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History :: Wireless / Radio

Derived From: Derived From Radio Pioneers & Core Technologies, FCC History

In 1885 German physicist Heinrich Hertz thought his proof of Maxwell's theories;

1. that electromagnetic waves behave in the same way as light, and
2. that light itself is electromagnetic in nature;

had no practical value since he could only send signals a few yards. Further, he saw no way of improving or amplifying the signal so that it could be received at a greater distance. Finally, his experiments showed that if two transmitters operated in the same proximity, the nearby receiver found both signals, producing nothing but static and hiss.

Thus, Italian inventor Guglielmo Marconi's 1901 transmission of a wireless signal from Ireland to Canada was an expression of faith as well as applied science. Marconi later described the prevailing skepticism of learned individuals by noting that achieving long distance wireless transmission of sound:

"...had been declared to be impossible by some of the principal mathematicians of the time - (the) chief question mark (being) whether wireless waves would be stopped by the curvature of the earth...some eminent men held that the roundness of the earth would prevent communication over such great distances as the atlantic."

But the "pip-pip-pip" (Morse code for the letter "s") that Marconi reported he heard at 12:30 p.m. on December 12, 1901 was just one of many remarkable events that gave true meaning to Oliver Lodge's proclamation that wireless communications had created a new " epoch in history." For wireless telegraphs had begun to appear on ocean-going vessels as early as 1891 - many of them donated for demonstration purposes by Marconi. For it was the opportunity to save lives and property on large ships that provided much of the early impetus to develop wireless communications via the radio waves. The 1899 collision between the coal-laden R. F. Matthews and the East Goodwin Lightship was just the first instance where the use of wireless radio saved lives. Because of the extremely dense fog and strong tides present that day, the lifeboats that came to the rescue might not have seen flares in time to get to the crash site prior to some loss of life. Thankfully the Trinity House Corporation, owner of the East Goodwin, was participating in a demonstration of Marconi radio systems and the ship's captain was able to quickly signal for help.

Thus, Marconi's integration of the work of Hertz, Righi, Branly, Lodge, and others led to an improved radio system based upon:

• Using a coherer to improve detection of the signal,
• Designing both the transmitting and receiving antennas so that they could be tuned to a specific frequency,
• Increasing the power, and
• Decreasing the transmitting frequency into the medium or short wave range.

These innovations paved the way for the next big breakthrough in wireless radio transmissions - sending the sound of a human voice over the air waves instead of just the dots and dashes of wireless telegraphy.

Canadian Reginald Fessenden was the larger than life man whose work, in combination with those others, introduced, in 1906, what we think of today as radio: music, news, talk, in fact any sound human beings can make. Experiences as the chief chemist in Edison's labs, work at Westinghouse, professorships in electrical engineering at Purdue University and the University of Pennsylvania, research in North Carolina for the U.S. Weather Bureau, and, finally, a founding partnership in the National Electric Signaling Company uniquely qualified him to solve the riddle of how sound waves traveled and what was necessary to transmit those waves wirelessly from one point to another.

Although best known for his 1906 Christmas Eve broadcast of music and voice from Brant Rock, Massachusetts , Fessenden actually made the first transmission of voice in 1900 while under contract to the Weather Bureau. His continuous wave theory - whereby a sound wave is combined with a radio wave and transmitted to a receiver where the radio wave is removed so that the listener hears only the original sound - describes how radio works today.

Fessenden proved his theory on December 23, 1900 from an island in the Potomac River. Speaking to an associate who was a mile away with a receiving unit, Fessenden said:

"One - two - three - four, is it snowing where you are Mr. Thiessen? If it is, would you telegraph back to me?"

Thiessen replied in the affirmative and the rest, as they say, is history.

With technologies for both long-distance and voice transmissions in place, one final event served as the capstone that made radio an essential technology for the 20th century. That event was the sinking of the Titanic in 1912. The "unsinkable" Titanic was equipped with a state-of-the-art Marconi radio system: a rotary spark transmitter, powered by a 5 kilowatt alternator that fed off the ship's lighting circuit, a four wire antenna hoisted 250 feet in the air between the ship's masts, and even a battery powered emergency transmitter. There was a guaranteed transmission range of 250 miles, but at night transmissions could go up to 2000 miles. The two radio operators expected to spend all their time sending and receiving personal communications from the wealthy passengers. And, in fact, from the April 12 sailing until the ship hit the iceberg just past midnight on April 15 they sent 250 such messages.

During the two hours from the first distress call until the radio operators abandoned the radio room they sent 30-35 messages, which were heard as far away as Italy; but not by a ship four miles away, because the radio operator was off duty.

"Sinking of Titanic Influences Wireless: In 1912, the Titanic Hit an iceberg and sent the first 'SOS' signal which was received by a nearby ship, that rescued many of the survivors. It was later learned another ship was closer, but had only one wireless operator who happened to be off duty. This resulted in the Radio Act of 1912 requiring two operators on all ships."

While over 1,500 people were lost in this tragedy, about 700 survived - with credit going, largely, to the wireless distress messages that the Titanic broadcast. In the aftermath of this international event several new regulations were put in place for every ship carrying more than 50 people. Included among these were requirements to provide sufficient lifeboats, hold drills, and maintain round the clock radio coverage.

Power

In 1909, when Marconi shared the Nobel Prize for Physics with Karl Braun, there was no question about the many significant innovations he had brought to the world of wireless radio. There was also no question that his achievements would likely not have been so great if not for the pioneering energy generation work done by Nikola Tesla, whom some consider the real father of radio.

Tesla, a Serbian-American of wide-ranging interests, immigrated to the United States at the age of 28 having already thought through one of his greatest scientific contributions - how to best use alternating current. Since Thomas Edison's company (later General Electric) was the primary advocate for and builder of direct current systems in the United States , it was natural that upon his arrival Tesla first went to work for Edison. But, it was not long before the two parted ways. Tesla then sold his patent rights for a polyphase system of alternating-current dynamos to Edison 's biggest business rival - George Westinghouse.

Today we know that the alternating-current (AC) approach prevailed and that Tesla-type induction motors are found in almost all appliances and power operations. While alternating current prevailed because it minimizes power loss across great distances, at the time, the competition between direct and alternating current systems was fierce.

One of the factors that helped the alternating current approach was Westinghouse's winning the contract to provide electrical light at the World's Columbian Exposition at Chicago in 1893. This Expo is identified by many scholars as one of the key events in America's burgeoning sense of itself as a major industrial power, leading the way in new technologies.

The successful lighting of the Expo was then a factor in Westinghouse winning the contract to install the first hydroelectric power machinery at Niagara Falls. All of the enormous motors at the power station bore Tesla's name and patent numbers.

After selling his patents to Westinghouse in 1885, Tesla set up his own lab and worked on a wide variety of projects. These ranged from a carbon button lamp to experiments on the power of electrical resonance.

This last set of experiments, on what Tesla called " a simpler device" for the production of electric oscillations, resulted, in 1891, in the device known today as the Tesla Coil. A Tesla Coil is a transformer made up of two parts - a primary and secondary coil, one inside the other. When electrically charged the interaction between the two coils produces a voltage high enough to make the air conduct electric currents. Getting the power high enough to make the air an effective conductor of currents is key to wireless transmission of radio waves.

Tesla pursued the application of his coil technology to radio. By tuning a coil to a specific frequency he showed that the radio signal could be greatly magnified through resonant action. However, before he was able to fully demonstrate sending a radio signal 50 miles, his laboratory and equipment were destroyed in a fire.

Thus, when Marconi made his famous 1901 Trans-Atlantic transmission, the power portion of his system was based on Tesla's findings. In fact, Tesla and Marconi remained in legal battles for patent priority even after both men died.

Just as Tesla made the foundational breakthroughs in power generation which allowed radio to happen, Sweden 's Ernst Alexanderson made the power breakthrough that allowed Fessenden to transmit the human voice across a long distance in 1906.

For the first two decades of radio (1885-1906), spark gap machines served as the transmitters for most wireless telegraphy. A spark gap transmitter worked in combination with an induction coil, a Morse key, some power source - usually a battery, an earth ground, and an aerial. Power was applied to the coil with the Morse key acting as the on/off device for the power. Once power was received, a capacitor was charged, which caused a spark to jump across the gap between the two metal balls of the spark gap transmitter. This, in turn, caused a current to flow in a tuned circuit, which produced oscillations. By adding an aerial and earth ground, these oscillations could be sent through the atmosphere. Tuning the frequency of the oscillations was dependent on the type and properties of the capacitor and coil.

Alexanderson came to the United States in 1902, at the age of 24, to work with General Electric on the new and exciting alternating current approaches to power generation. One of his early assignments was to build a transmitter that Reginald Fessenden could use to produce enough power to generate a continuous wave carrier. Fessenden's plan was to attach the sound waves from a human voice to this carrier wave and transmit this mix to radio receiving sets. To do this Fessenden knew that he needed a much higher frequency than the 60 Hertz produced by alternating generators of the time. To get a higher frequency he needed more power.

Through his own developments Fessenden had not been able to create a power generator that would produce even 1,000 Hertz. Nevertheless, in 1904, Fessenden contracted with General Electric for a machine which would generate a frequency of 100,000 Hertz.

The work took two years. In 1906 the Alexanderson Alternator, a 2 kilowatt, 100 kilohertz alternator, was used by Fessenden to carry out the first long distance broadcast of the human voice. Radio operators hundreds of miles in the Atlantic Ocean were astonished to hear a Bible and poetry reading. They were also treated to a woman singing opera, and a violin playing a Christmas carol.

Always knowing a good thing when he saw it, Marconi purchased 50 and 200 kilowatt Alexanderson Alternators for his trans-Atlantic transmissions. Marconi's Alexanderson Alternators, located in New Jersey, were used in 1918 to broadcast President Wilson's ultimatum to Germany at the close of WWI.

Unassuming Ernst Alexanderson produced over 300 patents and served as a leading figure in the development of facsimile communication and television as well as radio. Development of his alternators continued through the mid-1920's when 500,000 watt transmitters were developed. As great as these longwave alternators were they gave way in the late 1920's to vacuum tube shortwave transmitters that operated at a fraction of the cost and power.

The Quality that Made Radio Popular

Although it was the late 1920's before vacuum tube shortwave transmitters began to replace Alexanderson's mighty alternators, exploratory work using vacuum tubes as amplifiers in radio receiving equipment began around 1900.

Lee DeForest, an Iowa preacher's son who earned a Yale PhD, announced his Audion vacuum tube in a Scientific American article in 1906. Although he acknowledged in this article that he didn't have a "completely satisfactory theory" as to why the tube amplified the reception of radio signals, understanding this curious tube led other researchers, such as Edwin Armstrong, to significant breakthroughs in amplifying both radio transmissions and reception before, during, and after WWI.

Armstrong was 11 years old when Marconi's trans-Atlantic transmission occurred. It fired his imagination and he became a collector and creator of homemade wireless equipment. As a teenager his patient parents allowed him to build a 125 foot antenna in the yard so he could further his studies on radio. He was 16 when DeForest announced his Audion tube and one of these fragile, expensive tubes was added to his study equipment.

In 1912, as a junior at Columbia University he continued his interest in radio and the Audion tube by inventing a regenerative circuit that fed part of the current back to the grid in the tube. This strengthened the incoming signal. In fact, Armstong received distant stations so loudly that he could hear them without headphones - something unheard of at that time.

Further experiments led him to discover that by increasing the feedback into the tube even more he could produce rapid enough oscillations for the tube to act as a transmitter as well as a receiver. From this work Armstrong's regenerative circuit became the basis for continuous wave transmitters that are still at the heart of radio operations today.

When Armstrong entered the Army Signal Corp in WWI he did not leave the development of radio behind. Instead, as in so many areas of technology, work done for the U. S. military during times of war led to significant breakthroughs for civilian industry once the war was completed. So it was with vacuum tubes and radios during and after WWI.

In 1917, when the U.S. entered WWI, as a result of powers given to it by the Radio Act of 1912 (a law motivated in part by the Titanic disaster), the federal government shut down all private radio operations in the United States. This was not as drastic a measure as it might seem today since the commercial broadcasting we now know did not begin until 1920. But it was major blow to the thousands of amateur or "ham" radio operators who had discovered and begun to popularize the new medium of radio. Many of these men, like Armstrong, joined the Army, Navy, or Merchant Marine in order to put their now precious skills to work on behalf of the United States .

Whereas communication in previous wars had been dependent on runners, flags, carrier pigeons, smoke signals, and other methods, WWI's commanders wanted quicker, more reliable communication with the soldier in the field. And radio had advanced enough to believe this a feasible objective if the Army Signal Corp, working with General Electric/DeForest Radio and Telephone and Western Electric, could devise a way to go from the pre-War situation in which about 400 vacuum tubes were manufactured per week to making about 20,000 reliable, powerful tubes a week.

As often happens in times of war, the impossible was achieved and General George Squier, Chief Signal Officer of the Army, reported in 1919 that:

"...engineering advancement accomplished in less than two years represents at least a decade under the normal conditions of peace, and our profession will, it is hoped, profit by this particular salvage of war, which offers perhaps the most striking example extant of a minimum "time-lag" between the advanced "firing line" of so-called pure physics and applied engineering."

Thus, by the end of WWI, vacuum tubes were developed to the point where they were used for "electric-wave detection, radio-frequency, and audio-frequency amplification, radiotelephony, particularly in the airplane radiophone, continuous-wave radiotelegraphy, voltage and current regulators on generators, and for other miscellaneous purposes."

Armstrong's work for the Army signal corp fell into another area. His task was to develop a way to detect enemy shortwave communications. In the process of meeting this objective, in 1918 he developed an eight-tube receiver that could amplify radio signals to a degree never known before. He named this receiver the superheterodyne circuit and it remains the basic circuit used in nearly 100% of radio and television receivers today.

Armstrong had one other great invention up his sleeve - FM radio - which both greatly improved the quality of broadcasting and played a major role in making today's cellular and PCS phones possible.

In 1935 Armstrong revealed his final great work, motivated by his own dislike of the static he constantly heard on the radio. His original paper on frequency modulation was entitled "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation." Likely he did not imagine that this advance would be resisted. But, afraid that FM would make AM radio obsolete and slow down new developments in television, Armstrong's major financial backer withdrew its financial support.

So Armstrong established his own distribution channel by building a demonstration inter-city FM relay for New England 's Yankee Network. A shift in the location of the FM radio frequency, to accommodate the spectrum needs of the new television industry, made all Armstrong's FM equipment obsolete. It was not until the 1960's, after Armstrong's death, that the quality advantage of FM combined with stereo was enjoyed by most Americans.

But, beyond the quality that FM brought to radio broadcasting, it also played a role in development of Motorola's 1973 DynaTAC - the first cellular phone - invented by a Martin Cooper and his team.

Although mobile telephones had been around since 1946, it wasn't until the 1980's that the quality of frequency modulated sound, combined with reasonably priced microprocessors, digital switching, and a final decision on celluar system spectrum combined to make it feasible to offer the first commercial cellular phone services in the United States.

Today, an unbounded future for wireless radio transmissions remains as much an article of faith in innovative science as it was for Marconi and Fessenden over a century ago. Bluetooth, Wi-Fi, 3G phones, and cognitive radio are just a few of the technologies that will carry wireless transmissions successfully through radio's second century.