[RFI] Digital TV Problems

Jim Brown jim at audiosystemsgroup.com
Wed Apr 2 23:12:37 EDT 2008

On Wed, 2 Apr 2008 19:27:50 -0700 (GMT-07:00), Cortland Richmond 

>I was able to do some good by opening the modem safety ground  
>a 3-prong to 2-prong AC adaptor. This is often inadvisable for 

This is ALWAYS UNSAFE unless some other robust connection from 
that equipment to the power system ground replaces it. We've seen 
far too much of this in the pro audio world where I've worked for 
many years. People have been killed because safety grounds were 

>but a filter or ferrites effective at HF may work

Yes, if breaking the ground "did some good" then a suitable choke 
would likely help. It's also important to realize that the power 
line itself, not just the safety ground, is part of the radiating 
system, so a common mode choke on the power line would certainly 
be in order. 

>VDSL uses the HF spectrum, though it does not interfere with HF 
>much as BPL due to the better balance and closer spacing of 
>telephone wires.  ADSL uses the LF and MF spectrum from 100 KHz 
>through 1.1 MHz 

It would be great to know more about spectrum use, the location of 
any carriers, and what interference sounds like when it occurs. If 
you have, or can find, this information, please do post it. 


Jim Brown K9YC

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