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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. webin

    webin New Member

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    Feb 13, 2008
    Hillsboro,...
    Lowes stocks diplexers for $8.98, and F-Terminators for $2.97/4 or $5.97/10.
     
  2. webin

    webin New Member

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    Feb 13, 2008
    Hillsboro,...

    This doesn't seem to affect my pixellation at all. This is the diplexer Lowes sells: http://www.idealindustries.com/prodDetail.do?prodId=85-323

    When I hook it into my coax line just before the tivo, in either direction, it seems like it has zero effect on pixellation. It's actually worse than what I'm currently using... a 4-way splitter (5-900 mhz) and 6db of attenuation. I am using the splitter for the simple fact that it provided the female connection I needed to hook in the attentuator, but I'm thinking it may be helping block the moca too. I'd say this setup blocks 90% of my pixellation, so I'm not sure why I'm even playing with the diplexer.
     
  3. mbhuff

    mbhuff New Member

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    New York
    As been mentioned before, but easy to miss, even though a splitter is only rated for 5-900 mhz, that just means that's all it's designed for. It doesn't mean that it will definitely block everything >900 mhz. A diplexer or low pass filter is designed intentionally to block all signals > 860 or so. I diplexer or low-pass filter is only needed if it's possible that a MoCA signal (ethernet over coax cable) is being sent along the line.
     
  4. mulscully

    mulscully Member

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    May 31, 2003
    Malvern, Pa
    ok, last night out of no where massive pixellation snr all over the place 31 - 76 and signal strength jumping 45-95. all on 810 NBC Philly Area - channel 817.. as a matter of fact I noticed all the channnels pixalating were in the 500000khz area.. other channels were fine.. Added diplexer - no help - disconnected Moca - no help, reconnect Moca, left duplexer in and added 13 db of attenuation - FIXED..

    unless I missed it somewhere I think we should be trying to figure out if it is a freq range with the issue.. I know FIOS has been doing channel reallgnment, so not sure if 810 - 817 were in the 500000khz range before reallignment.. Maybe the Tivo is particularly sensitive within a freq range.. Maybe I did not notice it before because the pixalation was on channels I don't watch....
     
  5. hmm52

    hmm52 New Member

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    Feb 25, 2008
    Lower...
    TiVos are sensitive to signal but not within specific frequency ranges - in my experience. When Verizon's signals are off, as they have been on the local HDs for past 5-6 weeks, I see it on both an S3 and Toshiba cablecard TV, same channels. Locals are notorious here VHO8 Phila., Ambler CO but 3 prior months were solidly fine - no antenna or attenuators needed. (5-600Mhz range for locals also; same place as always). 14db currently clipped in at back of S3. 8db on Toshiba. All's well. For now.

    Major addition of channels is yet to come -- unless I missed it. Been overseas for awhile experiencing the incredible shrinking dollar.
     
  6. webin

    webin New Member

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    Feb 13, 2008
    Hillsboro,...
    Nope, hasn't hit you in PA yet. I think you're looking at early September.


    Tonight when I get home from work, my plan is to get the Fiber Solution Center to disable MOCA on my ONT, enable Ethernet, and break my IP lease. This should (in theory) get me back online, but with no MOCA signals on my network. If my light pixelation continues, then we'll know it's more than just those frequencies causing interference.


    ~~~~
    Update: It took the FSC tech guys about 10 minutes total to get my requests taken care of. At this point, my internet is over Ethernet, and there should theoretically be no MOCA on my network. On the ONT box, the Ethernet light is on, and the MOCA light is off.

    I'm still seeing very light pixelation on my worst offending TV channel. Previously, I was using 6db of attenuation, and right now I'm using none. I'd say it's comparable, or a little worse, than what I experienced with 6db of attenuation. I'll keep an eye on it and add a little attenuation back (or play with the diplexor) to see if I can knock the pixelation down to nothing.

    (This test has proven that the MOCA signal may be a contributing factor, but isn't the sole culprit.)
     
  7. mulscully

    mulscully Member

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    May 31, 2003
    Malvern, Pa
    update: after attentuation all is well with that Tivo... had Verizon install another set of CCs in a new tivo.. Both Tivos are hooked to the same splitter (only 2 things on that splitter) 1 tivo needs attentuation, other is fine without it.. Go figure....
     
  8. webin

    webin New Member

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    Feb 13, 2008
    Hillsboro,...
    See.. that's an interesting observation. To me, that says that the source of the pixellation is inside the tivo box, and varies from box to box. It makes me think about manufacturing tolerances and how one box could have a "weak link" that is introducing the pixellation (which I'm thinking is related to radio frequency interferance). I guess Cable Cards could also be the source, but I'm less electronically inclined to know how.
     
  9. Aug 7, 2008 #289 of 866
    johnhab

    johnhab New Member

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    So I'm in Northern Virginia and got FIOS about a 4-5 weeks ago. The guy came in, got the cable cards set up and it worked flawlessly on my S3 for 2 weeks. After that, well beyond pixelation, I would get virtually total un-usability (box would not respond to remote, would lock up and reboot by itself, etc.). Thought it was a bad hard drive but still talked with TiVo support and they concluded it was the strength of the FIOS signal (box works fine when you remove the input).

    So I've read most of this thread and went out and got the SmartHome attenuators and a diplexer. Through trial and error I estimate I need something like 28dB of attenuation (I have to split my signal and the splitter output is -7dB), but I cannot generate that exact number (21dB) with the SmartHome attenuators as the smallest increment they have is 3db (22dB cards can't tune, 20dB box operation stutters, see below), so a bunch of questions:

    1) Given my attenuation guess above, does anyone know of a place on the net that sells 1 and/or 2db attenuators, or alternatively a variable attenuator like Radio Shack used to sell, but has decided that it doesn't carry anything useful anymore (yes sarcasm but I don't understand why someone would go to RS to buy a cell phone or stereo when there's 10 other places much better suited to do so).

    2) In doing my testing I either get 29-30dB of S/N, which gets me fine reception on SD channels, but HD either doesn't tune at all or is pixelated, with signal strength of about 45. If I drop attenuation the smallest increment I can (22dB to 20dB), I then get 31-33dB S/N, signal strength jumps to 55-60, but then the box starts to choke (the background routines start to stutter, remote commands begin to not be acknowleged, etc.). Do I have any hope of getting a satisfactory result if I can change my attenuation by 1 or 2dB? My box seems extremely sensitive/to have a very narrow range in which it might work.

    3) If I have Verizon come out and reduce the signal strength at their closet, will that help my cause as I won't have to attenuate the signal so much that I begin to lose reception completely? Most of the #s I've seen in this thread have been in the teens or lower, not 27dB.

    4) Also I notice that one cable card usually has a slightly lower S/N than the other, e.g., one will have 31 dB S/N, while the other has 30dB, and also the signal strengths differ by 3-6 (not sure of SS units). Is that normal? Should I ask Verizon for another set of possibly "better matched" cable cards?

    5) Sorry if this is stupid question, but when I went on SmartHome and bought the attenuators, one of the "customers who bought this also bought" items was a tilt compensator? Would that help in this case by "leveling" the attenuation across the frequency spectrum such that HD channels won't cut out when the right S/N is achieved?

    6) I'm sorry but I haven't seen in the thread what ONT and MoCA means? Could someone decrypt the acronyms for me?

    7) Any other recommendations? After hours of fruitless trial-and-error I was seriously ready to take my S3 and throw it out the window -- but fortunately came to my senses! ;-)
     
  10. Aug 7, 2008 #290 of 866
    wmcbrine

    wmcbrine Ziphead

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    ONT = Optical Network Terminal -- the big box on (probably) the outside of your house. This is where the laser is.

    MoCA = Multimedia over Coax Aliiance -- this is the system Fios uses to send TCP/IP over your coaxial TV cables. It's used between the Verizon set-top boxes and the router, and (often, but not always) between the router and the ONT.
     
  11. Aug 7, 2008 #291 of 866
    johnhab

    johnhab New Member

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    May 14, 2006
    Thanks, that info helps. I'm in a large condo building, so I'm guessing the ONT is in a closet somewhere in the building. Verizon gave me two boxes within my unit: 1) a ZyXEL VDSL modem and 2) a 3rd-party wireless router that is Verizon branded. The tech said something like the VDSL modem was for pay per view/on demand stuff, but I don't remember exactly.

    So ONT was previously discussed because either 1) the best solution is to decrease the signal at the ONT and/or 2) attenuate it there vs. within my unit?

    And MoCA was discussed because the frequencies employed/signal strength/other characteristics of this system are wholly/partially the root cause for the TiVos overloading (aside from the TiVo circuitry issues mentioned)?
     
  12. Aug 7, 2008 #292 of 866
    webin

    webin New Member

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    Feb 13, 2008
    Hillsboro,...
    I'm sorry to hear you're having such a rough experience Johnhab. Have you looked around the forums to determine if you are having the "S3 pixellation/stuttering/rebooting" issues? I don't know much about them, but having your TV signal go from perfect to crap after 2 weeks makes me think it could be the box just as much as it's the signal (and "works perfectly when source is unplugged" is something specific I've heard from that line of troubleshooting).

    If it IS the FiOS signal, I've never heard of anyone needed more than 20db of attenuation, and most are much lower (I use 6db). You'd be the worst on the forums :) I have no idea what a tilt-a-whirl is, but I'd definitely recommend having a FiOS tech come out to troubleshoot your connection. They can use their equipment to check signal strength coming out of the ONT, as well as what's coming out of the wall by your TV. They should also definitely install a "low pass filter", which could presumably help somewhat. If you convince them that the issue is with their signal, you may/should be able to get them to do the service call for free.

    Good luck!
     
  13. Aug 7, 2008 #293 of 866
    SeanC

    SeanC ECT

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    I live in a condo and have exactly the same system. Because we have Zyxel modems we don't have to use the Verizon router (probably an Actiontec MI424WR), thus eliminating MoCA, because our internet comes from the modem and not the router. This only works if you aren't using Verizon cable boxes, which I am not, so I gave the heaveho to the actiontec, I still need to attenuate my signal though to avoid pixelation.
     
  14. Aug 7, 2008 #294 of 866
    hmm52

    hmm52 New Member

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    Feb 25, 2008
    Lower...
    It would be helpful if all FiOS TV users had the area in their profile; better yet their CO, central office. I've used FiOS TV since 11/06 and believe that signal problems are directly related to the VHO and CO serving you; occasionally the faults might be on the house or street level; never in my case. Varies month to month, and sometimes hour to hour. First tile not seen until 7/07, accompanied by a million friends; second catastrophic period was in 11/07 - always on Toshiba cc TV, not the Sony cc devices. Also seen by many, not all, served by VHO8 (Phila) at those times with VZ's own Motorola boxes.

    I've only seen reboots clearly caused by signals once. This was my fault as I had a distribution amp in antenna setup that was too much for the S3 and seriously interfering with tuner 0's QAM tuning, but not tuner 1's. When gain at ant. dist. amp was decreased or ant. coax removed, or QAM channel changed to an easier one, nasty reboot cycle stopped. But I've never needed anything near 28db of attenuation to eliminate pixelation. As others have said, there may be variation in tuners from TiVo to TiVo. The tuner is not their strength. 14db att. is where it's at now during a rough patch.

    Your starting point should be the signal level at coax end before TiVo. VZ tech can check this. VZ's recommended range is 0-6; for TiVo it should be 0; db or dbmv or something else I don't know. Tech should also give you a bunch of attenuators. VZ's are 3,6,8 and 9db I think. Should be all you need if you have enough of each.

    I don't like splitters inline, especially for devices very sensitive to signal, so avoid them. Better to have straight shot to VZ splitter near ONT. If you do it yourself, Lowe's has the tools, cable, and terminals you need (pass on the Phillips ends though). Care required with shielding and center wire protrusion should be minimal.

    Verizon installed a Low Pass Filter with other things 11/07. When pixelation returned in June after a perfect two months, I tested it in and out. In my setup it made no difference whatsoever to pixelation but I have little to no MOCA activity in house. I have since sent it to NJ FiOS TCF member. It made no difference in his case either but don't know his MOCA status.

    Early in the pixelation threads, there was discussion of tilt compensators. I don't remember anybody using them successfully. In the end it is Verizon's problem and their responsibility. TiVo owner's shouldn't have to do more than use a modest amount of attenuators from time to time. VZ is capable of providing a quality signal for extended periods of time. With some VHOs and COs, that's all they provide. In other areas their feeds fall into the ditch for short and long stretches. They need to be told this by customers even if it's a PITA for us. Much patience required as only the top techs and "Big Bosses" have the ears of the CO, maybe VHO. - my experience. When problem reaches them, resolution can be very quick - 24-36 hours.

    Antenna should be an easy alternative to attenuation if your pixelation is just on the locals. - common

    I've used up to 5 cablecard devices since '05. They are used for decryption, then display obviously. But I don't believe they make a bit of difference to tuning. When the cards are pulled, the diagnostic values, SS, SNR etc., remain exactly as they were. Same for premiums not in your package; they are tunable but not available to watch without authorization. The exception in my memory being SA cards years ago which had electrical flaws that necessitated modifications to Sony HD DVRs that had to use them because of provider.

    Good luck
     
  15. Aug 7, 2008 #295 of 866
    johnhab

    johnhab New Member

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    May 14, 2006
    But SeanC I have the ZyXEL but failed to mention that I also have a Verizon HD/DVR box as well (which has worked fine thus far), so that is inconsistent with your setup.
     
  16. Aug 7, 2008 #296 of 866
    johnhab

    johnhab New Member

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    May 14, 2006
    Thanks webin. No I haven't looked at those separate issue(s) because as I said I originally thought it was a bad hard drive but went through the diagnostics with TiVo support and they said since HD/other content played back fine when the cable wasn't connected, it almost certainly wasn't the HD, but the fact that the box locks up due to the overwhelming strength of the FIOS signal.

    Yeah unfortunately I'm coming to the conclusion that I'm going to have to have Verizon to come out again to fix it or at least get it to a point where the signal is at a level where I could fix it with what I have at hand (i.e., not having to attenuate the signal 27dB!).
     
  17. Aug 7, 2008 #297 of 866
    SeanC

    SeanC ECT

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    Yeah, I thought you might have a Verizon box. Oh well.
     
  18. Sep 9, 2008 #298 of 866
    lrhorer

    lrhorer Active Member

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    So in other words the Verizon representative lied to the subscriber.

    In fact, I am sure you are correct. The specifications for signal levels at the ONT have probably not changed, and it is somewhat unlikely there was any neighborhood wide change in levels at any time since the delivery of service.

    'Total horse pookey. There are hundreds of other things which can be causing the problem, over a dozen of which are extremely common.

    It doesn't mean you know what the hell you are talking about. Where and when did you get your engineering degree or NSCTE certificate?
     
  19. Sep 9, 2008 #299 of 866
    lrhorer

    lrhorer Active Member

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    Surely. Anything in the signal path can adversely affect it.

    One card, or one tuner? It could be a symptom of any one or more of them being bad or something else. You need to narrow down the symptoms a great deal. Do you have an M-card or two S-cards?

    You need to determine what the actual levels are. Once that is done, you can determine if attenuation, amplification, or equalization is appropriate. Until then, there's really not much definitive which can be said.

    Did he read out to you the actual levels of a number of carriers in the spectrum? We need hard data before we can really talk about either likely problems or solutions.

    No, first you need firm signal level data at the output of the ONT and at the back of your TiVo. Make sure all connections are tight (not too tight!) and al the connectoirs are properly crimped. Unless you are a champion weightlifter, you should be able to take the cable (not attached to any device), grasp the connector in one hand and the cable in the other and pull as hard as you can without the connector coming off in your hand. The connectors should thread easily and snuggly all the way down on the splitters, termination bocks, etc. There should be no evident cuts or kinks in the cables. Any cable which was at one time severely kinked should be replaced - the kink may have cracked the shielding.
     
  20. Sep 9, 2008 #300 of 866
    lrhorer

    lrhorer Active Member

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    That is an awful lot. I'm not saying it's impossible, but it's a lot.

    I don't follow you, at all. What is the output of the ONT at the lowest frequency (55 MHZ) and the highest frrequency (850MHz) carrier? How many TVs do you have? What are the cable distances to the TVs? What was the measured signal level at each set? An exact amount of attenuation is not necessary. The TiVo will receive signals across a wide range of levels. They just need to be fairly flat, no more than 1000MHz in frequency, within the receiver's sensitivity range, and not exceeding in total power the receiver's maximum limit. I don't recall the TiVo's actual sensitivity specs, but a full spectrum with no carrier much higher than -10dBmV and no carrier lower than -20dBmV should be fine.

    It is not necessary to maintain levels that closely. a variation of +/- 5dB should not be significant if all levels are appropriate.

    There is no difference between SD carriers or their reception and HD carriers. Indeed, the most common deployment in CATV systems is 2 HD channels and 1 SD channel per QAM. It's possible your FIOS system might be putting all the HD channels on one set of carreirs and all the SD on another, however. With more than 130 carriers capable of handling more than 150HD channels and 750 SD channels simultaneously, at this point in time they can dedicate channels to one or the other if they so choose.

    No, there's definitely something else going on. While it's true the large number of carriers greatly reduces the dynamic range of any receiver (by 22 dB for 133 carriers vs. 1 carrier, to be exact), the TiVo's dynamic range is much greater than that. Off the top of my head, I'm wanting to say the maximum input power to the unit is something like +13 or +16 dBmV, I think. Maybe someone else has the actual specs handy. For a perfectly flat spectrum of 133 carriers, that's a signal level of -9 or -6 dBmV for each carrier. I also don't recall the maximum sensitivity of the TiVo tuners, but it should definitely be something below -20d BmV.

    Attenuation is attenuation. It doesn't make any difference where it happens, unless your system is susceptible to some sort of ingress signal. In that case, attenuation may not help at all, and in any case you are better served attenuating the signal at the receiver. Then only exception is if the ONT itself is producing large amounts of intermodulation products ecasue of levels being too high. Such is possible, but not likely unless the signal levels are close to or exceed 35 dBmV for any carrier or 50dBmV total.

    The CableCards have nothing to do with signal levels or S/N. They do not receive the RF signals. They receive the demodulated signals from the tuners after passing through some number of logic stages. Noise in the tuner sections can and will produce errored bits in the digital signal stream, but the signal level and noise level of the digital bit stream is fixed by the internal circuitry and is not affected by any external signal.

    One is not trying to obtain a "right" S/N level. The higher the S/N ration, the cleaner the signal, period. Unfortunately, while the S/N level in a system increases one-for-one with increasing signal levels, the 3rd order distortion increases 2 dB for every 1dB increase in signal level. Every signal transmission is a trade-off between S/N and distortion. Unfortunately, the distortion also increases with the number of carriers, so a very wideband spectrum must be transmitted and received at a much lower level than in a more narrow bandwidth system.

    To answer your question, however, it depends on the actual signal levels with which you are dealing. The "tilt compensators" you saw mentioned are probably designed to attenuate the lower frequency carriers more than the high frequency carriers. This, to make up for cable loss in faqirly long cabe runs. It is likely, hgowever, the FIOS system may put out signals with a deliberate tilt, the high end in frequency also being higher in level than the lower end of the spectrum. If this is the case, then unless the signal passes through a fairly long run of cable, then probably not. Indeed, just the opposite may be the case, and if indeed the FIOS spec is for a 7 - 10 dB tilt from the low end to the high end, it may be necessary to run the signal through 100 feet or so of RG-6 to bring down the high end a bit.

    The absolute optimum is for every carrier to have precisely the same signal level at the receiver, but in practice this is never the case. Things will work perfectly well, however, as long as no carrier is too much higher than any other. A good rule of thumb in a system like FIOS with up to 133 carriers is no carrier should be more than 7 dB higher than any other. In some cases this may mean adding a tilt compensator if the lowest chanels are too high or in the opposite case running the signal through a few dozen feet of extra RG-6.
     

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