[RFI] DSL Filter Update
Christopher E. Brown
cbrown at woods.net
Sun Mar 8 18:43:14 PDT 2009
On Sun, 8 Mar 2009, Jim Brown wrote:
> On Sun, 8 Mar 2009 18:05:38 -0500 (CDT), Christopher E. Brown wrote:
>> A filter with a sharp cutoff starting around 3Mhz combined with heavy
>> common mode choke would have alot less impact on the sync rate.
> That's sort of the direction I was thinking about. Note that one can get
> quite serious with a common mode choke without affecting the
> differential mode circuit at all. Thanks for the info re: 2.2 MHz max
> bandwidth. The engineer friend I consulted on this told me 1.1 MHz.
> Sharp guy, but his experience in that industry was at least 4-5 years
> old, and he's been doing completely different things since.
> Jim Brown K9YC
Depends on the DSL gear, ADSL1 cuts off around 1.1, VHDSL uses much higher
Common use these days in the US is ADSL2+, with ADSL1 hardware cycling out
Also, remember that RF can impact *BOTH* ends. I have seen a couple cases
where enough signal made it into the line to impact both the CPE *and* the
DSLAM, as well as causing increased error rates for neighbors in the same
cable bundle. A serious common mode choke at both the CPE and at the NID
could be needed in severe cases. At my home I have chokes at both ends of
the line, only a single cylinder but my original DSL issues were not so
More information about the RFI