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169-476: Fessenden is best known for his pioneering work developing radio technology, including the foundations of amplitude modulation (AM) radio. His achievements included the first transmission of speech by radio (1900), and the first two-way radiotelegraphic communication across the Atlantic Ocean (1906). In 1932 he reported that, in late 1906, he also made the first radio broadcast of entertainment and music, although

338-440: A digital-to-analog converter , typically at a frequency less than the desired RF-output frequency. The analog signal must then be shifted in frequency and linearly amplified to the desired frequency and power level (linear amplification must be used to prevent modulation distortion). This low-level method for AM is used in many Amateur Radio transceivers. AM may also be generated at a low level, using analog methods described in

507-527: A diode which is configured to act as envelope detector . Another type of demodulator, the product detector , can provide better-quality demodulation with additional circuit complexity. Purdue University Purdue University is a public land-grant research university in West Lafayette, Indiana , United States, and the flagship campus of the Purdue University system . The university

676-400: A video signal which represents images. In this sense, the carrier wave, which has a much higher frequency than the message signal, carries the information. At the receiving station, the message signal is extracted from the modulated carrier by demodulation . In general form, a modulation process of a sinusoidal carrier wave may be described by the following equation: A(t) represents

845-522: A yield rate (the percentage of accepted students who choose to attend the university) of 24.9%. Purdue's freshman retention rate is 92%, with 81.5% going on to graduate within six years. The university started test-optional admissions with the Fall 2021 incoming class in response to the COVID-19 pandemic and has extended this through Fall 2023. Of the 62% of the incoming freshman class who submitted SAT scores;

1014-480: A 20,000 frequency spark and compressed nitrogen gap, such good results were obtained that a demonstration was given to a number of electrical engineers, who signed affidavits that they considered the articulation as commercially good over twenty-five miles, and the sets were advertised for sale..." (In a 1908 review, he conceded that with this approach "The transmission was, however, still not absolutely perfect.") Fessenden's ultimate plan for an audio-capable transmitter

1183-527: A Fessenden-Trott Scholarship was established at Purdue University's School of Electrical and Computer Engineering, in memory of Reginald Fessenden and his wife. Fessenden's home at 45 Waban Hill Road in the village of Chestnut Hill in Newton, Massachusetts , is on the National Register of Historic Places and is also a U.S. National Historic Landmark . He bought the house in 1906 or earlier and owned it for

1352-405: A cigar sticking out of his mouth and a hat pulled down over his eyes. At home he liked to lie on the carpet, a cat on his chest. In this state of relaxation, Fessenden could imagine, invent and think his way to new ideas. Fessenden also had a reputation for being temperamental, although in his defense his wife later stated that "Fessenden was never a difficult man to W O R K with but he

1521-436: A compromise in terms of bandwidth) in order to reduce the required channel spacing. Another improvement over standard AM is obtained through reduction or suppression of the carrier component of the modulated spectrum. In figure 2 this is the spike in between the sidebands; even with full (100%) sine wave modulation, the power in the carrier component is twice that in the sidebands, yet it carries no unique information. Thus there

1690-412: A continuous-wave (CW) transmitter. The idea of using continuous-wave radio signals was in direct conflict with the current orthodoxy that the abrupt "whiplash" effect produced by large electrical sparks was needed in order to create adequately strong signals. John Ambrose Fleming , a Marconi associate, was particularly dismissive in his book The Principles of Electric Wave Telegraphy , a detailed review of

1859-460: A digital signal, in which case the technique is generally called amplitude-shift keying . For example, in AM radio communication, a continuous wave radio-frequency signal has its amplitude modulated by an audio waveform before transmission. The message signal determines the envelope of the transmitted waveform. In the frequency domain , amplitude modulation produces a signal with power concentrated at

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2028-511: A few kilometers, on a couple of occasions the test Brant Rock audio transmissions were apparently overheard by NESCO employee James C. Armor across the Atlantic at the Machrihanish site. Until the early 1930s, it was generally accepted that Lee de Forest , who conducted a series of test broadcasts beginning in 1907, and who was widely quoted promoting the potential of organized radio broadcasting,

2197-400: A frequency and phase reference to extract the modulation from the sidebands. In some modulation systems based on AM, a lower transmitter power is required through partial or total elimination of the carrier component, however receivers for these signals are more complex because they must provide a precise carrier frequency reference signal (usually as shifted to the intermediate frequency ) from

2366-474: A general audience, using the alternator-transmitter at Brant Rock. Fessenden remembered producing a short program that included a phonograph record of Ombra mai fu (Largo) by George Frideric Handel , followed by Fessenden playing Adolphe Adam 's carol O Holy Night on the violin and singing Adore and be Still by Gounod , and closing with a biblical passage: "Glory to God in the highest and on earth peace to men of good will" ( Luke 2:14). He also stated that

2535-455: A great increase in the number of radio stations experimenting with AM transmission of news or music. The vacuum tube was responsible for the rise of AM broadcasting around 1920, the first electronic mass communication medium. Amplitude modulation was virtually the only type used for radio broadcasting until FM broadcasting began after World War II. At the same time as AM radio began, telephone companies such as AT&T were developing

2704-466: A greatly reduced "pilot" carrier (in reduced-carrier transmission or DSB-RC) to use in the demodulation process. Even with the carrier eliminated in double-sideband suppressed-carrier transmission , carrier regeneration is possible using a Costas phase-locked loop . This does not work for single-sideband suppressed-carrier transmission (SSB-SC), leading to the characteristic "Donald Duck" sound from such receivers when slightly detuned. Single-sideband AM

2873-422: A handful realize that the battle ever happened... It was he who insisted, against the stormy protests of every recognized authority, that what we now call radio was worked by "continuous waves" of the kind discovered by Hertz, sent through the ether by the transmitting station as light waves are sent out by a flame. Marconi and others insisted, instead, that what was happening was the so-called "whiplash effect"... It

3042-446: A handout distributed to the demonstration witnesses, which stated "[Radio] Telephony is admirably adapted for transmitting news, stock quotations, music, race reports, etc. simultaneously over a city, on account of the fact that no wires are needed and a single apparatus can distribute to ten thousand subscribers as easily as to a few. It is proposed to erect stations for this purpose in the large cities here and abroad." However, other than

3211-408: A human voice for instance, the frequency content (horizontal axis) may be plotted as a function of time (vertical axis), as in figure 3. It can again be seen that as the modulation frequency content varies, an upper sideband is generated according to those frequencies shifted above the carrier frequency, and the same content mirror-imaged in the lower sideband below the carrier frequency. At all times,

3380-413: A junior technician. He participated in a broad range of projects, which included work in solving problems in chemistry, metallurgy, and electricity. However, in 1890, facing financial problems, Edison was forced to lay off most of the laboratory employees, including Fessenden. (Fessenden remained an admirer of Edison his entire life, and in 1925 stated that "there is only one figure in history which stands in

3549-603: A lack of verifiable details has led to some doubts about this claim. He did a majority of his work in the United States and, in addition to his Canadian citizenship, claimed U.S. citizenship through his American-born father. Reginald Fessenden was born October 6, 1866, in East Bolton , Canada East , the eldest of the Reverend Elisha Joseph Fessenden and Clementina Trenholme 's four children. Elisha Fessenden

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3718-717: A larger company such as the American Telephone & Telegraph Company (AT&T). After the December 21, 1906, demonstrations, AT&T was said to be planning to acquire NESCO, but financial setbacks caused the telephone company to reconsider, and NESCO was unable to find another buyer. There were growing strains between Fessenden and the company owners, and Fessenden's formation of the Fessenden Wireless Company of Canada in Montreal in 1906 may have led to suspicion that he

3887-555: A lecture reviewing "The Early History of Radio in the United States", H. P. Davis, commenting on entertainment offerings, asserted that "Reginald Fessenden, probably the first to attempt this, broadcast a program Christmas Eve 1906", but did not provide any additional details, and his comment was little noticed at the time. The first widely publicized information about Fessenden's early broadcasts did not appear until 1932, when an article prepared by former Fessenden associate Samuel M. Kintner, "Pittsburgh's Contributions to Radio", appeared in

4056-407: A locomotive, and for a Corliss steam engine —one of the most efficient engines of the time. Programs in education and home economics were soon established, as well as a short-lived school of medicine . By 1925, Purdue had the largest undergraduate engineering enrollment in the country, a status it would keep for half a century. President Edward C. Elliott oversaw a campus building program between

4225-453: A monthly autobiographical series titled "The Inventions of Reginald A. Fessenden", with the intention of publishing the completed installments as a book. However, instead of reviewing his radio work, Fessenden immediately went on a series of tangents, including discussions of which races he believed were the most capable of producing inventions, and the proper approach that government institutions should be taking in order to support inventors. (At

4394-472: A pilot program in 1995 and made a permanent program in 1999. The College of Health and Human Sciences was established in 2010 and is the newest college. It offers BS , MS and PhD degrees in all 9 of its academic units. Purdue's College of Liberal Arts contains the arts, social sciences and humanities programs at the university. Liberal arts courses have been taught at Purdue since its founding in 1874. The School of Science, Education, and Humanities

4563-491: A practical system of transmitting and receiving radio signals, then commonly known as " wireless telegraphy ". Fessenden began limited radio experimentation, and soon came to the conclusion that he could develop a far more efficient system than the spark-gap transmitter and coherer - receiver combination which had been created by Oliver Lodge and Marconi. By 1899 he was able to send radiotelegraph messages between Pittsburgh and Allegheny City (now an area of Pittsburgh), using

4732-464: A prototype alternator-transmitter would be ready, and a few years beyond that for high-power versions to become available. One concern was whether at these high speeds the alternator might disintegrate due to the high rotation speed tearing it apart. Because of this, as a precaution, while the alternator was being initially developed it was "placed in a pit surrounded by sandbags". Fessenden contracted with General Electric (GE) to help design and produce

4901-531: A public university in the state of Indiana, subject to multiple levels of approval. That school now operates as Purdue University Global , and aims to serve adult learners. On July 1, 2024, Purdue launched Purdue University in Indianapolis , an extension of the West Lafayette campus, after the formal split of Indiana University–Purdue University Indianapolis . It conveys Purdue West Lafayette degrees and has

5070-584: A rather small (or zero) remaining carrier amplitude. Modulation circuit designs may be classified as low- or high-level (depending on whether they modulate in a low-power domain—followed by amplification for transmission—or in the high-power domain of the transmitted signal). In modern radio systems, modulated signals are generated via digital signal processing (DSP). With DSP many types of AM are possible with software control (including DSB with carrier, SSB suppressed-carrier and independent sideband, or ISB). Calculated digital samples are converted to voltages with

5239-523: A receiver of his own design. In 1900 Fessenden left Pittsburgh to work for the United States Weather Bureau , with the objective of demonstrating the practicality of using coastal stations to transmit weather information, thereby avoiding the expense of the existing telegraph lines. The contract called for him to be paid $ 3,000 per year and provided with work space, assistance, and housing. Fessenden would retain ownership of any inventions, but

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5408-483: A reception scheme for continuous wave telegraphy and telephony", and recognized him as "One whose labors had been of great benefit." There was suspicion by Fessenden that these two awards had not been made in sincerity but in order to placate him. In his wife's biography, referring to the IRE medal, she quoted the proverb "beware of Greeks bearing gifts". The Scott Medal came under additional suspicion because it had been awarded at

5577-535: A second or more following such peaks, in between syllables or short pauses in the program. This is very acceptable for communications radios, where compression of the audio aids intelligibility. However it is absolutely undesired for music or normal broadcast programming, where a faithful reproduction of the original program, including its varying modulation levels, is expected. In 1982, the International Telecommunication Union (ITU) designated

5746-529: A second short program was broadcast on December 31 ( New Year's Eve ). The intended audience for both of these transmissions was primarily shipboard radio operators along the Atlantic seaboard. Fessenden claimed that the two programs had been widely publicized in advance, and the Christmas Eve broadcast had been heard "as far down" as Norfolk, Virginia , while the New Year Eve's broadcast had reached listeners in

5915-586: A series of high-frequency alternator-transmitters. In 1903, Charles Proteus Steinmetz of GE delivered a 10 kHz version which proved of limited use and could not be directly used as a radio transmitter. Fessenden's request for a faster, more powerful unit was assigned to Ernst F. W. Alexanderson , who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50 kHz, although with far less power than Fessenden's rotary-spark transmitters. The alternator-transmitter achieved

6084-417: A similar tower erected at Machrihanish in western Scotland. In January 1906, these stations made the first successful two-way transmission across the Atlantic, exchanging Morse code messages. (Marconi had only achieved one-way transmissions at this time.) However, the system was unable to reliably bridge this distance when the sun was up, or during the summer months when interference levels were higher, so work

6253-499: A single sine wave, as treated above. However, by the principle of Fourier decomposition , m(t) can be expressed as the sum of a set of sine waves of various frequencies, amplitudes, and phases. Carrying out the multiplication of 1 + m(t) with c(t) as above, the result consists of a sum of sine waves. Again, the carrier c(t) is present unchanged, but each frequency component of m at f i has two sidebands at frequencies f c + f i and f c – f i . The collection of

6422-421: A spark gap transmitter with a specially designed high frequency 10 kHz interrupter , over a distance of one mile (1.6 km) at Cobb Island, Maryland, US. His first transmitted words were, "Hello. One, two, three, four. Is it snowing where you are, Mr. Thiessen?". The words were barely intelligible above the background buzz of the spark. Fessenden was a significant figure in the development of AM radio. He

6591-403: A special modulator produces such a waveform at a low level followed by a linear amplifier . What's more, a standard AM receiver using an envelope detector is incapable of properly demodulating such a signal. Rather, synchronous detection is required. Thus double-sideband transmission is generally not referred to as "AM" even though it generates an identical RF waveform as standard AM as long as

6760-591: A stable local signal, which would not become available until the development of the oscillating vacuum-tube . Fessenden's initial Weather Bureau work took place at Cobb Island , Maryland, located in the Potomac River about 80 kilometers (50 mi) downstream from Washington, D.C. As the experimentation expanded, additional stations were built along the Atlantic Coast in North Carolina and Virginia. However, in

6929-541: A year working for the Imperial Bank at Woodstock because he had not yet reached the age of 16 needed to enroll in college. At the age of fourteen, he returned to his hometown in the Eastern Townships and went to the nearby Bishop's College School , which granted him a mathematics mastership (teaching job) and a scholarship for studying in its college division at University of Bishop's College . Thus, while Fessenden

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7098-475: Is on–off keying , the simplest form of amplitude-shift keying, in which ones and zeros are represented by the presence or absence of a carrier. On–off keying is likewise used by radio amateurs to transmit Morse code where it is known as continuous wave (CW) operation, even though the transmission is not strictly "continuous". A more complex form of AM, quadrature amplitude modulation is now more commonly used with digital data, while making more efficient use of

7267-448: Is a great advantage in efficiency in reducing or totally suppressing the carrier, either in conjunction with elimination of one sideband ( single-sideband suppressed-carrier transmission ) or with both sidebands remaining ( double sideband suppressed carrier ). While these suppressed carrier transmissions are efficient in terms of transmitter power, they require more sophisticated receivers employing synchronous detection and regeneration of

7436-410: Is a varying amplitude direct current, whose AC-component is the speech signal extracted at the central office for transmission to another subscriber. An additional function provided by the carrier in standard AM, but which is lost in either single or double-sideband suppressed-carrier transmission, is that it provides an amplitude reference. In the receiver, the automatic gain control (AGC) responds to

7605-451: Is always positive for undermodulation. If m > 1 then overmodulation occurs and reconstruction of message signal from the transmitted signal would lead in loss of original signal. Amplitude modulation results when the carrier c(t) is multiplied by the positive quantity (1 + m(t)/A) : In this simple case m is identical to the modulation index , discussed below. With m = 0.5 the amplitude modulated signal y ( t ) thus corresponds to

7774-615: Is between the Stadium and Centennial Malls. The Bell Tower is considered an icon of the university and can be found on many Purdue logos and those of the cities of Lafayette and West Lafayette . Southwest of the Stadium Mall is the Edward C. Elliott Hall of Music , one of the largest proscenium theaters in the world. Elliott Hall of Music serves as the home of the WBAA (AM) and WBAA-FM studios, and

7943-560: Is nevertheless used widely in amateur radio and other voice communications because it has power and bandwidth efficiency (cutting the RF bandwidth in half compared to standard AM). On the other hand, in medium wave and short wave broadcasting, standard AM with the full carrier allows for reception using inexpensive receivers. The broadcaster absorbs the extra power cost to greatly increase potential audience. A simple form of digital amplitude modulation which can be used for transmitting binary data

8112-464: Is not favored for music and high fidelity broadcasting, but rather for voice communications and broadcasts (sports, news, talk radio etc.). AM is also inefficient in power usage; at least two-thirds of the power is concentrated in the carrier signal. The carrier signal contains none of the original information being transmitted (voice, video, data, etc.). However its presence provides a simple means of demodulation using envelope detection , providing

8281-423: Is now Butler University as Indiana's land-grant, as well as the addition of an agriculture department at what is now Indiana State University . By 1869, Tippecanoe County 's offer included $ 150,000 (equivalent to $ 3.4 million in 2023) from Lafayette business leader and philanthropist John Purdue ; $ 50,000 from the county; and 100 acres (0.4 km ) of land from John Purdue and local residents. On May 6, 1869,

8450-517: Is probably not too much to say that the progress of radio was retarded a decade by this error... The whiplash theory faded gradually out of men's minds and was replaced by the continuous wave one with all too little credit to the man who had been right... Beginning in 1961, the Society of Exploration Geophysicists has annually awarded its Reginald Fessenden Award to "a person who has made a specific technical contribution to exploration geophysics". In 1980,

8619-487: Is remembered for his call in 1894 to rebuild the original Heavilon Hall "one brick higher" after it had been destroyed by a fire. By the end of the nineteenth century, the university was organized into schools of agriculture, engineering (mechanical, civil, and electrical), and pharmacy; former U.S. President Benjamin Harrison served on the board of trustees . Purdue's engineering laboratories included testing facilities for

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8788-404: Is shown in the first waveform, below. For m = 1.0 {\displaystyle m=1.0} , it varies by 100% as shown in the illustration below it. With 100% modulation the wave amplitude sometimes reaches zero, and this represents full modulation using standard AM and is often a target (in order to obtain the highest possible signal-to-noise ratio ) but mustn't be exceeded. Increasing

8957-447: Is sometimes called double-sideband amplitude modulation ( DSBAM ), because the standard method produces sidebands on either side of the carrier frequency. Single-sideband modulation uses bandpass filters to eliminate one of the sidebands and possibly the carrier signal, which improves the ratio of message power to total transmission power , reduces power handling requirements of line repeaters, and permits better bandwidth utilization of

9126-464: Is surrounded by other buildings used for academic and cultural purposes. Near this section of campus is Felix Haas Hall, which was constructed in 1909 as Memorial Gymnasium in memory of the 17 Purdue University football players, coaches, alumni, and fans who died in the Purdue Wreck railroad accident of 1903. The structure was renovated in 1985 to house the computer science department . In 2006, it

9295-491: Is unnecessary to carry on the experimental developments any further, and specifications are being drawn up for the erection of five stations for doing transatlantic and other cable work, and a commercial permit is being applied for in England." However, the tower collapse did in fact mark the end of NESCO's transatlantic efforts. Fessenden had a very early interest in the possibility of making audio radio transmissions, in contrast to

9464-450: Is well known for its competitive engineering curricula. The university has also been integral in America's history of aviation , having established the first college credit offered in flight training ; the first four-year bachelor's degree in aviation; and the first university airport: Purdue University Airport . Purdue's aviation technology and aeronautical engineering programs remain among

9633-541: The Fleming valve (1904) and the crystal detector (1906) also proved able to rectify AM signals, so the technological hurdle was generating AM waves; receiving them was not a problem. Early experiments in AM radio transmission, conducted by Fessenden, Valdemar Poulsen , Ernst Ruhmer , Quirino Majorana , Charles Herrold , and Lee de Forest , were hampered by the lack of a technology for amplification . The first practical continuous wave AM transmitters were based on either

9802-642: The Indiana General Assembly voted to take advantage of the Morrill Land-Grant Colleges Act of 1862 and began plans to establish an institution with a focus on agriculture and engineering with the preliminary name of the Indiana Agricultural College. Communities throughout the state offered facilities and funding in bids for the location of the new college. Popular proposals included designating Indiana University or what

9971-463: The Mercury Seven . Many of Purdue's engineering disciplines are recognized as top-ten programs in the U.S. The college as a whole is currently ranked 4th in the U.S. of all doctorate-granting engineering schools by U.S. News & World Report . The university's Exploratory Studies program supports undergraduate students who enter the university without having a declared major. It was founded as

10140-591: The Purdue Airport . Lyles Porter Hall houses interdisciplinary healthcare facilities and classroom space within the College of Health and Human Sciences as well as the West Lafayette branch of the Indiana University School of Medicine . The western portion of campus consists of student housing, dining, and recreation facilities. The Córdova Recreational Sports Center, built in 1957, is the first building in

10309-481: The Radio Corporation of America (RCA), which also inherited the longstanding Fessenden legal proceedings. Finally, on March 31, 1928, Fessenden settled his outstanding lawsuits with RCA, receiving a significant cash settlement. After Fessenden left NESCO, Ernst Alexanderson continued to work on alternator-transmitter development at General Electric, mostly for long range radiotelegraph use. He eventually developed

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10478-590: The Slayter Center of Performing Arts and Cary Quadrangle, one of the largest all-male housing units in the country. Purdue University is ranked 43rd in the annual ranking of 2024 U.S. News & World Report. The 2022 annual ranking of U.S. News & World Report categorizes Purdue University-West Lafayette as "more selective". For the Class of 2025 (enrolled fall 2021), Purdue received 59,173 applications and accepted 40,759 (68.9%). Of those accepted, 10,157 enrolled,

10647-531: The West Indies . Anticipation of the 2006 centennial anniversary of Fessenden's reported broadcasts brought renewed interest, as well as additional questions. A key issue was why, despite Fessenden's assertion that the two programs had been widely heard, there did not appear to be any independent corroborating evidence for his account. (Even the Helen Fessenden biography relies exclusively on details contained in

10816-434: The carrier frequency and two adjacent sidebands . Each sideband is equal in bandwidth to that of the modulating signal, and is a mirror image of the other. Standard AM is thus sometimes called "double-sideband amplitude modulation" (DSBAM). A disadvantage of all amplitude modulation techniques, not only standard AM, is that the receiver amplifies and detects noise and electromagnetic interference in equal proportion to

10985-404: The frequency of the carrier wave is varied, as in frequency modulation , or its phase , as in phase modulation . AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with Roberto Landell de Moura and Reginald Fessenden 's radiotelephone experiments in 1900. This original form of AM

11154-400: The 1910s the teams became segregated, and remained so until a student protest in 1947. Black students were not allowed to live in the residence halls until the 1940s. Black males were able to live in cooperatives, but Black females were not allowed to live anywhere in West Lafayette. In 1946, the women's dormitories were integrated by an order of the governor of Indiana. Helen Williams became

11323-469: The College of Liberal Arts. The university's College of Agriculture supports the university's charge as a land-grant university for the study of agriculture throughout the state. The College of Education offers undergraduate degrees in elementary education , social studies education, science education and special education , and graduate degrees in these and many other specialty areas of education . The Purdue University College of Engineering

11492-477: The December 1932 issue of The Proceedings of the Institute of Radio Engineers . This reviewed information included in a January 29, 1932, letter sent by Fessenden to Kintner. (Fessenden subsequently died five months before Kintner's article appeared). In this account, Fessenden reported that on the evening of December 24, 1906 ( Christmas Eve ), he had made the first of two radio broadcasts of music and entertainment to

11661-649: The Fathometer and other safety instruments for safety at sea". After settling his lawsuit with RCA, Fessenden purchased a small estate called "Wistowe" (previously the home of Charles Maxwell Allen, the United States Consul, who had hosted Samuel Clemens there), in Hamilton Parish , near to Flatts Village in Bermuda . He died there on July 22, 1932, and was interred in the cemetery of St. Mark's Church, Bermuda. On

11830-457: The Fessenden 'first broadcaster' controversy continues." The American Telephone Journal account of the December 21 alternator-transmitter demonstration included the statement that "It is admirably adapted to the transmission of news, music, etc. as, owing to the fact that no wires are needed, simultaneous transmission to many subscribers can be effected as easily as to a few", echoing the words of

11999-525: The General Assembly established the institution in Tippecanoe County as Purdue University, in the name of the principal benefactor. Classes began at Purdue on September 16, 1874, with six instructors and 39 students. Professor John S. Hougham was Purdue's first faculty member and served as acting president between the administrations of presidents Shortridge and White. A campus of five buildings

12168-588: The January 29, 1932, letter used by the Kintner article.) There was general consensus in the centennial discussions that Fessenden had the technical means to make broadcasts, given the widespread reports about the success of the December 21 alternator-transmitter demonstrations. However, because of the station's very low power, even if the broadcasts had taken place it was questionable if the range could have matched Fessenden's claim of being heard hundreds of kilometers away. In

12337-582: The Submarine Signal Company which built a widely used aid to navigation using bells, termed a submarine signal , acting much as an underwater foghorn. While there, he invented the Fessenden oscillator , an electromechanical transducer . Though the company immediately began replacing bells and primitive receivers on ships with the new device, it was also the basis for entirely new applications: underwater telegraphy and sonic distance measurement. The later

12506-819: The United States at Manhattan in New York City, and later had a son, Reginald Kennelly Fessenden, born May 7, 1893, in Lafayette, Allen, Indiana. Fessenden's classical education provided him with only a limited amount of scientific and technical training. Interested in increasing his skills in the electrical field, he moved to New York City in 1886, with hopes of gaining employment with the famous inventor, Thomas Edison . However, his initial attempts were rebuffed; in his first application Fessenden wrote, "Do not know anything about electricity, but can learn pretty quick," to which Edison replied, "Have enough men now who do not know about electricity." However, Fessenden persevered, and before

12675-529: The West Lafayette campus to give a speech about the influence of technological progress on job creation. In the 1990s, the university added more opportunities to study abroad and expanded its course offerings in world languages and cultures. The first buildings of the Discovery Park interdisciplinary research center were dedicated in 2004. On April 27, 2017, Purdue University announced plans to acquire for-profit college Kaplan University and convert it to

12844-474: The agreement also gave the Weather Bureau royalty-free use of any discoveries made during the term of the contract. Fessenden quickly made major advances, especially in receiver design, as he worked to develop audio reception of signals. His initial success came from the invention of a barretter detector . This was followed by an electrolytic detector , consisting of a fine wire dipped in nitric acid, which for

13013-499: The antenna. The limited power handling ability of the microphone severely limited the power of the first radiotelephones; many of the microphones were water-cooled. The 1912 discovery of the amplifying ability of the Audion tube , invented in 1906 by Lee de Forest , solved these problems. The vacuum tube feedback oscillator , invented in 1912 by Edwin Armstrong and Alexander Meissner ,

13182-411: The available bandwidth. A simple form of amplitude modulation is the transmission of speech signals from a traditional analog telephone set using a common battery local loop. The direct current provided by the central office battery is a carrier with a frequency of 0 Hz. It is modulated by a microphone ( transmitter ) in the telephone set according to the acoustic signal from the speaker. The result

13351-401: The bandwidth of an AM signal is narrower than one using frequency modulation (FM), it is twice as wide as single-sideband techniques; it thus may be viewed as spectrally inefficient. Within a frequency band, only half as many transmissions (or "channels") can thus be accommodated. For this reason analog television employs a variant of single-sideband (known as vestigial sideband , somewhat of

13520-412: The basic ideas leading to reflection seismology , a technique important for its use in exploring for petroleum, and received patents for diverse subjects that included tracer bullets , paging, television apparatus, and a turbo electric drive for ships. An inveterate tinkerer, Fessenden eventually became the holder of more than 500 patents. He could often be found in a river or lake, floating on his back,

13689-451: The carrier frequency. For that reason, standard AM continues to be widely used, especially in broadcast transmission, to allow for the use of inexpensive receivers using envelope detection . Even (analog) television, with a (largely) suppressed lower sideband, includes sufficient carrier power for use of envelope detection. But for communications systems where both transmitters and receivers can be optimized, suppression of both one sideband and

13858-454: The carrier frequency. Passing the modulated signal through another nonlinear device can extract the original baseband signal. His analysis also showed that only one sideband was necessary to transmit the audio signal, and Carson patented single-sideband modulation (SSB) on 1 December 1915. This advanced variant of amplitude modulation was adopted by AT&T for longwave transatlantic telephone service beginning 7 January 1927. After WW-II, it

14027-400: The carrier itself remains constant, and of greater power than the total sideband power. The RF bandwidth of an AM transmission (refer to figure 2, but only considering positive frequencies) is twice the bandwidth of the modulating (or " baseband ") signal, since the upper and lower sidebands around the carrier frequency each have a bandwidth as wide as the highest modulating frequency. Although

14196-468: The carrier represent a net advantage and are frequently employed. A technique used widely in broadcast AM transmitters is an application of the Hapburg carrier, first proposed in the 1930s but impractical with the technology then available. During periods of low modulation the carrier power would be reduced and would return to full power during periods of high modulation levels. This has the effect of reducing

14365-460: The carrier so that the reproduced audio level stays in a fixed proportion to the original modulation. On the other hand, with suppressed-carrier transmissions there is no transmitted power during pauses in the modulation, so the AGC must respond to peaks of the transmitted power during peaks in the modulation. This typically involves a so-called fast attack, slow decay circuit which holds the AGC level for

14534-450: The carrier wave to spell out text messages in Morse code . They could not transmit audio because the carrier consisted of strings of damped waves , pulses of radio waves that declined to zero, and sounded like a buzz in receivers. In effect they were already amplitude modulated. The first AM transmission was made by Canadian-born American researcher Reginald Fessenden on 23 December 1900 using

14703-533: The classical universities, White believed Purdue should be an "industrial college" and devote its resources toward providing a broad, liberal education with an emphasis on science, technology, and agriculture. Part of White's plan to distinguish Purdue from classical universities included a controversial attempt to ban fraternities, which was ultimately overturned by the Indiana Supreme Court . White resigned in protest. The next president, James H. Smart ,

14872-540: The close of the seventh installment, Radio News included a disclaimer that it was "not responsible for any opinions expressed in Dr. Fessenden's article".) After eleven installments Fessenden had only covered his life up to 1893, having discussed virtually nothing about radio, and the series was quietly terminated at this point. In 1921, the Institute of Radio Engineers presented Fessenden with its IRE Medal of Honor . The medallion

15041-492: The company Chegg, which provides AI-generated "homework help" that some consider to be plagiarism. Purdue is organized into 10 colleges and schools. In 2010, the College of Health and Human Sciences was formed, through combining existing academic units, including the School of Nursing, the School of Health Sciences, the College of Consumer and Family Sciences, and non-humanities majors psychology and hearing and speech pathology from

15210-426: The concept of continuous-wave radio signals. Fessenden's basic approach was disclosed in U.S. Patent 706,737, which he applied for on May 29, 1901, and was issued the next year. It called for the use of a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology,

15379-404: The device's manufacturing costs to be considered reasonable, and contracted with other companies to build equipment that used Fessenden designs. This led to bad feelings and a series of patent infringement lawsuits. An alternate plan to sell the company as a whole was unsuccessful in finding a buyer. Eventually a radical change in company orientation took place. In 1904 it was decided to compete with

15548-423: The early spark-gap transmissions that could only transmit Morse code messages. As early as 1891, he had investigated sending alternating currents of varying frequencies along telegraph lines, in order to create a multiplex telegraph system. He would later apply the knowledge gained about tuning and resonance from his alternating current electrical work to the higher frequency currents used in radio, in order to develop

15717-521: The echo ranging potential. The echo sounding was invented in 1912 by German physicist Alexander Behm . At the outbreak of World War I , Fessenden volunteered his services to the Canadian government and was sent to London where he developed a device to detect enemy artillery and another to locate enemy submarines. Other efforts included a version of microfilm , that helped him to keep a compact record of his inventions, projects and patents. He also patented

15886-529: The end of the year was hired for a semi-skilled position as an assistant tester for the Edison Machine Works , which was laying underground electrical mains in New York City. He quickly proved his worth, and received a series of promotions, with increasing responsibility for the project. In late 1886, Fessenden began working directly for Edison at the inventor's new laboratory in West Orange, New Jersey , as

16055-411: The existing ocean cables, by setting up a transatlantic radiotelegraph link. The headquarters for company operations was moved to Brant Rock , Massachusetts , which was to be the western terminal for the proposed new service. The plan was to conduct the transatlantic service using Fessenden-designed rotary spark-gap transmitters . A 420-foot (128 meter) guyed antenna was constructed at Brant Rock, with

16224-471: The fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He later reported that, on December 23, 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile), saying; “One, two, three, four. Is It snowing where you are, Mr. Thiessen? If so, telegraph back and let me know”, which appears to have been the first successful audio transmission using radio signals. However, at this time

16393-494: The first Black faculty member in 1968. Purdue's campus is situated in the small city of West Lafayette , near the western bank of the Wabash River , across which sits the larger city of Lafayette . Mitch Daniels Boulevard (formerly State Street) divides the northern and southern portions of campus. Academic buildings are mostly concentrated on the eastern and southern parts of campus, with residence halls and intramural fields to

16562-524: The first person to walk on the Moon; and Eugene Cernan , who was the last person to walk on the Moon. The English department at Purdue launched the first Online Writing Lab (OWL), in 1994. Many colleges and universities use the Purdue OWL website as an academic writing reference source for proper word usage, punctuation, grammar, and style. Professors criticized the partnership, begun in 2020, between OWL and

16731-534: The formation of the National Electric Signaling Company (NESCO) to support Fessenden's research. Initially the new company was based in Washington, D.C., where a station was constructed for experimental and demonstration purposes. Two additional demonstration stations were constructed at Collingswood, New Jersey (near Philadelphia) and Jersey City, New Jersey (near New York City). In 1904 an attempt

16900-493: The former frequencies above the carrier frequency is known as the upper sideband, and those below constitute the lower sideband. The modulation m(t) may be considered to consist of an equal mix of positive and negative frequency components, as shown in the top of figure 2. One can view the sidebands as that modulation m(t) having simply been shifted in frequency by f c as depicted at the bottom right of figure 2. The short-term spectrum of modulation, changing as it would for

17069-404: The goal of transmitting quality audio signals, but the lack of any way to amplify the signals meant they were somewhat weak. On December 21, 1906, Fessenden made an extensive demonstration of the new alternator-transmitter at Brant Rock, showing its utility for point-to-point wireless telephony, including interconnecting his stations to the wire telephone network. As part of the demonstration, speech

17238-531: The high-powered Alexanderson alternator , capable of transmitting across the Atlantic, and by 1916 the Fessenden-Alexanderson alternator was more reliable for transoceanic communication than the spark transmitters which were originally used to provide this service. Also, after 1920 radio broadcasting became widespread, and although the stations used vacuum-tube transmitters rather than alternator-transmitters (which vacuum-tubes made obsolete), they employed

17407-448: The huge, expensive Alexanderson alternator , developed 1906–1910, or versions of the Poulsen arc transmitter (arc converter), invented in 1903. The modifications necessary to transmit AM were clumsy and resulted in very low quality audio. Modulation was usually accomplished by a carbon microphone inserted directly in the antenna or ground wire; its varying resistance varied the current to

17576-648: The lighting for the 1893 Chicago World Columbian Exposition . Later that year, George Westinghouse personally recruited Fessenden for the newly created position of chair of the Electrical Engineering department at the Western University of Pennsylvania in Pittsburgh (now the University of Pittsburgh). In the late 1890s, reports began to appear about the success Guglielmo Marconi was having in developing

17745-584: The middle 50 percent Composite scores were 1190–1430. Of the 31% of enrolled freshmen in 2021 who submitted ACT scores; the middle 50 percent Composite score was between 26 and 33. Purdue University is a college-sponsor of the National Merit Scholarship Program and sponsored 88 Merit Scholarship awards in 2020. In the 2020–2021 academic year, 127 freshman students were National Merit Scholars . Purdue offers both undergraduate and graduate programs in over 211 major areas of study, and

17914-401: The midst of promising advances, Fessenden became embroiled in disputes with his sponsor. In particular, he charged that Bureau Chief Willis Moore had attempted to gain a half-share of the patents. Fessenden refused to sign over the rights, and his work for the Weather Bureau ended in August 1902. In November 1902, two wealthy Pittsburgh businessmen, Hay Walker Jr. and Thomas H. Given, financed

18083-489: The modulating signal beyond that point, known as overmodulation , causes a standard AM modulator (see below) to fail, as the negative excursions of the wave envelope cannot become less than zero, resulting in distortion ("clipping") of the received modulation. Transmitters typically incorporate a limiter circuit to avoid overmodulation, and/or a compressor circuit (especially for voice communications) in order to still approach 100% modulation for maximum intelligibility above

18252-443: The modulation amplitude and carrier amplitude, respectively; the modulation amplitude is the peak (positive or negative) change in the RF amplitude from its unmodulated value. Modulation index is normally expressed as a percentage, and may be displayed on a meter connected to an AM transmitter. So if m = 0.5 {\displaystyle m=0.5} , carrier amplitude varies by 50% above (and below) its unmodulated level, as

18421-409: The modulation index is below 100%. Such systems more often attempt a radical reduction of the carrier level compared to the sidebands (where the useful information is present) to the point of double-sideband suppressed-carrier transmission where the carrier is (ideally) reduced to zero. In all such cases the term "modulation index" loses its value as it refers to the ratio of the modulation amplitude to

18590-400: The most competitive aviation-specific programs in the world. In the mid-20th century, Purdue's aviation program expanded to encompass advanced spaceflight technology, giving rise to Purdue's nicknames Cradle of Astronauts and Mother of Astronauts . 26 Purdue graduates have become astronauts, including Gus Grissom , one of the original Mercury Seven astronauts; Neil Armstrong , who was

18759-428: The nation created solely to serve university student recreational needs. Much of the northern part of campus sits on land purchased for the university by industrialist David E. Ross and author George Ade in the 1920s. Many of Purdue's athletic facilities are there, including Ross–Ade Stadium ( American football ), Mackey Arena (basketball), and Lambert Fieldhouse (indoor track and field). This area also includes

18928-415: The next few years set the standard for sensitivity in radio reception. As his work progressed, Fessenden also developed the heterodyne principle , which used two closely spaced radio signals to produce an audible tone that made Morse code transmissions much easier to hear. However, heterodyne reception would not become practical for a decade after it was invented, because it required a method for producing

19097-534: The next section. High-power AM transmitters (such as those used for AM broadcasting ) are based on high-efficiency class-D and class-E power amplifier stages, modulated by varying the supply voltage. Older designs (for broadcast and amateur radio) also generate AM by controlling the gain of the transmitter's final amplifier (generally class-C, for efficiency). The following types are for vacuum tube transmitters (but similar options are available with transistors): The simplest form of AM demodulator consists of

19266-501: The next two years he worked as the headmaster and sole teacher. (This lack of a degree may have hurt Fessenden's employment opportunities. When McGill University in Montreal established an electrical engineering department, his application to become its chairman was turned down.) While in Bermuda, he became engaged to Helen May Trott of Smith's Parish . They married on September 21, 1890, in

19435-777: The ninth-largest foreign student population of any university in the United States. The university is home to the oldest computer science program in the United States. Purdue is the founding member of the Big Ten Conference and sponsors 18 intercollegiate sports teams. It has been affiliated with 13 Nobel laureates , 1 Turing Award laureate, 1 Bharat Ratna recipient, 27 astronauts , 2 World Food Prize laureates, 3 Pulitzer Prize winners, 18 Olympic medalists, 3 National Medal of Technology and Innovation recipients, 2 National Medal of Science recipients, 3 Presidential Medal of Freedom recipients, 7 members of Congress , 3 U.S. governors , and 2 heads of state. In 1865,

19604-542: The noise. Such circuits are sometimes referred to as a vogad . However it is possible to talk about a modulation index exceeding 100%, without introducing distortion, in the case of double-sideband reduced-carrier transmission . In that case, negative excursions beyond zero entail a reversal of the carrier phase, as shown in the third waveform below. This cannot be produced using the efficient high-level (output stage) modulation techniques (see below) which are widely used especially in high power broadcast transmitters. Rather,

19773-516: The occasion of his death, an editorial in the New York Herald Tribune , "Fessenden Against the World", said: It sometimes happens, even in science, that one man can be right against the world. Professor Fessenden was that man. It is ironic that among the hundreds of thousands of young radio engineers whose commonplaces of theory rest on what Professor Fessenden fought for bitterly and alone only

19942-404: The other large application for AM: sending multiple telephone calls through a single wire by modulating them on separate carrier frequencies, called frequency division multiplexing . In 1915, John Renshaw Carson formulated the first mathematical description of amplitude modulation, showing that a signal and carrier frequency combined in a nonlinear device creates a sideband on both sides of

20111-489: The overall power demand of the transmitter and is most effective on speech type programmes. Various trade names are used for its implementation by the transmitter manufacturers from the late 80's onwards. The AM modulation index is a measure based on the ratio of the modulation excursions of the RF signal to the level of the unmodulated carrier. It is thus defined as: where M {\displaystyle M\,} and A {\displaystyle A\,} are

20280-473: The period leading up to the centennial, James E. O'Neal conducted extensive research, but did not find any ships' radio log accounts, or any contemporary literature, to confirm the reported holiday broadcasts. A follow-up article two years later further reported that a similar attempt to verify the details of the broadcasts had taken place in 1956, which had also failed to uncover any confirmation of Fessenden's statements. One alternate possibility proposed by O'Neal

20449-468: The rest of his life. Citations General information Amplitude modulation Amplitude modulation ( AM ) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave . In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal . This technique contrasts with angle modulation , in which either

20618-421: The same academic rigor as the flagship campus. Purdue currently has a 28-acre (11 ha) footprint in downtown Indianapolis that includes space in the existing engineering and technology buildings, and has established partnerships with companies for facilities and shared spaces throughout the metro area . Purdue had black graduates by the 1890s, and in 1905 a Black man ran for its track team. But some time in

20787-478: The same continuous-wave AM signals that Fessenden had introduced in 1906. Although Fessenden ceased radio research after his dismissal from NESCO in 1911, he continued to work in other fields. As early as 1904 he had helped engineer the Niagara Falls power plant for the newly formed Hydro-Electric Power Commission of Ontario . However, his most extensive work was in marine communication as consulting engineer with

20956-480: The same rank as him as an inventor, i. e. Archimedes ".) Taking advantage of his recent practical experience, Fessenden was able to find positions with a series of manufacturing companies. In 1892, he received an appointment as professor for the newly formed Electrical Engineering department at Purdue University in West Lafayette, Indiana; while there he helped the Westinghouse Corporation install

21125-432: The signal. Increasing the received signal-to-noise ratio , say, by a factor of 10 (a 10 decibel improvement), thus would require increasing the transmitter power by a factor of 10. This is in contrast to frequency modulation (FM) and digital radio where the effect of such noise following demodulation is strongly reduced so long as the received signal is well above the threshold for reception. For this reason AM broadcast

21294-575: The site of the country's first college-credit flight training courses. Amelia Earhart joined the Purdue faculty in 1935 as a consultant for these flight courses and as a counselor on women's careers. In 1936, the Purdue Research Foundation provided the funds for the Lockheed Electra 10-E Earhart flew on her attempted round-the-world flight. Every school and department at the university

21463-542: The sound was far too distorted to be commercially practical, although as a test this did show that with further refinements it would become possible to effectively transmit sounds by radio. For a time Fessenden continued working with more sophisticated high-frequency spark transmitters, including versions that used compressed air, which began to take on some of the characteristics of arc-transmitters patented by Valdemar Poulsen . Fessenden unsuccessfully attempted to sell this form of radiotelephone, later noting: "In 1904, with

21632-483: The state of the art as he saw it that was published in 1906. Reviewing Fessenden's patent, he wrote that "The creation of an electric wave seems to involve a certain suddenness in the beginning of the oscillations, and an alternator giving a simple sine-curve would not be likely to produce the required effect..." (In view of Fessenden's ultimate success, this statement disappeared from the book's 1916 edition.) Fessenden's next step, taken from standard wire-telephone practice,

21801-432: The suggestion of Westinghouse engineers, who were working for a company that had had financial disputes with Fessenden. In Helen Fessenden's opinion, "The Medal cost [Westinghouse] nothing and was a good 'sop to Cereberus'", and overall compared the medals to "small change for tips in the pockets of Big Business". In 1929 Fessenden was awarded Scientific American 's Safety at Sea Gold Medal, in recognition of his invention "of

21970-468: The term A ( t ) is constant and the second term of the equation has a functional relationship to the modulating message signal. Angle modulation provides two methods of modulation, frequency modulation and phase modulation . In amplitude modulation, the angle term is held constant and the first term, A ( t ), of the equation has a functional relationship to the modulating message signal. The modulating message signal may be analog in nature, or it may be

22139-434: The time-varying amplitude of the sinusoidal carrier wave and the cosine-term is the carrier at its angular frequency ω {\displaystyle \omega } , and the instantaneous phase deviation ϕ ( t ) {\displaystyle \phi (t)} . This description directly provides the two major groups of modulation, amplitude modulation and angle modulation . In angle modulation,

22308-422: The top graph (labelled "50% Modulation") in figure 4. Using prosthaphaeresis identities , y ( t ) can be shown to be the sum of three sine waves: Therefore, the modulated signal has three components: the carrier wave c(t) which is unchanged in frequency, and two sidebands with frequencies slightly above and below the carrier frequency f c . A useful modulation signal m(t) is usually more complex than

22477-494: The transmission medium. AM remains in use in many forms of communication in addition to AM broadcasting : shortwave radio , amateur radio , two-way radios , VHF aircraft radio , citizens band radio , and in computer modems in the form of QAM . In electronics , telecommunications and mechanics , modulation means varying some aspect of a continuous wave carrier signal with an information-bearing modulation waveform, such as an audio signal which represents sound, or

22646-822: The two reported holiday transmissions, Fessenden does not appear to have conducted any other radio broadcasts, or to have even given additional thought about the potential of a regular broadcast service. In a 1908 comprehensive review of "Wireless Telephony", he included a section titled "possibilities" that listed promising radio telephone uses. Neither the main article, nor this list, makes any reference to broadcasting, instead only noting conventional applications of point-to-point communication, enumerated as "local exchanges", "long-distance lines", "transmarine transmission", "wireless telephony from ship to ship", and "wireless telephone from ship to local exchange". The technical achievements made by Fessenden were not matched by financial success. Walker and Given continued to hope to sell NESCO to

22815-479: The types of amplitude modulation: Amplitude modulation was used in experiments of multiplex telegraph and telephone transmission in the late 1800s. However, the practical development of this technology is identified with the period between 1900 and 1920 of radiotelephone transmission, that is, the effort to send audio signals by radio waves. The first radio transmitters, called spark gap transmitters , transmitted information by wireless telegraphy , using pulses of

22984-404: The university established programs in veterinary medicine, industrial management, and nursing, as well as the first computer science department in the United States. Undergraduate humanities courses were strengthened, graduate-level study in these areas were slowly established. Purdue awarded its first Bachelor of Arts degrees in 1960. The official seal of Purdue was officially inaugurated during

23153-407: The university under the G.I. Bill , first-year classes were taught at some of these sites to alleviate the demand for campus space. Four of these sites are now degree-granting regional campuses of the Purdue University system . On-campus housing became racially desegregated in 1947. After the war, a decade-long construction program emphasized science and research. In the late 1950s and early 1960s

23322-562: The university's centennial in 1969. Consisting of elements from emblems that had been used unofficially since the 1890s, the current seal depicts a griffin , symbolizing strength, and a three-part shield, representing education, research, and service. In 1975, Purdue University joined ARPANET , an early packet-switching network that would ultimately become the foundation for the modern internet. In recent years, Purdue's leaders have continued to support high-tech research and international programs. In 1987, U.S. President Ronald Reagan visited

23491-521: The west, and athletic facilities to the north. The Purdue Mall is the central quad of Purdue University and was created to connect the academic campus with Ross-Ade Stadium. It is also known as the Engineering Mall due to its proximity to several engineering buildings. The most prominent feature of the Purdue Mall is the 38-foot (12 m)-tall concrete Engineering Fountain . The Purdue Bell Tower

23660-504: The work was entrusted by the Brown Hoisting Machinery Company" and "The only wonder is that the tower did not fall before.") In a letter published in the January 19, 1907, issue of Scientific American , Fessenden discounted the effect of the tower collapse, stating that "The working up to the date of the accident was, however, so successful that the directors of the National Electric Signaling Company have decided that it

23829-488: The world wars. Inventor, alumnus, and trustee David E. Ross coordinated several fundraisers, donated lands to the university, and was instrumental in establishing the Purdue Research Foundation. Ross's gifts and fundraisers supported such projects as Ross–Ade Stadium , the Memorial Union , a civil engineering surveying camp, and Purdue University Airport . Purdue Airport was the country's first university-owned airport and

23998-562: Was a Church of England in Canada minister, and the family moved to a number of postings throughout the province of Ontario. While growing up Fessenden attended a number of educational institutions. At the young age of nine he was enrolled in the DeVeaux Military school for a year. He next attended Trinity College School in Port Hope, Ontario , from 1877 until the summer of 1879. He also spent

24167-427: Was a cheap source of continuous waves and could be easily modulated to make an AM transmitter. Modulation did not have to be done at the output but could be applied to the signal before the final amplifier tube, so the microphone or other audio source didn't have to modulate a high-power radio signal. Wartime research greatly advanced the art of AM modulation, and after the war the availability of cheap tubes sparked

24336-402: Was an intensely difficult man to play politics with." However, one of his former assistants, Charles J. Pannill, recalled that "He was a great character, of splendid physique, but what a temper!", while a second, Roy Weagant , ruefully noted that "He could be very nice at times, but only at times." In 1925, Radio News , saluting Fessenden as "one of the greatest American radio inventors", began

24505-574: Was appointed general manager of the company. The legal stalemate would continue for over 15 years. In 1917, NESCO finally emerged from receivership, and was soon renamed the International Radio Telegraph Company. The company limped along for a few years, until it was sold to the Westinghouse Electric & Manufacturing Company in 1920, and the next year its assets, including numerous important Fessenden patents, were sold to

24674-515: Was completed by the end of 1874. In 1875, Sarah A. Oren , the State Librarian of Indiana, was appointed professor of botany. Purdue issued its first degree, a Bachelor of Science in chemistry, in 1875. The first female student was admitted that autumn. Emerson E. White , the university's president from 1876 to 1883, followed a strict interpretation of the Morrill Act. Rather than emulate

24843-608: Was dedicated in 1877. University Hall originally housed the office of the president, a chapel, and classrooms. At the request of John Purdue , he was buried in the Memorial Mall, directly across from the main entrance of University Hall. The area south of Mitch Daniels Boulevard is home to Purdue's agricultural, fine arts, life sciences, and veterinary buildings. This area also includes the Krannert School of Management, Horticulture Gardens , Discovery Park , Lyles Porter Hall and

25012-402: Was developed for military aircraft communication. The carrier wave ( sine wave ) of frequency f c and amplitude A is expressed by The message signal, such as an audio signal that is used for modulating the carrier, is m ( t ), and has a frequency f m , much lower than f c : where m is the amplitude sensitivity, M is the amplitude of modulation. If m < 1, (1 + m(t)/A)

25181-495: Was established in 1874 with programs in Civil and Mechanical Engineering. The college now offers BS , MS , and PhD degrees in more than a dozen disciplines. Purdue's engineering program has also educated 27 of America's astronauts , including Neil Armstrong and Eugene Cernan , who were the first and last astronauts to have walked on the Moon , respectively, and Gus Grissom , a member of

25350-416: Was formed in 1953. In 1963, the School of Humanities, Social Sciences, and Education was established, although Bachelor of Arts degrees had begun to be conferred as early as 1959. In 1989, the School of Liberal Arts was created to encompass Purdue's arts, humanities , and social sciences programs, while education programs were split off into the newly formed School of Education. The School of Liberal Arts

25519-569: Was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science, technology, and agriculture; the first classes were held on September 16, 1874. Purdue University is a member of the Association of American Universities and is classified among "R1: Doctoral Universities – Very high research activity". Purdue enrolls the largest student body of any individual university campus in Indiana, as well as

25688-428: Was gold plated, and somehow Fessenden became convinced that earlier awards had been solid gold, so he angrily returned it. Only after Greenleaf W. Pickard investigated the matter and determined that the prior medals were also plated was Fessenden willing to relent. The next year Philadelphia's Board of Directors of City Trusts awarded Fessenden a John Scott Medal , which included a cash prize of $ 800, for "his invention of

25857-542: Was involved in some type of military research or training during World War II . During a project on radar receivers, Purdue physicists discovered properties of germanium that led to the making of the first transistor . The Army and the Navy conducted training programs at Purdue and more than 17,500 students, staff, and alumni served in the armed forces. Purdue set up about a hundred centers throughout Indiana to train skilled workers for defense industries. As veterans returned to

26026-576: Was made to link the General Electric plants in Schenectady, New York, and Lynn, Massachusetts, a distance of 185 miles (298 km), however the effort was unsuccessful. Efforts to sell equipment to the U.S. and other governments, as well as private companies, met with little success. An ongoing area of conflict, especially with the U.S. Navy, were the high prices Fessenden tried to charge. The Navy in particular felt Fessenden's quotes were too far above

26195-411: Was no reason to doubt Fessenden's account, in part because it had not been challenged in the years immediately following publication of the Kintner article. Although Fessenden's claim for the first radio broadcast in 1906 is recognized as an IEEE Milestone , in view of the contrasting opinions among radio historians, Mike Adams summarized the situation as "More than 100 years after its possible occurrence,

26364-443: Was one of the first researchers to realize, from experiments like the above, that the existing technology for producing radio waves, the spark transmitter, was not usable for amplitude modulation, and that a new kind of transmitter, one that produced sinusoidal continuous waves , was needed. This was a radical idea at the time, because experts believed the impulsive spark was necessary to produce radio frequency waves, and Fessenden

26533-580: Was renamed in honor of retired Provost Felix Haas and began to also house the Statistics department. East of the Memorial Mall is the Purdue Memorial Union , Purdue's student union building, and the adjacent Union Club Hotel. University Hall is the only building remaining from the original six-building campus. Construction began in 1871, when the building was known as "The Main Building". The building

26702-451: Was renamed the College of Liberal Arts in 2005. The Daniels School of Business offers management courses and programs at the undergraduate, master's, and doctoral levels. The university's College of Pharmacy was established in 1884 and is the 3rd oldest state-funded school of pharmacy in the United States. The Purdue Polytechnic Institute, formerly known as the College of Technology, offers bachelor's , master's and PhD degrees in

26871-556: Was ridiculed. He invented and helped develop one of the first continuous wave transmitters – the Alexanderson alternator , with which he made what is considered the first AM public entertainment broadcast on Christmas Eve, 1906. He also discovered the principle on which AM is based, heterodyning , and invented one of the first detectors able to rectify and receive AM, the electrolytic detector or "liquid baretter", in 1902. Other radio detectors invented for wireless telegraphy, such as

27040-516: Was still a teenager, he taught mathematics to the school's younger students (some older than himself) for four years, while simultaneously studying natural sciences with older students at the college. At the age of eighteen, Fessenden left Bishop's without having been awarded a degree, although he had "done substantially all the work necessary", in order to accept a position at the Whitney Institute , near to Flatts Village in Bermuda , where for

27209-515: Was suspended until later in the year. Then, on December 6, 1906, the Machrihanish radio tower collapsed in a gale, abruptly ending the transatlantic project before it could begin commercial service. (A detailed review in Engineering magazine blamed the collapse on sub-standard construction, due to "the way in which the joints were made by the man employed for the purpose by the sub-contractors to whom

27378-481: Was that perhaps something similar to what Fessenden remembered could have taken place during a series of tests conducted in 1909. A review by Donna L. Halper and Christopher H. Sterling suggested that debating the existence of the holiday broadcasts was ignoring the fact that, in their opinion, the December 21 demonstration, which included the playing of a phonograph record, in itself qualified to be considered an entertainment broadcast. Jack Belrose flatly argued that there

27547-592: Was the base of operations for Purdue Bands and Orchestras until the completion of the Marc and Sharon Hagle Hall in 2022. West of the Elliott Hall of Music is the Armory Building. The Armory Building was rebuilt in 1918 after a fire and houses the university's ROTC programs and other clubs. The Purdue Memorial Mall, south of the Purdue Mall, is the original section of campus. It is a popular meeting place for students and

27716-440: Was the basis for sonar (SOund NAvigation Ranging), echo-sounding and the principle applied to radar (RAdio Detection And Ranging). The device was soon put to use for submarines to signal each other, as well as a method for locating icebergs, to help avoid another disaster like the one that sank Titanic . While the company quickly applied his invention to replace the bells of its systems and entered acoustic telegraphy it ignored

27885-610: Was the first person to transmit music and entertainment by radio. De Forest's first entertainment broadcast occurred in February 1907, when he transmitted electronic telharmonium music from his laboratory station in New York City. This was followed by tests that included, in the fall, Eugenia Farrar singing "I Love You Truly". (Beginning in 1904, the U.S. Navy had broadcast daily time signals and weather reports, but these employed spark transmitters, transmitting in Morse code). In 1928, as part of

28054-474: Was to insert a simple carbon microphone into the transmission line, which was used to modulate the carrier wave signal for audio transmissions, or, again using modern terms, used to produce amplitude modulated (AM) radio signals. Fessenden began his research on audio transmissions while still on Cobb Island. Because he did not yet have a continuous-wave transmitter, initially he worked with an experimental "high-frequency spark" transmitter, taking advantage of

28223-446: Was to take a basic electrical alternator , which normally rotated at speeds that produced alternating current of at most a few hundred cycles-per-second ( Hz ), and greatly increase its rotational speed, in order to create electrical currents of tens-of-thousands of cycles-per-second (kHz), thus producing a steady continuous-wave transmission when connected to an aerial. However, it would take many years of expensive development before even

28392-831: Was transmitted 18 kilometers (11 miles) to a listening site at Plymouth, Massachusetts. A detailed review of this demonstration appeared in The American Telephone Journal and a summary by Fessenden appeared in Scientific American . A portion of a report produced by Greenleaf W. Pickard of the Telephone Company's Boston office, which includes additional information on some still existing defects, appeared in Ernst Ruhmer 's Wireless Telephony in Theory and Practice . Although primarily designed for transmissions spanning

28561-443: Was trying to freeze Walker and Given out of a potentially lucrative competing transatlantic service. The final break occurred in January 1911, when Fessenden was formally dismissed from NESCO. This resulted in his bringing suit against NESCO, for breach of contract. Fessenden won the initial court trial and was awarded damages; however, NESCO prevailed on appeal. To conserve assets, NESCO went into receivership in 1912, and Samuel Kintner

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