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Location: Mauston, Wisconsin | All bets are off, Padre! The Yooper is the Twilight Zone!!!!!!!! My guess would be a pulsed electromagnetic/RFI source on or near south shore of the lake.
Elf may have been shutdown/closed operationally, but are they maintaining it and sending a pulse signal as a way to keep the system available if needed?
Another source of pulsed EMI/RFI could be electric fences for cattle or dogs, assuming there are homes on or near the lake, these systems all use the earth as part of the circuit, therefore your sonar maybe picking up the pulses as a pulsing current typically is composed of many frequencies within the pulse bandwidth.
Is the lake close to a NWS weather radar location? Or is there an airport close by?
Have fun!
Al |