Noise or RFI of S7 and higher is often experienced, which makes operating amateur ham radio frustrating or impossible. This happens with so many different antennas and equipment that the ARRL actually has a question on the exam about it. So, in support of the ARRL’s guidance, here is that question and answer from the Extra Class Exam;

E4E07 How can you determine if line noise interference is being generated within your home? 

C. By turning off the AC power line main circuit breaker and listening on a battery operated radio. 

What’s next? If turning off the main breaker and listening on a battery-operated radio removes the interference, then next steps would be to turn the main breaker on and turn each individual breaker off till the noisy circuit is found. Next, find the item on that breaker causing the issue, which might be the breaker itself. If it is the breaker, then you should replace it and keep your house from a possible fire. If it’s a device on that circuit, replace it. 

Here is a testimony from Christine Shustak who did it right:

For years, I’ve been plagued by pretty nasty noise levels in my home. After seeing that noise at 20 over 9 on 10 meters, I finally got motivated to figure it out.

Moved the shack to battery power, and killed the grid power to the house.

Noise dropped to s3.

I then turned off all the breakers, and then started adding them back, one at a time. One breaker kicked the noise through the roof.

The culprit?

A Chinese, power supply for my Samsung laptop. Unplugged the supply, no noise.

I should have done this years ago.