Rain Fade Explained - What It is & How To Fix

April 22, 2021
by
Tom

Why Does Satellite TV Signal Go Off In Rain?

There are few things more frustrating than sitting down to watch your TV programme only to find that you have poor or no signal message pop up on the screen, this may be accompanied with blocky pictures & pixelation and you look outside to find to see that it’s raining. You may be wondering, why does my satellite/ Sky signal go off in rain? And what can I do to stop this? In this blog, I discuss why this happens and offer some suggestions to stop this happening anymore, or at least dramatically reduce it. Let's begin.

 

Rain Fade Explained

The negative effect that rain has on satellite signals is called rain-fade. This refers to the absorption of a radio/ microwave signal by atmospheric conditions, such as rain, ice, snow. As the satellites for satellite and Sky TV are in space the signals need to pass through this before it reaches your satellite dish, which in turn feeds your satellite receiver which needs to be at an acceptable level for reliable reception. Now, the greater the amount or the heavier the rain the greater the effect the rain-fade will have, this may see the signal received by the satellite dish drop below the suggested minimums and offer poor reception. Also, the higher the frequency, the greater the effect of rain will be on the signal. As satellite TV uses very high frequencies with very small wavelengths within the Ku Band (10.7-12.75Ghz), these are more effected by rain then when compared with terrestrial TV services which use a much lower frequency. This effect is increased further with services such as satellite broadband which use higher frequencies still within the Ka band.

 

How To Improve Satellite Signal in Rain, Remove Rain Fade

Within the section I offer some suggestions on how to remove rain-fade from your satellite signal. I’m sure that you could have guessed by now but the greater the improvement on the satellite signal reliability/ robustness – usually measured as Carrier to Noise Ratio (C/N) or Modulation Error Ration (MER) the less likely your TV is to fail in the rain. Within the trade we call the point where a digital TV picture fails, The Cliff Effect. You’re even safely on the cliff edge or your off it, the picture quality does not degrade gracefully like it did in the old analogue days. It is our job as installers to get as faraway from the cliff edge as possible so that you’re not likely to fall off.

For your reference the suggested minimum readings for reliable satellite TV reception are: Strength - 52dB, MER - 10dB.

 

Align Satellite Dish For Peak Reception

I have already written a previous blog offering advice on how to align a satellite dish which I recommend that you read when you’re done here. You may find that despite having a satellite signal that works the majority of the time that the dish is slightly offline and improvements can be made by altering the alignment. This can be because it was never aligned properly when installed or it has moved slightly, this can happen in high wind especially when the dish is old and rusty. This is not as easy task without the correct equipment so you may need the assistance of a satellite engineer with a decent TV spectrum analyser or alignment tool, even some of the cheaper satellite alignment tools are not easy to use when aligning a dish for peak reception. If choose to do this yourself you may find that inside the settings of your satellite TV or receiver that you have some signal readings that you can strive to improve when playing around with your satellite dish alignment. Some have readings such as MER and information on Bit Error Rates. Sky boxes have information on the satellite signal strength/ quality but it should only be used as a guide and really isn’t that helpful.

 

Don’t forget the Skew Adjustment!

This is often overlooked, even sometimes by people within the trade. The Skew adjustment is the angle that the LNB sits within it’s holder. This needs to be set correct so that the dish can differentiate between horizontally and vertically polarised signals. As the satellites for satellite TV are in geo-stationary orbit and rotate around the equator, if you could see all the different satellites in their orbital positions when looking south in the northern hemisphere or north in the southern hemisphere, these would form an arc in the sky. With the highest point being due south (northern hemisphere)and the further east or west you deviate the lower this would be. Now if you can imagine the effect this would have on the satellite signal polarisations, they would gradually become more diagonal the further off due south you get and you must make an alteration on the LNB adjustment to be able to maximise the signal quality. It can make a very big difference to your reception if this has been set wrong. An example of this using Dishpointer for the Astra 2 satellites situated at 28.2E which broadcast Sky and Freesat signals to the UK would require a skew setting of -13.4.

 

Upgrade The LNB

Changing your satellite LNB for a better quality model could see some improvements to your satellite signal which can reduce the effect of rain-fade. The gain of the LNB shouldn’t be that important if you have relatively short cable runs but you should look for an LNB with as low a Noise Figure as possible. This is the amount of electrical noise introduced into the signal by the LNB itself, the greater the number the more it will reduce your C/N and MER readings. Some of the earlier models have quite high noise figures so you may see that your satellite/ Sky TV signal fails a lot less in the rain with a new LNB.

 

Install A Larger Dish

I’m sure you will appreciate the larger the dish, the more of the signals that will be reflected to your LNB offering a stronger and more reliable signal. Depending which satellites and countries TV you wish to receive and your location that you wish to receive it will effect what size satellite dish you require. I have already written an article on what size satellite dish do you need which may help you, within this I suggest the minimum suggested dish sizes for the receptive satellites in the north and south UK, but just because it is a suggested minimum doesn’t mean it’s a bad idea to install a larger dish. It may not make you popular with the wife but a larger satellite dish can help improve your satellite signal in rain. For example in the South of the UK a Zone 1 43cm mini-dish would normally offer reliable reception for Sky and Freesat TV, but on occasion when customers request a larger dish to improve the signal quality, I install 60cm Zone 2 satellite dish which normally only would be installed North UK and Scotland. 

It Might Be Water Penetration On The Coax!

Obviously, the natural response to you losing satellite signal in heavy rain and thunderstorms would be to assume that it’s rain-fade that is causing the problem, but this may be a red-herring. It could be that water in penetrating the coax cable that connects between your LNB and satellite receiver and causing a cable short which will stop the DC voltage flowing from the satellite receiver to your LNB causing no satellite signal. The most common reason for this would be that the LNB rainwater cover has not been pulled down the protect the F connectors or that the cables have not been weatherproofed correctly. You must pull down the rainwater where you have an LNB that has one and you may want to consider a smear of silicone grease around the connection, or a wrap of self-amalgamating tape (not easy to get around multiple connectors) or weatherproof F connectors.

 

No Installer Can Guarantee a 100% Signal All The Time

No installer in the world can guarantee that you will have a reliable signal all the time, there are simply too many things that can go wrong and things that can effect a satellite signal, even if everything has been installed correct. If you signal is only go off in torrential rain or lighting storms there is a chance that very little can be done to improve things, short of putting a ginormous satellite dish up which may require planning permission. On the other hand if your satellite signal is failing at the slightest hint of rain or cloud cover you know things can be improved and the methods suggested above can be tried.

 

Get a TV Aerial/ Stream TV Instead

If you’re not a Sky subscriber or you do not subscribe to another satellite TV service, you may want to consider installing a TV aerial instead and getting your live TV through this. Although TV aerials/ antennas are not immune from the effects of rain on the signal, because they operate at a much lower frequency not as affected by rain and because they receive their signals from land based transmitters and not satellites in space, rain is not as significant with regards to reception. In the UK free TV via a TV aerial is called Freeview, in Ireland it is Soarview and has numerous TV channels and HD content. Some subscription based services like BT Vision use a TV aerial for their live TV services,

 

Alternatively with the internet changing our viewing habits, you could get your TV service through here. If you’re after Sky services you could subscribe to something like Now TV or if you just want normal terrestrial TV services something like Britbox instead. It wasn’t that long ago that phrases such as TV on demand, streaming content and IPTV were little known, but now we are blessed with options, too many to name here so I recommend that you do some research into what you wish to receive.

 

Rain Fade & Satellite TV Questions – In The Blog Comments Section Please

 

If you have any questions, please do call our telephone lines… No, I am joking! PLEASE DO NOT DO THAT! To be honest I am amazed that my blogs reach the audience that they do but a big downside is that people seem to think that I have the time, motivation and patience to offer free over the phone technical support and advice. I do not so PLEASE DO NOT CALL OUR TELEPHONE LINES WITH QUESTIONS, these are intended for customers only and we are only a small business that serves Sussex and parts of Kent. If you post your comments in the Blog Comments Section below and are patient for a response I personally endeavour to answer all of these myself, but work and life commitments often mean I may not be able to do this as fast as you like.

Please also do not privately e-mail questions or fill out our website contact forms, again these are intended for customers only looking for installations and quotes. I do not have the time to privately answer comments and questions so I have stopped responding to these. By posting your questions/ comments within the Blog Comments Section below you will:

-Help the blog

-Give future readers the benefit of questions asked and answers given

-Provide me with a central location to answer questions(This really speeds things up my end)

-Stop me having to answer the same questions, again and again.

That being said and that min-rant over. I will help where I can. I hoped you enjoyed this blog, please do keep an eye out for future ones.

 

Until next time,

Tom

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