Scientific theory and verification

James Clerk Maxwell performed the theoretical physical research that correctly predicted the existence of radio (and all other electromagnetic) waves. Heinrich Rudolf Hertz was the experimental physicist who created radio waves in a controlled laboratory manner. Neither Maxwell nor Hertz, though, devised systems for actual general use or described the application of the technology.

Developments, parallel to these individuals and after, are engineering investigations that lead to 'the invention of radio': the objects, processes, or techniques of information transception. Many individuals contributed to the art of wireless, in the air, earth, and water; this includes the precursory work in wireless telephony and wireless telegraphy.

David E.Hughes, eight years before Hertz's experiments and nearly two decades before Gugliemo Marconi’s demonstrations, induced electromagnetic waves in a signalling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals. In 1885, T.A.Edison used a vibrator magnet for induction transmission. In 1888, Edison deployed a system of signalling on the Lehigh Valley Railroad. In 1891, Edison attained the wireless patent for this method using inductance.

From 1886 to 1888 inclusive in his classic experiments, Heinrich Hertz had proved that the properties of radio waves were consistent with Maxwell’s electromagnetic theory. He demonstrated that radio radiation had all the properties of waves (now called Hertzian waves), and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.

Hertz’s setup for a source and detector of radio waves comprised a primitive radio system capable of transmitting and receiving space waves through free space. His transmitter was not at all efficient and was severely limited in power output. Its dipole antenna differed from the vertical quarter-wavelength antenna that was subsequently adopted by Marconi and others in that it was not grounded.

Hertz used the damped oscillating currents in a dipole antenna, triggered by a high-voltage electrical capacitive spark discharge, as his source of radio waves. His detector in some experiments was another dipole antenna connected to a narrow spark gap. A small spark in this gap signified detection of the radio wave. When he added cylindrical reflectors behind his dipole antennas, Hertz could detect radio waves about 20 metres from the transmitter in his laboratory. He did not try to transmit further because he wanted to prove electromagnetic theory, not to develop wireless communications.

Hertz seemed uninterested in the practical importance of his experiments. He stated that " It's of no use whatsoever... this is just an experiment that proves Maestro Maxwell was right - we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there. " Asked about the ramifications of his discoveries, Hertz replied, " Nothing, I guess. " Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application." Hertz died in 1894, so the art of radio was left to others to implement into a practical useful form. His discoveries would later be taken up by entrepreneurs looking to make their fortunes. Marconi's 1895 experiments followed Hertz's work (among others) by using a spark source in what became known as a spark-gap transmitter.

Priority in the invention of radioTesla’s pioneering contribution to radio technology was a reworking of the primitive Hertz spark-gap transmitter; introduction of the coupled tuned circuit with the energy storage capacitor and discharger repositioned to the primary side of the transformer. This is the classic Tesla coil configuration, with primary and secondary circuits tuned to vibrate in harmony. These modifications allowed significantly higher levels of radio-frequency energy to be concentrated into a damped or partially damped wave, and ultimately a practically undamped wave. Some historians credit Reginald Fessenden in 1900 for making these improvements. Others credit Adolph Slaby. Still others say it was Ferdinand Braun, in a hastily improvised demonstration performed in September 1898. Braun, together with Marconi, received the Nobel Prize in physics for this replication of Tesla’s discovery.

Actually, it was Nikola Tesla who first revealed the basic techniques for improving transmitter performance. He did this in a series of U.S. patents, starting with his "System of Electric Lighting", Patent No. 454,622, dated June 23, 1891, the accompanying drawing of which clearly shows an energy storage capacitor and a discharge device on the primary side of a resonance transformer. In1893, at a public meeting of the National Electric Light Association in St. Louis, this radio-frequency power supply circuit was used to demonstrate the world's first practical radio transmitter.

His patent "Means for Generating Electric Currents" No. 514,168 of February 6, 1894, describes a variation of the 1891 circuit. Between September 15, 1896 and November 18, 189817 patents were granted to Tesla for apparatus and methods directly related to the production of high power radio-frequency electrical currents.

On 2 September 1897 Tesla filed his first application which was directly related to wireless transmission and reception, resulting in two patents that were subsequently issued as "System of..." and "Apparatus for Transmission of Electrical Energy", dated March 20 and may 15, 1900 respectively.

In 1904 Marconi got his own patent, declaring principles that Tesla had developed. The issue of patent infringement by Marconi was addressed in a lawsuit brought by Tesla in 1915. Nothing significant resulted from this litigation and shortly thereafter the Marconi Wireless Telegraph Company of America itself sued the United States for alleged damages resulting from the use of wireless during World War I. In response, a 1935 ruling by the United States Court of Claims essentially invalidated the fundamental Marconi patent. It was decided that the basic apparatus associated with radio communications had, in fact, been anticipated by Tesla.

Exercises for control

21.Translate the following expressions into English: беспроводная связь, обобщить результаты, присоединить приёмник к прибору, провести практические испытания, принимать звуковые сигналы, обнаружить электромагнитные колебания, важное изобретение, знание теории.

22. Make up word combinations using the words from two given columns:

to possess audible signals

to perfect electrical oscillations

to transmit a receiver

to construct invention

to discover experience

to attach the results of experiments

to solve electrical energy

to prove the problem of transmitting

to generate free wire to the device

to summarize the existence of electromagnetic waves

23. Give the derivatives to the words: engineer, success, introduce, to detect, significance, scientist, electricity, receiver, existence, invention.

24. Change the word order to make complete sentences:

1. of his | secret | inventor | didn’t make | The great | discovery.

2. is | of Popov’s | telegraphy | experiments | The wireless | the result.

3. between | and the sea | communication | He | the shore | radio | effected.

4. knowledge | of our | in the field of | college | a broad | The students | radio | possess | engineering.

5. was very | for science | of electromagnetism | practical | important | and | The discovery | life.

6. at a distance | could | The receiver | electromagnetic | detect | waves.

7. the Navy | electricity | Popov | into | introduced.

8. warning of | was | His device | approaching | thunderstorm | used for.

25. Translate from English: 1. Hertz proved by experiments the existence of electromagnetic waves. 2. Popov paid attention to the works of Hertz. 3. The receiver detected the waves at a long distance and recorded waves generated by lightning discharges. 4. Popov hoped to perfect his device. He wanted it to transmit signals at a distance by means of rapid electrical oscillations. 5. Hertz proved by experiments the existence of electromagnetic waves. 6. Popov paid attention to the works of Hertz. 7. The receiver detected the waves at a long distance and recorded waves generated by lightning discharges. 8. Popov hoped to perfect his device. He wanted it to transmit signals at a distance by means of rapid electrical oscillations.

26. Translate the sentences into English: 1. Используя свои широкие теоретические знания и практический опыт, Попов сконструировал несколько важных приборов. 2. В 1898 г. Попов изобрел приемник, который мог принимать звуковые сигналы. 3. Ученый делал доклады о своем открытии на собрания научных обществ. 4. В жизни мы пользуемся предметами, изобретенными Поповым. 5. Попов решил много практических проблем в области радиотехники. 6. Его первый приёмник мог обнаруживать электромагнитные волны и передавать их на расстояние нескольких метров. 7. Через несколько лет он продемонстрировал передачу слов по беспроводному телеграфу. 8. Попов осуществил радиосвязь между берегом и морем.

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