[NA] Ethernet over Coax

Discussion in 'Technical Corner' started by weilke, Jan 15, 2012.

  1. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    I have my home-office in a basement guestroom. This is also the room with the central electrical panel and where the cable-TV and satellite wiring come together. The cable modem that I use for primary internet access is located in that room and hardwired to it a firewall that I use to create a satellite to the main-office network. Now I need to create a wired connection from the 'safe' side of that firewall to two other rooms in the house. Wifi is out and I am not so thrilled about using an ethernet-over-powerline adaptor as the one I have is rather slow and not terribly robust (needs occasional re-setting to maintain its speed). The design of the house doesn't lend itself to the stringing of cat5 without having to drill through concrete and rafters. So if I could make use of some of the otherwise idle coax runs to carry network traffic it would really make my life easier.

    Does anyone have experience with consumer grade Coax MoCA adaptors (or any other method to feed ethernet via coax) ?

    What brands to use ?

    Any security issues to be aware of (is there a way to create 'pairs' of transmitters that only talk to each other) ?

    Thanks.
     
    Last edited: Jan 15, 2012
  2. denverpilot

    denverpilot Tied Down PoA Supporter

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    First question: Physical Layer

    When you say "come together" are there individual "home-runs" to every co-ax jack in the house that all come back to a junction panel in that room, or is the house a series of one-room-after-the-other T-connections?

    Re-using the co-ax cable is maybe possible if they're all individual circuits and you don't have to share the TV signals to places where you also need Networking. Multiplexing the TV signals and the Ethernet (or other protocol) is trickier. Are there already unused co-ax jacks where you need to go?

    I've never had great luck with those either. Some people do. Mine are sitting in a box in the basement un-used after trying them for a while. (They also make a hell of a racket on some Ham Radio HF bands and I didn't really want to add to that bigger picture problem. "Broadband over Power Lines" being mentioned in most Ham Radio groups will get you shot.)

    How about access to return air ducts? Ethernet is low-voltage and in almost all cases, it can be run INSIDE return air ducts. I recommend that to people in older houses.

    It works well to get from floor to floor, and you can "pop out" to closets, etc... usually it's fairly easy to find a way to get from "here" to "there" via return air ducts. Plenum-rated cable, and if you're a geek/picky about things, a little fire-stop putty to seal up the ductwork wherever you pop in and out of it.

    Don't use forced air ducts though, I believe in most places that even having low-voltage electrical running through them is a no-no, per the electrical code.

    I'm no electrician, but I've seen both done. If the forced air ductwork gets hot enough to melt Plenum-rated Ethernet cable, that's definitely not a good thing.

    One common method I've also seen is to go up a return air duct, as high in the structure as you can, then pop out the top and continue up the wall into an attic above the living space, after drilling a hole in the header at the top. Then pop back down into closets or into upper story walls from above.

    Haven't needed to use them.

    Typically no need.

    Twisted-pair cable is intentionally "leaky" and signals in theory could be read inductively by just putting a device around the cable itself. If someone has that kind of access to your house, there's easier ways to get your data.

    Co-ax is designed to keep signals inside it. The outer conductor is called a "shield" for a reason.

    Can't really recommend a product for the link layer conversion, but I haven't run into a house yet where UTP runs couldn't be made... just have to be a little "creative". And yeah, it's a bunch of work.

    There are companies who'll do this type of thing... they'll come in, you tell 'em where to put the main patch panel, and they'll put jacks in every room with four or so RJ45 connectors, or a combination of RJ45 and co-ax connectors fed with 75-ohm (TV) co-ax. They figure out where the holes need to go, and patch things up pretty nicely so you don't see the mess.

    There's one run of both Ethernet and co-ax from my basement to the living room. The former owner found a spot between joists from the basement and drilled through the overhead drywall, right up through the floor in a corner of the living room. He put up some little square conduit on the ceiling along a ridge where heating ductwork lowers the ceiling to hold the cables, and it looks fine for a basement. Can hardly tell it's there.

    In the living room, it comes out behind the entertainment center, so no one sees the small hole in the hardwood oak floor.

    Originally it was just co-ax... and since there was some extra, I just taped some Cat 5 or 6 (whatever I had) to the co-ax and used it as a pull cable to pull up the Ethernet and then crimped on the RJ45 once it was up in the living room.
     
  3. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    There are individual runs from the panel to each room that has a coax jack. The ones that have satellite boxes are connected to the sat 'switch' with a 4-way splitter. The rooms that dont have a sat box are simply loose ends.

    I dont have a TV in the upstairs office, so no need to 'share' the coax between sat/cable and network (which seems to be the claim to fame of the MoCA boxes).

    The basesment is completely built out, any place I want to get to the return, I have to start cutting drywall. Not in the mood for that.

    I faintly remember using coax with BNC connectors to build 10baseT office networks back when dinosaurs roamed the world and a megabyte was still considered 'data'. Twisted pair was some newfangled thing that you used to connect more expensive hardware.

    Shouldn't it be possible to simply connect the coax to my router using a RJ45-coax adapter and the upstairs PC using a coax-RJ45 adapter ?

    Oh sure, just add money. When we built out our office, I had a guy do the cat5 wiring to a patch panel in the computer closet. That was as simple work as it gets on top of a hanging ceiling and before the walls were closed in. But if I multiply what I paid for that with the size of my home.....

    My previous home was owned by microsoft engineers before I bought it. That place was wired like an office-building with dual RJ45 jacks in a number of rooms and a spot in the 'gun room' that held one of those internally cooled 19in racks with their various network components and servers :yesnod: . Wasn't included with the sale though....
     
  4. SCCutler

    SCCutler Administrator Management Council Member PoA Supporter

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    I know it can be one, because AT&T runs the Uverse tv and data through the existing coax in my house. Works fine.
     
  5. JeffDG

    JeffDG Touchdown! Greaser!

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    When I saw the title, it took me back to old Thinnet and Thicknet coax...ahhhh...memories.
     
  6. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    Verizon does the same thing for FIOS-based home networks.

    Look up "multimedia over coax alliance" for the standards on this.
     
  7. jtheune

    jtheune En-Route

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    I think I may have a vampire tap stashed away somewhere ...
     
  8. JeffDG

    JeffDG Touchdown! Greaser!

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    You have the big loops of cable on the wall?.

    One of my favourite stories was when a client unhooked his 10-Base-2 connector from his Compaq Luggable (remember those), and dropped it behind his desk...across the slightly exposed prongs of his plug-in...110VAC through the whole network...killed just about everything!
     
  9. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    They use those MoCA boxes, the only problem I see with them is that they are $100 and up per box if you buy them at the consumer level.

    I had Fios at one point and they used the coax as well. Never worked at the fiber level, so I cant say whether the MoCA thing worked.
     
  10. flhrci

    flhrci Final Approach

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    One other option if you do have unused coax lines is another cable modem on each one depending on how much the cable company would charge you or modem and router on one with a shorter run of ethernet to the other room. Just a thought.

    Used to work cable tv so I have seen multiple modems on one account.

    David
     
  11. gkainz

    gkainz Final Approach

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    My token ring rolled off into the bit bucket, otherwise I would donate it to your efforts. :D
     
  12. mikea

    mikea Touchdown! Greaser! Gone West

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    Use the Google, Luke. There are some ActionTec routers that have MoCA that go on eBay for ~$24. You need at least two. Verizon used to install them.
     
  13. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    7 bucks per modem. Wouldn't help me to get the 'inside the firewall' connection to the upstairs office though.
     
  14. denverpilot

    denverpilot Tied Down PoA Supporter

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    Nailed up SSH tunnel. Free. Some assembly required.
     
  15. John221us

    John221us En-Route

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    I think 10Base2 (thin Ethernet) was RG58 and Arcnet was RG62. I think I still have some of the connectors and terminators, but you would need an adapter. It couldn't be that hard to get UTP down there. Cutting drywall is no big deal. Just get a plastic jbox and cut it in. You can always cover it with a blank plate.
     
  16. Old Geek

    Old Geek Pattern Altitude

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    Cable TV coax is 75 ohms and thin Ethernet is 50 ohms. I still suspect a short run will work though.