Topband: DSL RFI

[Larry Pasman]

I have seen many times in the chats that some are experiencing rfi with in the dsl.

Being a retired Telephone man (ATT) I have come across this problem many times and usually its a simple cure.

First of all make sure all cabling from the modem to the router and or computer is Cat series 5 shielded ( premade large modular plug).

The problem occurs most likely from the NID (network interface) mounted on the outside of the house to the splitter and modem. This wire is not shielded, either standard telephone wire or a small plug modular cord. The cord is nothing more than a very fine wire wound around a cotton core to make it flexible (nice antenna). Replace all wiring from the NID to the modem and router with a shielded  conductor wire. You may have to make you own ends. Radio Shack and Menards sells modular plug kit to make you own cords. A premade cat series 5 cable will not work as the plug won't match unless you cut off the plugs and replace them with the smaller 4 conductor plugs. You can also buy Cat series 5 wire and add you own plugs.

At the NID is usually a terminal block so may not need for a plug at that end.

Also you may need to provide a common ground from the NID to your power panel, Most telephone companies just drive a ground rod at the NID and call it good, some require  ground  to the power ground. If you have a ground rod there can the a reactance between the power ground and the telephone ground.

The lightening arrestor in the NID is a gas heat operated  protector and can feedback rf  from the ground to the telephone wiring unless there is a common ground.