Art Bernstein, N2KA, writes on the Yankee Clipper Contest Club mailing list:
Some time ago I posted a bit concerning whether or not anyone was hearing a signal on 160 meters, just at and above the FT8 frequency of 1840 kHz. I received some suggestions and also that no one else was hearing it.
After doing a lot of eliminating around the shack and determining it was coming from the outside, I did some research to find out who transmits on 160 meters in addition to Radio Amateurs.
What I found was interesting and brought back some memories from years ago I had never experienced.
Fishnet Buoy Beacons. For those not knowing what they are, they are buoys that help fishermen locate their nets that have been left to catch fish. I would have thought GPS would be used these days. These beacons typically have a range of 10-15 miles over salt water and I probably live around 10 miles or less from the salt water. Normally it wouldn’t be a problem when using narrower bandwidths on CW or SSB, but on FT-8 bandwidths are typically 3-5 kHz wide. At night the zero beat frequency is about 1841.35, during the day I just checked it to be a couple hundred Hz higher (drift due to heating?)
Anyone have any ideas regarding procedures to follow here? It is likely an unlicensed radiator interfering with a licensed service. It has no identifier. Already sent message to ARRL Regulatory desk and to Division Leader.