ADSL modem Interferece on phone line

  Jackplug Jake 17:05 11 May 2007


I'm experiencing quite bad, pulsing interference on my telephone line which I have narrowed-down to being connected to the ADSL modem.

I have proven this by removing all extensions from the main socket and connecting a wired phone via a micro-filter so that it is the only device in use. In this configuration the line is perfect. However, if I then connect the ADSL modem to the same micro-filter I get interference on the phone line.

I've tried changing the micro-filter and running a separate modem lead to the socket (I have also replaced the modem and the master socket) but the problem still persists. It is worse when using a cordless phone.

Broadband works fine and BT have checked the line and say there's no problem.

I can't identify a specific time when this started and so can't link it to any event.

Could this be anything other than a line fault of some description?

  lpl56407 17:14 11 May 2007

Have you tried connecting the ADSL modem directly to the BT socket, i.e not through a filter?

  Jackplug Jake 17:29 11 May 2007

Thanks for the reply,

I haven't tried that, but I'll give it a go and post back the results.


  bjh 17:52 11 May 2007

I found that my modem PSU was creating some interference. It lessened by putting the modem & psu on its own phone & power sockets, some distance from the phones etc.

  daba 22:45 11 May 2007

Have you tried another micro-filter ? Some are not so good, or it could be faulty.

Remember, when connecting everything back up that it is your phones, Sky box, etc. which need filtering, not the modem. The filter's job is to isolate the phones from the broadband noise on the telephone cable.

In my house, because nearly all the phones are DECT, my modem plugs into the BT master socket WITHOUT a filter, (there is no phone needed there). The DECT base unit plugs into an extension socket via a filter, and the phone/alarm clock upstairs plugs into another extension socket via another filter.

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