On 1/12/2020 10:14 AM, Lee STRAHAN wrote:
The point to all this is try looking at the noise with a SDR radio that
should give you a wider bandwidth picture.
RIGHT! It is quite likely that the noise K2KW and crew are chasing is
NOT generated by the power system, but rather some electronic or power
control device in a home or business. Traditional methods used to "pin
point a pole" make no sense for this kind of noise, which is why I keep
on saying "LOOK AT THE SPECTRUM."
The traditional methods that ARE applicable are what Lee describes and
loop antennas, in both cases connected to 1) an RX with a spectrum
display (best) or 2) a portable RX using a loop antenna that tunes to
the frequency(ies) where you hear the noise. For example, the broad
coverage RX in my Kenwood TH-F6A talkie uses an internal loopstick below
10 MHz; the antenna input can be manually switched between that loop and
the SMA connector. That's the upside; the downside is that it's not
very sensitive, so you have to be either pretty close to the source or
an external loop needs a preamp.
Another very important point -- virtually all noise generated by the
power system is IMPULSE NOISE that is the result of arcing, and it looks
like horizontal lines on a fast waterfall. Electronic noise, including
that generated by power-handling and control equipment like motor
controllers, industrial equipment, and switch=mode power supplies, looks
like humps on a spectrum display and slightly "squiggley" trails of
those humps on a waterfall.
A study of NK7Z's website is quite worthwhile. I also strongly STUDYING
my own application note. k9yc.com/publish.htm
Bottom line -- audio frequency spectrum and o-scopes are the WRONG tools
for anything but impulse noise, and a spectrum display is the RIGHT tool
for electronic noise.
73, Jim K9YC
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