Underwater radio communication is an important component of global technology in the 21st century, but at the same time continues to be a very challenging part as it has many uses in various spheres including underwater diving, deep sea exploration, oil exploration, naval submarine operations etc.
Communication with underwater submarines is difficult because radio waves don’t travel well through thick electrical conductors like salt water. The obvious solution is to surface and raise an antenna above the water, then use ordinary radio transmissions. Early submarines had to frequently surface anyway for the oxygen needed by their diesel engines. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months.
Now, with India planning a larger fleet of nuclear-powered submarines, which can prowl underwater for several months at a time, the Indian Navy has acquired a new advanced facility to communicate with the silent predators. India is among a handful of nations in the world that has state-of-the-art very low frequency (VLF) transmitting station. This new facility would provide a boost to the Navy’s ability to communicate with deployed ships and submarines on an uninterrupted basis throughout the year. Admiral RK Dhowan, Chief of the Naval Staff, inaugurated the new transmitting station at INS Kattaboman, Tirunelvelli, Tamil Nadu recently.
The new facility incorporates modern technology and will provide the Navy enhanced reach, redundancy and operational features. Indian Navy has an elaborate communication infrastructure, including modern satellite communication facilities, to link and network its deployed units around the world with their home bases and command and control centres. The new VLF station will strengthen this infrastructure and provide the Navy additional operational advantages.
The new facility equipment has been constructed by Larsen & Turbo divisions in Chennai and Bengaluru. Interestingly, the facility boasts of the highest masts structures in India, as well as several other unique engineering feats. VLF transmitters require huge antennae suspended high above the ground. These antennaes, in India, are developed by DRDO.
VLF radio waves (3–30 kHz) can penetrate seawater to a depth of approximately 20 meters. Hence a submarine at shallow depth can use these frequencies. A vessel more deeply submerged might use a buoy on a long cable equipped with an antenna. The buoy rises to a few meters below the surface, and may be small enough to remain undetected by enemy sonar.
Due to the low frequency, a VLF broadcast aerial needs to be quite big. In