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 Post subject: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 2:54 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 424
Location: Loveland,CO
In the last few months , I get bad noise on my AM radios. No certain time, but mostly late afternoon/ night time. To me it sounds like a light dimmer or electrical arc.
I took my pocket radio into the garage by the breaker box and turned off one breaker at a time with no change. It seems to be coming from inside the house , as
when I take my radio out to the driveway , all is good. :?:

Any ideas what to try next ?

Dave


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 3:14 am 
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Joined: Feb Mon 21, 2011 4:19 pm
Posts: 215
Location: San Marcos, CA 92069
Look for battery powered devices - if you have any UPS powering things, check those. If you have cable TV, check the cable feed with your radio to see if that is bringing the noise into your house.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 3:53 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4690
Location: North Port Florida
I have the same problem in my new house.

Been testing a little bit at a time but no solution yet

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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 4:05 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 424
Location: Loveland,CO
nash wrote:
Look for battery powered devices - if you have any UPS powering things, check those. If you have cable TV, check the cable feed with your radio to see if that is bringing the noise into your house.


No cable TV here. The only newer change was switching from wireless internet , because of signal loss from trees, to Century Link service about 4 months ago,
but this seems to have started maybe 2 months ago.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 5:44 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 33304
Location: SoCal, 91387
neondave wrote:
In the last few months , I get bad noise on my AM radios. No certain time, but mostly late afternoon/ night time. To me it sounds like a light dimmer or electrical arc.
I took my pocket radio into the garage by the breaker box and turned off one breaker at a time with no change. It seems to be coming from inside the house , as
when I take my radio out to the driveway , all is good. :?:

Any ideas what to try next ?

Dave

Having your pocket radio near the breaker box won't show anything.

Determine which breakers are for which rooms, maybe labeling them on the panel.

Then have someone turn off both breakers for each room, one room at a time, while you are in that room with the radio. Ideally when the offending room is found, the noise will stop. Then have them turn one, then the other breaker off, to narrow it down as to which AC outlet is supplying the trouble maker.

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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 11:47 am 
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Joined: Aug Mon 26, 2019 3:39 pm
Posts: 33
Location: Germany
I have a problem like that as well. However mine is power suuply based and only shows up on the FM band (also the High band), I get loud buzzing. This does not happen on the TA/LW/MW.

In my case, it is a computer monitor power supply that causes the issue. If I turn off the monitor, the buzz goes away, it's completely repeatable.

That being said, I would look at anything battery powered that may have been purchased since the issue started, like a battery powered door bell, speaker or something like that.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 12:55 pm 
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Joined: Feb Wed 08, 2012 3:09 am
Posts: 349
Location: Detroit, MI suburbs
My refrigerator wreaks havoc on AM reception on any radio near it. Try unplugging your refrigerator.

Larry


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 10:01 pm 
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Joined: Apr Thu 21, 2011 2:00 am
Posts: 4316
Location: Georgia, 30236
I have found that any of the wall mount plug in power supplies can go noisy at any time. I unplug each of those in turn as well, If you find one that has gone noisy, find one at a thrift store rated for the same voltage, but higher current and one that looks like it hasn't seen much use.

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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Wed 13, 2019 10:20 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 10354
Location: Mountains of Mourne. Ireland.
Some cordless landline phones will communicate with the dock-station/charger cradle when removed from it.

Greg.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Thu 14, 2019 1:51 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 424
Location: Loveland,CO
I've been home most of the day. I got up at 4:30am and the noise just started at 5:30 pm. All outside automatic lights were on before this. When the time is right I'll cut the main breaker and see what happens .

Maybe it's coming from outside the house, if so , there may be nothing I can do . We do have underground service where we live.

Are there 'whole house ' line filters ?

The investigation continues :lol:


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Thu 14, 2019 2:01 am 
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Joined: Apr Sun 15, 2012 3:10 pm
Posts: 1016
Location: Buffalo, NY
zacrobmer wrote:
If I turn off the monitor, the buzz goes away, it's completely repeatable.

A TV in son's 2nd floor bedroom, is pretty much directly underneath my VHF Hi Yagi, on the roof.
Nothing but Shingles, plywood, attic space, ceiling in between. When I turn off his TV, the SNR of TV station RF Ch5 (79 MHz) improves
by 2 to 3 dB. I think it seems to come from the LCD / LED backlight of the TV...
Likewise completely repeatable. There is no FCC ID printed anywhere on the TV.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Thu 14, 2019 3:18 am 
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Joined: Mar Tue 27, 2012 1:24 pm
Posts: 1092
Could be an LED lightbulb or CFL lightbulb going bad. They will put out hash sometimes even when the bulb itself is working well visibly. It happened to me a few years ago. Perfectly fine CFL bulb on the porch, that suddenly decided to coat the AM band south of 660 khz with AC hash. I have an LED bulb I use now and then that was great, RFI-wise, when new, but decided to put roving noise on the AM band after it was a few months old.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Mon 18, 2019 1:12 am 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 202
I just said this in another thread!
I had bad noise AM band to 30 MHz caused by an outdoor Dawn to Dusk motion sensing light.
The light did not need to be lit, they were always noisy.
I put a Corcom line filter on it and that quieted it. But during some (hurricane) reconstruction on the home,
I replaced all my outdoor lights, I bought and tested two for noise output with my portable radio. One had a little
noise output the other was very quiet, so I bought and installed 4 more.
Mikek


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 Post subject: Re: Radio interference ( AM )
PostPosted: Nov Mon 18, 2019 2:42 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3314
Location: Waukegan, IL
Things i found in my house that emit RFI. Dimmable LED Bulbs. Photocell timers. Motion sensor lights. Time to start unplugging stuff to see what it is.

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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Wed 04, 2019 3:38 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 424
Location: Loveland,CO
I got home after work,..all was good, then THE NOISE CAME AGAIN. I turned off the main breaker for the whole house. The noise was 95% gone, but I could still here it very faintly , so I'm guessing its coming from outside the home.?

It's been over an hour now and no interference . There is no certain pattern when it starts or stops. :? Fun with AM


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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Wed 04, 2019 6:16 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2784
Location: Burbank, CA and Thailand
Instead of turning things off one at a time, turn everything off except the circuit that powers the radio. Then turn things back one one at a time. If any contribute noise turn them back off, then continue with the others. This will tell you which circuits have equipment that are causing noise.

Assume that the noise has more than one source. Maybe neighborhood power is noisy and the problem is cumulative, radiating from many different places.

Consider that some of the noise may be totally unrelated to equipment in your home. Power lines, transformers, gas and water lines, your neighbors, etc. can all be sources of AM radio noise.

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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Wed 04, 2019 8:11 am 
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Joined: Mar Tue 27, 2012 1:24 pm
Posts: 1092
David Kulka wrote:
Instead of turning things off one at a time, turn everything off except the circuit that powers the radio. Then turn things back one one at a time. If any contribute noise turn them back off, then continue with the others. This will tell you which circuits have equipment that are causing noise.

Assume that the noise has more than one source. Maybe neighborhood power is noisy and the problem is cumulative, radiating from many different places.

Consider that some of the noise may be totally unrelated to equipment in your home. Power lines, transformers, gas and water lines, your neighbors, etc. can all be sources of AM radio noise.


True enough. A few years back a neighbor who was over a block away would turn on their washer and it would send out alien, outer space sounds on 2-8 mhz. It was using the powerlines as a radiator. I tracked it down using my SW digital portable, riding around on my bike, because it was obvious it wasn't coming from my house, nor the nearby neighbors'.


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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Wed 04, 2019 1:28 pm 
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Joined: Sep Thu 26, 2019 1:56 am
Posts: 111
Location: Peterborough, New Hampshire, 03458 USA
All good ideas and things to check. I would add another thing not mentioned, the portable radio you are using to check for noise. I had a battery powered LaCrosse weather radio with AM/FM. It was showing noise on AM everywhere in my house and even around the yard. I couldn't isolate anything. After noticing my car radio had different results, I went to Walmart and bought a $17 Sony AM/FM model ICF-P26. It is very selective to noise sources and has analog tuning which makes things easier looking for noise.

I found most of the things causing AM noise in my house only radiated out 2-6 feet and weren't causing a problem in my lab. The Sony did enable me to find 2 culprits that were affecting my lab. One was a built-in USB charging port in my 5 foot power strip that I wasn't using and had forgotten about. I opened up the strip and disconnected it. The other was a 12 volt switcher type power supply for outside landscape lighting 50' away from my lab. Of course, 75' of semi-buried cable makes for a pretty good antenna. I solved that one by replacing it with a linear power supply.

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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Wed 04, 2019 10:27 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 737
Location: Rockaway , nj 07866
Street lights can cause noise on the am band , I've had it happen here , had to pull teeth to get the power company to fix it , they did however 10 years later it does it again sometimes .
a dipole outside hooked to the radio helps get rid of it


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 Post subject: Re: Radio interference ( AM )
PostPosted: Dec Thu 05, 2019 12:40 am 
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Joined: May Thu 04, 2017 1:08 pm
Posts: 292
Location: Raleigh, NC area
One of my cheap AA5 radios can only pull in the strongest stations. That would be about ONE around here: WPTF 680.

Well, I noticed that when the station was weaker, I was hearing a sort of tone in the background. I did the whole circuit breaker thing, walking around the house with a battery operated radio. Couldn't find it. I even turned off the battery backup on the cable modem/router. Then I remembered that the alarm system has a battery. Disconnected that and poof, noise gone.

Well that alarm system is 20-some years old. Never caused a problem before. Then I remembered I had recently installed an Envisalink board into the alarm system, so I could bring the old alarm system into the 21st century. I used the battery radio to check near that little board.

Wow! It was so noisy!!! I looked closely at the board and saw they used a switching power converter chip, running at 340kHz. One half of 680kHz where WPTF is sitting. The layout of the chip and associated components was also very bad, as if the designer took no care for EMI.

Long story short, after trying to fix the poor power supply layout on the Envisalink board, I remembered that those low frequencies are usually not radiated; they are usually conducted. So I shielded the input 12V/GND wires to the little PCB, and the problem went away. I guess the wires conducted the noise out of the board and then radiated that into the house, even 30 feet away.


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