[Asterisk-Users] X100P noise on ADSL line.

[Stewart Nelson]

> I have a single analog line coming into the house.. This line 
> is for my 
> ADSL and home phone.. My Asterisk box uses an X100P card to 
> connect to 
> the analog line.. I have a microfilter on the line etc.. The 
> rest of my 
> phone system works inbound and outbound calls via a VoIP 
> provider over 
> the ADSL line..
> 
> The problem I am having is that the X100P seems to introduce a lot of 
> noise on the line when it its connected to the "phone" socket on the 
> microfilter and this causes the ADSL quality to drop quite 
> badly.. When 
> the X100P is not connected I have a signal to noise ratio of 29dB 
> downstream and 30dB upstream (this stays the same when I connect an 
> analog phone) when I connect the X100P the SNR drops to 12dB 
> downstream 
> and 30dB upstream.. At 12dB I get a large number of CRC errors and 
> errored seconds on the ADSL connection..
> 
> Anyone got any ideas why the X100P would cause this kind of 
> deterioration?

I suspect that it's not the X100P, but noise from your PC's power
supply or motherboard.

1. With the X100P connected, cycle power to the ADSL modem so it
   renegotiates.  If the noise is relatively narrowband, the
   noisy bins will be avoided and the SNR should improve.

2. Try two filters in cascade.  Plug the new filter into the
   phone socket of the existing filter, and the X100P into the
   phone socket of the new one.

3. Try a long (25-foot or 50-foot) cord between the filter
   and the X100P.  Try winding the cord into a coil about
   8 inches in diameter.

4. Try a ferrite clamp-on core, such as those used to suppress
   noise in car stereo systems, around the cord from the X100P.
   If the core has a sufficiently large opening, make a two or
   three turn coil with the phone cord.

5. Try putting the X100P in a different PCI slot, so it is as
   far as possible from noisy boards such as video.

Good luck,

Stewart