On 1/13/2021 6:15 AM, Dave Cole wrote:
You may find that the phase type noise reducers don't work so well on
power line noise... It can help-- but mostly it will not be very
effective for distributed RFI sources.
The source of transmission can be distributed, (not in all cases), along
several hundred, to several thousand feet of power line. This means
that depending on the distance traveled down the power line, the
distance to your sense antenna, and the distance to your main antenna,
RFI will arrive at different times, and hence different phase
relationships to each other, from every point along the power line that
carries the RFI.
Yes, this is excellent advice about noise cancellation. Phase is a
function of both time and frequency, and in the case of noise, time is
the result of the distance the noise wavefront travels to get to the
noise canceller (in the air and in coax from the antennas). Physically
large sources (as a fraction of a wavelength) cause result in the
arrival of multiple wavefronts, spread out over time, thus with
different phase. We can tweak the canceller to kill one, but not the
others, or the others less well.
73, Jim K9YC
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