Despite constant navigation on its waters, many aspects of the ocean remain mysterious. Ships have been facing the ocean’s hidden surfaces and unpredictable storms for most of history. By releasing sound waves, and measuring the time it takes for them to return, Sound Navigation and Ranging (sonar) aids with travel, navigation, and detection. In the early 1900s, a stubborn Canadian-born inventor created the first successful echo-ranging device — the Fessenden oscillator.
Reginald Fessenden created hundreds of patents throughout his life. He heavily studied radio waves, a kind of electromagnetic radiation. He eventually turned to their transmission through water, which led to the invention of the Fessenden oscillator. Before Fessenden’s invention, the tragedy of the RMS Titanic opened many eyes to the dangers lurking under the surface of the ocean. Organizations, such as the Submarine Signal Company (SSC), aimed to create a device that would prevent another disaster. It was the SSC, right here in Boston, that asked for Fessenden’s help with the receiver of its submarine bell system. He was not impressed by the product and wanted to create his own transmitter. When SSC executive Harold Fay denied his request, Fessenden invented a receiver and a transmitter through a loophole in his orders.
In the early 1900s, a stubborn Canadian-born inventor created the first successful echo-ranging device — the Fessenden oscillator.
The Fessenden oscillator was the first modern transducer used in sonar, and its design was similar to a microphone. It consisted of a steel cylinder with an inner copper tube that vibrated with an alternating current. In 1914, the oscillator sent and received morse code in Boston Harbor. Fessenden and SSC engineers also successfully tested it against an iceberg in Canada that same year. However, World War I broke out soon after, and the SSC focused on using the device for underwater signaling, not echo-ranging. This was not Fessenden’s intention, as he created the device to prevent situations like the RMS Titanic. He tried to sell the device’s ranging potential to the British Royal Navy and fell out of favor with the SSC. It was not until 1923 that the SSC sold the product as an echo-ranging device. Prior to 1923, the device was otherwise used as a telegraphy system. Fessenden’s invention was the earliest practical form of ship sonar, and part of its technology, along with the ideas behind it, are still used by modern ships. His strong-willed ambition, while causing conflicts in the early 1900s, continues to benefit society more than a century later.
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