[RFI] Quidance on finding noise?

[AA5CT]

One 'arc' strike per half cycle is visible (like a spark gap 
transmission), yet, not an arc.
Have you ever seen an O-scope used this way? Synced to
the line rate? To see the strikes per cycle?

This matches the 'arcing' sources I've tracked down before.

I had a real-time Spec An I could put in Zero Span mode and
trigger from the "Line" and observe sometimes two or three
strikes per 1/2 cycle on one noise source about 10 yrs back.

One could also hear the change in 'tonal' quality as the strikes
would sometimes be 2 and sometimes 3. This source turned
out to be a primary wire to a fuse holder that had broken loose
and was 'moving' (like bouncing) slightly in the wind. One 
could visually see the arc and I even managed to capture 
the arc in a still picture I included in a pdf file documenting
that adventure too. Maybe it was more than a decade back?

Too bad I don't have a video of the Spec An in Zero Span mode
although I'll have to check an older PC to be sure. The nice 
thing about a Spec An with that capability is I could widen-up 
the IF bandwidth and the "strikes" would then sharpen-up and 
become quite distinct. 
de AA5CT
.
.
 

    On Thursday, January 9, 2020, 4:31:06 PM CST, Michael Martin <mike at rfiservices.com> wrote:  
 
 Not an arcing source.

Get BlueMail for Android On Jan 9, 2020, at 3:39 PM, Don Kirk <wd8dsb at gmail.com> wrote:
Hi Jim,

I looked at that RFI noise in sync with 60 hertz video you wanted me to
look at using my soundcard scope, and attached is what I captured.  Very
obvious 120 hertz.

I also just took another look at Kens audio recording using another
recording he supplied me which gave me more time to listen without human
voice on top of the noise, and I do in fact see 120 hertz bursts (not 60 as
I initially reported), but not narrow bursts like the recording you had me
look at.

Either way I believe the info we have supplied Ken should help him track
down the source.

Thanks,
Don (wd8dsb)

On Thu, Jan 9, 2020 at 12:43 PM AA5CT <jwin95 at yahoo.com> wrote:


 Don,

 Can you feed this video's audio into the analysis software and
 see what it gives? As can be clearly seen there is a 'pulse' for
 each 1/2 cycle of the AC waveform, or two pulses for a complete
 cycle of 60 Hz mains.


 https://www.youtube.com/watch?v=C-S5ef-Ne6Y


 Also note that the first 'breakdown' shifts around, while the second
 breakdown is fairly constant; this is due to materials or the structure
 involved in the area of where the arc forms.


 Note: Scope triggered from local "Line" voltage, also shown overlaid
 as a single cycle as seen on the scope's CRT.


 de AA5CT

 .
 .

 On Thursday, January 9, 2020, 10:46:02 AM CST, Don Kirk <wd8dsb at gmail.com>
 wrote:


 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)

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