What size dish would be needed to nearly eliminate rain fade? (1 Viewer)

mmcl26554

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Feb 18, 2006
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Although rain fade is not a big problem it seems to happen at the most inopportune times. So I was wondering what size dish would nearly eliminate it. If there is a large dish available would it be able to get 110,119, & 129? For those who would ask, I have verified my 1000+ is pointed to receive max signal and there are no obstructions. I am on Western Arc as my locals are on 129 only.
 

3HaloODST

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One of these for each sat oughtta do it:

http://i54.tinypic.com/1263dht.jpg

So 3 for 110 119 & 129.

In all seriousness though, getting a bigger dish only at most shaves off a couple of minutes of disruption. Due to the nature of the Ku band, if rain droplets in clouds are large enough (~2cm,) then the signal can be blocked completely, during which time not even the dish in the picture can do anything about it. Even if droplets are only ~1cm, there will be significant attenuation.
 

RickDee

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One of these for each sat oughtta do it:

http://i54.tinypic.com/1263dht.jpg

So 3 for 110 119 & 129.

In all seriousness though, getting a bigger dish only at most shaves off a couple of minutes of disruption. Due to the nature of the Ku band, if rain droplets in clouds are large enough (~2cm,) then the signal can be blocked completely, during which time not even the dish in the picture can do anything about it. Even if droplets are only ~1cm, there will be significant attenuation.

Are you sure about your rain drops sizes? 2.54cm = 1 inch. A 2cm rain drop would be awfully BIIIIG! Even 1cm would be bigger than average!!
 

3HaloODST

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Are you sure about your rain drops sizes? 2.54cm = 1 inch. A 2cm rain drop would be awfully BIIIIG! Even 1cm would be bigger than average!!

You're right. I am mistaken. It's more like ~1cm that would nearly "block" AKA absorb the signal completely. 2cm is pretty darn big, no doubt. I'm terrible with metric. Anyway, we're talking about rain drops in clouds, "droplets" is a little misleading, but I am talking about the drops, before they fall as precipitation.
 

mmcl26554

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Feb 18, 2006
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I don't think I ca afford that one! One observation I have made is that 119 is my strongest signal and 129 the weakest. When rain moves in I lose 129 first and then 119 and 110 but sometimes I don't lose 110 and 119 at all so I was thinking if I can get more signal for all three it could reduce rain fade a lot. I know you could use a 7 foot C band antenna which can be had free just for removing them. When I had Starband satellite internet some were talking about doing just that as rain fade was a problem for satellite internet.
 

3HaloODST

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Yeah, 129 is a good bit lower on the horizon than the other two sats for most cities. This means more atmosphere for the signal to travel through. More atmosphere = higher probability of rain fade.
 

3HaloODST

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Could it also be the the effective radiated power of 129 is lower than 110 and 119.

I suppose that depends on where you live. Overall though, Ciel-2 is just as powerful as the rest. For example, on most TPs with my 1000.2, I get about 77-78 on 110. On 129 TP 21 I get 77-80. On 119 I get 82-86 on the strongest TP. The only reason 129 appears to be "weaker" on most transponders is due to 8PSK modulation vs QPSK modulation. TP 21 on 129 is still QPSK, thus it has similar readings to 110/119. TP 7 on 110 is 8PSK, and you will find that it has similar readings to most of 129's TPs. This doesn't mean that the signal is actually weaker, it's just that 8PSK uses different FEC algorithms.

The signal strength meter on the receivers would be more accurately described as a signal quality meter. I have found though that as the actual signal strength drops, the gap between 8PSK and QPSK readings gets narrower. QPSK is really only marginally more resistant to rain fade. So this brings us back to other factors, such as, the elevation of 129. The lower elevation means more atmosphere for the signal to travel through, and again, more chances for rain fade.

Sooner or later 110/119 will be switched to 8PSK, as soon as DISH gets rid of all QPSK (legacy) receivers out in the wild. When this happens, 110/119 will have comparable "signal strengths" according to the receivers' meters. The lower numbers don't necessarily actually mean that there is in fact a weaker signal.
 

Jim5506

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No, 129 is a relatively new satellite and has normal signal strength.

I have an old D1000 peaked very carefully and My 129 and 110 are about the same with 119 about 15 points higher.

Some of the apparrently lower signal on 129 is also due to the modulation difference, SD channels on 119 are QPKS whereas HD channels are MPEG4 8PSK.

The biggest reason for 129 to drop out first during heavy rain is that it is lower on the horizon so you are looking through more atmosphere and potentially more water vapor of all types, 110 and 119 are more overhead so the atmosphere the signal travels through is shorter.

If you think Dish has rain fade problems, DirecTV has more problems because some of their frequencies are more susceptible to absorption by water vapor.
 

3HaloODST

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If you think Dish has rain fade problems, DirecTV has more problems because some of their frequencies are more susceptible to absorption by water vapor.

Yes. DirecTV primarily looks at 99, 101, & 103, typically these days using a Slimline dish with the SL3 LNB. In some areas you will be looking at 99, 101, 103, 110 & 119. Again using a Slimline, but with a SL5. Anyway, 99 & 103 are Ka band (vs Ku band for 101, 110, 119.) DISH uses exclusively Ku on all of their sats. 99 & 103 also carry DirecTV's HD programming.

Long story short, Ka band has an even narrower wavelength than Ku. Therefore, smaller raindrops can affect the Ka band that would otherwise have no effect on the Ku band. What this means is that the Ka band will have more rain fade.
 

Jim5506

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Local cableco uses 10' dishes but they still experience rainfade during really heavy rain, you cannot eliminate rainfade.
 

mmcl26554

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Feb 18, 2006
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I think I will look around for a 1 meter or larger used dish, move the 129 LNB to it and see what happens. Maybe I can find a 5 foot BUD free for removing it. I'll post back the results.
 

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