Wednesday, February 21, 2007

Rain Interruptions

Interesting comments are being made about rain interruptions that occur on Dialog TV because there was an interruption on Sunday 18th Feb 2007. Rain interruptions is common among DTH operators all over the world. Usually a study on the expected signal loss time as a result of natural events that could take place during a year is carried out and an acceptable time period for signal loss is determined. We are not aware whether such a study has taken place in Sri Lanka and if not then we hope that a study is carried out.

The most interruptions occur during heavy rain. Earlier there were interruptions in the signal for light rain and now Dialog TV should be commended for improving their systems and the signal loss occurs only during heavy rains. Heavy rains at the receivers end results in a loss of signal for the receiver but then as the rain ceases the signal is restored but some may see that the signal does not return when the rain ceases too and this is due to heavy rains near the uplinking station.

However a method of restoring the signal should be adopted such as by increasing the transmitter power if possible. To avoid any interruptions to the uplinking station will something like moving the station to a dry zone or moving it up to a higher elevation work? At the moment if Dialog goes to undertake moving the station then it will again result in an interruption of services as well as a very high cost to move all the equipment. So maybe they should look at an alternative solution to reduce the frequency of interruptions due to rain because totally eradicating the rain interruptions will be an impossible task. They should look at reducing the time in which the signal is interrupted during rain. Signal loss due to rain is one of the biggest drawbacks of KU Band based satellite systems and should be handled properly to minimize its effects.

It is indeed very annoying to loose the signal during a movie or during a tense moment in a cricket match so we hope that a solution is found to this problem or at least to reduce the duration of the problem.


Lisura said...

Last sunday was the worst day ever. The outage lasted more than 30 minutes for most areas in Colombo !

On a normal day the signal quality should be around 60%. And it drops when it rains but can come to 30% without any degrade in video / audio. If it drops below 30% only the picture gets distorted !

As admin said this is a common phenomenon in Ku band signals.

Dear Tomiya,

Compare the quality of Dialog TV with our analog comet cable and see the difference. Eventhough you see something on the screen the quality of analog cable tv is hopeless compared to the DVD quality picture which is delivered by Dialog TV.

And DTV have confirmed that with the introduction of new processing equipment in the coming months the picture quality will improve further !

Vishkid said...

I don't want DTV to come out with a warning across the site "DTV might not be available during rain" ... no no nothing like that :D

Since this is a valid and applicable scenario in SL whether, they should just keep a general note of the rain-satellite phenomenon so that nobody is mislead.

The fact is that, this is a marketing point against DTV and a point for those such as LBN cable. :)

hush said...


OK DTV have double the problem as they downlink and uplink again but LBN is not out of it cause they also have to down link through satellite and if its KU band channels even with a bigger dish there is bound to be some issues. same goes for comet.

hush said...

another thing I came across is that Sri Lanka is almost on edge of EIRP footprint of IS12 satellite. Thus these rain attentuation is more on edges than in near the centre of the beam.

hope dialog considers to ster the beam a bit more so that Sri Lanka comes off the edge towards middle a bit. possible as transponders on IS12 is steerable spot beams.just a thought for improvement on this issue other than increasing the power of uplink.

Vishkid said...

Valid point - tks for the info.