Strategic importance of underwater radio communication Communicating with submerged submarines is one of the most complex challenges in radio engineering. Conventional radio bands such as HF, VHF, or UHF are almost completely absorbed by seawater within a few centimeters. For this reason, navies around the world rely on very low frequency (VLF) and extremely low…

The Duga-3 over-the-horizon (OTH) radar—globally known as the “Russian Woodpecker” because of its distinctive 10 Hz tapping sound on shortwave radio—remains one of the most iconic, powerful and controversial radio-engineering systems of the Cold War. Between 1976 and 1989, millions of radio operators, aviation professionals, HF engineers and intelligence agencies detected its intense burst transmissions…