Old-timers may remember the "Russian woodpecker," an over-the-horizon (OTH) radar system in the 1980s that moved through the HF spectrum, creating major interference on the ham bands whenever its signal passed through. Now, according to the ARRL Letter, a mysterious foghorn-like signal has been disrupting communications on the 40, 30 and 20-meter bands. The IARU's Region 1 Monitoring Service says it has traced the source of the signal to a Chinese OTH burst radar system.
