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FIOS TV pixellation fix - attenuate to SNR 31

Discussion in 'TiVo Series3 HDTV DVRs' started by AbMagFab, Nov 19, 2007.

  1. jpulver

    jpulver New Member

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    Mar 27, 2007
    See my post above from six days ago. I have a low-pass filter at the ONT, which has had no effect on the picture quality through my four Verizon set-top boxes, which I have in addition to my TiVo HD.

    I have added 16 db of attenuation (two 8 db attenuators) to the cable attached to the TiVo HD box. I had been told by TiVo to continue to add attenuation until the pixellation stops. (Fourteen db nearly fixed it; 16 db absolutely stopped the problem.)

    Now, finally, after adding the low-pass filter and the attenuation (as TiVo had recommended), I have finally eliminated the pixellation entirely. These changes have not affected the picture quality through the TiVo HD nor through the four STBs.

    Spread the word!
     
  2. ah30k

    ah30k Active Member

    2,211
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    Jan 8, 2006
    Where did you get your LPF? Is that a standard RatShack item?

    Anyone know if the LPF will fix the audio dropouts?
     
  3. jcostom

    jcostom New Member

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    Mar 6, 2002
    I added a 20 dB attenuator on Friday (tried 3 and 16 first), and throughout the weekend, we've been pixelation free. We didn't have it all the time, but since adding the attenuator, it hasn't returned. I don't have a low-pass filter installed at this time. What symptoms would I be seeing were I in need of the low-pass filter?
     
  4. thegeek

    thegeek New Member

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    Dec 16, 2002
    Wesley...
    Instead of a low pass filter, has anybody tried a diplexer? You could ask your installer if they could toss you a MoCA NID and a pair of terminator caps. Heck, some installers are even putting in a MoCA NID even if it's not needed, so you might already own a spare one :)

    The NID is basically a diplexer that allows an installer to splice in a MoCA signal on top of another provider's video feed, since they run on different frequencies.

    There are 4 ports on a MoCA NID.

    RF out
    ONT In
    Home Coax
    CATV In

    In this application, you would plug your coax feed into ONT In, and then another cable into the RF out and have that feed the Tivo. Cap the other two off with 75 ohm terminator caps.
     
  5. Jul 1, 2008 #245 of 866
    ah30k

    ah30k Active Member

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    Jan 8, 2006
    Th problem is that if there are any STBs on the RF-LAN then the MoCA is already diplexed onto the RF cable and will get into the TiVo through the ONT-in.

    edit - proved wrong. isn't the first and certainly won't be the last. I thought a diplexer added the two signals together but it turns out there is a low-pass on one input and a high-pass on the other prior to them getting added together.
     
  6. Jul 1, 2008 #246 of 866
    thegeek

    thegeek New Member

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    Dec 16, 2002
    Wesley...
    I was suggesting putting the NID right at the Tivo.

    FYI, I'm parked at an SNR of 37 dB and it's purring like a kitten though I've only had the cards installed as of a few hours ago. The installer was kind enough to leave me with a handful of attenuators.

    I had to throw 16 dB of attenuation to get it down to an SNR of 31 dB which drove the signal strength down to around 50. Got piles of uncorrecteds and the picture was breaking up. I'll keep the attenuators around just in case, but so far so good.

    I currently do not have MoCA.
     
  7. Jul 1, 2008 #247 of 866
    ah30k

    ah30k Active Member

    2,211
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    Jan 8, 2006
    If you don't have MoCA then no worries.

    If you did have MoCA on your local RF LAN (ie Verizon supplied STBs) then the MoCA signals would traverse through the NID un-impeded.

    edit - proved wrong. isn't the first and certainly won't be the last. I thought a diplexer added the two signals together but it turns out there is a low-pass on one input and a high-pass on the other prior to them getting added together.
     
  8. Jul 1, 2008 #248 of 866
    bhaas

    bhaas New Member

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    Aug 5, 2003
    MD
    the Tivo site specifically states a LPF or diplexer can be used (support article 5-12-01).

    A diplexer combines or splits out two different frequency bands, effectively filtering one from the other. A sat/antenna diplexer's cutoff on the antenna side is about 800MHz, and MoCA typically runs 950-1050MHz.

    One word- a filter or diplexer may not always be a full solution- MoCA is designed to be able to run the "wrong" way across splitters and suffer lots of attenuation, so even a filter will not always knock it down completely.

    RS has them for $21.99, p/n 16-2567. Circuit City has one for $8.95.
    You need to install the diplexer "backwards"- connect the cable from the wall to the "TV" terminal (one terminal end), and connect the TiVo to the "ant" terminal. You need to put a 75Ohm termination cap on the "sat" terminal (6-pack at RS for a few dollars).

    FWIW< I put one in on the HD I was having issues with and it DID make a significant difference.
     
  9. Jul 1, 2008 #249 of 866
    ah30k

    ah30k Active Member

    2,211
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    Jan 8, 2006
    You're right. After further looking into it, I was mistaken. Thanks.
     
  10. Jul 7, 2008 #250 of 866
    Deanq4

    Deanq4 TiVo Lover!

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    Sep 30, 2005
    Forest Grove OR
    did you put it at the wall terminal or on the ONT?
     
  11. Jul 7, 2008 #251 of 866
    bhaas

    bhaas New Member

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    Aug 5, 2003
    MD
    its sitting between the tivo and the house cabling. Make sure the "ant/sat" side is conected to the wall side, and the "ant" terminal connects to tivo, and the "sat" terminal is properly terminated.

    Putting it at the ONT will have little to no effect as far as I can tell, since the MoCA runs amongst the STBs and the router (or ONT, depending on which generation your local FiOS insall is), and would still be present at the TiVo is you only filter at the ONT.

    BTW- saw a diplexer at Home Depot for $9.95.

    I'll try to bring it into work tomorrow and get some S11/S21/S22 traces to show the filtering characteristics versus frequency.
     
  12. Jul 8, 2008 #252 of 866
    Deanq4

    Deanq4 TiVo Lover!

    156
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    Sep 30, 2005
    Forest Grove OR
    Thanks, My issue is that when I add the right amount of att. I lose signal on a couple of channels. most of them are running between 50-60 (a little low for me) was wondering is the diplexer would help with that. I am thinking I might be able to lower the number if Attueters so that I still get a good signal (70+) and still keep the SNR to 30-31.
     
  13. Jul 8, 2008 #253 of 866
    bhaas

    bhaas New Member

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    Aug 5, 2003
    MD
    It seems correct that adding a diplexer wil allow you to remove some attenuation, since the attenuators serve the dual purpose of cooling the desired signal down and also the MoCA signal. I would add the diplexer/filter and remove 3dB of attenuation, see what that does.
    Its frustrating, but trust me- this is exactly the same thing engineers do in the hardware lab- adjust one thing, check. Adjust one other thing a small amount, check. Adjust again, check. repeat.
     
  14. Jul 8, 2008 #254 of 866
    Deanq4

    Deanq4 TiVo Lover!

    156
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    Sep 30, 2005
    Forest Grove OR
    Thanks I will try it out. Going to hit a Home Depot tonight and see it they have the diplexor reported. There is a ratshack on the way home (sorry not paying $21 for a diplexer) to the 75ohm caps. Will report back later.
     
  15. Jul 9, 2008 #255 of 866
    rickster30us

    rickster30us New Member

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    Jul 9, 2008
    About 2 weeks ago after nearly a year my S3 started pixelation on certain Starz channels. It does not do it all the time but has been getting worse over the past week. I have FIOS... I tried attenuating the signal but it did no good. When my SNR is around 34 or 35 I have no problems. When it starts pixelating the SNR jumps all over the place but usually 31 or less. I get tons of uncorrected SRs. The frequency affected is 621. I have read the posts and I don't think attenuating is my issue. I have VZ coming out today. However, around 10 pm last night the pixelating stopped. It is still not pixelating as of 3:30 PM. I don't know what is going on. I am getting some Corrected RS but no Uncorrected. I have 2 VZ boxes in addition to my TIVO. Any idea what I should do or tell Verizon. I don't understand why it starts and stops. It has stopped now for nearly 24 hours and I didn't do a thing. Any help is greatly appreciated. I also have FIOS Internet. I do not use the VZ DVR where I can play it from any room. Just the standard HD DVR boxes from VZ. BTW... What is MoCA?
     
  16. Jul 9, 2008 #256 of 866
    bhaas

    bhaas New Member

    174
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    Aug 5, 2003
    MD
    ask them for a lowpass filter to install between the TiVo and the wall cabling, or buy a diplexer.
    MoCA is pretty much ethernet over coax, except it runs at 1GHz, above where TVs and STBs can see. Except, apparently, TiVo.

    It's how the STBs get their program guide data, how they communicate with the mother ship about your PPV/VOD requests, and how the boxes receive the VOD shows.
     
  17. Jul 9, 2008 #257 of 866
    Gerhard

    Gerhard New Member

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    Sep 29, 2002
    FYI:

    Today I added SAT/CTV Diplexers as low-pass filters to both my S3 Tivo and the output from the ONT (with 75 ohm terminators on the high-side of the diplexr).

    On Universal HD I was getting tons of RS Uncorrected errors, so I lowered dB attenutators to a single 6dB one at the Tivo after the diplexer.

    The RS Uncorrected errors have completely stopped. Video quality is still good, I'm just not getting any picture loss.

    I do have a bunch of NM-100 units through-out the house, plus the ones built into the Motorola cable boxes.

    I'm still not happy with the distortion / marco blocking /pixelization or whatever you get with action / reapid motion... and I wonder if that's a limitation with the S3 and MPEG compression, but the signal distortion issues seem to be solved.
     
  18. Jul 9, 2008 #258 of 866
    Gerhard

    Gerhard New Member

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    Sep 29, 2002
    So the way it used to work is that if you had standard cable and you didn't have a low pass filter at the point that the cable came into your house, the ehternet-over-cable would go outside your house and back up stream.

    Since FIOS is fiber, it really shouldn't be an issue, but I put one at both ends simply for network security as a "just in case." (Though it really should not be needed... you never know.)

    I've actually separated out the MoCA network from the rest of the house network. (My firewall has multiple segments, and I'm using VLANs to give the NM-100, Tivos [3 of them], Denon AVR, AppleTV, and Motorola STBs their own internet connection.) You never know what information those devices could be used to collect, and I'm not going to just trust Verizon to protect me!

    -grin-
     
  19. thegeek

    thegeek New Member

    230
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    Dec 16, 2002
    Wesley...
    Most new installs use MoCA from the ONT to the router for the internet portion of FiOS as well. If you're not set up to have data run via ethernet from the ONT to your router then tossing a diplexer at the ONT filter MoCA will kill your internet.
     
  20. Gerhard

    Gerhard New Member

    231
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    Sep 29, 2002
    Nope, in my case there is an ethernet connection running to my computer room directly from the ONT.

    What verizon typically does is install a router with a MoCA connection and then feeds that into the house cable from somewhere else in the house.

    The Verizon tech that did the inital install was unable to explain to me why this was required. So I told him no, as why would I want Verizon installing something on my network that I have no clue what it's doing? (I had FIOS Internet before TV existed, so my router did not have a MoCA bridge in it...).

    [The MoCA bridge is only required if you want the STB's from Verizon to actually get program data or do on-demand stuff, which is not needed if you have Tivos or don't care about on-demand.]

    Currently, I use NIM-100s to bridge MoCA onto the cable system in the house, and that bridge is located in the computer room - not next to the ONT.
     

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