Sunday, August 19, 2007

Installing DSL splitter in phone box

The phone wiring in my house is fairly ... adventurous. Obviously, various previous owners added to the existing cabling by running new cables, as well as extending from one jack to somewhere else. There doesn't appear to be any ryhme or reason to where you might find a phone jack. My master bedroom has 4 jacks nailed to the baseboard in various locations. Three of those jacks are even on the same phone line.

All this crazy wiring is adding echo effects that are less than helpful for DSL. DSL, like any digital signal, likes sharp edges and not blurry, echoy, line noise. Less outlets should translate to higher DSL speeds, because the digital signal is not as much degraded. Also, every jack that shares the line with the DSL signal, needs to have one of those DSL filter pigtail thingies plugged in, which tend to look ugly or be great toys, depending on who you ask. All good arguments for trying to install a DSL splitter as close as possible to the phone network hand-off point also known as demarcation point or "demarc". On the right is a typical phone network termination box as installed by Pacific Bell/SBC/AT&T for a while now. On the left is the original box from when the house was constructed.

The neat thing about these new boxes is that they have a RJ11 jack for your phone handset for each line, so it's easy to determine whether a problem is due to inside wiring or a problem for the phone company. There is some space in the customer accessible, lower half of the box where I'm going to put the DSL splitter.

Here is the splitter I'm using. It came with the house, i.e. the previous owner used splitters wherever they needed to terminate the DSL wiring. I'm not quite following the logic behind that, but oh well, easy enough, I didn't have to go out and get a splitter. It has a RJ12 jack on one side for the line to the phone company, and two RJ12 jacks on the other side, one for the DSL line, and one filtered for the phone line.

Here's everything put together. As you can see there is some space, but not a whole lot. Actually, it's quite tight. I didn't take a photo of my final arrangement, where I moved the splitter to the left half of the box in order to be able to close it reasonably weather tight. We'll see how this goes. If it becomes a problem, I'll place the splitter in the old phone wiring box, but so far it looks and works just fine.

When I moved in I measured DSL line speed according to Broadband Reports at 4.2MBit/s down and just over 600 up. With the splitter in the phone box, I now reliably get 4.9 MBit/s down and still around 600 up. Depending on the remote site, time of day, etc. some test sites even gave me 5MBit/s down.


Peter said...

Nice job. I did the same thing with my DSL line to put the data signal on it own pair. When one of the phone company's techs saw it he said that those little indoor splitters don't provide "strong enough" filtering for use in the box and that I should buy one of the bigger filters designed for such use. I've never heard of strong vs. weak filters. Either it filters at its corner frequency or it doesn't. The roll-off may be steeper on a more expensive filter but I don't know that I'd call that stronger. Then again, these are the guys who spent three months debugging my line that they provisioned too high to begin with (despite my telling them numerous times that the noise level on the line was way too high). Anyway, my filter's been working fine for years.

Bernhard said...

Heh, yeah, I thought of you and your troubles when I wrote this. There are various "professional" outdoor splitters at $50+ a piece. Their main advantages are better electronics and usually a ruggedized case, but I didn't see the need to spend that money unless I actually have a problem I can't solve with the splitters I have (and I have a few now...)

Peter said...

Yeah, since the splitter fits inside the box, it should be OK especially since we rarely get fog.