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RFI Noise Source???

Mudfoot

Mudfoot

Elmer
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Jun 17, 2009
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Southeast Ohio
Just started hearing this noise. I can pick it up on my vertical from 21 to 30 mHz.

Anyone have any idea what it is?

http://db.tt/56O32eBx

http://db.tt/56O32eBx

I don't hear it at all on any of my dipoles, which is what I use 99% of the time. It sounds close and quickly drive you nuts. I'm gonna try to pick up an old CB walkie talkie and canvas the area around my QTH. As long as it remains vertically polarized I'll be happy.
 
Last edited:

m42duster said:
Just started hearing this noise. I can pick it up on my vertical from 21 to 30 mHz.

Anyone have any idea what it is?

http://db.tt/56O32eBx

http://db.tt/56O32eBx

I don't hear it at all on any of my dipoles, which is what I use 99% of the time. It's sounds close and quickly drive you nuts. I'm gonna try to pick up an old CB walkie talkie and canvas the area around my QTH. As long as it remains vertically polarized I'll be happy.
Click to expand...

I think something that has digital electronics is gonna be the culprit.
Can we assume that the radio that was used for the purpose of making the recording was in the AM mode since you said you were gonna utilize a CB walkie-talkie for the purpose of trying to locate it?
Since it is spread out across the band I wonder did you try and find a pattern to the harmonic pattern spacing?
As in every 20kc, for example.
 
Yes it was AM, but you can hear it on SSB also. It's present with continuous tuning. I know it's close. I'm gonna try to make a little handheld loop for a Shortwave receiver instead.

It'll give me something to do trying to find it.


I eliminated my house by tripping breaker and running rig on a gel cell.
 
m42duster said:
Yes it was AM, but you can hear it on SSB also. It's present with continuous tuning. I know it's close. I'm gonna try to make a little handheld loop for a Shortwave receiver instead.

It'll give me something to do trying to find it.


I eliminated my house by tripping breaker and running rig on a gel cell.
Click to expand...

I gonna bet that you find it or at least narrow it down to house or building or maybe even something to do with the utilities.
A small loop is a very good choice for locating rfi most of the time. ( that is if the source cooperates in the matter)
The indication offered by a small loop is very pronounced with regard to directivity when you utilize the 'null' and has proven to be very effective.
I was able to find an unattended 2 meter radio that was inadvertantly locked into transmitt on the output of the repeater.
People that were talking on the channel at the time were in another town and they did not notice it.
Even after I advise them as to what I was hearing they continued to carry on their conversation without realizing the true nature of the situation.
It was quite the challenge I thought at first.
But then after giving it some thought I began to realize a few things and then proceeded with the hunt in my mobile with the small loop in hand. (talk about distracted driving.lol)
Four miles from my qth is where I found it.
It was coming from a ham I had talked to before but had not met yet.
I knocked on the door of the house (no antennas were apparent from the front of the house) and advised his wife about my theory and she went and retrieved her husband.
I advised him and he said he would go check.
After he returned from upstairs he advised me that his radio was not causing it.
I thanked him and when I got into my vehicle the transmission I had been detecting had ceased.
I was later told by a 'ham' friend of his we had in common that the radio had somehow (I forget) gotten locked into transmitt and was inadvertantly left unattended.
The tricky part in this situation was locating a transmission that was weaker than the repeater while the repeater was being used.
 
I'm going to make a little floating loop for 15 with a variable cap in series. Then a smaller loop inside. I need to borrow my buddies little Yacht Boy SW radio.

This is if I have trouble finding it. If it's still there when I get off work in the morning I'm gonna dig out my old emergency help CB that I scored from my neighbor. I just remembered I got that. Power it with a gell cell and carry it around.

It has to be close since I can hear it on my Gainmaster on 15 meters. I'm thinking its within a stones throw from my house.

Again, I'm thankful that nasty noise is vertically polarized. I usually use the GM to ragchew with the locals on 10 and 11 meters, but I can still work them all on my fan dipole.
 
Found it.

3 houses down in their garage. Battery tender trickle charger on a guys riding mower. He took it off and let me bring it home. Gonna RFI proof it for him.
 
RADIOOMAN said:
Good deal.
Curious about the brand/model.
Might be useful information for some.
Click to expand...

Here's a pic. My dad has a box of toroids I'm going to root through first. It has a long ass cord on it.

IMG_1434_zps208f429f.jpg
 
Well that was a trip! I'll know next if I hear such a thing. I can sit in my car with the engine running and hear a medium high rashy noise through the receive on my radio. I keep my squelch turned fully counterclockwise in order to hear distant stations 60 or more miles away. The noise goes away when I shut down the engine. Of course I need to redo my ground. I bought a Browning noise filter but haven't installed it yet,especially after I've that filters are a poor attempt to reduce or eliminate the offending noise.
 
RADIOOMAN said:
Tanks
Almost forgot to ask; Please tell us what you used and your method of fox hunting.
Click to expand...

When I track powerline noise I use an Arrow 7 element 440 hand held beam with a Yaesu VX-2 or a VX-3 HT. They both receive VHF and 440 mHz AM and have selectable attentuation. I do a rough search on 136.000 mHz AM then swith to UHF AM. I can pinpoint the exact pole/s radiating RF. The local power company supervisor has been trained by Mike Martin of RFI Services - Radio Frequency Interference and Power Line Noise I then call him to come out to confirm and get a crew scheduled to come out to fix.

It's nice to track down the source if you can, since it saves the power company's investigator time. They have the big money equipment to pinpoint the exact source. Ultrasonic locator, hot stick, O' scope to read noise signatures at your antenna to compare with the source.

In this case, since the noise was so broad banded, I knew it had to be close. I took an old GE 40 channel walkie and walkied up and down the street and alley. Keep in mind that I know all of my neigbors, once I heard the noise peak I took the antennna off and held it up to the power meter that fed 3 suspected garages. I knew it had to be feeding back using the wiring as a radiator. Simple, crude and cheap, but it worked.
 
m42duster said:
When I track powerline noise I use an Arrow 7 element 440 hand held beam with a Yaesu VX-2 or a VX-3 HT. They both receive VHF and 440 mHz AM and have selectable attentuation. I do a rough search on 136.000 mHz AM then swith to UHF AM. I can pinpoint the exact pole/s radiating RF. The local power company supervisor has been trained by Mike Martin of RFI Services - Radio Frequency Interference and Power Line Noise I then call him to come out to confirm and get a crew scheduled to come out to fix.

It's nice to track down the source if you can, since it saves the power company's investigator time. They have the big money equipment to pinpoint the exact source. Ultrasonic locator, hot stick, O' scope to read noise signatures at your antenna to compare with the source.

In this case, since the noise was so broad banded, I knew it had to be close. I took an old GE 40 channel walkie and walkied up and down the street and alley. Keep in mind that I know all of my neigbors, once I heard the noise peak I took the antennna off and held it up to the power meter that fed 3 suspected garages. I knew it had to be feeding back using the wiring as a radiator. Simple, crude and cheap, but it worked.
Click to expand...

Good job.
And thanks for describing how you did it.
 
I had something similar - a really annoying alternating noise on AM and SSB just destroyed my receive.

It was so strong you could hear it in the mobile around the whole neighborhood up to about 2 football fields away from the source.

I thought I had tracked it to a utility box and the power company sent a specialist out with all the super fancy equipment and we opened the case and he said....no, it's coming through the power lines into the box but it's coming from somewhere else.

The guy was like a bloodhound and we walked around 3 houses until he decided which one it was coming from and we knocked on the door. The homeowner let us inside and he searched every room until finally it got really strong in the home office. He had the owner turn off the fax, computer, fan, etc and finally he flipped the switch on the power supply (which had a backup system built in) and the noise just vanished. So the noise was being generated in this power supply and was somehow running back down the power lines and the out into the whole neighborhoods wiring. Really bizarre.

The owner said he'd leave it off and get a new power supply, a week later I got the noise again. Nothing I could do really.....unluckily for the homeowner or luckily for me they went into foreclosure and moved out.

Airwaves have been quiet ever since. I never would have believed that something so small could have found a way to disturb such a large area with such strong interference.

The specialist told me that he's seen paper shredders etc mess things up and he said on the majority of the calls he gets its something like that OR it's something a homeowner has installed directly in the electrical wiring.
 
had the house to myself last night so i powered up the radio from a 12v jump pack and turned off the main house breaker, wow 3 s units of noise gone, turned power back on and then 1 breaker at a time till i found out what room it was,, the flat screen tv in one of the rooms was making 3 s units noise without even being turned on, that tv will be replaced soon!
 

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