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Noise

Sure wish I could find source. Shows up a couple times a day, for a hour or so, then is gone. Is about 4 mHz wide. Don't think it's in my house. Does not stay long enough for me to locate.image

Lew N4CO

Answers

  • Greg - K5GJGreg - K5GJ Member ✭✭
    edited April 2016
    Lew:  Happy Monday.  What antenna are you running on? That looks very similar to an oscillation I used to get with the amplified 1m loop I would use for demos at hamfests.  It turns out it was out-of-band overload that I could knock down with a small external filter.

    Good luck and 73,
    Greg - K5GJ

  • edited May 8
    Lewis,

    Hard to see with the current zoom level but I'm guessing this is power line noise from an arcing element on your AC power distribution.  There are lots of articles both here on the community and via Google on the steps to locate it.

    If you record the audio using something like Audacity using a side band filter, then play back and zoom in, if it is AC power line noise, your will see noise peaks every 8.33 ms (1/120 - you get an arc on each peak of the AC cycle - both negative and positive).

    Quick way to isolate outside your own QTH if you can, run the radio from a battery then **** the AC power to your house.

    Stu K6TU
  • Lewis CheekLewis Cheek Member
    edited January 2018
    Gone now, think it's from a house behind my qth, as my OCF Dipole is at that end of yard. Glad it's gone, but makes it hard to locate that way. :)
  • Ken - NM9PKen - NM9P Member ✭✭
    edited June 23
    I have seen similar patterns with the following sources:

    1) The little halogen "hockey puck" under counter lights in my kitchen do this when they are turned on.  I don't know if it is the old wall wart power supply, or an arcing halogen bulb in one of the units.  It really wipes out from 160 Meters through 15 Meters.  My XYL leaves them unplugged when I am in the shack!

    2) The charging circuit on my neighbor's camper trailer generates a wideband pulsing noise whenever he plugs it in to charge the batteries before he goes on a camping trip.  Fortunately this only happens two or three times a year and he only plugs it in the day/night before and then for a little while after he returns to top it off for storage.  I am lucky that it hasn't happened during a major contest weekend....yet!

    3) I haven't traced it yet, but either my variable speed blower on my HVAC or my neighbor's pool pump generates a pattern that is wide, but a bit different from this one.

    I would not be surprised if it was a Plasma TV.

    You can get additional clues by zooming in to one of the interference groups in the pattern and posting them, too.  They might reveal some interesting stuff.

    Good luck tracking it down.  

    Ken - NM9P
  • edited January 2018
    Looks a bit like the noise pattern I get when our washing machine is running.  That would also account for time periodicity.
  • Lewis CheekLewis Cheek Member
    edited June 23
    Someone asked about more detail picture, here it is.image
  • Ken - NM9PKen - NM9P Member ✭✭
    edited December 2016
    Hmmm. Carriers spaced somewhere between 15 and 16 kHz.... I have seen similar from a laptop power supply when charging the battery. Also from other poorly designed switching power supplies. Lots of sources.....
  • Lewis CheekLewis Cheek Member
    edited April 2016
    Don't think it's in my qth, as I have nothing that comes on like a charger, dish washer, etc. No luck with locating so far. Gone now.

    Lew N4CO
  • Ken - NM9PKen - NM9P Member ✭✭
    edited December 2016
    Does anyone near you have an "invisible Fence?"

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