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New MPEG4 more susceptible to rain fade?

Discussion in 'DIRECTV General Discussion' started by MalibuRacing, Oct 18, 2007.

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  1. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    One other thing to realize is the 850 and 1900 are both fairly close together (I think in the same overall band) so the differences are important as you mention. Ku and Ka are very different bands (to the home at least) so the punch that might have been there got eaten by the water molecules just as VOS states.

    Many people didn't think Ka could be useful for national coverage on a small dish receiver, DIRECTV sharpened their #2 black pencils and designed solutions to the problems. :)

    Cheers,
    Tom
     
  2. K4SMX

    K4SMX Hall Of Fame

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    I can't really comment personally here in this drought-stricken area, but there are a couple of things I've noticed reported here more than once:

    The Ka's, as expected, fall off faster and deeper than the Ku's. The greater absorption by water molecules is clear.

    The mpeg4 decoder seems to do a better job of maintaining un-pixelated video at previously unusable signal strengths (30's - 50's) than the mpeg2 decoder, at least in some receivers. It'll be interesting to note differences in the 6 (is it?) different HD receivers now in use in this respect.

    So this is sort of a good new bad news scenario.

    For the first time in since D10 went live, I am presently in a dense cloud (RVR=~30') at 4,300' elevation and 103(b) has not dropped at all out of the 90's. So apparently dense, low-lying clouds are not going to be an issue, just the towering cumulus. We'll see what happens when the real rain clouds arrive later today....

    I'm amazed they can accomplish this mission at all with 130 watt/per polarization transmitters, per Tom's post. Very impressive.
     
  3. l8er

    l8er Icon

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    I recently switched from E* and experienced rain fade with their system just about any time it rained anything at all.

    We had some severe storms move through last night and with the new SlimLine D* dish, I only lost signal for a minute or two during a torrential downpour. During most moderate to even heavy rain the D* signal hasn't gone out.
     
  4. Blurayfan

    Blurayfan Hall Of Fame

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    I was recording a MPEG4 HD PPV this morning while we had heavy rain and never lost the signal with my AU9 (slimline). The program never even pixelated.
     
  5. hasan

    hasan Well-Known Member

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    Ogden, IA
    I agree with VOS on this one. A larger dish will have more gain, but it probably does not make up for the increased loss due to water.

    Overall, I think the biggest problem is dish alignment. If you are not peaked on the new sat for HD, then the slightest increase in attenuation due to precip (in the far field ...high t-boomers located to your south) may cause problems. If you start out with a very strong signal, that's one thing....but what I've seen from people reporting sigs on the new sat (when they first started to show up), was a LOT of people with marginal signals due to poor alignment. If this isn't corrected, rain fade will be consistently problematic.

    So, the problem has little or nothing to do with mpeg-4, rather increased attenuation at the new frequencies coupled with marginal alignment in the first place.
     
  6. jtn

    jtn Banned User

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    especially in areas with strong rain downpours (tropical areas) like in Florida. It is believed that MPEG2 is less susceptible than MPEG4 to rain fade. The frequency does make a difference. There will always be pluses and minuses per frequency.
     
  7. bubbers44

    bubbers44 Legend

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    Proper dish alignment is the most important thing to avoid rain fade. The slightest misalignment means you are not getting the required signal to penetrate average rain clouds with average rain attenuation to the signal reaching your dish. Thunderstorms blocking the signal will not allow even a properly aligned dish to work because of attenuation of the signal. Sloppy alignment probably is the cause of 90% of rain fade. I think that is my problem right now and when the next rain problem comes and I see the signal strength drop off I am going to nudge the dish a bit and prove it is an alignment problem, not lack of signal strength from the satellite. My 3LNB antenna was not as subject to rain fade as my new slimline 5LNB.
     
  8. pdawg17

    pdawg17 Hall Of Fame

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    So if there are large numbers of people with alignment problems is it OUR fault and therefore should be paying $70? I think that is going to be the issue here...
     
  9. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    You have 90 days to keep having someone come out for free to get your system setup right. I used this and had them out four or five times in the first week. If you wait longer you will need to find a CSR that will be nice and waive the service call charge.
     
  10. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    And don't wait much longer! There is a small window, right after the new HDs have launched where you are more likely to find a sympathetic CSR. They know several people's installs haven't been really tested until now.

    Cheers,
    Tom
     
  11. hasan

    hasan Well-Known Member

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    Did I say whose fault it was? I was answering a technical question and never addressed D* policy issues. Please, don't put words in my mouth, I make enough mistakes of my own.:)
     
  12. pdawg17

    pdawg17 Hall Of Fame

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    Sorry it sounded that way...I wasn't aiming my statement at you at all...you brought up a good point and I was just making my own point :)

    I know you have 90 days but that's from the point you join D* correct? How about people who had their slimline installed 8 months ago before there was a 103b satellite?
     
  13. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Read Tom Robertson's post.
     
  14. Milominderbinder2

    Milominderbinder2 Cutting Edge: ECHELON '08

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    The appointment is tomorrow afternoon...

    - Craig
     
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