View Full Version : Satellite signal fade at night in Spain and loss of satellite TV channels at night

18th June 2011, 06:11 PM
Satellite signal fade at night in Spain and why do you lose some satellite TV channels at night in Spain.

UK Satellite TV currently is transmitted from four satellites: Astra 2a, Astra 2b, Astra 2d and Eurobird 1.

These four satellites, and most other TV satellites, are in a geostationary orbit.

Geostationary orbits are useful because they cause a satellite to appear stationary with respect to a fixed point on the rotating Earth. This allows a fixed antenna or satellite dish to maintain a link with the satellite.

The satellite orbits in the direction of the Earth's rotation, at an altitude of 35,786 km (22,236 mi) above ground, producing an orbital period equal to the Earth's period of rotation,

These geostationary satellites are not totally "stationary", as they do appear to move in a figure of eight over a 24 hour period. However, this is hot the actual satellite themselves "wobbling". The satellites appear to move due to the earth’s spin, which is like a spinning top and has a slight wobble. This slight wobble can cause a drop in the signal reception strength in some fringe reception areas like the Costa Blanca and Spain.

It just so happens that his wobble occurs at night, which is a problem as that is the most popular time for watching TV!

Should the satellites actually drift out of their designated position, which is a 100km by 100km by 100km box in space they have onboard control systems that will move them back into position. Normal drift is corrected around once every month if needed.

But there are two times a year when there is a more significant drop in satellite signal strength in fringe reception areas like the Costa Blanca and Spain.

Around March and October time, the satellites are in "eclipse mode". This is when the satellites are unable to use their solar panels for power, as the earth is blocking the solar energy from the sun. At these times of year, the satellites can be in the earth’s shadow for over an hour. When this happens the satellites have to rely on their onboard battery backups, which, when the satellites switch over to them, there is a noticeable drop of about 5 or 10% in the output of the satellite and thus the signal appears to be weaker. Again this is an issue as it happens for a period of two weeks in March and October at around 10pm - 12am, when people are most likely to want to watch TV.