I just got off the phone with a Voom CSR who was setting me up for a 24" dish upgrade next week due to ongoing rain-fade problems. She told me that its a good idea to buy a bottle of Rain-X and ask the installer to wipe it on the new dish before he installs it. She said it "helps reduce rain-fade a lot." Just wondering if anyone else has heard of this or tried it?
Rubbing Rain-X on the dish helps reduce rain-fade?
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Rain-X huh? Thats a good one. All the dish does is collect the signal and reflect it to the Lnb. Tha larger the dish the more area to collect and reflect.
:clap Very funny stuff StoneMan.You could almost make a case for this. You know how water changes the angle of reflected light rays? Just put a stick in a body of water, and see how it appears to bend at a sharp angle in the water, when it is actually straight. This is because the water changes the angle of the reflected light rays that allow you to see the stick. Now consider that light rays are just a form of radiated energy, which is what the satellite is projecting for the antenna to reflect, and focus onto the LNB (your eye). If there are hundreds of tiny droplets of water on the surface of the dish, won't they scatter the energy at various angles that are different from the angle that the curvature of the dish is supposed to reflect them at? And when some of the energy is not focused on the LNB because of this scattering effect, won't the signal drop?
I'm sure that most of the problem is scattering of the energy in the atmosphere when it has to pass through the water droplets which are much more prevalent in the air between you and the satellite dish, but the effect could be much more pronounce if it is scattered where it is trying to to foucus the energy. If rainx keeps the droplets from forming on the dish surface, then the scattering at the dish could be reduced. Question is, is it significant enough to matter in a rain storm.
If a slightly larger dish is all that's necessary to make the atmospheric scattering negligable, then perhaps the dish is more important than the atmosphere in rain fade, and a slight gain due to the elimination of rain drop scattering at the dish might give you performance that is nearing that of getting a larger dish.
Anyone have any facts that poke holes in my theory?
I'm sure that most of the problem is scattering of the energy in the atmosphere when it has to pass through the water droplets which are much more prevalent in the air between you and the satellite dish, but the effect could be much more pronounce if it is scattered where it is trying to to foucus the energy. If rainx keeps the droplets from forming on the dish surface, then the scattering at the dish could be reduced. Question is, is it significant enough to matter in a rain storm.
If a slightly larger dish is all that's necessary to make the atmospheric scattering negligable, then perhaps the dish is more important than the atmosphere in rain fade, and a slight gain due to the elimination of rain drop scattering at the dish might give you performance that is nearing that of getting a larger dish.
Anyone have any facts that poke holes in my theory?
First of all, what you're referring to above is actually refraction of light, not reflection. That being said, Rain-X coats a surface with a film that causes the water to bead up and roll off a surface, it doesn't prevent droplets from initially forming on the surface. So, in that respect, if you want to take it there, the Rain-X itself, and if the rain is continuous, the larger beads of water would cause more refraction of the electromagnetic waves. Besides the surface of the dish is parabolic, so any refracted energy is going to be fed to the dish's feed horn anyway. The larger dish doesn't make the atmospheric refraction negligible, it just has more surface to catch more electromagnetic waves and focus them on the feed horn. The Rain-X remedy is as ridiculous as it sounds.Scotty said:
brainiac said:
In order to see the refraction of light, it has to be reflected through the lense of your eye, where it is focused on the retina.
In the water example, light from the sun travels through space, through atmosphere, and then through a body of water in which you are observing the stick. Refraction is the change in angle of the light beam as it passes from one medium to another. So it must bend on the way in, and on the way out again, as it is reflected off the object you are viewing.
From the LNB's perspective, energy arriving on the dish would be passing through the convex surface of a droplet of water, refracted, then reflected at a different angle off the surface of the dish (concave), then it would have originally, if the droplet would not have been there. With rainx, the droplets formed are very tiny, and roll of the surface quickly, as opposed to large droplets which may stay adhered to the surface of the dish for a relatively much longer time. That's why rainx works so well on a windshield. With the large droplets and no rainx, you can't see very well because the light rays are scattered at many different angles as the are reflected off objects in front of you and refracted through the rain drops. This results in a blurry image in front of you. With rainx, the drops are so minimized as make the water droplets less convex, and the light rays don't refract as much through them, and so you see a clearing picture through your windshield.
Why doesn't the same analogy work on the dish? Light is nearly the same as the energy being broadcast by the satellite, just from a different part of the spectrum. The same effects of refraction and reflection should apply, don't you think?
Also, the parabolic shape of the dish (concave), doesn't buy you anything if the energy is reflects is scattered by the droplets and doesn't focus on the LNB.
I'm not saying this works or it doesn't work, I'm just saying that it seems logical that it might work.
TechCop said:Now we just need someone who has easy access to their dish to test out the theory....
Just Rain-X the lower half of the dish and see if the rain fade affects the top half of the picture first....
roflmao! That sure let the hot air out of my balloon!!
During a heavy storm my 18" allows the signal to drop to zero. We're having some weird heavy end of summer rain here in western pa, so I'm going to try to test this theory (on the whole dish!
). I just can't dismiss it out right like the rest of you have. I'll report back the 1st rain storm we have.
The only way to prove this would be to take 2 identical Dishes and mount them right next to each other and then put 2 satellite receivers on the exact same channels.
I don't think the rainex would work because there are hundreds of thousands of drops of rain which would be in the path of the beam at any given time during a storm. Getting rid of a few hundred drops of water on the Dish is not going to make a difference
I don't think the rainex would work because there are hundreds of thousands of drops of rain which would be in the path of the beam at any given time during a storm. Getting rid of a few hundred drops of water on the Dish is not going to make a difference
I realize that I misread what you were saying about the stick in the water. Sorry about that. With that being said, the way a parabolic dish works is that any waves that hit the surface should hit the feed horn as they're reflected back. However, I guess we disagree about how Rain-X works. Rain-X causes the water to form larger droplets or beads so that they roll off the surface. What do you think a foggy windshield is? It's a windshield covered with minute droplets or water. Rain-X pulls these particles together to make them roll off. And that's exactly my point -- bigger droplets, more refraction. So with the constant presence of the droplets and the coating of Rain-X (which acts essentially like clear wax), the waves that should be reflected back to the feed horn are refracted on the way and miss the horn. But to be honest, this whole "remedy" is neither here nor there. Rain fade is caused by too many water droplets or ice crystals in the atmosphere whose separation are approximately the same wavelength of the radiation of concern, causing severe attenuation. The droplets hitting the dish have a negligible effect. The damage is done long before the rain hits the dish. But hey, for anyone who wants to try it, knock yourself out!Scotty said:
You counter to my argument makes much sense. But fogged up windows are different from windows that are getting rain on them. Fog is usually on the inside and rain on the outside. But you're right, fog is just very tiny water droplets. And it's very difficult to see through this thin film of water droplets. So I guess I'm wrong about the tiny droplets scattering light less. It made sense until you mentioned a foggy window.
But somehow the rainx still lets me see better through a hard rain. If it's just because it waxes the windshield, and lets the droplets get big fast, and so therefore run off faster due their own weight, it still causes the water to clear faster and allow me to see. Won't it have the same affect on the dish with the LNB as the eye? I guess the real reason that this probably won't work is that the effect of water droplets at the dish is not nearly so massive as the effect of the much greater amount of droplets in the air, as I think you or someone said.
Now i've heard that the reason we see blue sky is because the space between particles in the sky is such that only the blue wavelengths of light make it through. Something to do with hydrogen in the air? So you're saying that water vapor just happens to be spaced at exactly the wavelength that would block the satellite's radiated energy too? So why didn't they just pick a different wavelength and solve all this nonsense with rain fade. My guess, is that it's not that water vapor is spaced at the same wavelength. It's just spaced randomly, and scatters and absorbs the energy at random.
All that said, however, I'm probably full of BS about this logic behind rainx. I've been reading all over the web, trying to find something to support my logic, but have come up with zilch. Here's a very technical explanation of rain-fade and other issues that affect dish reception:
http://www.geo-orbit.org/sizepgs/Noise.html#anchor1149220
This one explains it a little more simply, and talks about refraction and scattering and such, but from the air droplets, not the ones on the dish.
http://www.spacecom.com/customer_tools/html/rain_fade.htm
Who knows, though. The two author's could be as full of hot air as I am!
But somehow the rainx still lets me see better through a hard rain. If it's just because it waxes the windshield, and lets the droplets get big fast, and so therefore run off faster due their own weight, it still causes the water to clear faster and allow me to see. Won't it have the same affect on the dish with the LNB as the eye? I guess the real reason that this probably won't work is that the effect of water droplets at the dish is not nearly so massive as the effect of the much greater amount of droplets in the air, as I think you or someone said.
Now i've heard that the reason we see blue sky is because the space between particles in the sky is such that only the blue wavelengths of light make it through. Something to do with hydrogen in the air? So you're saying that water vapor just happens to be spaced at exactly the wavelength that would block the satellite's radiated energy too? So why didn't they just pick a different wavelength and solve all this nonsense with rain fade. My guess, is that it's not that water vapor is spaced at the same wavelength. It's just spaced randomly, and scatters and absorbs the energy at random.
All that said, however, I'm probably full of BS about this logic behind rainx. I've been reading all over the web, trying to find something to support my logic, but have come up with zilch. Here's a very technical explanation of rain-fade and other issues that affect dish reception:
http://www.geo-orbit.org/sizepgs/Noise.html#anchor1149220
This one explains it a little more simply, and talks about refraction and scattering and such, but from the air droplets, not the ones on the dish.
http://www.spacecom.com/customer_tools/html/rain_fade.htm
Who knows, though. The two author's could be as full of hot air as I am!
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