For quite some time I had seen a very high noise floor across most of the HF bands and it seemed to be getting worse. Very often the noise floor would be S9 or S9+ on 80 meters, 40 meters, and 20 meters. Making SSB contacts was very difficult because I simply couldn’t hear the other stations. FT8 was working fairly well, but it was clear from the decoding window that there were a lot of stations being replied to that my equipment wasn’t hearing.
Then we had a significant power outage due to a wildfire. My FT-897D has battery power, the batteries were fully charged, so I turned on the radio … and the noise was gone! The noise floor was down to about S3 or S4 across all the bands. The noise was definitely QRM … man-made interference.
Google search indicated that an AM radio with a reasonable antenna could be used to track down a noise source. I had an AM/FM/Short Wave little radio somewhere. I found it, put in some batteries, tuned to 540 kHz where an AM radio station was supposed to be, and heard the same noise which was covering up the radio station.
Thinking that the noise was coming from somewhere in the neighborhood, I went outside and found the noise decreasing as I went away from the house! The noise source was somewhere inside the house. Next stop was the basement and the circuit breaker panel. I turned the breakers off and on one by one. When I turned the breaker off for the “West Bedrooms”, the noise went away. It came back as soon as the breaker was turned on.
The house has two upstairs bedrooms on the west end that we don’t use as bedrooms. One has been converted into a study / piano room where Nina has her desk, computer, and stuff as well as the piano. The other room has my desks, computers, ham radio equipment, and all that related stuff. The noise was coming from one of these two rooms.
It wasn’t coming from Nina’s study. In my room the noise was much louder and as I ran the radio around the room the culprits were immediately clear!
I had two power strips with USB ports in the room. As soon as I switched them off, the noise mostly went away. I knew there was another of these power strips in the master bedroom. Turning that one off eliminated the rest of the noise.
These were expensive power strips! They are now replaced with normal cheap strips with no USB ports. I picked up an Anker six-port USB power supply which produces no noise. It’s now taking the place of the USB ports on those expensive power strips … which power strips are now at Deseret Industries. Hopefully they’ll be used in houses that don’t listen to AM or Short Wave radio!