Developed beginning in the 1830s, a telegraph line was a person-to-person text message system consisting of multiple telegraph offices linked by an overhead wire supported on telegraph poles.
In 1837, however, Carl August von Steinheil of Munich, Germany, found that by connecting one leg of the apparatus at each station to metal plates buried in the ground, he could eliminate one wire and use a single wire for telegraphic communication.
Morse in the United States and James Bowman Lindsay in Great Britain, who in August 1854, was able to demonstrate transmission across a mill dam at a distance of . US inventors William Henry Ward (1871) and Mahlon Loomis (1872) developed electrical conduction systems based on the erroneous belief that there was an electrified atmospheric stratum accessible at low altitude.
The ground was used as the return path for current in the telegraph circuit, to avoid having to use a second overhead wire. By the 1860s, the telegraph was the standard way to send most urgent commercial, diplomatic and military messages, and industrial nations had built continent-wide telegraph networks, with submarine telegraph cables allowing telegraph messages to bridge oceans.
A more practical demonstration of wireless transmission via conduction came in Amos Dolbear's 1879 magneto electric telephone that used ground conduction to transmit over a distance of a quarter of a mile. In the 1890s inventor Nikola Tesla worked on an air and ground conduction wireless electric power transmission system, similar to Loomis', which he planned to include wireless telegraphy.
Preece first noticed the effect in 1884 when overhead telegraph wires in Grays Inn Road were accidentally carrying messages sent on buried cables.
Inventors realized if a way could be found to send electrical impulses of Morse code between separate points without a connecting wire, it could revolutionize communications. The successful solution to this problem was the discovery of radio waves in 1887, and the development of practical radiotelegraphy transmitters and receivers by about 1899, described in the next section.
During the Great Blizzard of 1888, this system was used to send and receive wireless messages from trains buried in snowdrifts.
A more practical demonstration of wireless transmission via conduction came in Amos Dolbear's 1879 magneto electric telephone that used ground conduction to transmit over a distance of a quarter of a mile. In the 1890s inventor Nikola Tesla worked on an air and ground conduction wireless electric power transmission system, similar to Loomis', which he planned to include wireless telegraphy.
In tests across the Bristol Channel in 1892, Preece was able to telegraph across gaps of about .
The first practical radio transmitters and receivers invented in 1894–1895 by Guglielmo Marconi used radiotelegraphy.
Also, the relatively short distances that a practical Preece system could span meant that it had few advantages over underwater telegraph cables. ==Radiotelegraphy== Over several years starting in 1894, the Italian inventor Guglielmo Marconi worked on adapting the newly discovered phenomenon of radio waves to communication, turning what was essentially a laboratory experiment up to that point into a useful communication system, building the first radiotelegraphy system using them.
Preece and the GPO in Britain at first supported and gave financial backing to Marconi's experiments conducted on Salisbury Plain from 1896.
Inventors realized if a way could be found to send electrical impulses of Morse code between separate points without a connecting wire, it could revolutionize communications. The successful solution to this problem was the discovery of radio waves in 1887, and the development of practical radiotelegraphy transmitters and receivers by about 1899, described in the next section.
After Marconi sent wireless telegraphic signals across the Atlantic Ocean in 1901, the system began being used for regular communication including ship-to-shore and ship-to-ship communication. With this development, wireless telegraphy came to mean radiotelegraphy, Morse code transmitted by radio waves.
Beginning about 1908, powerful transoceanic radiotelegraphy stations transmitted commercial telegram traffic between countries at rates up to 200 words per minute. Radiotelegraphy was used for long-distance person-to-person commercial, diplomatic, and military text communication throughout the first half of the 20th century.
Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires.
By 1910, communication by what had been called "Hertzian waves" was being universally referred to as "radio", and the term wireless telegraphy has been largely replaced by the more modern term "radiotelegraphy". ===Continuous wave (CW)=== The primitive spark-gap transmitters used until 1920 transmitted by a modulation method called damped wave.
The primitive spark gap transmitters used until 1920 transmitted damped wave, which had very wide bandwidth and tended to interfere with other transmissions.
The vacuum tube (valve) transmitters which came into use after 1920 transmitted code by pulses of unmodulated sinusoidal carrier wave called continuous wave (CW), which is still used today.
By 1910, communication by what had been called "Hertzian waves" was being universally referred to as "radio", and the term wireless telegraphy has been largely replaced by the more modern term "radiotelegraphy". ===Continuous wave (CW)=== The primitive spark-gap transmitters used until 1920 transmitted by a modulation method called damped wave.
This type of emission was banned by 1930.
Since 2003, knowledge of Morse code and wireless telegraphy has no longer been required to obtain an amateur radio license in many countries, it is, however, still required in some countries to obtain a licence of a different class.
A 2021 analysis of over 700 million communications logged by the Club Log blog, and a similar review of data logged by the American Radio Relay League, both show that wireless telegraphy is the 2nd most popular mode of amateur radio communication, accounting for nearly 20% of contacts.
This makes it more popular than voice communication, but not as popular as the FT8 digital mode, which accounted for 60% of amateur radio contacts made in 2021.
As of 2021, licence Class A in Belarus and Estonia, or the General class in Monaco, or Class 1 in Ukraine require Morse proficiency to access the full amateur radio spectrum including the [frequency] (HF) bands.
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Page generated on 2021-08-05