On Wed, 2 Apr 2008 19:27:50 -0700 (GMT-07:00), Cortland Richmond
wrote:
>I was able to do some good by opening the modem safety ground
with
>a 3-prong to 2-prong AC adaptor. This is often inadvisable for
>safety
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
removed.
>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
as
>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.
73,
Jim Brown K9YC
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