Radio telegraphy was the original wireless
Did you know that Marconi sent the first transatlantic message by radio in 1901, but Tesla is credited as the inventor of the idea?
This little-known dispute was resolved by the U.S. Supreme Court in 1944 based, in part, on Tesla’s disclosure of radio communication circuits in a lecture he gave in 1893.
Marconi’s first patent was dated 1897. Marconi’s practical applications received the most publicity and his early credit as the inventor. Such inventions followed by lawsuits were as common in early radio as they are in today’s high-tech industries.
In the early days, radio was used exclusively for sending and receiving messages without the wires that telegraphs required, hence the term “wireless.”
If you were to listen to a radio receiver back then, all you would have heard across the entire band was the buzzing dots and dashes of Morse code.
The original spark gap transmitters splattered swaths of frequencies — they couldn’t be tuned to any one frequency.
Their transmissions were like lightning during a thunderstorm, producing static across the entire band. The SOS sent by the sinking Titanic in 1912 would have been a buzzing “. . . – – – . . .”
One of the first vacuum tubes used in radio, the Fleming Valve, was essentially a lightbulb with a metal plate near the hot filament.
When this plate had a more positive charge, it attracted the negatively charged electrons from the hot filament, causing a current to flow in one direction — hence the name “valve.”
Fleming discovered that his tube could function as a reliable detector of radio signals. It replaced a more rudimentary system that required radio operators to spend valuable minutes adjusting the position of the thin “cat whisker” wire touching a galena crystal.
A significant breakthrough in radio came when inventors added a wire grid electrode to the vacuum tube between the filament and the plate.
Lee De Forest discovered that radio signals fed from the antenna to the grid allowed the tube to detect and amplify the signals. As a result, weak signals were easier to detect.
The Westinghouse Co. sued De Forest, claiming that it had invented this new type of radio. As a result of that lawsuit, lasting from 1917 until 1924, radio operators were prohibited by law from using the vacuum tube receivers.
During these years, my father was a commercial radio operator on a ship in the Caribbean owned by the United Fruit Co.
He would tell the little-known story of how career operators smuggled vacuum tube radios onto their ships in boxes marked “books.” They weren’t going to let legal squabbles keep them from receiving critical messages using the best equipment available.
Later, developers tried filtering circuits to narrow both the transmitted and the received frequencies in an attempt to isolate the increasing number of radio signals coming from land and sea.
These circuits helped, but the problem was finally solved by vacuum tube transmitters in World War I, which produced a precise and narrow signal called continuous wave, or CW for short.
The next major development, called amplitude modulation (AM), was huge. It allowed the CW signals from vacuum tubes to be modulated or altered by sounds such as human speech and music.
As a result, radio was transformed overnight in the 1920s from a tool for two-way communications to broadcasting, and radio receivers became household appliances for entertainment and news.
AM is still used today in spite of the invention of television, FM (frequency modulation) and satellite radio. CW was used whenever the United States military needed reliable, long-distance communications until a few years ago, when satellites became the primary method.
CW telegraphy is still used by amateur radio operators to communicate with other amateurs around the world.
Bill Liggett — call sign K0SLO — has been an amateur (ham) radio operator since 1959. He has a doctorate in applied social psychology and retired from School District 51 as director of research and program evaluation in 2007. He has volunteered at the Western Colorado Math and Science Center since 2001.