Digital and DBS Services


Author: Dr. Albert Powell, Colorado State University.
Additional contributions: Tom Williams, Oregon State University.

This page has the following sections:


The Concept of Digital vs. Analog Satellite Broadcasts:

Most satellite transmissions use conventional analog broadcasting, similar to those your TV set sees in conventional TV. Receiving these broadcasts requires your downlink to pick up a certain strength or amount of signal. This is one of the main reasons that a larger dish (antenna) on downlinks usually helps create a better picture. An analogy might be made to collecting rain in a dish; the larger the dish, the more raindrops you collect.

However, a number of services now exist which use digital, not analog broadcast transmissions. Receiving a digital signal is very different from receiving an analog signal in two important ways:

  1. A digital signal either is or is not sensed by the satellite receiver. Whether the signal is weak or strong is irrelevant; as far as the receiving equipment cares, it's either present or it's not. (In the digital world, everything is plus or minus, not "almost plus" or "nearly minus".)
  2. A digital signal is usually compressed, meaning that it doesn't take up as much room as a conventional analog signal. Think of a freeway with two lanes each way. An analog signal might need two lanes to travel; a digital signal can be compressed to fit into one lane, or even half of one lane.
Why use digital transmission? Because it costs lots of money to use satellites. The program producer has to pay the satellite owner to use the channel which carries their program, and costs can run $900+ per hour for a single satellite channel! Using digitally "compressed" signals, producers can fit two, three or more digital signals onto one satellite transponder. However, they pay the same price as they do for one analog signal which uses the same channel/broadcast space. That means their cost is much lower per signal for every program they broadcast, reducing their operating cost per program considerably.

Because (from the receiver's point of view) digital signals are either present or not, they can be received on smaller satellite dishes (although the satellite sending the signal to earth must be more powerful, in order to provide a strong enough signal for the smaller dish). This has led to the emergence of programming services which use 3-foot or smaller downlink dishes.

Digital services are sometimes referred to as "DBS" services, which stands for "Direct Broadcast Satellite". This means that the service always travels from the producer up to the satellite, then is downlinked at the viewer's location. There is no cable company or other local delivery vendor. Therefore, DBS refers to a method of delivery, not to a specific business or company. This kind of satellite programming is also referred to as "Direct to Home", or "DTH" service. The acronym "DSS" refers specifically to the service provided by DirecTV.

There are currently two types of digital service. One is the type of DBS system which uses a digital-only satellite. Examples of this are DirecTV, USSB, PrimeStar and The Dish Network, which will be explained later. The other system is digital transmissions over standard C and Ku-band satellites. Most transmissions on these standard satellites are analog, but more services will begin using digital transmissions on C and Ku satellites in order to send more than one program over a single transponder. As this becomes more popular, those who want to view these programs will have to buy a digital de-coder in order to receive and decode the program feed. (See the end of this document for more comments about this type of adaptation.) 


Services Available:

The players in consumer-oriented digital programming services are DirecTV, USSB (United States Satellite Broadcasting), Primestar and The Dish Network (Echostar). They have different business approaches and offer differently oriented program services. Reviews of these services were been published in Video Magazine in early 1996, and information was also published in the December 1996 issue of Consumer Reports.

Do not make a decision about which service to select based only on the cost of their downlink equipment. There are some real differences in the programming available on different services. Some offer many sports channels, others have few; some offer many more pay-per-view options than others, and movie or other premium channel offerings also vary considerably.

There is another important fact to note: the small dishes used by all these digital services are not steerable; they are fixed in one position, and can only "see" the specific satellite which carries the program service to which you subscribe. This is different from conventional analog downlinks, which are steerable so they can look at any satellite in the sky. 

Programming:

In all cases, you pay for the programming separately. You can sign up for many channels of service, or just a few. With PrimeStar, you pay for all services and the downlink through them. If you buy a DirectTV/USSB compatible dish, DirecTV supplies the "conventional cable" services and USSB supplies the "premium" services such as all-movie channels. You can spend just about as much money as you want to on programming, including pay-per-view (PPV) events. The programs carried on these services change from time to time. Some carry more movies, some are heavier on sports than others, and some have multiple programming options which can cost you anywhere from $25 to $55 a month (plus any pay-per-view programs you elect to watch).

If you use The Dish Network, they sell you the downlink and provide the programming as well. As of December, 1996, their service was $300 annually, and they offered their "Top 50" stations, which include some premium channels, and 32 digital music channels. After the first year of service, the Dish Network fee can be paid monthly at $25. 10 pay-per-view channels are also available.

The digital satellite services cannot legally provide the basic broadcast network feeds (ABC, NBC, CBS, FOX) to you unless you live outside the broadcast range of TV stations carrying these networks. This is an FCC ruling which protects the local network affiliates from being bypassed by the satellite services. All receivers do have a connector to which you can attach a conventional TV feed, with the assumption that you will install your own antenna or buy just the local TV service from a local cable system. (Most cable TV companies offer a basic package which includes only local network affiliates.) The FCC created this policy because they do not want to totally bypass your local TV stations, which would cut you off from local news broadcasts. 


Compatibility:

Analog and digital systems are not compatible. The result is that:

This means that if you want to watch non-commercial broadcasts like the educational programs available from many universities and professional organizations, you will not be able to receive them with a digital downlink which is designed for PrimeStar, DirecTV or Dish Network service.

In the near future, some of the programs on conventional satellites will be changed to digital feeds. The motivation for this is to save money; instead of being to send one program over a channel, the program producers will be able to compress the signals digitally and send two or more programs over one channel on a satellite. A type of digital compression called MPEG II will be used. This type of digital compression is currently used by the digital satellite services, and it provides very good picture and audio quality. However, there is no assurance that the rest of the industry will agree on one digital standard, so it is not clear how many different channels a viewer with any particular capability will be able to receive. Whatever the digital format used, these digital programs will not be viewable on an analog satellite downlink.

To view these digitally compressed programs on a conventional steerable downlink will require adding a digital decorder at each downlink. How much these will cost depends on the production volumes and how fast they sell. Current costs are about $1000 per decoder, but prices will fall as more are produced and sold. Some predictions are that the price will be under $500 within two years.

Another issue in receiving digital broadcasts on a conventional steerable downlink is the condition of the downlink itself. In order for the signal to be received, the downlink will have to be in tip-top shape; the dish will have to be very accurate (no bends or large dents) and the steering mechanism will have to be very precise. Many downlinks will not be in sufficiently good condition to pass this test. Because of their tendency to deform easily, mesh dishes, although suitable for analog C and Ku signals, are not regarded as suitable for digital service. If an existing conventional downlink is not in excellent condition, it may be most practical for a homeowner wanting digital service to purchase one of the digital-only services.

Also, all downlinks have noise filters called "LNB's". In most cases, the Ku-band LNB will need to be upgraded in order to receive digital signals. Retail for such an LNB is about $150, plus an hour's labor to install it.

The bottom line is that some homeowners may have large analog and small digital dishes side-by-side until there the evolution of satellite delivery moves a bit further ahead.


If you have specific questions about this topic, please send them to Jeff Poley at ADEC. He will arrange an answer to you via email. 

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Copyright 1997, Dr. Albert E. Powell, Jr.
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