23Mar2017

TV, Internet Outages In March, April 2017 After Equinox

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We are currently experiencing one of two annual equinoxes.

IF you find that your radio or TV broadcast is briefly dropping out or if your internet becomes sketchy over the next fortnight, don ‘t get upset with your council, you can blame the sun.

It all has to do with the fact we are currently experiencing one of two annual equinoxes — the moment the plane of Earth’s equator passes through the centre of the sun.  The Autumn Equinox for the Southern Hemisphere was March 20 and during this time no part of Earth was tilted towards or away from the sun.

While it might be interesting, what exactly does it have to do with your TV and internet? Satellites orbit the equator at an altitude of about 36,000 kilometres and this generally doesn’t cause any issues, except for the 14 days after an equinox when the sun passes behind them and releases energy capable of disrupting its signal.

Despite lasting only10 minutes, the effects can be widespread. The interference from solar radiation is particularly harmful to geostationary satellites — they’re the ones responsible for TV and radio broadcasts, telecommunications, and regional NBN connections. University of NSW’s School of Electrical Engineering and Telecommunications senior lecturer Dr Elias Aboutanios said these interferences are called sun outages.

“Most geostationary satellite communication works in the microwave [frequency]. And the sun transmits those same frequencies,” he told theABC. “[At the equinox] it’s like you have this tiny light bulb, passing in front of a massive projector. You can’t see the light bulb. The background noise — provided by the sun — blinds you from seeing the satellite, much like with visible light.”

Dr Aboutanios said the of multiple satellites sharing the same signal can help reduce the level of interruption, but admits this solution is usually too expensive when the outages are so brief.

“If you place another satellite such that it’s displaced from the first satellite by more than the period of the outage then you can hand over the signal, and when that second satellite experiences its own outage, then you hand back,” he said.

“It’s quite expensive to mitigate the effect by focusing an antenna on another satellite, so it’s kind of accepted that you have a degraded picture quality or a broadcast is interrupted for very short periods in the year.”

While the equinox has already occurred, the weeks following are when you might notice the disruption because its when the sun, satellites and Earth receivers align.

Space weather expert Dr Brett Carter said because of a difference in latitude, not all cities would experience the disruption at the same time.

“As you start to move away from the equator, the geostationary satellite belt is like a ring around the Earth. You could imagine where the shadow of those satellites falls on the Earth changes with the day and the latitude,” he said. “The lower your latitude, the closer to the equinox your maximum disturbance will occur.”

WHEN TO EXPECT AN OUTAGE

• Darwin — March 26 at 10:55am

• Brisbane — April 1 at 11:38am

• Perth — April 2 at 9:18am

• Adelaide — April 3 at 10:59am

• Canberra — April 3 at 11:35am

• Sydney — April 3 at 11:36am

• Melbourne — April 5 at 11:33am

• Hobart — April 6 at 11:34am

Source: News.Com

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