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MoCA:Ethernet over Coax for your multimedia devices

August 1, 2010

Click diagram for a larger view

Home automation is about interconnecting and automating devices wherever they are throughout your home. Sometimes automation becomes a real challenge to implement–you can’t move the devices, you can’t get wires to them, and you want to control them from several other locations that also don’t have any infrastructure in place to support your efforts. 

Unless you designed and built your own home your sprinkler controller is probably mounted in some inconvenient place on a garage wall. Your thermostat is mounted exactly where you would expect it to be for properly sensing air temperature, but not where you would most like to control it . Most likely your TV and other multimedia devices are located wherever the builder chose to run your antenna coax, and your phones, if not cordless, are positioned wherever the same builder chose to place your RJ-11 wall plates. TV goes there, you sit here. End of discussion.

Lighting is one of the most common things to automate. Their switches are at least placed with some attention to convenience for the user, usually where the electrical code (and good practice) dictate. But they were wired, naturally enough, with only what was needed to make them turn on and off lights. You probably don’t have any extra wiring hidden in the walls, waiting to assist you in your quest for automation. 

 Whole-house automation control systems have to reach out and touch these things while also supporting new controls and user interfaces where you want them. Unless you are prepared to open up walls and add lots of new wiring, you will need to take advantage of every in-place or reasonably-priced signal path you have available—Wireless RF (as in WiFi, ZigBee, and Z-wave), existing AC power wiring, existing telephone wiring, existing cable TV coax, existing doorbell and security system wiring, etc. A comprehensive, highly distributed automation system may use all of these interconnect methods to communicate to all devices and endpoints. 

 Fortunately there are all kinds of ways to make use of existing communication paths for home automation without degrading their performance or interfering with their original purpose. 

 This post is about using your existing Cable TV coax to get Ethernet to multimedia devices- your TV, your Netflix-enabled blue-ray player, and your Media PC. I’ll write later about taking over unused pairs in your telephone wiring for other whole-house automation situations. 

 When wireless won’t do: Ethernet over Coax 

 One of the rules in the Unwritten Homebuilder’s Code is that no Ethernet-compatible twisted-pair wiring shall terminate anywhere near where any Ethernet-enabled media device will likely be located. Only Coax and no more than one Coax shall terminate in such locations. 

 The diagram at the top of this post shows one method I used to get wired Ethernet at several locations where I needed the bandwidth and reliability of a wired connection but had only the single Verizon FiOS coax cable feeding the Verizon set-top box. 

 The technology to do this comes from the Multimedia over Coax Alliance, or MoCA. They developed a way to superimpose IP traffic in Cable TV bandwidth without interfering with normal Cable channelization. If you have Verizon’s FiOS service you already have MoCA technology in use. The Verizon-provided Actiontec MI424-WR router injects IP onto the cable for use by the Verizon- Motorola set-top boxes. 

 You can extract Ethernet off of the cable for your Internet-enabled media or automation devices. If you have FiOS you need only obtain a MoCA Coax-to-twisted-pair converter and a compatible Cable TV splitter. D-Link, Netgear, and others make such converters, but they are fairly expensive. 

 The low cost alternative? Get another Actiontec MI424-WR  router just like the one Verizon installed. They go for as little as $10 on Ebay. Connect it as shown in Figure 2, turn off its WAN and its DHCP and routing features, and voila…you have four RJ-45 switched Ethernet ports AND an additional WiFi access point with its own SSID (you can turn it off, too, if desired). Nifty and cheap, and you can do this anywhere you have coax and need Ethernet. 

 I have the four routers shown to get wired Ethernet performance near my family room TV, my media room, the master bedroom, and one of the upstairs bedrooms. 

 Don’t have FiOS? Your Cable TV coax is not in use? Just locate an additional MI424-WR anywhere you have a co-located coax and Ethernet port. Use a splitter to inject Ethernet onto the coax if it is already in use for Cable TV. MoCA Internet traffic doesn’t seem to bother most conventional analog or digital cable TV systems, but be careful: cable systems that do not isolate incoming programming from house wiring may attenuate or in other ways not react too well to renegade MoCA traffic originating inside a home. 

You can learn all you need to know about ethernet-over-coax at the moCA website – http://www.mocalliance.org/ 

 //Mark

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From → AMX, Home Automation

3 Comments
  1. Good stuff. I just did the same thing to get Ethernet to my TV area. I did purchase a MoCA bridge from Actiontec that cost $77 if you can’t or don’t want to purchase the second router from Ebay (this assumes you have FIOS.)

    You can also purchase a pair of them if need be. Not cheap but not terribly so if you had to purchase a wireless bridge to do the same thing.

    Just make sure the splitter you use at the far end is capable of supporting two way signaling and a minimum of 1000Mhz. A lesser splitter could block guide or VoD data, or otherwise bork the signal to your FiOS or some other Digitial Cable STBs.

    • Excellent…glad to see other MoCA users out there. Seems to be a fairly well-kept secret, considering how many homes (in North America at least) were wired with coax-only where the TV would logically be placed.
      I had read that Actiontec introduced more MoCA devices but haven’t seen any at retail in my favorite haunts. Netgear has some available locally but rather expensive.
      I have tried some of the Ethernet over Powerline adapters. Worked OK, but as an Amateur Radio operator I quickly found them to be a disaster…splattered RF over nearly all of the HF radio band. Nasty little buggers. And they aren’t inexpensive, either.
      Wireless-n is good enough for HD if the network is well managed. Many of the newest media players and TVs have it built-in, so I’m not expecting many folks to jump onto MoCA if they are starting now with the latest gear.

      I used a Motorola MoCA-Ethernet box for awhile that had coax loop-through, eliminating the need for an external splitter. And you are quite correct about the choice of splitter, it does need to be two-way and have sufficient bandwidth. I was able to find some that were labeled with these specs, I think it would be safe to say that if it isn’t labeled as 2-way and >1000 MHz, don’t use it :-)

      Thanks for your response!
      //Mark

  2. Great site. A lot of useful info here. I’m sending it to several friends ans also sharing in delicious. And naturally, thanks for your sweat!

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