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Author Topic: Horrible RFI, still hunting for source(s)  (Read 4111 times)
KF4WDD
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Posts: 3




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« on: October 06, 2017, 08:44:59 AM »

Hi - I have very bad RFI on the HF bands using a 30 ft. end-fed wire antenna in my backyard.  Friends have the same noise when they hook up their radios at my house.  We've concluded my radio and power supply aren't the problem, but haven't figured out what is causing the RFI. 

I tuned my car radio to 540 AM and drove down my street and the nearby streets.  There is a loud humming sound on top of the base level of static.  The hum isn't there when I drive away from my neighborhood.  There are no above-ground power lines where I live, just electrical boxes approx. 3 cubic feet on people's property, but not everyone's.

If you have any insight/suggestions/ advice, I'd appreciate it.  Next step is to shut down all power to the house and hook up my radio to battery power to see if this makes any difference, but I'm concerned about what I'm hearing on the car radio at/near my home.  Thanks.

73,
Ben (KF4WDD)
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KB8FE
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Posts: 5




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« Reply #1 on: October 06, 2017, 10:54:43 AM »

I would think 'direction' and 'distance' would be the most helpful information.  So I would suggest making a conveniently sized directional loop tuned to some frequency of interest, say 7.040 Mhz, 14.060 Mhz (or whatever).  Attach that to your rig, run off battery power where necessary and take readings from various positions around your neighborhood.  Watch your S meter for indications of changes of signal strength.  Log all the information such as your position (street intersection), strength of signal, direction of signal (via compass or map).  If you find you are able to close in on one area, reduce your receiver sensitivity and keep narrowing down the search area.  Even if you cannot completely pinpoint the problem you will have helpful notes for future investigation.  Check for noise throughout the day and night to find out if it subsides or disappears at any time and if so, when it returns or gets stronger.
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K0BT
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Posts: 362




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« Reply #2 on: October 06, 2017, 11:29:13 AM »

A few years ago something decided to throw hash all over HF at my house. I tried shutting off each breaker individually, which didn't have much effect so i cruised the neighborhood, but the noise was loudest near my house. I shut off the main breaker and the noise went away.

My wife and I had gotten new cell phones and two separate chargers were generating noise from two different rooms.



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KB8FE
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Posts: 5




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« Reply #3 on: October 06, 2017, 05:22:32 PM »

K0BT brings up a good point.  If I were to work with the breakers (which is a good place to start) I would go down through the breakers (slowly) one at a time but leaving them OFF as I go.  If I find that I reach a breaker where noise stops, solve the problems associated with circuits that relate to that one breaker.  After solving that set of problems I would start going backwards and turning ON the breakers (slowly) one at a time and leaving them ON.  If I find that turning one of those ON introduces a new set of problems, solve those problems.  Then continue working backwards until ALL of the breakers are back ON.  This should help detect multiple circuits (breakers) that have problems.
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WB4SPT
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Posts: 496




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« Reply #4 on: October 08, 2017, 08:57:16 AM »


I tuned my car radio to 540 AM and drove down my street and the nearby streets.  There is a loud humming sound on top of the base level of static. 

73,
Ben (KF4WDD)

Get a small transistor AM radio.  They are reasonably directional.  The car may tell you that there is something going on in the neighborhood, but no help to DF. 
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ZENKI
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Posts: 1439




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« Reply #5 on: October 09, 2017, 01:48:44 AM »

Get a cheap SSB portable like Degen, you can use the telescopic whip as a E field probe and find most of the noise if it comes from your house

You can easily build a small loop like this W0IVJ design which you can plug into the Degen SSB portable. You can DF any noise with this loop.

http://tomthompson.com/radio/ReceivingLoop/loop.html

You can also this handy EMC probe from Germany. Just plug a little Mobile Phone AAA battery powered speakers into it and with the variety of probes can hear the noise and ID the source very quickly. Its a broad band  all frequency probe that uses various E and H field probes. Amazing what you find sniffing around your house with this device.
Its called the EMC Spion and its sold as a kit.

http://www.box73.de/product_info.php?products_id=2763

Finding HF noise is very simple when you have the right tools. In a modern world no ham can  afford  not to have these QRM tracing tools.


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N8EKT
Member

Posts: 593




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« Reply #6 on: October 09, 2017, 08:46:13 PM »

A portable am radio is needed for tracking down power line noise, pet fences and data over power lines.
These days everything creates rf interference at some frequency at some level.
Many utilities these days use smart grid power line communications data below 500khz but they may be using HF frequencies as well.
DSL over phone lines uses HF frequencies and can also create interference
We all assume that BPL is dead but it could be that someone near by is using X10 devices or something else that communicates over the ac wiring in the same way
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K2BKR
Member

Posts: 2




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« Reply #7 on: October 12, 2017, 03:38:24 AM »

I just went through this myself as the "buzz" was getting worse over time. I used a handheld AM radio and walked around the house and couldnt pin it down. My ham club suggested that I contact the electric company, which I did. They sent a tech out who connected his analyzer to my dipole and located two distinct frequencies and said they were close based on signal strenght. He used a small Dish antenna and walked the street locating a loose wire atop an insulator then took off in the car, there he found two blocks away another pair of loose wires atop a transformer. Both signals direct matches to the source off of the antenna. He called me and said that they fixed the wires and do I here anything else. I tuned my 857d to the frequencies, switched to am. One signal gone the other still there. So he came out again connected up to my dipole and it was quiet except for the one frequency. I pulled the main breaker for the house and it disappeared. So with that I turned it back on and flipped breakers on off until we found one. Turned out the secondary buzz that was masked by the louder buzz due to the eletric company was coming from my two cable tv boxes. Unplugg them and the buzz went away. I just ordered ferrites beads to snap on their power cords. I know hoave a lower noise level and can stations now that I never heard before, Hope this story helps someone..73's k2bkr

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ZENKI
Member

Posts: 1439




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« Reply #8 on: October 13, 2017, 02:53:31 AM »

Again you using  the wrong techniques.

1. Get a Shortwave receiver and use a loop. I posted a link
2. Get a Air band receiver/ 2 meters or 70cm  in the AM mode and use a  good yagi.
3. Trying to  pinpoint HF QRM with AM receiver  is really not  an  effective way of doing things.
4. If you dont want to build  something buy the MFJ receiver with  the included Yagi, that would be far more helpful than your AM radio.
5. If you dont want to do the above get a portable SSB receiver like the Degen 1103 and use it on Shortwave.

I have been able to find any HF noise within 30 minutes use the above tools and techniques.

I just went through this myself as the "buzz" was getting worse over time. I used a handheld AM radio and walked around the house and couldnt pin it down. My ham club suggested that I contact the electric company, which I did. They sent a tech out who connected his analyzer to my dipole and located two distinct frequencies and said they were close based on signal strenght. He used a small Dish antenna and walked the street locating a loose wire atop an insulator then took off in the car, there he found two blocks away another pair of loose wires atop a transformer. Both signals direct matches to the source off of the antenna. He called me and said that they fixed the wires and do I here anything else. I tuned my 857d to the frequencies, switched to am. One signal gone the other still there. So he came out again connected up to my dipole and it was quiet except for the one frequency. I pulled the main breaker for the house and it disappeared. So with that I turned it back on and flipped breakers on off until we found one. Turned out the secondary buzz that was masked by the louder buzz due to the eletric company was coming from my two cable tv boxes. Unplugg them and the buzz went away. I just ordered ferrites beads to snap on their power cords. I know hoave a lower noise level and can stations now that I never heard before, Hope this story helps someone..73's k2bkr


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