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| PROCEDURE | PROGRAM |

Introduction : Satellite Television Receiving Only (TVRO)

Based on my technical works and understanding during completing final year project at 

Wangsa Maju  Earth Station, Kuala Lumpur


International Television Broadcasting Service

It is a service whereby the broadcaster transmit the required program for television broadcasting via an international communications network connecting different countries. In most cases, the transmission is via satellite. The international television connection is the one way transmission path from the transmitting broadcasting organization of television programs to the receiving organization. Generally, the television signals from the broadcasting organization is transmitted to the International television Circuit (ITC). Then, the signal from ITC is transmitted to the satellite and is received by the corresponding television broadcasting organization via the earth station and ITC at the receive side. Television transmission via the satellite link includes the transmission of single-destination and multi-destination.

Satellite Television Receiver

A satellite receiver will receive all the programs that is transmitted by the broadcaster to the satellite that the receiver is on track. If the program is transmitted by the broadcaster is an encrypted or encoded signal, the receiver must also need a decoder in order to view the program.

Basically, the satellite receiving components consists of :

the antenna depends on the frequency band used.

GHz) to L-band frequency (about 1.5 GHz).

audio signals.

sounds.

Satellite Look Angles

Navigation around the earth’s oceans became more precise when the surface of the globe was divided up into a gridlike structure of orthogonal lines: latitude and longitude. Latitude is the angular distance, measured in degrees, north or south of the equator and longitude is the angular distance, measured in degrees, from a given reference longitudinal line.

At any point on the earth surface only a limited number of geosynchronous satellites are visible. They are located in a geo-arc whose apex is due south and is lower in the sky the farther north your location. In the southern hemisphere the geo-arc apex is due north. You can aim at any satellite in the geo-arc by setting your antenna dish at the specific elevation (El) and azimuth (Az) angles can collectively known as ‘look angles’ (the azimuth and elevation coordinates to which an earth station antenna must be pointed to receive signals from the satellite). Elevation angles can range from 0 degree to 90 degrees (angle measured upward from the local horizontal), but reception from satellite must not lower than 5 degrees. Azimuth angles are measured from 0 degree to 360 degrees (angle measured eastward -clockwise- from geographic north to the projection of the satellite path on a horizontal plane at the earth station).

Elevation and Azimuth Calculation

Example and steps of calculation :

Wangsa Maju Earth Station : Latitude (Le) = 3 degrees North

Longitude (le) = 101 degrees East

Agila2 (satellite Transponder) : Latitude (Ls) = 0 degree

Longitude (ls) = 146 degrees East

 

Step 1 : Find the Central angle,

Cos g = Cos Le Cos (ls – le)

Cos g = Cos 3 Cos (146- 101)

          = 45.0807 degrees

 

Step 2 : Find the Elevation angle, El

El = Arctan [(6.6107345 – Cos g) / Sin g] - g

    = Arctan [(6.6107345 – Cos 45.0807) / Sin 45.0807 ] – 45.0807

    = 38.08085896 degrees

 

Step 3 : Find the Intermediate angle,

΅ = Arctan [Tan (ls – le) / Sin Le]

    = Arctan [Tan (146 – 101) / Sin 3]

    = 87.0041039 degrees

 

Step 4 : Find the Azimuth angle, Az

Az = 180 - ΅

     = 180 - 87.0041039

     = 92.9958961

 

Notes:

rs - radius from the center of earth to satellite (42164.17 km)

re - radius from the center of earth to earth station (6378.137 km)

          ratio, rs / re = 6.6107345

 

Le – North latitude; no. of degrees in latitude that the earth station is North from the

        equator.

Le – West longitude; no. of degrees in longitude that the earth station is West from

        Greenwich.

Ls – sub satellite point at North latitude.

ls - sub satellite point at West longitude.

 

Hemisphere Station (Le)     Position of Satellite (ls)     Azimuth angle, Az

                North                                 East                         Az    = 180 – intermediate angle

                North                                 West                        Az    = 180 + intermediate angle

                South                                 East                          Az    = intermediate angle

                South                                 West                         Az    = 360 – intermediate angle