Satellite TV will have Sun-Stroked!

Satellite TV will have Sun-Stroked!​

Even on a cloudy day the sun can cause trouble if is`s lined up behind your chosen sateliite. Solar Outage season is upon us.


The sun may have been most noticeable by its absence this summer, but every year, in the autumn and in the spring, whether you can see it or not it has a dire effect on satellite tv reception.

The problem is caused by the huge amounts of radiation that the sun produces, much inthe same radio frequency range as is used for satellite tv transmissions.

When the sun appears to be close to a satellite (only in line-of -sight terms, of course - it is some 93 million miles farther away), a dish pointed at the satellite also picks up the microwave `noise` from the sun, and this can swamp the tv signal.

It is as though the dish is`looking ` directly into the sun and so it can`t `see` the satellite in front. The receiver cannot distinguish between the noise and the signal and the system experiences signal drgradation - anything from a lowering of carrier to-noise levels to the complete loss of signal commonly called a sunor solar `outage`, or sun fade.

When the useful signal is reduced in this way the reciver is likely to briefly `pixellate` or freeze the tv image, drop or stutter the sound, or even lose its lock on the signal so you lose the programme. And it can happen every day for several days.

As the sun appears to move across the sky each day so it will go `behind` the satellite each day (see panel How it Happens) until it has moved sufficiently far from that satellite for the dish to no longer pick up the noise.

The effect lasts only a few minuttes each day as the sun moves across the sky and away from the satellite and, of courst, it happens only during daylight hours,so it does not effect prime-time tv. However, watch tv ( or record a programmme while out) in the daytime in early October and you may well experience the problem.
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How it Happens​

The Earth is rotating on its axis once every 24 hours and is in orbit around the sun once every year. The rotation appears to make the sun move across the southern sky in an arc while the orbit makes this path move during the year - low in the sky in winter and hghest in the summer.

Thw satellites, although orbiting the Earth, appear to stay in the same position in the sky - in the plane of the Earth`s Equator. At the same of the sping and autumn equinoxes, the sun`s path crosses the equatorial plane and so it approaches the satellite and, asthe Earth and the satellites spin around, each bird passes in front of the sun.

The timing of the approach and conjunction depends bothon position of the particular satellite in the arc and the position from which it`s viewed on the Earth`s surface.

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Other effects​

As well as micowaves, the sun produces a great deal of visible and heat radiation, and so when it is `behind` a satellite this radiation is also picked up by the dish. If the dish is light in colour and/ or shiny enough it will gather up the heat and light from the sun with reasonable effciency ane it on the LNB. This can seriously heat up the LNB andeven melt plastic parts of the LNB or its mount. It`s simillar in principle to using a magnifing glass on a sunny day to start a fire.

In the early days of Astra a large number of marconi `blue cap LNBs used for the new sky service had their plastic feedhom caps melted in this way.

Most dishes these days are designed to withstand the problem and UK cloud cover does much to alleviate it, but if you`re worried the only protection against this is to move the dish off alignnment or to cover it while the sun is in its sights.


Solar Outage Timetable..