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
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