[Asterisk-Users] X100P noise on ADSL line.

[Stewart Nelson]

> I have tried another microfilter, the long cable and the cascaded 
> microfilter and all made no difference at all..

> I dont think it is the microfilter or the internal house cabling.. Also 
> the fact that a standard analog phone doesn't do it also points to the 
> X100P..

> I can't move the X100P to another PCI slot because I only have two in 
> this PC and the other has a TDM400P.. The only thing I could do is setup 
> a completely new PC with Asterisk and go from there..

> Guess this means that as usual I have bumped into a problem that no one 
> else has (of knows they have :) )..

If you can't fix the noise problem, you may be able to tweak some
DSL parameters to improve things.  I'm on ADSL here in Paris, and
my downstream noise margin is only 7 dB.  But I believe that CRC
errors cause me negligible VoIP impairment.

Some stats:
Router / modem uptime: 25 days
Downstream speed: 7168 kbps
CRC errors: 235
Packets received: 35,904,163

So, less than 1 in 100,000 packets lost because of CRC error.  I'm
sure that more are lost on the Net, or are delayed enough by
jitter to not be played.  I am quite happy with overall voice quality.

How many CRC errors are you getting?
Do you run in interleave or fast mode?  At what speed?

Is it correct that the X100P causes trouble even when it is on-hook
and idle?  If so, you could temporarily substitute an old analog modem;
you wouldn't even have to configure it for use.  If you have the
same noise problem, you'd know it wasn't the X100P at fault.

You might also try shorting tip and ring together (on the phone side
of the filter) with the X100P connected.  (Of course, your POTS line
will appear busy during this test.)  If you still have noise, it
must be "common mode" (line to ground) and you can maybe filter it
with a ferrite core, or by grounding your PC case.  If the noise
goes away in this case, and is also absent with the modem test,
then I'd start to suspect the X100P as the source.

Also, see if the noise gets reduced when the system has shut the
monitor down, and the monitor is also turned off (log in via SSH
from another machine).

If your ADSL modem software can produce a graph or table of bits-per-bin,
try comparing the results after negotiation with X100P, and after negotiation
without X100P.

--Stewart