[RFI] Quidance on finding noise?

[Don Kirk]

Hi Ken,

Using 3 different audio software tools, I come up with a frequency of 60
Hertz, not 120 Hertz.  Typically power line noise has bursts at a frequency
of 120 hertz (arcing each half of the sine wave).

If it really is not power line noise which I suspect it's not, you will
probably have a somewhat easier time locating it.  It appears you have a
good idea what direction it's coming from assuming the gain of the
beverages are similar to each other.  If so I would say the noise is from
the East North East.  If it were me I would use a portable tuned loop with
portable preamp and portable HF receiver that would allow me to hear the
noise just outside the house of KC4D, and then I would use the null (or
peak) of the tuned loop to guide me right to the source while heading in
the East North East direction (I consider this method a form of infinite
triangulation because as you walk you continue to use the null of the loop
to guide your direction of travel), I would reduce receiver gain or install
attenuation as I get closer to the source so that I could still detect the
null as I rotate the loop.  In my experience you should be able to narrow
in on this noise within 15 to 30 minutes of walking.  Most folks probably
are not willing to invest in a preamp (buying or building one).

The problem is that overhead power lines can radiate the signal, so you
need to stay away from the power lines as much as possible.  When this is
the case, I then do true triangulation by going to different locations away
from power lines to get headings, and then I plot the headings on Google
Earth to see where they intersect.

You should probably be able to hear this noise with a portable AM broadcast
band radio too, and you might be able to just use the built in loop stick
antenna to guide you to the source (using the null and peak method) but if
you can't throw in attenuation as you get close you might have some
difficulty when you get very close to the source, but I would certainly try
this method.  When you get right next to the source you might be able to
hear it up on 136 MHz AM (if you have a police scanner this would be a tool
you might try as the aviation band on the radio will provide AM reception),
but this is probably not even necessary but might be very helpful in
confirming you have located the source.

If you want to assume it could be a street light (I see a lot of street
lights on the main roads near KC4D), and you know the approximate time the
noise shows up each day, I would listen on my cars AM radio while parked
out on the side of these roads to see if I could catch the noise coming on
when the lights turn on (observing both street lights and house lights,
etc.).  This assumes you are able hear the noise (a lot of new car radios
have such good noise blankers that you can't hear this type of noise).

There are a lot of other tools I use such as portable SDR receiver, but
again that's normally more than most folks want to mess with for a one time
situation.

I would recommend driving the streets up to an approximate 1 mile radius
and note the noise level during the day and during the night, and note
where the noise was horrible at night but not during the day (this might be
the very first thing I would try to do to isolate the problem while keeping
things simple for you).

Everyone has their own technique, and you need to work with whatever tools
you can easily obtain.

Keep us posted.
Don (wd8dsb)