From: Christopher E. Brown <firstname.lastname@example.org>
Subject: Re: [RFI] DSL Filter Update
Date: Sunday, 8 March, 2009, 7:05 PM
On Sat, 7 Mar 2009, Roger Parsons
Just to advise the group that a couple of other
stations have had success with this filter. Nick, VE3FJ,
also checked out its frequency response with the following
Of course in theory the stop band attenuation should
continue to increase with frequency, but in practice there
will be strays across the filter that will cause a
performance drop at higher frequencies.
Keep in mind that ADSL2+ has signaling up to 2.2Mhz, and
that the default S/N threshold to use a channel is normally
6 - 9 db (default varies between DSLAM vendor/model,
providers tune based on cable plant. Metro area
providers with newer cabling and shorter runs can leave it
around 6, older or lower density cable plants (longer
average run length, more pairs feeding into single location)
tend to need it tweaked higher).
3 - 6 db rolloff at 2.2Mhz or below *will* limit the DSL
line max rate.
A filter with a sharp cutoff starting around 3Mhz combined
with heavy common mode choke would have alot less impact on
the sync rate.