The Last 50 Feet – The Phone Line

In rural North America, the most prevalent form of internet connectivity is via DSL, which leverages the existing telephone system copper wires that go to most homes. The telephone company / Internet Service Provider (ISP) typically sells bundles of telephone service and internet access to their customers. The ISP is generally responsible for the lines up until the demarcation point via a Network Interface Box (NIB) on the outside of your house. From that NIB on, the wiring is under the homeowner’s responsibility. And it is this area we will focus on, as there can be many challenges to overcome.

Keeping in mind that the telephone wiring in most homes is based on standards and practices from over 50 years-ago, it should not be surprising that trying to overlay a high-speed digital transmission over it could run into some issues. The biggest one is line noise caused by cordless phone base stations, fax machines, that old Ma’Bell phone and the DVR all plugged into a very long string of wire running through the house. The quality of that wire is designed for analog voice frequencies, not for high-frequency, high-speed digital signals, so losses in level combined with a loss of quality can dramatically cut down the speed at which a DSL modem can operate.

If done absolutely right, this can work, but the problem is, it quite frequently is not, so we need to pay attention to our wiring to ensure we get the internet service we pay for. There are two approaches here, the first is to split the DSL line out before it even gets to the home wiring, and the other is to follow some recommendations on checking and improving the wiring you use today.

If you really care about the quality of your internet service, then my strongest recommendation is to get a competent tech or the ISP to install an outdoor DSL splitter near the Network Interface Box (NIB) and run the DSL line on a CAT5 cable to wherever you want the modem located. Then terminate the CAT5 into a surface-mount RJ-11 box that you will plug the DSL modem into. This will ensure you have the cleanest, most isolated DSL signal possible and should allow you to get the maximum speed. Many have even been able to upgrade to the next speed tier from the ISP after this change.

Here are some tips for those that plan to continue sharing the telephone line with the DSL modem. 

  • Double check that all connected devices (like fax machines, DVRs, cordless phone base stations) have a DSL filter on them
  • Make sure all devices and cables are well plugged in, a loose connection generates noise which can interfere with the DSL
  • Make sure the wire between the wall jack and the DSL modem is fresh, as short as possible and well connected

If your speed test results show upload rates of less than 300Kbps (0.3Mbps) you likely still have a wiring issue, so one final test is to unplug all other telephone-line connected gear in the house and see if that allows the speeds to get back over 500Kbps on upload. If it does, then one of those phones or devices is creating interference. If you can’t isolate which one, then installing the splitter recommended above would be the way to go.

You can get objective metrics on the state of your line by looking at the right pages of your DSL modem go to the WebUI for your modem (varies by vendor/ISP) and see if you can find the page that shows the connection statistics. The ones you are interested in are the Signal to Noise Ratio (SNR) and the line Attenuation values. Specifically, a SNR of less than 10db is considered marginal and I would look into the wiring right away. Here is more info on interpreting SNR values:

Many homes have wiring that is older than 15 years and whose connections might be corroded, so cleaning up connections can pay off.

People who have looked into their wiring and found issues have been able to more than double their measured internet speeds in some cases with just simple steps like removing a splitter that was sharing the DSL modem line with a cordless base station.

If you deploy the recommended DSL splitter approach, you will see much higher performance and just as importantly, a much more stable connection. In my personal case, I was then able to step up to my providers highest level of service, even though I’m supposedly ‘too far away’ for it. It is amazing what a few feet of the right kind of wire in the right configuration can do.

Typical DSL installation using house wiring

Typical DSL installation using house wiring

Recommended wiring with DSL splitter

Recommended wiring with DSL splitter

Published on by Jonathan Foulkes.