek the consent of these bureaus. This caused protests from broadcasters and even filed legal prosecutions. It is not clear that if Echostar can continue to do so, it will become the only satellite broadcast service company that treats local channels as a component. It is currently broadcasting in New York, Boston, Washington, D.C., Chicago, Atlanta, and Dallas, and will soon include several eastern and central cities in this list. Echostar does not have the ability to transmit all the local channels in the selected city, and it cannot provide services to a large market that far exceeds 20 in the near future.
Echostar Satellite 3 broadcasts on local channels, so an additional dish antenna is needed for reception. In mid-1998, Echostar Satellite 4 had begun work, and it broadcasts local branch channels in the western region.
Among other satellite live broadcast companies, none of them 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 so that users can benefit from it. Decoder manufacturers are developing an additional function that allows local channels and satellite channels to be perfectly combined in the program forecast table, making it easier to switch between the two. USSB is taking the lead in implementing a research project to determine which antenna should be the best for each zip code area, so that salesmen can buy the most suitable ground antenna. Many users cannot receive local channels from the air because of where they live. For these users, you can choose a branch program summary network (the branch is probably not the branch in the subscriber's residential area) to receive the main network program. According to the "Family Watching Satellite Program Law" re-promulgated in 1994, roof-mounted antennas are used Subscribers of the receiving network cannot receive this package 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 FCC rules and regulations.
17. What kind of satellite live broadcast system should be used?
Which satellite live broadcast system should be used depends on many factors, such as the type of program you want to watch, the antenna size you want to use, the amount of funds you plan to invest, and what orbital locations are available where you live. Choice, and other factors.
DIRECTV and USSB have the most types of channels. This should be the best choice for subscribers who want to have a large selection of programs with electric power and can bear multiple services. National Rugby League (NGL) football fans and other sports enthusiasts can also choose DIRECTV, and users who want to watch many Premium services, pay-per-time 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 among rural users. Primes+ar is also the only company that tweeted local weather forecast information on the weather forecast channel.
Echostar is in a leading position in terms of low prices, with the lowest hardware and program costs, and now has a channel capacity with high power. In addition, Echostar has local branches in some major cities. In this regard, it is the only company that does so. Echostar has more super station type programs, which seems to be the only source of S+ar Trek programs. For viewers who wish to watch Catholic programs, the "Angels in the Air", an associate of Echostar, will be the best choice.
Every service provider has serious debt problems, and they continue to operate at a loss. When choosing a satellite live broadcast service provider, users should consider whether the company has enough funds to continue operating, otherwise, once the company ceases operations, the hardware purchased by the user will become a waste product. 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 whether the "Angel in the Air" will succeed, but even if it declares bankruptcy, the user's DISH hardware can still be used to receive Echostar's programs. At present, DIRECTV, USSB and Jiashengxing will all survive. And will succeed.
18. How many of these systems have been bought? How much is it expected to buy?
So far, DIREC and USSB claim that they have bought more than three million licensed decoders, and this number is growing at a rate of thousands per day. Primes+ar claims to have nearly two million subscribers, but its growth rate has slowed down compared to the past. Echostar Nanzai already has more than one million subscribers, and its growth rate is almost as fast as DIRECTV. Industry experts predict that by 2000, the total number of satellite live broadcast subscribers will reach about 14 million, but this estimate seems too optimistic. Since the satellite live broadcast service began to work, the number of subscribers has been growing at a rate of one million per year. In 1998, it has exceeded this growth rate. The satellite live broadcast service companies have not reached their very optimistic subscriber number estimate. The sales speed 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 live broadcast service company began to provide subsidies for equipment purchases in 1997. By doing so, the time to reach the point of operating loss and win is much longer than originally planned. DIRECTV and USSB originally expected to achieve a loss-to-win balance when it had 3 million subscribers, but in order to protect the long-term sustained growth rate, it now seems that DIRECTV can only achieve a loss-to-win balance when it has nearly 4 million subscribers, and in 1998 Here, the number of its users has reached 400. The USSB also achieved a loss, a win, and a tie in 1998.
The price of decoders has been lowered a lot. A few years ago, the price of the first-generation decoders ranged from US$700 to US$900. Now it has fallen to between US$100 and US$400. One of the reasons for the price drop is decoder subsidies. Therefore, the price reduction promotion will enable the satellite live broadcast service authorization to continue to maintain a high growth rate.
What other services do these satellite live broadcast service companies provide?
Data service may be the most exciting development direction in the satellite live broadcast service. Since the signal is transmitted in digital packet form, these systems can pass any combination of video, audio and computer data to the decoder. Almost all decoders are equipped with a high-speed data interface, this interface 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 service companies reserve a certain amount of bandwidth for data services, but the development of data services is extremely slow.
Echo Star Company took the lead in launching a data service, the name of this service is AGCAST, used to provide services for rural and rural markets. AGCAST is a leaflet-style broadcast news service that can display agricultural news and information on a computer connected to the DISH decoder data interface. The price of the software and cable is $70, and the monthly service fee is $35. Echostar launched a microcomputer decoding card in mid-1998. The hardware will be produced by ADAPTEC and will be jointly launched with some user data services announced soon.
DIRECTV company cooperates with the computer software company to produce a kind of computer system based on WINDOWS95, this kind of system is difficult to receive the DIRECTV program combined with the data service. The hardware is produced by ADAPTEC or other companies, and it went on the market 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 start to broadcast AC-3 audio on some channels in mid-1998 (perhaps its PPV channel for each dues movie). The company seems to be the only satellite live broadcast service company that currently has an AC-3 decoder. DIRECTV has been broadcasting AC-3 on its engineering channel for some time. It has AC-3 broadcasting technology, but it says it can't carry out this kind of business at present, because there is no DSS decoder for AC-3. However, this company does intend to launch some AC-3 broadcasting services in the near future.
PRIMESTAAR may add AC-3 services 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 broadcasting frequencies used by satellite live broadcast service providers, all satellite live broadcast service systems will be down under severe thunderstorm weather conditions. In order 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 visual digital products have affected the viewing effect, some people feel very upset, and some people hardly notice these problems. However, digital products are indeed an inherent shortcoming of satellite live broadcast services.
Some cable TV users, after connecting their video cassette recorder (VCR) to the TV, can watchRecord the programs of another channel while on one channel; or use the video cassette recorder to record the programs of two cable TV channels when going out. Like all the decoders, the satellite live broadcast service can only decode one channel at a time. When using video cassette recorders and TV sets at the same time, it is necessary to equip each machine with a decoder. In addition, some models do not have a program timer, and the timer of the video cassette recorder cannot be connected to it, and it is not possible to record more than one channel of programs at the same time.
Many users who live in the West Coast area are disappointed that the broadcast time of the program is too early, because these companies use the East Coast area broadcast time convention in most of the programs.
Although almost all decoders have a parental lock protection function, occasionally, some violent and pornographic programs that are not given a limit level may still be broadcast, so viewers who set the lock protection limit according to the normal setting mode , It is still possible to watch this program, and the parental lock protection function will lose its effectiveness.
21. Are there any plans for high-definition television broadcasting?
DIRECTV announced that it plans to launch two-price full-time high-definition television (HDTV) pay-per-time channels at an appropriate time. The premise of this plan is that high-definition television manufacturers can produce high-definition televisions that meet their requirements before the specified time. DIRECTV, a high-definition television company, has demonstrated high-definition television broadcasting in 10801 and received it with RCA’s projection-type television prototype. If this plan is implemented smoothly, by then, the United States will be able to receive at least a portion of high-definition television programs. The plan of terrestrial broadcasters is that each of the top ten major markets 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 can be 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 scale when adding high-definition channels.
A few years later, the prospect of high-definition broadcasting has formed a considerable scale. As for when high-definition television channels can be opened, it is mainly determined by the sales volume of high-definition televisions 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 television channels. Echostar has no plans for a high-definition television channel. Echostar has not announced plans for their definition television channels.
22. What hardware is required to receive high-definition broadcasts?
DIRECTV said that they hope that after DSS decoders are installed in all high-definition TVs in the next few years, it will only cost about US$50 for each TV to install DSS decoders, so it will have an impact on the cost of TVs. Not big. if it is like this. The DSS owner only needs to connect the definition TV with the dish and the satellite receiving antenna, and does not need to connect with the existing decoder. However, doing so also means that additional conditional access and debit cards are required, so let's wait and see how DIRECTV implements their plan.
Most types of satellite live broadcast 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 type of machine will be quite expensive and it is impractical to manufacture it. It seems that existing decoders will never be used for high-definition TV reception. Instead, new decoders and/or the TV itself (TVs with built-in direct broadcast decoders) will be used.
23. Can more than one TV be connected to one dish antenna?
The satellite broadcast dish-shaped receiving antenna is connected to the decoder through a coaxial cable. Dish antenna appliances, depending on the model, have one or two coaxial connectors, so when a dish antenna can be connected to more than one decoder at most, be sure to buy one that allows more than one decoder to be connected to a dish antenna Kit equipment. Channel Mas+er, and possibly other companies, sell a product named Mul+iswi+ch. This product leads from a dual-output dish antenna with two coaxial outputs, allowing the connection of four decoders. The basic products of most manufacturers can only connect to one decoder, so in this configuration, such a super unit is required.
24. How do the audio/video systems at home connect to the satellite live broadcast decoder?
There are many ways to connect a decoder to the audio/video system at home. TVs with S-video input can use the S-video output jack on the decoder to display pure component (Y/C) video. It is like being directly connected to a satellite link. For channels that use digital tape or fiber optic cable sources for broadcasting, this is the most cutting-edge connection method. In these channels, the use of Y/C interface can avoid the conversion of digital component signals to NTSC, so the best image quality can be obtained. For most decoders, if the user chooses to use the radio frequency output to connect to the TV, the sound of the TV will not have stereo or surround sound effects. The stereo effect can only be obtained through the direct audio output port of the satellite broadcast decoder.
25. Is the compression mechanism used by the satellite live broadcast system really effective?
Yes, but there is some controversy over the quality of the final result. Most businesses use high compression ratios, so digital products occasionally occur. Each service provider must make a compromise between the degradation of its system quality and the increase in the number of channels in the system.
Many users say that the video and audio quality is very good, and the performance of the system is also very good. But other users pointed out that at least on some channels, there are obvious digital products. The quality of the channels varies greatly, in part due to some differences in the source material. When the video and audio quality of all services are very satisfactory, digital TV appears.
26. How does the conditional access system work?
in most systems. The satellite broadcast decoder can receive a processor board the size of a credit card. The name of this board is Smar+Card. The board can be inserted in front of the decoder to allow the decoder to receive programs within the authorized authority. The authorization data stream and the video and audio information are sent to each transponder together. When it is necessary to suppress piracy activities, the householder can easily replace the Smar+Card board. Pirated DSS Smar+Card boards have been manufactured and are being sold. Most of these piracy activities occur in Canada. Other systems seem to have not been pirated yet. DIRECTV used several electronic countermeasures (ECM) methods to temporarily suppress pirated cards. The company sued several pirates and successfully helped prosecute some of the manufacturers. DIRECTV said it will continue with piracy activities. DIRECTV company for safety. You can also choose to use the method of replacing all cards. It has done this once, and of course it may do it again.
27. Where is the direct broadcasting satellite located in the sky?
Direct broadcast satellites operate at several orbital positions at an altitude of 22,300 miles above the equator, and these orbits are located above the equator corresponding to the United States. The satellite dish antenna points to the south at a certain angle above the horizon, and its angle depends on how far away the secret position is from the equator. Satellites in northern parts of the United States (such as Minnesota) appear to be taller. DIRECTV/USSB’s satellites are positioned at an orbital position of 101 degrees west longitude, which passes through the West Nebraska region from south to north. In the eyes of residents in the central region of the United States, this satellite is about true south. In the east coast area, the satellite is located to the southwest. In the West Sea area, it is located to the southeast.
Echostar’s main satellite is located at an orbital position of 119 degrees west longitude, which passes through the western Nevada region from south to north. In the eyes of residents of the west coast of the United States, this satellite is about true south. In other areas, the satellite is located in the southwestern direction. The "Sky Angel" and Echo's east coast satellite is positioned at an orbital position of 61.5 degrees west longitude. The conventional satellite of Primes+ar is positioned at an orbital position of 85 degrees west longitude.
28. Where is the uplink facility for direct broadcasting satellites located?
USSB uses a fully digital facility located in Oakdale, N.S., which is very close to São Paulo. Its two Ka-band uplink parabolic antennas with a diameter of 9 meters are installed in a special cover. This special cover has microwave transparency and can protect the antenna from weather conditions.
29. What are the technical details of the DSS system?
This system has three working satellites, they are: Direct Broadcast Satellite 1, Direct Satellite 2, and Direct Broadcast Satellite 3. Each satellite has 16 transponders, powered by a 120-watt traveling wave tube amplifier (TWTA), capable of digital and analog transmission.
These satellites work on the Broadcast Satellite Service (BSS) frequency (12.2 to 12.7GHZ) of the KU band spectrum, using circular polarization. They can emit 58 to 53dBW of radiated power to the continental United States and southern Canada. Each satellite weighs 3,800 pounds. When the antenna and solar wing are deployed, the satellite is 26 meters long and 7.1 meters wide. The solar universal wing panel can provide 4300 watts of electricity.
The DSS system adopts the four-phase phase shift keying (QPSK) modulation method, and the encoding method for the digital data on the radio frequency carrier is MPEG-1LayerII. Before MPEG encoding, the audio is more than a surround sound effect. Use MPEG-2 syntax to encode the video, the sampling rate can reach CCIR601-1 can handle 720×480 images, but the current resolution is lower.
This system uses a statistical multi-program encoder, the name of this encoder is S+a+Mux, it can dynamically based on the video content and taking into account other programs multiplexed on the same transponder. Change the bit rate. Each direct broadcast satellite can be configured with 16 120-watt transponders, or 8 240-watt transponders, or 8 240-watt transponders, which are configured by satellite solar panels. Determined by the generated DC power. Under the two error control modes of the DSS structure, each transponder can be allocated to information at a rate of 40 megabits per second, and a rate of 10 megabits per second is allocated to error control; in the low error control mode, each transponder can be allocated to information at a rate of 40 megabits per second. The rate of 23 Mbits is allocated to information, and the rate of 17 Mbits per second is allocated to error control. To achieve the same end-to-end usability, the signal strength required by the high-error control method is 3Db higher than that of the low-error control method.
DST-1 operates in low-error control mode, while D-Sat-2 and DST-3 operate in high-error control. Therefore, DIRECTV and USSB have 16 240-watt transponders that work in a high-error control mode and 16 120-watt transponders that work in a low-error control mode. After the fourth satellite is launched, all transponders will be changed to 240 watts, but DIRECTV said they have no plans to launch a fourth satellite.
30. What is a high-rate direct broadcast satellite, and how is it different from a general direct broadcast satellite?
A few years ago, the Federal Communications Commission reserved a broadcast spectrum and several fatigued satellite orbit locations in the United States for the television service called Direct Broadcast Satellite (DSS). These satellites are separated by nine degrees (the interval between conventional satellites is two degrees). These satellites can be broadcast with more dominant power to enable particularly small satellite receiving antennas for interference-free reception. This is the definition of direct broadcast satellite by the Federal Communications Commission. It has also issued satellite direct broadcast business licenses to several companies, namely DIRECTV and Echostar.
Other broadcasters without a satellite live broadcast license can use conventional satellites to provide direct-to-home services. For users, the direct-to-home service is the same as the licensed satellite live broadcast service. The difference between the two is that the former usually requires the use of a larger dish-shaped receiving antenna (although this antenna is much better than a conventional parabolic antenna). Small) And this kind of antenna requires professional installation. Therefore, the fixed color mirror of the satellite live broadcast is often used to refer to the direct-to-home service provided from a fixed satellite location with a small dish antenna, but the term high-power live broadcast satellite is a special term used by the Federal Communications Commission to refer to the satellite live broadcast service. .
The high-power satellite live broadcast service of the Federal Communications Commission in the United States has reserved eight orbital positions, four of which are used to provide services to the East Coast region. The other four orbital locations are used to provide services to the West Coast area. At each orbital position, the Federal Communications Commission allows up to 32 broadcasting frequencies (ie transponders) to be set. When the Federal Communications Commission assigns direct broadcast satellite frequencies to applicants, it also allocates an equal number of orbital positions for its east coast satellites and west coast satellites. The guiding ideology is to allow each company to simultaneously broadcast from its east coast satellites and west coast satellites, thereby providing coverage to the entire United States.
However, with today’s advanced technology, three of the four eastern orbital positions (that is, 101 degrees west longitude, 110 degrees west longitude, and 119 degrees west longitude) can actually cover the entire United States. These orbital position supplements are called Full-Conus orbital positions, and of course they are also the best orbital positions.
31. Are there any other satellite live broadcast business plans at these orbital locations in the United States?
Ropert and Murdoch’s news companies have purchased the right to use 28 transponders at the 110-degree west longitude orbit. Recently, the company announced that it would cooperate with Primes+ar to provide a new high-powered Primes+ar company with many channels at an orbital position of 110 degrees West. The company will be composed of a medium-power, and mostly rural business company. And it has become an important and well-funded high-power satellite live broadcast service company.
Because the cable television group owns Primes+ar, Wharton is worried that this plan will not improve the competitiveness of cable television, so it is somewhat dissatisfied with this plan. However, many people have benefited from the three giants in the satellite live broadcast business. All three use high power, and of course the dish antennas used are very small.
Primes+ar said that it could provide this type of high-power service as early as April 1998. The company firmly believes that the plan will be approved by the Federal Communications Commission before the end of 1998. They may decide to take existing users from itThe ancestors of equal-power satellites are moved up by moving users’ antennas, replacing and/or enhancing users’ decoders; the company may also leave existing users on medium-power services indefinitely. This migration activity is very laborious and also requires a lot of investment. The stock owner of Primes+ar, TCL, has the right to use 11 transponders at the orbital position of 119 degrees west longitude (this is the position of Echostar's main satellite orbital position). The Federal Communications Commission needs to make a ruling on this issue. Primes+ar said that if it allows it to use the orbital position of 110 degrees West longitude, it can auction off the right to use satellite capacity at 119 degrees West longitude. The USSB company has the right to use three transponders at the 110-degree west longitude orbital position, and it seems that the company is preparing to carry out some business in this location.
Canada, Mexico, and some South American countries also have satellite orbital positions that can actually provide services to the entire North America. At least part of them will be auctioned off of their spectrum, and some American companies are expected to win these orbital positions to provide services to the United States. --------- The basic concept of the antenna The main characteristic parameters of the antenna
Some parameters are commonly used in engineering to characterize the characteristics of antennas used for transmitting or receiving. They are pattern, main lobe level, gain, polarization, bandwidth, standing wave ratio, noise temperature, etc. Only a few of the main parameters are briefly introduced here.
pattern, main lobe width and side lobe level
Whether the antenna power radiation strikes is concentrated can be expressed by the parameter of the main lobe width; the angle between the two vector diameters when the radiation power in the main lobe is half of the maximum value is called the main lobe width. The smaller the width of the main lobe, the sharper the pattern, which means that the antenna radiation is more concentrated. The ratio of the maximum value of the side lobe to the maximum value of the main lobe is called the side lobe level, which is generally expressed in decibels and is defined as:
101g maximum side lobe power/main lobe maximum power
If the ratio of the corresponding power between the maximum value of the side lobe and the maximum value of the main lobe is 0.01, the side lobe level is -20dB.
If the intensity of the anti-antenna radiation strike in each direction is represented by the length of the vector from the origin, the envelope formed by connecting all the vector endpoints is the antenna pattern. It shows the relative size of the antenna's radiation in different directions. This pattern is called a stereo pattern. The direction of the vector radius represents the direction of radiation, and the length of the vector radius represents the intensity of the radiation strike. The pattern contains many lobes, and the lobe containing the largest radiation direction is called the main lobe. The others are called the first side lobe, the second side lobe and so on. We can also use gain to express the degree of concentrated radiation from the antenna. The gain of an antenna in a certain direction is defined as: under the same input power, the square of the electric field intensity (E2) produced by the antenna in a certain direction and the electric field intensity produced by the lossless ideal point source antenna in the same direction and the same position The ratio of the square of (E02), usually expressed as G.
G=E2/E02 (same input power)
Similarly, the gain can also be determined as follows: Under the condition that the same electric field strength is generated in a certain direction to a certain position, the ratio of the input power (Pino) of a lossless ideal point source antenna to the input power (Pin) of the antenna is called Is the gain of the antenna in the direction of the point.
G=Pino/Pin (the same electric field strength)
usually takes the gain of the antenna in the direction of maximum radiation as the gain of this antenna. Gain is usually expressed in decibels. Namely: G=101gPino/Pin antenna gain calculation: G=η4πS/λ2=η(π/λ) 2D2 where S- antenna aperture area (m²); λ- working wavelength (m); D- parabolic aperture (Namely face diameter) (m); η-antenna efficiency.
The noise temperature of the antenna:
The noise entering the antenna mainly comes from the cosmic noise of the Milky Way and the thermal noise from the earth and atmosphere. Antennas with different apertures, different frequency bands, different elevation angles and different environments have different antenna noises. In the C-band, the cosmic noise is very small, mainly the thermal noise of the earth and the atmosphere. In the Ku band, these noises also increase with frequency. At the same elevation angle, the larger the antenna size, the narrower the beam, so the noise temperature TA (K) of the antenna is smaller, but as the elevation angle increases, the difference becomes smaller. For the same antenna size, the larger the antenna elevation angle Φ, the lower the noise temperature TA (K) of the antenna, and vice versa, the smaller the Φ, the higher the TA. This is because the smaller the elevation angle Φ, the greater the thickness of the signal passing through the atmosphere, and the stronger the meteorological noise and atmospheric noise.
Polarization of electromagnetic waves:
The polarization form of electromagnetic wave can be divided into linear polarization wave and circular polarization wave. Linear polarization wave can be divided into horizontal polarization and vertical polarization wave. Circular polarization wave can be divided into left-handed and left-handed according to the direction of electric field rotation. Right-hand circularly polarized wave. At present, the satellite signal side of our country must use linear polarization wave.
Only when the polarization of the receiving antenna is consistent with the polarization of the received electromagnetic wave can the signal be effectively received, otherwise the quality of the received signal will be deteriorated, or even no signal can be received at all. This phenomenon is called polarization loss Match. When a rectangular waveguide is used as the feed, its polarization direction is determined by the direction of the waveguide port. The narrow side of the waveguide port is parallel to the ground plane for horizontal polarization, and the wide side is parallel to the ground plane for vertical polarization. When a circular waveguide feed is used, the direction of the probe in the waveguide should prevail. It is worth noting that the linearly polarized wave transmitted by the satellite transponder is defined based on the satellite's axis system. Therefore, only when the longitude of the ground station antenna and the satellite are the same, the polarization direction of the wave on the ground is the same as that of the satellite. Same, there should be a slight deviation in other regions. Therefore, during installation, the feed should be slightly rotated left and right to maximize the level indication of the receiver to achieve polarization matching.
Antenna polarization adjustment
1. When linear polarization and circular polarization coexist, adjust the polarizer
The right-handed circularly polarized wave is launched to the leased international communication satellite, while the horizontally polarized wave is launched by our satellite. When changing from a rent-collecting satellite to a Chinese satellite, you have to rotate the phase-shifting dielectric sheet in the antenna feed to make it perpendicular to the horizontal plane, and adjust the rectangular position so that the narrow side of the waveguide output port is parallel to the horizontal plane, and then you can receive Horizontally polarized waves.
2. When only linear polarized waves are received, the adjustment of the polarizer.
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