Wireless telegraphy

wireless telegraphradiotelegraphywirelessradiotelegraphradio telegraphyradio telegraphW/TradioMarconi wirelessradiotelegraphic
Wireless telegraphy or radiotelegraphy is transmission of telegraph signals by radio waves; Before about 1910 when radio became dominant, the term wireless telegraphy was also used for various other experimental technologies for transmitting telegraph signals without wires, such as electromagnetic induction, and ground conduction telegraph systems.wikipedia
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Guglielmo Marconi

MarconiMarconi WirelessMarconi's Wireless Telegraph Company
Radiotelegraphy was the first means of radio communication; the first practical radio transmitters and receivers invented in 1894–5 by Guglielmo Marconi used radiotelegraphy.
Guglielmo Marconi, 1st Marquis of Marconi FRSA (25 April 1874 – 20 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio transmission, development of Marconi's law, and a radio telegraph system.

Radiotelephone

radiotelephonyradio telephoneradiophone
It continued to be the only type of radio transmission during the first three decades of radio, called the "wireless telegraphy era" up until World War I, when the development of amplitude modulation (AM) radiotelephony allowed sound (audio) to be transmitted by radio.
"Radiotelephony" means transmission of sound (audio) by radio, in contrast to radiotelegraphy (transmission of telegraph signals) or video transmission.

Spark-gap transmitter

spark gap transmitterspark transmitterspark transmitters
The primitive spark gap transmitters used until 1920 transmitted damped waves, which had very large bandwidth and tended to interfere with other transmissions.
Spark-gap transmitters were the first type of radio transmitter, and were the main type used during the wireless telegraphy or "spark" era, the first three decades of radio, from 1887 to the end of World War 1.

Morse code

MorseInternational Morse CodeMorse-code
In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code.
On the other hand, when the first airplane flight was made from California to Australia in 1928 on the Southern Cross, one of its four crewmen was its radio operator who communicated with ground stations via radio telegraph.

Telegraph key

Morse keykeyfist
In a manual system, the sending operator manipulates a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves.
Keys are used in all forms of electrical telegraph systems, such as landline or "wire" electrical telegraphy, and "wireless", or radio telegraphy.

Beat frequency oscillator

BFObeat-frequency oscillator
To make CW transmissions audible, the receiver requires a circuit called a beat frequency oscillator (BFO). In his "heterodyne" receiver, the incoming radiotelegraph signal is mixed in the receiver's detector crystal or vacuum tube with a constant sine wave generated by an electronic oscillator in the receiver called a beat frequency oscillator (BFO).
In a radio receiver, a beat frequency oscillator or BFO is a dedicated oscillator used to create an audio frequency signal from Morse code radiotelegraphy (CW) transmissions to make them audible.

Continuous wave

CWcontinuous-wavecontinuous-wave operation
The vacuum tube (valve) transmitters which came into use after 1920 transmitted code by pulses of unmodulated sinusoidal carrier wave called continuous waves (CW), which is still used today.
In early wireless telegraphy radio transmission, CW waves were also known as "undamped waves", to distinguish this method from damped wave signals produced by earlier spark gap type transmitters.

Telegraphy

telegraphtelegramcable
Beginning about 1908, powerful transoceanic radiotelegraphy stations transmitted commercial telegram traffic between countries at rates up to 200 words per minute.
Wireless telegraphy developed in the early twentieth century.

Amateur radio

ham radioamateur radio licenseamateur
Although this type of communication has been mostly replaced since its introduction over 100 years ago by other means of communication it is still used by amateur radio operators as well as some military services.
This radio callbook lists wireless telegraph stations in Canada and the United States, including 89 amateur radio stations.

Amplitude modulation

AMamplitude modulatedamplitude-modulated
It continued to be the only type of radio transmission during the first three decades of radio, called the "wireless telegraphy era" up until World War I, when the development of amplitude modulation (AM) radiotelephony allowed sound (audio) to be transmitted by radio.
The first radio transmitters, called spark gap transmitters, transmitted information by wireless telegraphy, using different length pulses of carrier wave to spell out text messages in Morse code.

Radio receiver

receiverreceiversRadios
Radiotelegraphy was the first means of radio communication; the first practical radio transmitters and receivers invented in 1894–5 by Guglielmo Marconi used radiotelegraphy.
So spark transmitters could not transmit sound, and instead transmitted information by radiotelegraphy.

Damped wave

damped
The primitive spark gap transmitters used until 1920 transmitted damped waves, which had very large bandwidth and tended to interfere with other transmissions.
Damped waves were the first practical means of radio communication, used during the wireless telegraphy era which ended around 1920.

Nikola Tesla

TeslaNicola TeslaTesla, Nikola
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.
Upon his arrival, he told reporters that he planned to conduct wireless telegraphy experiments, transmitting signals from Pikes Peak to Paris.

Arc converter

Poulsen arcarc transmitterArc transmitters
The first transmitters able to produce continuous waves were the arc converter (Poulsen arc) transmitter, invented by Danish engineer Valdemar Poulsen in 1903, and the Alexanderson alternator, invented 1906-1912 by Reginald Fessenden and Ernst Alexanderson.
The arc converter, sometimes called the arc transmitter, or Poulsen arc after Danish engineer Valdemar Poulsen who invented it in 1903, was a variety of spark transmitter used in early wireless telegraphy.

Alexanderson alternator

Alexanderson Radio Alternatoralternator transmitterhigh frequency alternator
The first transmitters able to produce continuous waves were the arc converter (Poulsen arc) transmitter, invented by Danish engineer Valdemar Poulsen in 1903, and the Alexanderson alternator, invented 1906-1912 by Reginald Fessenden and Ernst Alexanderson.
It was used from about 1910 in a few "superpower" longwave radiotelegraphy stations to transmit transoceanic message traffic by Morse code to similar stations all over the world.

Detector (radio)

detectordetectorsquadrature detector
In his "heterodyne" receiver, the incoming radiotelegraph signal is mixed in the receiver's detector crystal or vacuum tube with a constant sine wave generated by an electronic oscillator in the receiver called a beat frequency oscillator (BFO).
Unlike modern radio stations which transmit sound (an audio signal) on an uninterrupted carrier wave, early radio stations transmitted information by radiotelegraphy.

Salisbury Plain

Salisbury Plain Training AreaSalisbury PlainsImber Range
Preece and the GPO in Britain at first supported and gave financial backing to Marconi's experiments conducted on Salisbury Plain from 1896.
In September 1896, George Kemp and Guglielmo Marconi experimented with wireless telegraphy on Salisbury Plain, and achieved good results over a distance of 1.25 mi.

Amos Dolbear

A.E. DolbearAmos Emerson Dolbear
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 1899 his patent for it was purchased in an unsuccessful attempt to interfere with Guglielmo Marconi's wireless telegraphy patents in the United States.

William Henry Preece

William PreeceSir William Henry PreeceSir William Preece
The most successful creator of an electromagnetic induction telegraph system was William Preece, chief engineer of Post Office Telegraphs of the General Post Office (GPO) in the United Kingdom.
Preece also developed a wireless telegraphy and telephony system in 1892.

Heterodyne

heterodyningHeterodyne detectionfrequency shifting
In the detector the two frequencies subtract, and a beat frequency (heterodyne) at the difference between the two frequencies is produced:.
In 1901, Reginald Fessenden demonstrated a direct-conversion heterodyne receiver or beat receiver as a method of making continuous wave radiotelegraphy signals audible.

Imperial Wireless Chain

Beam Wireless ServiceImperial and International Communications LtdBeam Station
The Imperial Wireless Chain was a strategic international communications network of powerful long range radiotelegraphy stations, created to link the countries of the British Empire.

Shortwave radio

shortwaveshort waveshort-wave
The most advanced standard, CCITT R.44, automated both routing and encoding of messages by short wave transmissions.
Early long distance radio telegraphy used long waves, below 300 kilohertz (kHz).

Radio

radio communicationradio communicationswireless
Radiotelegraphy was the first means of radio communication; the first practical radio transmitters and receivers invented in 1894–5 by Guglielmo Marconi used radiotelegraphy.
The first practical radio communications systems, developed by Guglielmo Marconi in 1894-5, transmitted telegraph signals by radio waves, so radio communication was first called "wireless telegraphy".

Transmitter

radio transmittertransmittersradio transmitters
Radiotelegraphy was the first means of radio communication; the first practical radio transmitters and receivers invented in 1894–5 by Guglielmo Marconi used radiotelegraphy.
Spark transmitters could not transmit audio (sound) and instead transmitted information by radiotelegraphy, the operator tapped on a telegraph key which turned the transmitter on and off to produce pulses of radio waves spelling out text messages in Morse code.

Electrical telegraph

electric telegraphtelegraphtelegraph line
Wireless telegraphy or radiotelegraphy is transmission of telegraph signals by radio waves; Before about 1910 when radio became dominant, the term wireless telegraphy was also used for various other experimental technologies for transmitting telegraph signals without wires, such as electromagnetic induction, and ground conduction telegraph systems.
Resistance movements in occupied Europe sabotaged communications facilities such as telegraph lines, forcing the Germans to use wireless telegraphy, which could then be intercepted by Britain.