The History of Marine Radio

Marine radio improves communications on and over the water.

Early ship-to-ship or ship-to-shore communications consisted of flag signals and bells or foghorns, each with severe limitations such as requiring clear line-of-sight or having a limited audible range. The invention of marine radio radically improved communications on and over the water.

Inventors

Researchers such as O.A. Steinheil and S.F.B. Morse attempted to discover a means to use telegraphy without wires---especially over water---as early as 1795. In the late 1800s, Graham Bell recommended trailing wires behind ships at sea to provide a ground connection for telephones on board, and Thomas Edison submitted patents for a system using static electricity for long-distance communications. Based on Heinrich Hertz's work on electro-dynamic waves and incorporating telegraph signals designed by Morse, Guglielmo Marconi produced and patented an efficient and successful system for wireless signals, using electric oscillations of high frequency.

Early Equipment

Marconi's system used spark-gap transmitters, in which electrical sparks jump a gap and create radio frequencies by generating oscillations. In 1906 Reginald Fessenden demonstrated a system using high-speed alternators to transmit audio radio signals. George D. Squier, while working for the U.S. Army Signal Corps, discovered how to direct the signals from alternator-transmitters in specific directions. Eventually the development of more efficient vacuum-tube transmitters caused radio operators to phase out the use of both spark gap and alternator transmitters by the early 1920s.

Marine Radio Uses

The United States Navy began using Marconi's system on its ships by 1905 and by 1912 radio transmitters assisted communications on all major passenger liners. Marine radios also sent mail packets between Belgium and England, maintained contact between fishing vessels and provided communications in emergencies such as the sinking of the Titanic. By 1910 bulk-carriers, freighters and towboats on the Great Lakes and inland rivers used marine radio for commercial river communications with land-based stations. Despite its expanded commercial use, in 1913 the Navy lobbied the government for a monopoly of radio transmitters. The Navy temporarily obtained its goal in 1917, when the government took over control of all radio communications during World War One.

Amateur Interference

While difficult to obtain, technical information on radio construction could be located by determined amateurs, and by 1912 these amateurs sometimes dominated the airwaves. Navy stations in Newport, Rhode Island, Washington, D.C. and Boston reported various cases of interference by amateurs, some from maliciousness and some from crude and inefficient equipment. After amateurs disrupted a distress message from the torpedo boat destroyer Terry, the Navy published its support of laws placing operating restrictions on amateurs. In 1912, "An Act to Regulate Radio Communication" became the first U.S. regulation of radio, including limiting amateurs to certain frequencies and permitting some to apply for special licenses allowing access to better wavelengths.

Advanced Equipment

Advancements in marine radio equipment continued during and after World War One. Vacuum tubes replaced early spark gap and alternator transmitters, providing greater versatility and accuracy in radio transmissions. However, their disadvantages included high costs, the need for frequent replacement and large battery power requirements. Eventually more favorable alternatives developed, included oscillating crystals and superheterodyne receivers---which mix two or more signals together to achieve greater selectivity of desired frequencies. These advances became common after World War II, and have since been enhanced by the development of solid-state electronic circuits.

References

• United States Early Radio History: Thomas H. White
• "A History of Wireless Telegraphy:" J.J. Fahie; 1901
• Inland Marine Radio History Archive: Overview