Who's up for a good mystery?

Al Carey · From: Dublin, NH USA

I have an intermittent noise in my home (basement)studio which is driving me up a wall. If anyone would be willing to help solve this I would be most grateful.

This is a long post, and I apologize in advance, but I need to give you all the steps I've done and what I've learned so far.

Here is a sample I recorded of the noise coming out of a guitar amp. The same noise comes thru several different amps and guitars, using different outlets, cords, even from a battery-powered amp with no physical connection to AC wiring.
http://www.youtube.com/watch?v=QIXRZMnjqwc

The noise has a duration of ~4 seconds, and happens every ~2 minutes. Sometimes it comes on more often for a longer time, but that is the "standard" pattern.

What I've done and what I've learned:
1. The noise comes thru an amp with a guitar plugged into it.
2. The amp can be standard AC-powered, or battery powered with no connection to AC power.
3. The same noise is picked up by several different guitar and amps, using different interconnect cables.
4. The noise is also picked up by a stereo headphone extension cable, plugged into a line in on my mixer.
5. The noise can be picked up in the same manner at the neighbor's house across the street(I brought a guitar and amps to their house and tested).
6. The noise can be picked up out on the street using battery powered equipment.
7. The noise still exists when the main breaker to the entire house house is off.
8. The noise is NOT picked up when the main breaker is off, AND the neutral wire from the street is disconnected at the panel.
9. The noise is not picked up by TV, radio, or stereo.

My conclusion from this is that the noise is carried by the AC neutral line, but then is emitted into the air.

The local power company came out and they could not detect the noise. They said it is not radio, but they could not tell anything else. They also said that the noise does not originate within there system and their is nothing else they can do to help me.

I've been having a long-running discussion about this with the guys at gearslutz as well:
http://www.gearslutz.com/board/studio-building-acoustics/810721-please-help-intermittent-electrical-noise.html

Anyone has read this far, thank you. And anyone who can offer any kind help, a BIG thank you!
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Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Bruce Derr · From: Lee, New Hampshire, USA

Have you tried turning off each circuit in your house at the breaker panel one by one? Might help isolate the source. Maybe it is a controller switching something like a heater or pump? Do you have an acquarium?

Stephen Cowell · From: Round Rock, Texas, USA

+1 on the aquarium... check your neighbors. There are simple modifications that can fix this noise... basically you install a line filter on the aquarium heater plug. Radio Shack has line filters, or did.

Here's some website info that should help:

http://www.rfiservices.com/tips.htm

Things most commonly found to cause interference are:

Door Bell Transformers
Electric Blankets
Heating Pads (of all kinds)
Recessed Ceiling Light Fixtures
Furnace Control Circuits
TV Top & Stereo, Amplified Antennas
Aquarium Heaters
Screw In Photocells
Low Energy Compact (screw in) Florescent Lights
Touch Control Lamps
Clean Air Machines (table top and furnace type)
Light Dimmer Controls
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Al Carey · From: Dublin, NH USA

I still get the noise when the main breaker to the house is off. So no circuits are powered.

The noise goes away when the neutral is disconnected at the panel, at which point there is not physical connection to the street or power company.

Is there something in an aquarium that would match the timing pattern of the noise?
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Marvin Born · From: Ohio, USA

The list that Stephen provided is very good. Add to that list furnace and gas water heater igniters. Could also be a outside light, such as sodium, etc. They have a starter.

It sounds like some kind of arc. The problem is external to you home, since you switched off the main breaker and opened the neutral. The electric lines in our house are acting as antennas and carrying the signal.

There are two ways for the signal to get into you equipment, RF and induction, I would go with RF first, (regardless of what the power company says.) Find someone with a RF spectrum analyzer and connect the input to your neutral line and look at the RF spectrum, especially the low frequencies.

Locate some amateur radio operators and see if they can help you. Most cities have a "ham" club and many have an interference committee. This is most likely some kind of strong RF signal.

If you can't find a spectrum analyzer, than take a battery powered shortwaye radio and put the antenna very close to the power wires in your breaker box with the main turned off and tune all the way through the spectrum to hear the noise. Use you battery guitar amp as a monitor to know when to listen.

If you hear the noise on the radio. Walk the neighborhood and notice where it gets the strongest signal and close in on the source. If it is in someone home, you will have to get them to let you in in to search. (This will be hard.)

I have done many interference hunts, this sounds like a interesting one.

There is a stage in your amps that is acting like a detector and changing the RF noise to audio that you can hear. Since it can be heard in our amp, it is somewhere in the RF spectrum. Find the frequency first and then track it down. Knowing the frequency also will help determine what the device is. Most noises are repetitive frequency wise. Once you find it keep looking lower until you find the fundamental and use that as the listening frequency. The lower end of the broadcast band like 550 KHz is a good place to start. Find an open freq in your area and use that.

The repetition rate and duration time are good clues. When it changes, what else changes, outside temp., sunlight, rain, etc.

Marvin

Al Carey · From: Dublin, NH USA

Marvin Born · From: Ohio, USA

That is the type of device you need; however, the RF Explorer's lowest frequency is 15MHZ, it was designed to find actual transmitter problems, like harmonics, etc. I suspect your problem is much lower, that is why the power company did you no good. Their equipment may not go low enough in frequency. What you really need is something that goes down in the 100KHz range.

Try a little portable radio in the low end of the AM broadcast band first. You may here it there. (you have to use an AM detector, SSB or FM will not work.
Keep in touch, I may have other ideas you you do your testing.

Are you going to the Dallas steel Show?

There is a Amateur Radio group, called ARRL, whose hq is in Newington, Conn Their RF engineers are really sharp. You can google them for the web site.

Marvin

Tim Marcus · From: San Francisco, CA

keep in mind that the entire RF spectrum has changed dramatically within the past few years.

There are a lot of strange problems resulting from the sale of the "white spaces" here in San Francisco. Add in wiring from the early 1900's and you can get into some serious hair pulling.

Maybe you can try one of those equitech balanced power units for your studio. I have heard really good things about those devices cleaning up even the dirtiest power in warehouses converted to audio spaces. Not cheap though - maybe a local hifi dealer can demo one for you.
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Al Carey · From: Dublin, NH USA

I'm not going to the dallas show, I wish I could.

I'll try an AM radio, but I'd still like to find a way to measure it.

There's a ham group in the next town, I'll see if someone there can be of help.

Thanks again, I'll report back.
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Greg Cutshaw · From: Corry, PA, USA

I had that problem once. Tracked it down with a portable AM radio. It was a line transformer about 150 feet!!!!!!! from my house arcing like crazy. I've since experienced this noise all over our city as our electric company doesn't replace arcing transformers until they finally fail.

Greg

Paul Arntson · From: Washington, USA

Noise always takes the easiest path back to its source.
"The noise goes away when the neutral is disconnected at the panel" points in my mind to some other user on the system that shares the neutral with you.
If the noise bathes you all the time it could disappear if you open the neutral, interrupting the return path.
Can you temporarily separate the neutral and the ground to see if it's one or the other?

The radio buzzing I get is much more of a buzz and it does come from the power company. They called it an "arcing cutout" on somebody's transformer. It goes away when it rains. It could be within a mile or two of me.

Can you find it with an AM radio if you go around your neighborhood within a radius of several blocks of your house? You might experiment with touching an exposed part of the radio chassis to see if you can get it louder as it travels through you back to the ground?

Are the pulses precisely timed or are they apparently random? Is there any commercial usage within several blocks that might have an induction heater, a neon sign, or an arc welder? Is it consistent around the clock and in different weather conditions?
Is there a spread spectrum transmitter of any kind or a cell tower or maybe a radar?
High voltage lines? Substation?

Can you hook up an oscilloscope to the speaker output and look at the signal?

Dave Grafe · From: Hudson River Valley NY

What Paul said.

Stephen Cowell · From: Round Rock, Texas, USA

Al Carey · From: Dublin, NH USA

Thanks for all the good info, guys.

The noise is so consistent in its timing, it doesn't seem to me like something malfunctioning, except that it shouldn't be dumping its noise onto the AC lines. But not ruling anything out, certainly.

The noise is very consistent in its pattern: a 4 second burst every 2mins 8secs. Occasionally there will be a 2-3 minute period when it will be on more frequently, for a longer duration, but I have not found any consistency to that in terms of time of day, weather, anything I can see going on outside, etc.

I live in a fairly rural area, on a cul de sac of 12 houses. There are a couple small farms nearby, but no power stations, commercial or retail within a couple miles.

The power co ee told me that many devices use the neutral lines for communication, atomic clocks is one example he gave me.

Stephen: do you have an example of the model of radio I should look for? A quick amazon search turned up some expensive examples. Obviously I need something handheld.
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Al Carey · From: Dublin, NH USA

Another note: I sent an email to the local ham radio group, I'm waiting to hear back.
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Stephen Cowell · From: Round Rock, Texas, USA

Al, if you can't get a ham to bring some kind of 'snooper' rig then you might get by with a scanner tuned to the AM airplane band... up near 120MHz. I gather a broadcast AM radio didn't work?
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Al Carey · From: Dublin, NH USA

Stephen Cowell · From: Round Rock, Texas, USA

Al, since you hear the noise with a battery-powered amp, you might just start there... use a single-coil guitar... go around your neighborhood and see where it gets louder. You should be able to hold the guitar next to the outside electrical panel and hear the noise loudest. One of your neighbors has an aquarium heater going... offer to put a free line filter on it for them, this should fix all.

http://www.smarthome.com/_/Troubleshooting_Training/Noise_Filters_Attenuation_PLC_RF/_/t/1TZ/nav.aspx

The cheapest one should work fine.
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Al Carey · From: Dublin, NH USA

I've already walked up and down the street with a "test rig" consisting of guitar patch cord --> Apogee Jam --> iPod running Garageband.

That's how I discovered the noise was running throughout the neighborhood. Unfortunately, I couldn't detect a difference in the strength of the noise vs general 60hz hum.
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Jerry Fleming · From: Roanoke, Virginia, USA

Hi Al,

A couple of thoughts… Do you live near an airport or military base or perhaps near a terrestrial microwave path? It sure sounds like high intensity RF such as radar or chirps to me because of the reoccuring frequency. I agree with Steven and Greg most transformers generate broadband noise that would be pretty constant and easy to track down.

One thing to consider is a ham that is operating in a digital mode. I agree contacting the local amature radio club is a great place to start. We love a challenge! You can look up your neighbors that are operators who may be able to help.

I have also seen wireless weather stations generate some pretty nasty harmonics. Food for thought...

Best regards & Good Luck,

Jerry Fleming W4YKK

Marvin Born · From: Ohio, USA

The wireless weather station is a good idea, they normally operate in the 432 to 440 mhz, sharing space with the hams. However it does sound like telemetry updating.
Marvin

Jim Pitman · From: Waterbury Ctr. VT 05677 USA

One of the ham club guys may have a "Spectrum Analyzer"
It's kinda like an oscilloscope but rather than plotting amplitude vs time it plots amplitude vs frequency. You plug antenne into it. One can scan the entire magnetic spectrum.
The club may be interested in helping you in a geeky way.
Start with an omni-directional broadband antenna and scan for frequencies. It's likely a harmonic of a much higher RF frequency that lies is in the audio spectrum obviously. It is so strong it can be amplified by hi impedance inputs with hi gains like a guitar amp. Once the frequencies are found zoom in on them using the controls to narrow the bandwidth. See which frequency it is by watching it come and go with what your hear. Pug in a directional antenna. Rotate it to find what direction it is coming from. The signal will be strongest when pointing at the source. Go find out what's in line.
I do this for a living once in a while but I'm looking for small EMI leaks from new electronic products.

Al Carey · From: Dublin, NH USA

I haven't heard back from the ham club, but you guys have me hopeful they'll be willing and able to help...
_________________
Sierra U-12, Gretsch 6120, Fender Tele, old tube amps, etc...

Len Amaral · From: Rehoboth,MA 02769

There is a small device called a "Hum-X)that cured a lot of hum and external problems when I was gigging such as neon beer signs and beer coolers, etc.

Al Carey · From: Dublin, NH USA

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