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Author Topic: QRM Noise on LW, MW and SW -- SOLVED!  (Read 842 times)

KG4LAC

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QRM Noise on LW, MW and SW -- SOLVED!
« on: September 22, 2022, 02:28:10 PM »

I finally found and resolved an interference problem causing QRM from LW, MW and into SW.

First noticed several months ago when I heard terrible noise wiping out from around 660 kHz to around 695 kHz.

Here is a screenshot of the noise.
https://misc.kg4lac.com/2022-MW-QRM-Example.jpg

I also noticed noise, though not as severe, in the longwave and shortwave frequencies.

Switched antenna. Same results.

First thought, “What has changed recently?”. Only thought was a new electrical meter (type remotely read). I contacted the electric company. While waiting for the electric company to call or reply I continued debugging.

Since my main receiver is an SDR I need my PC and power for the SDR.

Used a portable, battery powered, receiver inside and outside in an attempt to determine if the noise was in my QTH or in the area. Sometimes the noise was gone and other times I was still hearing the noise. Argh!

Noticed the electric company repairman’s truck in the street one day. Went outside and had a pleasant conversation with him. He admitted others complained about “strange problems and interference” from the new meters. He promised to get back in touch with me when he obtained an “old style” meter as he planned to replace the new meter with the older style meter.

Weeks went by and I hadn’t heard from the electric company repairman.

We lost power on Monday, September 12, 2022. While waiting for the electricity to return I thought I’d check with a portable, battery powered receiver again. No noise. I’m hearing WFAN, NYC, NY on 660 kHz around 2030 UTC (4:30 PM EDT).

I was determined to find the cause of the interference. I turned off all house power except for the circuit including my radio room. Checked 670 kHz. All noise/interference is gone. This is good as I’m able to continue. Here is a screenshot.
https://misc.kg4lac.com/2022-MW-QRM-Gone.jpg

Turned on the electrical circuits, one-by-one, until the problem returned. Then turned off the circuit causing the problem and continued turning on the remaining circuits to determine if I had more than 1 cause of QRM. Luckily, no, only 1 circuit was the cause.

On the problem circuit is a power strip, a FIOs box, a TV and a DVD player. Initially thought it was either the power stirp or the FIOs power cord brick. No, both are OK. Plug in the TV. Still OK. Plug in the DVD player. Terrible noise returned! The DVD player is a Memorex. It’s at least 20 years old. Here is a picture of the problem.
https://misc.kg4lac.com/2022-QRM-Cause.jpg

Now, no more interference and it’s a happy day!
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SWMAN

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #1 on: September 22, 2022, 06:34:52 PM »

So it was actually the DVD player and not the Smart Meter ?
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KD6VXI

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #2 on: September 23, 2022, 04:37:39 AM »

Smart meters typically don't make noise.

The circuit breaker trick is one of the first I use when trying to track down noise.

Now I'm on a vertical in a subdivision with houses piled on top of each other, I don't even try to hunt down noise.  Much easier to go mobile into the rain forest or go to the waters edge.

Good job on finding your noise.  Glad you didn't have to put on a tin foil hat for the meter :)


--Shane
WP2ASS / ex KD6VXI
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AA7IS

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #3 on: September 23, 2022, 08:05:54 AM »

Don't take it to goodwill, put it in the driveway and run it over with the car before disposing of it.  ;D
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WB8VLC

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #4 on: September 23, 2022, 09:38:25 AM »

Did you narrow it down to see if it is the DVD player itself or the power supply for the DVD player or a combination of both items?
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KG4LAC

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #5 on: September 23, 2022, 02:04:39 PM »

Did you narrow it down to see if it is the DVD player itself or the power supply for the DVD player or a combination of both items?

I was so overjoyed with finding the source I haven't touched the DVD player since Thursday. Perhaps, I'll look into the cause, but for now, I'll simply leave the DVD player alone.
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KG4LAC

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #6 on: September 23, 2022, 02:07:58 PM »

So it was actually the DVD player and not the Smart Meter ?

Yes, for some unknown reason, the Memerox DVD player was the cause. Interesting as the DVD caused no problems until early in 2022.
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AC2EU

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #7 on: September 23, 2022, 07:39:50 PM »

probably bad capacitors!

RENTON481

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Re: QRM Noise on LW, MW and SW -- SOLVED!
« Reply #8 on: October 10, 2022, 07:02:09 PM »

One of my DVD players did the same thing. I just unplugged it when not using it. Some of the electronics devices put out RFI. YMMV.
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