UK satellite reception in Europe

[tony scanlon]

Monday, 24 February 2014

UK satellite reception in Europe: why do I lose my signal in the evening?

Over the past few weeks, since the migration of BBC TV and radio services to new satellite Astra 2E, there have been reports from viewers in Europe around the edge of the UK spotbeam saying that they lose access to BBC (and other) channels in the evenings.

This has prompted a number of conspiracy theories, such as that the power of the satellite beam is being deliberately reduced during primetime TV or that the satellite isn't working properly.

So what's the cause of the daily "wobble", which results in viewers around the edge of the spotbeam - notably across Germany, the Alps, northern Italy, southern France and parts of Spain, to lose channels in the evening?

To understand the problem, we need to look at the sharp drop-off around the edge of the UK spotbeam.

The main UK free-to-air broadcasters required a better satellite set-up to combat issues regarding broadcast rights, royalties and copyright matters.

So a sharper spotbeam for the UK was created. Reception from the new spotbeam rapidly drops off around the edge, meaning that within 100 miles (160km), dish sizes can go from 80cm to 130cm or more. It's in these zones that the daily variations are most noticeable. The slightest change in circumstances or transmitting parameters, which would otherwise not matter, has the power to knock out reception.

Some internet users have concluded that the Astra 2E satellite must move around every day as an explanation of the daily cycles. Although satellites can move around a bit at their orbital position, modern satellites will keep to their orbital position with minimum variation. The slightest movement could affect reception on the ground around the edges of the spotbeam, but for the some of the main reasons behind the daily cycle, we have to look elsewhere:

Thermal distortion on the part of the satellite's antennas itself can impact on reception. This is a natural effect, but could be exaggerated by the very sharp drop off around the edge spotbeam.

Second, there is the theory that the position of the sun with regards the satellite is a factor. Viewers have reported losing channels at the time of the evening. That's when the sun is directly opposite the Astra 2E satellite in the sky*, shining straight at the satellite. The bright sunlight is not the main factor here, though. Instead, the sun's radiation and the effects of the ionosphere are an issue.

Both issues aren't normally a factor for domestic satellite TV reception. But for viewers living around the edge of the spotbeam, they can be part of the reason why reception disappears in the evening. Reception of services broadcast via the pan-Europe beam goes unaffected, simply because the signal is much stronger.

A bigger dish, quality LNB and cables can help overcome daily cycle variations. Also, because Astra 2E is slightly to the east of the other Astra 2 satellites, a slight tweak to the dish may also help sustain a reliable signal for longer. For some viewers, the signal is only lost in the evenings when the weather is bad and thick cloud reduces the already weaker evening signal.

Viewers who don't live in the UK, Ireland, northern France, Belgium or the Netherlands must note that the signals on the Astra 2E/F spotbeams are not intended for their reception, and any out-of-area reception is a bonus.

*Astra 2E orbits above the equator at around 28.35 degrees East longitude. When the sun is over 151.65 degrees West it is opposite Astra 2E in the sky. Astra 2E, as all geostationary satellites, is located nearly 36,000 km above the earth - far enough away so as not to be in the earth's shadow at that particular time. From Astra 2E's perspective, in the late evening (GMT), the sun is shining straight over the earth and straight "in its face", or straight at its transmitting and receiving equipment. Note that it's not the bright light, but rather the sun's energy that causes issues for satellites, and that any resulting detrimental effect on reception is outside of its intended coverage area.

On earth, we have similar issues when the sun gets in the way. From late February into March and again around early October, there are numerous issues with "sun outages", when the sun is directly behind the satellite we are receiving a signal from. TV satellites transmit with enough power in order for viewers in the main footprint (or spotbeam) area to continue viewing, but around the edges of the footprint (or spotbeam), reception can be affected.

In the analogue era, viewers saw an increase in "sparklies"; comet shaped marks on the picture, as a result of sun interference. In the digital era, blocking or loss of signal can occur.

The time such interference is likely to occur and its duration depends on your location, which satellite you are receiving from, and the size of your dish. The bigger the dish, the shorter the interference time, and the fewer days of interference you have. In the UK, interference from the sun could be a issue for some Sky and Freesat viewers during the next 14 days, for a few minutes after 10am each morning. Internet sun outage calculators can be found via Google.

BRITISH TV BLACKOUT IN EUROPE

Special coverage

What’s changed? a516digital investigates and compiles a coverage map with dish sizes. . ITV regions begin move European viewers lose more UK channels as ITV organises its HD channels on satellite. . Migration of main UK channels to Astra 2E complete ITV and Channel 4 moved to the new, tighter Astra 2E UK spotbeam after 0300 GMT on 11th February 2014. How big should my dish be? Dish size guide for Astra 2E reception Q&A: main reception questions Answers to questions raised about the satellite change.