I don't have any SeaTalk instruments, most of my electronics are more than a decade old, are different brands and are not interfaced. When I first heard the interference I thought it was some inconsiderate operator sending a digital transmission. When I tried shutting down the Standard Horizon CP150 GPS the interference disappeared. I do have the GPS wired to provide data to a laptop but it wasn't connected at the time. Perhaps you could find a frequency and mode where the noise is particularly loud and begin turning your other electronics off one at a time.