On 3/21/2021 1:28 PM, Charles Plunk wrote:
Its sounds like 120hz to me (power lines ). I recorded a segment and run
it through Audacity, expanded it out, and can see the spikes at about
that rate.
Sound of the noise in an RX can be deceptive. Some electronic noise
sources SOUND like impulse noise but they are not. The excellent DF
advice from several very smart guys is exactly right IF it is impulse
noise, but because most electronically generated noise comes from power
handling or control equipment (switch mode power supplies in equipment
and battery chargers, variable speed motor controllers), it will also
have very strong components at power frequencies. And all power control
noise will show the same 60, 120, and their harmonics, just like impulse
noise.
These power control devices use square and rectangular waves in the
range of 10-20 kHz to do their thing, and they produce strong harmonics
all the way up to 10M and beyond. Unlike impulse noise sources, they
don't usually get up to 2M or 440 MHz where we can chase them with our
directional antennas tuned to those frequencies -- instead, we must
chase them where we can hear them. In addition, most of us have MANY
noise sources, so it's easy to get on a wild goose chase if you don't
know which kind of noise you're chasing.
THAT'S why I keep urging folks to study the waterfall FIRST.
73, Jim K9YC
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