[RFI] RFI and Speed Stream 5667 DSL Modem

[Cortland Richmond]

I worked with an ADSL modem a couple of years ago that had problems 
with RF noise on the power line. This responded well to added 
common-mode filtering at the power input. But I also had to float the 
wall-wart's grounding pin, as only the "hot" wires were filtered, and 
any noise between Vcc and/or chassis/digital ground and the signal 
wires was seen as an input.  This is not acceptable for safety reasons. 
A second choke of sufficient value may be wound with wire able to handle 
30 amps short-fault current, if you use a high-enough permeability core.


Cortland