[RFI] Telephones and DSL

[Jim Brown]

On 12/13/2012 1:27 PM, Tim Duffy K3LR wrote:
> It's important to note that just because you sniff noise on the Telco line
> does not mean there is anything wrong with it. The Telco line can become an
> excellent re radiator of noise (maybe from loose pool hardware associated
> with the 14 MV line?) through no fault of its equipment.

RIGHT.  BUT --  it can also be hot with RF trash because of poor 
termination or poor common mode rejection at a noisy piece of 
equipment.  Even the best CAT7 will radiate common mode trash from a 
router or Ethernet switch with this kind of fault, and coax will radiate 
trash put on its shield by noisy equipment with a "Pin One Problem" at 
the coax connector. An example is a noisy TV (plasma or otherwise) or 
cable box with the coax shield going to the circuit board, not to the 
chassis.  That design error couples RF both ways -- our signals into the 
set, and its noise out of the set, where it radiates to our equipment.  
Exactly this sort of fault will make the CATV system hot with noise, but 
it isn't the cable company's fault (unless it's their cable box doing 
the deed).

73, Jim K9YC