Hi Jim,
I will try and repeat with my scope triggered on line noise when I get home
from work. When I used a sound card scope I only saw big spikes at a
frequency of 60 Hz but could have been fooled based on my simple setup but
normally when using this simple setup I see distinct 120 Hertz spikes when
doing analysis on audio from arcing power lines, and I did not see that
when looking at the KC4D RFI video.
Stay tuned, will do this later this afternoon.
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
|