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.
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
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