Archive for March, 2012

I wanted Ethernet in my living room. Under the best of circumstances, I was lucky to be able to stream 720p HD movies over wireless, but streaming 1080p was out of the question. Running ethernet to the living room was my first choice, but not convenient. DECA to the rescue! DirecTV Ethernet over Coax Adapter. Its exactly what it sounds like. It allows you to run Ethernet over the existing coax in your house. It’s very similar to MoCA ( Multimedia Over Coax Adapter). I had been looking at the Netgear MCAB1001, but at $90/pair , I started thinking about other options. I looked over at the network rack in my office, and saw a DirecTV provided box with coax on one end, and ethernet coming out the other! A few minutes of google-fu later, and it looks like my DirecTV DECA box is a lot like a MOCA box, but just uses a different frequency. And… They’re only $20 a piece on ebay! However, I couldn’t find a lot of statistics on the DECA. I wasn’t sure what kind of speeds I could expect, and I wasn’t sure if streaming movies would prevent me from using my whole home DVR.

I can now answer some of those questions!

Lets start with what my setup looks like:

* My whole house is wired with RG6

* I have a pretty recent SWM Dish. (Installed December 2010)

* I have 4 DirecTV receivers in the house. 2x HR24 HD DVR’s, and 2xH24 HD receivers (The HD Receivers can watch DVR content from either DVR’s via the Whole Home DVR solution).

* I started with a DECA broadband adapter (Part #DECABBIMRO-01), and then I bought another on ebay. They look like this, but less expensive when bought on ebay. I paid $19 for the first one I bought on ebay, and $12 for the second one.

* I added the new DECA Broadband adapter using a “green label” 2 way splitter. All of the other splitters in the house are also “green label”. If I recall correctly, these are about $5 each.


Setup is pretty self explanatory. Disconnect the Coax from the back of your Receiver/DVR, and put the splitter inline. The splitter has two outputs. The one labelled “DC Power Pass” should go to your DECA Broadband Adapter, and the other should go back to your receiver. Plug the ethernet into a switch on both sides (or into whatever you want, doesn’t have to be a switch), Power on the DECA device, and you are ready to pass packets!

I then ran iperf across the connection.The short version is that I got 100Mbps performance, even when watching HD content streamed from one DVR to another. Latency is very very low also.

I wrote the above about ~4 months ago, and never posted it because I wanted to show my iperf results. Since then I moved my mac mini and no longer have anything on the other end to run iperf to, and keep forgetting to plug my laptop in to test it so I can copy/paste the results. So I’m posting it anyway :) But, trust me, it works great. Latency is slightly higher than when running over standard cheapo switches – but only about 2ms higher. I’d call that a huge success.

Theres still a lot of unknowns here — I only know about my setup. I’m not sure how this would work with RG59 coax, nor do I know how it works with older dishes, or older equipment. But feel free to post in the comments with anything you learn.

Theres also security implications here — though IMHO, much less than with MOCA. In both cases you’re creating a bridge between their network and yours — in the case of MOCA you’re potentially opening up your LAN to the entire neighborhood unless you filter it. With DECA, you’re creating a bridge between your network, and the DirecTV satellite network, which won’t get beyond your satellite dish (since its a receiver only). I already had “their” Broadband adapter in my DMZ before I even realized everything it did. That does mean that I’m at a slight disadvantage in the way I do this, because I only have DMZ access wherever I use DECA’s to extend my LAN — but that’s ok with me.