In the late 19th century, inventors and experimenters sought to send telegraph signals without the use of wires. They used the term “wireless telegraphy” (or simply wireless) to describe sending Morse Code (dots and dashes) through the air. Once wireless telegraphy was shown to be feasible in the late 1890s, experimenters worked to develop continuous wave transmitters that could send voices and music by means of wireless telephony. By World War I (1914-18) the term “radio” had come into common use in America to describe both wireless telegraphy and telephony. This first museum gallery displays some of this early equipment.
The first wireless transmitters operated by generating sparks. When a “spark gap” is connected to an antenna and ground system, dots and dashes of Morse code can be transmitted as they are generated using a telegraph key. But spark transmitters can not carry voices or music because they don’t generate the continuous waves required. Arc transmitters and high frequency alternators were improved transmitters developed before World War I. Both could generate the continuous radio waves needed for radio telephony, allowing voice and music to be heard over the air. Beginning about 1920 they were slowly replaced with far more efficient vacuum tube transmitters that would dominate radio for decades. Initial wireless receivers used “coherer” detectors connected to Morse inkers, a device that printed out the dots and dashes on a paper tape. (We have a replica on display.) Later improvements included magnetic and crystal detectors, and later, vacuum tube detectors.
Until 1920, radio was solely used to communicate “point-to-point,” often where it would be difficult to string wires. Ship-to-shore communication was one early application, as was communication between the mainland and offshore islands. Radio operators saw wireless as a way to undercut high rates charged by telegraph companies, such as Western Union. Amateur operators (“hams”) steadily improved their transmitters and receivers. Often highly competent technically, they formed a cadre of knowledgeable people to assist the U.S. Army and Navy in World War I, and to help popularize radio’s use in communities across America.
The fact that anyone with a suitable receiver could “listen in” to wireless, however, was initially considered a serious disadvantage of radio as those sending messages couldn’t count on privacy! Only slowly did a few experimenters realize that this could actually be an advantage, and the idea of broadcasting to a wider audience was slowly developed by several people in widely scattered locations. When KDKA in Pittsburgh and a handful of stations elsewhere debuted on the air late in 1920, radio as a means for entertainment began to capture the public’s fancy.
On the stairs leading to the museum’s second gallery, there are brief displays about U.S. Navy radio transmitter NAA that dominated the Potomac River in the early 20th century. This stairway also includes information about the museum building, and Bowie’s role in broadcasting.