Jim Lux wrote:
> Part 15 limits aren't all that strict. They very much
rely on low power,
> localized interference, and the willingness of the user to
turn off the
> equipment if it interferes or to accept interference.
There's an
> underlying philosophy of Part 15 and its implementation
that also seems to
> assume "point sources". BPL, by having a distributed
source, probably
> doesn't fit within those assumptions.
Jim's comments are right on. I can hear part 15 devices on
HF for a distance of about 1/2 to 1 mile when the devices
are working correctly and about 7-10 miles when they are
not. A neighbor's computer about 2-3 miles away was 30-40dB
out of noise floor here because it coupled differential mode
signal to the power lines! That's the same coupling BPL will
intentionally use.
If you consider I live on a dirt road in a very low
population area where I am surrounded by open fields and
woods, it really speaks volumes of how poor part 15 is at
preventing radiation. The reason I don't complain about the
half-dozen or so sources is I can work around them by
moving. They are narrow band sources, and even if they land
on a DX station they don't stay long before drifting off.
As Jim points out, BPL is a different animal. Unlike
computers and switching power supplies, BPL will be there
24/7 and will always be worse case levels since it is dumped
right into the power lines. It is also broad spectrum, not
narrow carriers that drift around.
73 Tom
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