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@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@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)
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|