How does satellite television work

This is how satellite TV reception works

Unobstructed view to the south

Since satellite antennas have to be aligned to an orbit position somewhere above the equator for reception, an unobstructed view to the south from the mounting location of the antenna is required in Germany. You also have to keep a sufficient distance to obstacles such as trees or outbuildings so as not to 'shadow' the satellite signal. Depending on the location in the Federal Republic of Germany, the most important satellites ASTRA 19.2 ° East and Eutelsat 13 ° East are between 28 ° and 35 ° above the horizon. This makes it easy to determine appropriate distances from obstacles.

Align receiving systems

A digital satellite system must be optimally aligned for perfect reception. Since the satellites for broadcasting TV and radio programs are always at the same point above the earth, it is possible to roughly align their positions with just a compass and the two values ​​for azimuth (angle of rotation) and elevation (angle of inclination). For fine tuning, there are simple calibration tools for private individuals that can save a lot of effort. If you want to calibrate a large satellite distribution system, you cannot avoid a powerful measuring receiver and digital calibration. Especially since often antenna signals z. B. for VHF, DAB + or DVB-T and several components and cable routes are involved.

Azimuth - Horizontal orientation

The azimuth is the angle for the horizontal alignment of the satellite dish. It is also called the horizontal angle or the angle of rotation and corresponds to the movement that you make when you turn your head to the left or right. In the most frequently received orbit position in Germany, ASTRA 19.2 ° East, the azimuth is 160 ° to 170 ° - if you turn clockwise from a view to the north almost completely to the south.

The elevation angle

The elevation is the angle for the vertical alignment of the satellite dish. It is also called the angle of elevation and corresponds to the movement you make when you lower your chin or lean your head back. Depending on whether you are in the northern or southern regions of the world, the elevation angle is smaller or larger. For ASTRA it is 19.2 ° East in Hamburg to the north, 28.26 °, in the southern metropolis of Munich it is 34.24 °. At the equator, you would have to look straight up into the sky to aim for the satellite - because the satellites, following the rotation of the earth, are "positioned" over the equator, the elevation angle there is exactly 90 °.

Quadruple satellite signal

The broadband signal broadcast by the satellite uses two frequency ranges in two polarizations: The frequency ranges are the low band from 10,700 - 11750 MHz and the high band from 11750 - 12750 MHz. By using these frequency ranges in vertical and horizontal polarization, lowband and highband can be used twice. This results in a total of four sub-areas, namely low band vertical, low band horizontal, high band vertical and high band horizontal. These sub-areas are referred to as IF levels. Separate programs are transmitted in each of the four ZF levels. The German standard orbit position ASTRA 19.2 ° East offers hundreds of TV and radio programs on its four ZF levels.

LNB generates the reception signal

The LNB converts the satellite signal by mixing it with a local oscillator frequency (LOF) to a frequency range of 950 - 2150 MHz. The satellite signal can be transmitted over a well-shielded broadband coaxial cable. In the low band, the LOF is 9,750 Mhz. In the high band it is increased to 10,600 MHz. Due to physical restrictions, only the signals of one IF level can be completely transmitted over a single coaxial cable. This limitation explains why there are no restrictions or special technical solutions such as B. subscriber-controlled single-cable solutions are not possible to operate several satellite receivers with free program selection on a single antenna line. It also becomes clear why Quattro LNBs have four outputs for supplying larger satellite distribution systems - namely one for each ZF level.