Q I am having problems with satellite reception in southeast France and wonder if any other readers are having a similar problem and have found a solution?

Most of the UK free to view channels are now broadcast on Astra 2D which has a smaller footprint than either Eurobird 1 or Astra 2A/B – the other ‘Sky’ satellites.

Astra 2D channels are broadcast on frequencies from 1074Ghz to 10921Ghz and it is the channels at the lower end of that range that are causing me problems. Things are fine during the day but during winter evenings and nights I get no signal on ITV1, 2 & 4 (10714 – 10758) and a frozen picture on BBC1, 2, 3, 4 & News24 (10773).

I can pick up all the other Astra 2D channels broadcast from 10788 – 10921 which means I can tune into regional BBC1, BBC2 and ITV1 channels. However this does not help with BBC3, 4, News24 and ITV2 & 4 which have no alternative frequencies.

I have an 85cm dish mounted on the roof of my apartment building (3 floors) in Barcelonnette (Department 04). I am told that the maximum size dish I can have is 90cm as anything larger than that would require planning permission. I have calculated that the larger dish would enable me to receive only 12 per cent more signal. I really don’t know how significant that increase would be.

If any of your readers can help I would be most grateful.

Brian Taylor

A From the information you have given me, it seems more likely that the problems you are encountering are more likely to be due to a mis-aligned dish, ie the signal quality is too low rather than the dish size itself.

Your first step should be to get an engineer to come out and align the dish properly although often this is not as simple as it sounds because a lot of installers do not have the correct meter due to its high cost. Therein lies the cause of a lot of installation problems.

As the problems reported occur on both horizontal and vertical channels and only at certain times, it’s reasonable to assume that there is nothing wrong with the physical workings of the LNB and, for that matter, the satellite receiver.

All the problems occur on transmissions from the Astra 2D satellite and the coverage area, or footprint, of that particular satellite is more tightly focused onto the UK than that of Astra 2A and 2B.

In the UK and northwest France, the signal strengths of all three Astra satellites are the same. In fact the signal strengths of Astra 2A and 2B are the same all over France but the signal strength of Astra 2D weakens considerably the further south and east in France that you are located. The main Free-to-Air channels like BBC, ITV and FilmFour all use the Astra 2D satellite and that is why it is more likely that one, or all, of these channels will be the first to disappear when there are problems with a satellite dish installation.

When satellite signals start to weaken, the satellite installer will compensate for this by fitting a larger dish. The larger the dish, the more signal it is capable of collecting and sending to the satellite receiver. Another rule is that the larger the dish, the more difficult it is to align properly.

Digital satellite signals have two properties – strength and quality. Strength can be considered as the amplitude of a signal but it is the signal quality which is far more important and much more difficult for the installer to get right. It doesn’t matter how large the satellite dish is, if the installation produces a poor signal quality, then problems will arise.

There are several factors that can lead to poor signal quality on a satellite dish installation. The dish itself should not be twisted or dented and it has to be perfectly aligned . . . and that means to an accuracy of less than half a millimetre. The LNB has to be ‘skewed’ correctly in its holding clamp … many installers don’t bother doing this and it is the main reason why there are problems with BBC and ITV. The satellite signal should not pass through leaves or tree branches and only the best quality low loss satellite cable should be used. The cable shouldn’t be kinked, joined, have sharp bends, be damaged by staples or stretched when it is pulled through the conduit.

A satellite dish that produces poor quality will work fine until the weather turns cloudy or it starts to rain and then the problems, usually with ITV or BBC, will start. Also, the satellites appear to be static but are in fact in a high altitude orbit travelling extremely fast. The three Astra 2 satellites are located in a 70km square cube and are constantly being adjusted to stay in position. This adjustment could happen every 12 hours and a poorly aligned dish will suddenly stop working on certain channels and, again, it’s usually BBC and ITV that suffer first.

Some installers only align a satellite dish using a signal strength meter. This is a low cost in-line device which measures the amplitude of the strongest signals from the Astra 2A and 2B satellites. Satellite Beepers work in exactly the same way and neither is capable of measuring the signal quality of a satellite installation. The result is perfect pictures when the sun shines and disappearing channels when it starts to rain.

The only way signal quality can be maximised correctly is by using a meter which measures the bit error rate of a particular frequency and the wise installer will choose one of the weaker Astra 2D frequencies to maximise. The lower the bit error rate, the higher the signal quality and when the weakest frequency is tweaked to perfection, the rest will follow and BBC and ITV should not disappear in all but the mightiest of downpours.

John Sidwell is the managing director of Big Dish Satellite, which has supplied and installed several thousand satellite systems in France