[Top] [All Lists]

[RFI] DSL modem problem

To: <rfi@contesting.com>
Subject: [RFI] DSL modem problem
From: John Kaufmann <john_w1fv@telocity.com> (John Kaufmann)
Date: Tue, 14 Nov 2000 22:28:26 -0500
At 09:58 PM 11/14/00 -0500, Michael D. Brown wrote:

>Has anyone had any luck in solving a problem
>of an hf transmitter getting into their DSL modem?
>I emailed the manufacture of the modem, but
>got no response. Response from my ISP was
>that DSL modems were indeed very sensitive
>to rf, and that they didn't know of any fix.
>Mike K9MI

Is there a specific frequency band that causes problems with the 
modem?  DSL systems, depending on the speed, use lower portions of the HF 
spectrum (in telephone lines, of course, and not over the air) that could 
be susceptible to interference from the lower HF bands, particularly 160 
meters.  Supposedly the spectrum of DSL signals is notched so that it 
doesn't radiate on the amateur bands, since it was recognized by DSL 
engineers that even small leakage could cause interference to amateur 
radio.  Indeed my DSL modem doesn't appear to produce any discernable RFI 
in my receiver on 160 meters.  However, this does not mean that the modem 
won't be susceptible to external interference, just like any other 
electronic device.  If the modem is an external unit, try the same fixes 
you would use for other RFI problems, like power line filters and chokes or 
ferrite beads (you may need a lot for low frequencies) on the telephone 
line and the line from the modem to your PC.

73, John W1FV

FAQ on WWW:               http://www.contesting.com/FAQ/rfi
Submissions:              rfi@contesting.com
Administrative requests:  rfi-REQUEST@contesting.com
Questions:                owner-rfi@contesting.com

<Prev in Thread] Current Thread [Next in Thread>