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Old 06-02-2012, 9:13 AM
kruser kruser is offline
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Join Date: Nov 2007
Location: St. Louis County, MO
Posts: 2,318
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Turning the breaker off and then back on a circuit at a time is a good method as long as the noise does stop when you kill the main.
I've also reduced the sensitivity of my "sniffer" radio (your G6) by turning on any attenuators. I ended up using an old and small transistor radio.
I'm in an apartment so I did not have good results. It all depended on what the neighbirs had plugged in.
Plasma TV's are known as a very bad noise source. My number one killer was afaulty dimmer in one of those pole or torcier lamps. It was one of the old quartz type that they outlawed due to fires from the lamps extrmeme heat.
It was in a neighbors apartment and was wiping out radio + my DSL connection. In this case, the lamp was located just inside the wall that all the power meters and main disconnects were located. So it was inducing its signal on the electrical wiring throughout the building. I was lucky and found it by using the AM radio. Then the neighbor was a nice kid whose DSL was also having issues but he never matched his DSL issues with when he turned that lamp on! He let me replace the dimmer with a fixed on/off switch as he said he always ran it full out anyway. Problem solved.
Then a had a bad case of noise again with the stronger signals in the AM broadcast range and I tracked that to something riding on the shield of the incoming cable tv coax. I thought I was screwed but a call to the cable co brought them out and they checked and cleaned all grounds in the amp cabinets mounted around the building. That helped but not fully. I still had a high noise floor. One day, it stopped so I suspect it was something noisy in a neighbors apartment that was riding along the coax as common mode noise.
In between that, I purchased a magnetic loop antenna and that cured all my noise problems.
I still like to use my longwires from time to time though so one day I come home to yet another noise source that was loud all over the bands.
I tracked that noise to be riding on the shield of another neighbors coax cables that fed to him from his directv dish on the roof. My longwire passed right over his coax at right angles. I moved my longwires to the other side of the large roof and that helped a ton. I later became freinds with that neighbor and he did the unplug the sat receiver test for me and the noise did stop. He let me try all kinds of filters but nothing I tried would fully stop the noise. His dish was also located very near my scanner antennas and the new loop so I moved the entire dish to the furthest corner of the roof away from my antennas and that also cured most of that noise. I'd also tried grounding his receiver at the inside end but that did nothing at all. Same for grounding the dish coax at the dish end, no help.
Most of the noise I find seems to ride on the AC power wires or the shields of coax and it is almost always what it called common mode noise. It can be hard to stop.
Then I have a decent size power sub-station that is only maybe 200 yards from me. That thing is noisy but only when they switch loads around. Sometimes they will get a bad insulator that is arcing or a loose connection on the pole but the power co is very good at responding to and fixing RF noise complaints. The guy that does their noise issues gave me his cell number and told me to call him directly so he can get here quick as a lot of that noise comes and goes with the wind or even the humidity. It will start up when the humidity dries out during the day and then it goes away again at night when the humidity rises.
This guy has all kinds of things for finding it but he usually uses an ultrasonic receiver with a small parabolic dish that he listens for the noise when he gets close.

With any luck, your noise will stop when you kill your main and then only start back with a single breaker. Then just figure out what that breaker runs and start unplugging things on the circuit. As you turn the breakers back on, give each one some time for equipment to start back up or become warm. I had one that took several minutes before the noise would start so I did my test in reverse by listening as I turned each breaker off. As soon as I hit the correct breaker, the noise stopped.
Suspect items can be anything but watch for lamps/lights that are on dimmers, motion activated outdoor ligthing, many of the newer lamps can also cause noise. Both the CFL and LED types as well as some flourescent fixtures as most use electronic ballasts these days.
I've also found some cheap no name made in China computer power supplies that put out harmonics or noise on a wide range of frequencies in the HF and lower bands.

Your breaker switching idea is a very good starting point though and hopefully killing the main will stop your noise so you then know you have control of the noise and can usually find and cure it.
I don't have that luxury as I think I'd piss off a lot of people if I killed the main power coming into the apartment complex!
Sometimes it can be hard to fix or even find but give your breaker killing test a try and see what happens.

As rafdav said, please post back with your findings and good luck!
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