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Author Topic: Noise on 40 m  (Read 3445 times)
WB2JNA
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Posts: 97




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« on: July 21, 2017, 06:49:43 AM »

Lately I have noticed lots of noise on 40 meter CW after about 9 pm. It sounds like a buzzing noise and varies in intensity from about 7000 kc to 7100 kc. Any ideas what it might be, or does it sound like a local thing? I hear it on my dipole, not on my Hi Q Loop. Thanks for any ideas!
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KB4QAA
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Posts: 3256




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« Reply #1 on: July 21, 2017, 02:07:50 PM »

In all likelihood it is local interference since there is not a worldwide clamor complaining about it.
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WB2JNA
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Posts: 97




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« Reply #2 on: July 22, 2017, 06:44:29 AM »

Thanks. It improved a bit when I unplugged a computer (which was already turned off anyway). Maybe this info helps others with a similar problem. Sounds like a real local issue!
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NK7Z
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« Reply #3 on: July 22, 2017, 08:28:48 AM »

I have a small blog entry on various ways to reduce RFI in the shack, see:
http://nk7z.net/rebuilding-the-shack/
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KC4ZGP
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Posts: 1637




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« Reply #4 on: July 22, 2017, 10:47:10 AM »


About 9:00p.m. eh?

Streetlights?

Kraus
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N3HKN
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Posts: 151




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« Reply #5 on: August 13, 2017, 11:15:27 AM »

I also find that the "off" PC is not the culprit but the switching power supply in the PC is. Always try turning off the power supply or pulling the PC's plug. Also leaving an "unused" AC to DC power device (laptop or phone) plugged in can make a mess of a band.
Dick N3HKN
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K0UA
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Posts: 1380




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« Reply #6 on: August 13, 2017, 11:24:15 AM »

I had something similar happen one day, except it was much worse.  It wiped out 160 thru 6 meters, and I even heard some squelch breaks on 2m FM.   It was a switch mode power supply for my homes data switch.  It had worked silently for years, and one day decided to  become a wideband rf transmitter.  It was even still powering the data switch!.  I replaced it with a linear supply, and problem solved.  I kept the thing for a while thinking it might be useful as an aid in contesting.  You know slink over and plug it into the location of a big rival contester.  HI HI, Just kidding about that, I threw it away. I suppose some bypass capacitor went south or something.
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