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Moca works without POE filter - Do I still need to get one?

Discussion in 'TiVo Roamio DVRs' started by The TiVo Dude, Dec 25, 2013.

  1. The TiVo Dude

    The TiVo Dude New Member

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    Jun 9, 2004
    So if Moca works just fine w/o the POE, do I need to add one for any reason?
     
  2. sjsaliba

    sjsaliba New Member

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    Mar 30, 2008
    My understanding is the purpose of POE filter is to prevent your media signals from transmitting back through your outside cable to your 'neighbors' cable.
    It took my about a year researching basically how MoCa works and how to successfully setup in my home. It appears to be working fine and I have POE installed on the main cable line coming into my home.
     
  3. dianebrat

    dianebrat I refuse to accept your reality TCF Club

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    boston'ish
    As sjsaliba says, it's not going to make a difference as to your network operation, but it blocks your data from getting out to your neighbors and causing issues with them. My dad did MoCA without a POE filter on cable and Comcast had complaints from the neighbors.

    If you're on FiOS, you don't need a POE filter since the cable does not leave the building, it comes from the ONT.
     
  4. k2ue

    k2ue Retired RF Engineer

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    Actually a POE filter will make a difference in your network operation -- it will strengthen the MOCA signal. Splitters are designed to have high isolation between ports, so when a MOCA signal needs to travel from a source on one output of a splitter to a destination on another port, there is rather large attentuation. Most of the MOCA signal will go back thru the splitter(s) in the direction intended by splitter design, and wind up dissipated (lost) in the line drop amp feeding your house. But when a a POE filter is present the MOCA signal reaching the filter is reflected by the filter, and propagates thru the system just like the cable signal, in the forward direction, reaching all points in the house with only splitting loss.

    With a MOCA filter the path loss between any two points is only the sum of their individual splitting losses from the POE (the trip from source to POE, then POE to destination), but without it will be the isolation value between the ports (typically >20dB) times the number of splitters to cross to reach the destination! And the wider band and higher quality your splitters, the greater the likely isolation (attenuation in this case).

    So it is always good to have a MOCA POE Filter.
     
  5. nooneuknow

    nooneuknow TiVo User Since 2007

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    Cox Cable...
    I couldn't have said it any better, myself! :up:

    It does make for a better MoCA network, to keep your frequencies isolated, stopping any from escaping outside your home (and stopping any that aren't yours from entering your home)
     
  6. HarperVision

    HarperVision TiVo's Italian Cuz!

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    Paradise...
    But what if you want to split your cable bill with your neighbor, so they can just throw a couple minis in their house to be a parasite off your Roamio Pro? ;)

    Great explanation k2ue!
     
  7. DCIFRTHS

    DCIFRTHS I dumped SDV / cable

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    The POE filter is designed to reflect the signal? How does it accomplish this? I always thought these types of filters greatly attenuated the signal they were tuned too.
     
  8. k2ue

    k2ue Retired RF Engineer

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    Simple LC (Inductance/Capacitance) Filters are reflective, and attenuate by refusing to accept energy in the rejection band. The illustrative analogy would be a rope tied to a wall: if we whip the rope to create a wave, the wave moves down the rope, is refected by the wall, and comes back to our hand. Absorbative filters, which only absorb and do not reflect, are more complex, requiring internal resistors as well as LC elements, and are almost never encountered in a controlled impedance environment like cable distribution, for the simple reason that the signals reflected by simple LC filters are absorbed on the first bounce by the controlled 75 ohm impedance of the connected device(s) -- it is only necessary for one end of a transmission line to be terminated to control reflections. It is a common assumption that everything connected to a transmission line system would be matched to it (completely accepting/absorbing all signals sent to it), but that is not the case, some devices do their job by simple rejection.
     
  9. nooneuknow

    nooneuknow TiVo User Since 2007

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    Cox Cable...
    I think this explains something that has been nagging at me for awhile (although has nothing to do with MoCA, since I already have gigabit infrastructure and Cat5e going to nearly every room). Although, I do utilize a MoCA POE filter at the drop (lateral-run entrance) point, since they came with my Tuning Adapter self-install kits, which were free.

    Moving along, attenuators were my savior, way back to the TiVo HD, and even more important for my Premieres. I used to seem to be the only one preaching how great they were, and how people should use them. After sharing my findings with TiVo, they updated their knowledgebase articles to mention them.

    Move forward a couple years, and SDV is being "deployed", meaning they were insisting we needed TAs, and right away, or lose many channels. I get them, set them up, and they merely gave Cox a way to read the signals remotely, for nearly 8 months, before they started shifting anything to SDV.

    Ever since they deployed TAs, attenuators were stricken, by my Cox market, as an acceptable means to reduce signal strength. All techs were instructed to remove them, on sight, and instead utilize more splitters, capping off any unused ports with terminators (the VERY tamper resistant type, which I just happen to have the correct tool to remove, if I need to).

    I've wondered what the harm is in attenuators, and what the gain was by installing more splitters. I think your explanation about reflection and termination, as opposed to absorption, answers that question. It's much better than a Cox tech/rep stating "All we know is that we are no longer allowed to install them, are to remove any we find, and resolve any excessive signal issues with splitters."
     
  10. k2ue

    k2ue Retired RF Engineer

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    There is no functional difference between an attentuator and a terminated splitter being used as an attenuator, except that the conventional attenuator probably has flatter frequency response. The isolation properties of the splitter have no significance when used as an attenuator. The only two explanations for insisting on splitters are either: a) obsessive standardization, seeking to remove attenuators from their inventory, because they can simulate them with splitters; or b) surprising ignorance of transmissionline techniques by someone in a position of authority.

    QAM stands for Quadrature Amplitude Modulation, and by its nature is sensitive to amplitude. So no piece of equipment handling a QAM signal should be driven to limiting -- the removal to the highest portions of the amplitude modulation. Accordingly, unless the manufacturer of the equipment specifically states that it can handle signals larger than its Signal Strength indicator's range, it is wise and prudent to reduce the signal strength to within that range, by any practical distortionless means -- attenuators or splitters.
     
  11. nooneuknow

    nooneuknow TiVo User Since 2007

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    Cox Cable...
    I really can't find anything I disagree with, in what you said.

    I can say that splitters provide a better, more consistent, overall level of attenuation from low frequencies, to high frequencies, while attenuators hit the frequencies harder at one end, while barely changing them at the other extreme.

    This all started when they went to a 1GHz RF network, and I honestly can say that attenuators would often "fix" problem channels, and "kill" ones that were working fine. I do get a better balance, now. Before they went to 1GHz, attenuators were something I couldn't live without, and also without a whole plethora of values to use (often changing to -6dB ones in the winter, and -3dB ones in the spring/fall, as well as none required in 113 degree summers).

    Cox refuses to fix the AGC (Automatic Gain Control) stress condition that is present on my end-of-the-line RF network interface, so rather than having their equipment compensate for the seasons, I have to do it myself. :mad: :rolleyes:
     
  12. k2ue

    k2ue Retired RF Engineer

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    Attenuators designed for current cable use will have very uniform attenuation from near DC to 1GHz or above. But there are plenty of attenuators around that were designed only for Outdoor Antenna use, either VHF/UHF, or worse VHF only, and they will indeed have erratic performance over various channels on a modern cable system. And certainly any attenuator purchased or deployed before 1GHz cable systems were widely deployed should not be used, as they simply were not designed for the job. But cable companies have a plethora of well designed products suitable to their purposes available now. Perhaps the move to splitters was based on not having to ascertain the quality of every attenuator they encounter, especially if many were deployed in their system before they increased their bandwidth. That would make some sense, as splitters are normally well marked as to their bandwidth, whereas attenuators are normally not so marked..

    Your cable signal should not vary significantly with the seasons, even at the end of the line. If it does there is something wrong the cable company should be fixing. Properly operating cable system equipment is moisture-tight and temperature stable.
     
  13. nooneuknow

    nooneuknow TiVo User Since 2007

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    Cox Cable...
    The attenuators I have been speaking of are not rated, other than the -dB ratings. They came off Cox trucks before 1GHz rolled. I always ask if they have any when they are out, and they usually just have the same ones, which they only have because they removed them. So, I think you are right in your assessment.

    Your assessment of my AGC stress condition, and change of the seasons adjustments are also correct.

    I get these lines from Cox:

    1. "We do not support TiVo"

    2. "We will not re-engineer our network to accommodate your TiVos"

    3. "You are at the end of the run, and the only customer connected to it. It is not worth re-engineering our network for one customer who uses equipment that we do not support"

    4. "You can not force us to fix anything we don't want to"

    After working my way up to high management, I was told this: "We do not have the power to force our network maintenance engineers to fix anything they don't want to. It is their call, and we can not override them".

    One time, when the maintenance engineer in charge of my network segment rolled up, he nearly slammed my hand in the truck door, and then sped-off, as soon as I answered his question of what equipment I was using. The answer was "Your cablecards used in TiVo DVRs".

    I complained to corporate, and hinted they were lucky I had good reflexes. I am now on some sort of blacklist of people not to engage, or talk to. Calls I place are supposed to be returned, but never are.

    After three years of getting these same lines, and this treatment, I'm done trying. I can get nowhere. The FCC would not help me, nor could TiVo. Now you know why I'm so angry sometimes...
     
  14. k2ue

    k2ue Retired RF Engineer

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    If I were you I'd be using a DirecTV Tivo in a heartbeat, and the hell with cable. Even if you still need cable for internet -- they have to fix the line if it won't run a cable modem -- that IS supported equipment.
     
  15. HarperVision

    HarperVision TiVo's Italian Cuz!

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    Paradise...
    Ditto
     
  16. nooneuknow

    nooneuknow TiVo User Since 2007

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    Cox Cable...
    I've already placed all my eggs in the TiVo Roamio basket. Done and done. I'm stuck with what I have (for many reasons, which I'll spare everybody the details on).

    Their idea of "fixing the line" is to swap out splitters to different values.

    If that brings my cable modem and Tuning Adapters within the acceptable signal strength and SNR, their work is done (going by their playbook).

    I think you've figured out I can do that myself. It's not worth the way they treat me, and setting aside a whole day for them to come, when I can do everything they can, except analyze the signal, say it shows AGC stress, tell me they will send maintenance, and then maintenance never comes, or leaves without doing anything (beyond the splitter swapping the techs already did).

    I've hijacked the thread. I did not intend to. Sorry everybody...

    I'll still be watching for on-topic matters, and will try to help and contribute, if I can.
     
  17. DCIFRTHS

    DCIFRTHS I dumped SDV / cable

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    Thank you so much for the explanation :)
     
  18. The TiVo Dude

    The TiVo Dude New Member

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    Jun 9, 2004
    And thanks to all for the great responses.

    Search is my friend, but I was still confused. No longer.

    I installed a POE filter yesterday.

    Thanks again.
     
  19. grey ghost

    grey ghost Member

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    Feb 1, 2010
    Where did you get your POE filter? I've been like you, my Tivo worked without a filter, so I didn't see the need to put one on. I guess I really need to go purchase one.
     
  20. k2ue

    k2ue Retired RF Engineer

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    Just search on MOCA filter on ebay, or you can order one from TiVo.
     

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