Question

State in brief for artificial satellites are used in transmitting television programmes over large distances

Answer 1

The satellites that transmit TV to the masses are called “Broadcast Satellites. “ The best way to envision this activity is to think of a satellite that is positioned at 36,000 km over the equator, acting as a reflector of what is sent to it from the ground. The satellite is placed into a “geo-synchronous orbit (GSO).” In this orbit the satellite’s flight speed is exactly in sync with the speed of the Earth’s rotation. Therefore, the satellite is absolutely still in relation to the Earth’s surface. As the Earth rotates, the satellite flies and they remain motionless relative to each other.
The satellite is fed the TV programming through RF transmissions from one or multiple “gateways” that are locked onto the satellite’s “gateway or feeder band” antennas. In most situations these feeder bands are operating in a different frequency range, than the transmission to the end users. In most situations the TV programming is compressed and a multiplexing scheme is used to separate the individual channels.
When the feeds reach the satellite, they are converted to the frequencies used by the end customers and re-transmitted out over different satellite antennas to the customer’s receivers. Most broadcasts are encrypted and again multiplexed so that the customer’s receiver equipment must be in good standing, to properly decrypt and unpack the individual TV channels. Part of the encryption is also used to determine which of the transmitted channels are available to the customer, based on their subscription of services. Many schemes have been used in this area, to combat pirating of the signals.
A broadcast satellite in such an orbit can “see or broadcast” to about one third of the world between +/- 40 degrees of the equator. The further from the equator the less direct and therefore less strong the signal will be. Some use broader antenna’s and reach to +/- 45 degrees, but due to the angle that the customers must use from over 40 degrees, these signals are quite challenged with any poor weather conditions or obstructions. Base on these parameters, a satellite company could place three of these GSO’s, equally separated around the world and provide services to all customers living in the populous areas of the world. No operator does this, mostly due to the very different programming and languages that would be necessary.
Satellite operators must also obtain what are called “landing rights” or licensing in every country for which they intend on having customers using their services. These licenses are for the use of the frequencies required in each country to reach the customers. These licenses regulate the specific frequencies the operator is allowed to use, and the amount of power amplification they are allowed to apply to those RF signals .
There is also a United Nations group named the International Telecommunications Union (ITU), that manages the frequency licenses on an international basis. They perform the function of coordinating the operator’s use of frequencies so as to prevent interference between the operators.
This is the most efficient method of providing TV programming due to the vast reach of each satellite. However, this method is starting to be challenged by the interactive way customers are starting to watch TV. Since the customer’s equipment is only a one way transmission, there is no way for the current services to allow the interactive nature of today’s younger TV watchers. All TV is provided in a linear method (TV shows broadcast as set times) from Broadcast Satellites.

Answer 2

Artificial satellites help in long distance transmission of television programs. The picture or sound to be transmitted is first converted into electrical signals. They are then converted into a special type of waves and transmitted in air from a transmitting antenna so as to reach the artificial satellite. The signals received are then amplified and re-transmitted by the instruments fitted on the satellite. The antennas fixed in a number of stations on the earth including those of cable operators receive the signals and re-transmit them. The television sets receive the signals and reconvert them in the form of images and sound.