WICHITA FALLS MAN
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The Signal: A Local Radio Frequency Interference Story
It was just 10 days before Christmas 2024 when I noticed a strong tone on 14.040 MHz. My first thought was that someone was jamming the frequency. Spinning the dial, I found the tone on 14.080, 14.120, 14.160, and 14.200 MHz. I also found it on 7.040 and 7.080 MHz. The regular spacing of the signal was interesting. Was it something in the house, or was it coming from outside? Was it internal to the radio? No, I heard it on two other radios. By the way, I'm no Radio Frequency Interference (RFI) expert!
I started unplugging the half-dozen "wall wart" power supplies (known troublemakers), but that didn't solve the problem. It wasn't coming from our computers or TVs. Next, I checked other electronic items in the room and nearby rooms. That didn't help. Before flipping circuit breakers (my wife was watching TV), I put a small antenna on my tiny QRP Labs QCX Mini 20-meter CW transceiver and sniffed around the house and yard. As I walked down the street, the tone got louder and louder. As I approached a big Christmas light display, the signal was so loud I had to turn down the volume.
I didn't go past the house to confirm or eliminate the display as a suspect. I was happy to know the signal was not coming from my home. I'll wait until the display shuts down to see if the signal disappears. It's not shutting down the whole band so, for now, I can work around the noise.
One reason I was happy to know the signal was outside my home was an incident that happened 4 or 5 years ago. I noticed a "Cable TV" truck outside at about the same time our Internet went out. I checked with the technician and learned that he had pulled the plug on our service because we were somehow interfering with the cable service of nearby neighbors. Was it the three Ham Radio antennas that made us a suspect, or was he actually detecting something? He said another tech would come out the next day to explore further.
Such a tech did appear the next day. He just happened to be a Ham Radio operator. He thought my ground plane antenna was re-radiating garbage. He re-routed our cable farther away from the antenna, declared the problem solved, and re-connected our service. I didn't ask for a more detailed explanation. I was happy neighbors wouldn't be coming to the house with torches. I hope my 15-year-old Yaesu 857D is clean, but I put a low-pass filter inline!
UPDATE: I went mobile with the QCX Mini setup and found the strongest signal at the intersection where the Christmas decorations were located. All the decorations were off - no lights or inflatables. I drove a block in all directions, but that intersection had the strongest signal. Could there be power supplies still energized even if not under load? Two houses down on the other side of the intersection is a house with four solar panels on the roof. Could an inverter be causing the noise? And would either house cause a noise every 40 Kc across a band? I do not know. I'll watch and watch for a while. Maybe it will go away as quickly as it arrived.
Wichita Falls Man