[RFI] Telephones and DSL

Cortland Richmond ka5s at earthlink.net
Sun Dec 9 19:38:58 EST 2012


Downstream, ADSL (up to 2.3 mbps) and ADSL2 (up to 12 mbps) spectrum is 
as high as 1.1 MHz and ADSL2+ (up to 23 mbps) as high as 2.2 MHz.   If 
you are on 160 you could directly affect ADSL2+. You can indirectly 
affect ADSL and ADSL2 if your RF desensitizes the DSL RF front-end.

As long as you pass both conductors of the twisted pair through the same 
core a ferrite should not bother it.

The farther down the copper you are from DSL equipment at the cabinet or 
Central Office, the less signal arrives at your residence, and the more 
likely RF will be a problem. An older type of DSL (carrierless amplitude 
phase modulation, CAP) was so sensitive to noise that ringer current 
relays in the customer Central Office would drop the link before maximum 
"reach"; the customer had put the subscriber modems (not made by *my* 
employer) there for convenience. It worked a LOT better when they were 
in a more distant room. That was around 1994.


On 12/9/2012 1906, rick darwicki wrote:
> Question about DSL. Can too much ferrite kill the DSL signal or mess up the SNR? Is the DSL signal affected by say a 160 tuned circuit/trap or is it a DC thing and not RF? I'm looking to cure 1 KW modem problems, right now I don't lose link but I can lose a page and have to refresh.

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