Can I get cable internet along with my DirecTV?

Discussion in 'DIRECTV Installation/MDU Discussion' started by wxman, Jul 5, 2013.

  1. HoTat2

    HoTat2 Hall Of Fame

    Nov 16, 2005
    You're most likely correct that a sat./OTA diplexer would prevent "interference" between the cable internet and satellite signals and I stand corrected on that point.

    But almost as bad instead it may prevent proper reception by the modem of the cable internet signal for DOCSIS 3.0 standard signals.

    As for a a similar DSL "training signal" phase for cable internet service I doubt that since whereas DSL uses a point-to-point type topology, DOCSIS for cable internet systems is a point to multipoint type where the CMTS at the CATV headend chooses the particular downstream and upstream frequency that many subscribers in a group use on a time-shared basis.

    Therefore if one of those subscribers assigned to a group with a given down/upstream frequency and is unable to receive the downstream signal because of a SWiM sat/OTA diplexer in line with the modem which blocks it, then that sub. will simply be SOL, and just not able to access the network.

    I know of no provision in the DOCSIS standard for the CMTS to make a special accommodation and change the downstream frequency just to suit one subscriber in a group with a reception problem caused by a component on the customer's premise. .
  2. slice1900

    slice1900 Well-Known Member

    Feb 14, 2013
    It would make for an interesting experiment to see what happens if you add a diplexer (used simply as a band pass filter as an experiment, without anything connected to the SAT side) to a DOCSIS 3.0 system configured to use frequencies above 900 MHz and see if it causes problems. Then try rebooting the modem and see if it clears the problems.

    What you say makes sense, but I wonder how well it would perform in practice to assume that all channels will work for all customers on the same node, given that the cable company has no control over how screwed up the cable plant inside people's houses is? It doesn't seem like it would be too difficult for a training phase to test the modem to head node connectivity for each modem when it is started up, and block the channels that have problems from being used for data destined for that modem. It is extra work, but when compared with everything the head node is doing already to manage connectivity for hundreds of attached modems it isn't that big of a deal.

    However, perhaps it isn't really a problem in the real world and that extra work isn't required. If the only time it would matter is if someone has a filter inline with their cable modem it isn't something they'll bother doing, they'll remove the filters instead. So I'd agree with you that diplexers shouldn't be used in this situation unless it could be proven/demonstrated that DOCSIS will work around the filtering.
  3. wxman

    wxman New Member

    Jun 7, 2010
    Yes I am paranoid! :grin: I've had so many problems with this house that I hate to tempt fate. It's not just the hole. Where I want the new hookup to be is upstairs on the back side of the house. The wire would have to run along one side of the house and halfway around the back then up to the second floor. I don't want that showing, even if I didn't mind another hole. (If the installer were to drill on the side of the house with the cable connection, he would have to go through a laundry room to get to the living room.)
  4. peds48

    peds48 Genius.

    Jan 10, 2008
    You might be surprised on how well tech can conceal these cables.
  5. Bill Broderick

    Bill Broderick Icon

    Aug 25, 2006
    Long Island
    Not necessarily. You said that your house is pre-wired for cable. Is there a cable outlet in the room where you want the cable modem? If so, and the pre-wire was done properly, the cable installer should be able to run the new cable to the exact same location where the beige wire already runs. The beige wire likely runs to a centralized distribution point where the various runs to the other rooms begin. The cable installer would just need to connect the new coax with the coax that runs to the room that you want the modem to be.

Share This Page

spam firewall