Radio Days

Today is National Radio Day, as my friend and radio news person

Amy Beckham Morris

reminds me. It celebrates the invention of radio so obviously somebody invented radio on this day, right?

Well, that's a bit of a story.

It begins with the discovery of electromagnetic induction by Michael Faraday in 1831. Faraday was an interesting character. He is one of the most influential scientists in history, though he received little formal education, and was entirely self taught. He was originally an apprentice bookmaker, but he read all the books that passed through. His book The Natural History of a Candle, based on Christmas lectures given to children, is a remarkable thing and well worth reading.

Faraday discovered that an electric current could be induced in a circuit by a changing magnetic field. Just holding a magnet near is not good enough, It has to be moving, or, if an electromagnet, then have a varying current passing through it. This is how wireless charging works for cell phones.

Faraday's law of induction became part of a miscellaneous collection of results linking electricity and magnetism. In 1861, James Clerk Maxwell formalized the results mathematically, and in so doing noticed that they were inconsistent unless a term was added in which a changing electric field would behave as a current and create a magnetic field. He published one of the landmark works of theoretical physics, A Dynamical Theory of the Electromagnetic Field, in 1864. This was the first unified field theory in the history of physics, and was profoundly influential on 19th and 20th century physics. Einstein had pictures of Newton, Faraday and Maxwell on his office wall.

After this, it was a very short step to showing that, so modified, it was easy to derive a wave equation for the electromagnetic field. The propagation speed of these waves had a couple of interesting properties -- it did not depend on the motion of either the source or the observer, being dependent only on the electromagnetic properties of a vacuum. And it seemed to be approximately equal to the speed of light, which had been measured in the recent past.

Maxwell asserted that it was the speed of light, providing a theoretical foundation for understanding optics, and dispensing with the notion of an ether. The basic idea was one of mutual induction -- a changing electric field creates a magnetic field and a changing magnetic field creates an electric field. Set one of them waving and the other waves along with it. 

His theory was put to the test by Heinrich Rudolph Hertz. In 1886, he was experimenting with a pair of Riess spirals, a coiled wire with a pair of metal balls at each end separated by a gap. These, invented by Peter Theophil Riess, were commonly used in experiments on electromagnetic induction. Hertz had been set the problem of testing Maxwell's prediction by his PhD adviser, Heinrich Helmholtz, but thought it too difficult at the time. But he noticed that if he discharged a Leyden Jar (a primitive form of battery) across the gap in one spiral, a spark appeared across the gap in the other, even though they were not touching. Between 1886 and 1889, Hertz conducted a series of experiments showing the existence of an electromagnetic wave was responsible, ane measuring its speed (the speed of light) and its wavelength (about 4 meters, which is in the RADIO band; hey! we've arrived somewhere important!).

Or maybe not. In 1893, Hertz published his results in Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space. In it, he said: "It's of no use whatsoever... this is just an experiment that proves Maestro Maxwell was right—we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there." Asked about the applications of his discoveries, Hertz replied: "Nothing, I guess."

As it happens, Hertz was not the first to see radio waves. He was just the first to understand what he was looking at. The earliest observation was by Instrument Maker to the King George Adams around 1784 when he . . . oh! Discharged a Leyden Jar and noticed sparks in some nearby conductors. An important lesson in science – how an experiment is understood depends on the environment in which it occurs, and the understanding your have when you see it. Fortune favors the prepared mind. So the unit of frequency is the Hertz, not the Adams.

On 1 June 1894, at a meeting of the British Association for the Advancement of Science at Oxford University, Oliver Joseph Lodge gave a memorial lecture on the work of Hertz (recently deceased) and the German physicist's proof of the existence of electromagnetic waves 6 years earlier. Lodge set up a demonstration on the quasi-optical nature of "Hertzian waves" (radio waves) and demonstrated their similarity to light and vision including reflection and transmission. Later in June and on 14 August 1894 he did similar experiments, increasing the distance of transmission up to 55 meters (close to 200 feet). In these lectures Lodge demonstrated a detector that would become standard in radio work, an improved version of a detector invented by Édouard Branly, which Lodge called a coherer. It consisted of a glass tube containing small metal filings between two electrodes. When the small electrical current induced by radio waves from an antenna was applied to the electrodes, the metal particles would cling together or "cohere." That (effectively a switch) closed an electric circuit which allowed the current from a battery to pass through it. To turn the switch off, you smacked it around a bit to separate the filings. In Lodge's setup the slight impulses from the coherer were picked up by a mirror galvanometer, a very small mirror which would rotate in the magnetic field created by that induced current, and which would deflect a beam of light being projected on it, giving a visual signal that the impulse was received. This is a common instrument of the time for measuring small currents, because the light can be reflected on a wall quite a ways off so that even small rotations are noticeable.

BTW, using a small current to control a larger one makes this an early version of a transistor.

Lodge also appears not to have seen any value in using radio for signaling or wireless telegraphy, but his lectures as well as his invention of a device for radio tuning in 1898 would lead to a series of later patent disputes with the Marconi Company over priority in the invention of radio.

In November 1894, Indian physicist Jagadesh Chandra Bose invented a sort of exploding transmitter. He used gunpowder to power a radio pulse and used it to ring a bell through several intervening walls. To accomplish this, he invented the antenna, using two metal plates atop 20 foot poles, one at each end.

In 1894-5, Russian physicist Alexander Stepanovich Popov improved Lodge’s receiver design and used it to help the forest service track lightning strikes. The lightning discharge created a radio pulse that Popov could detect up to 30 km away. It caused something like a telegraph key to tap, and could automatically record lightning strikes on a piece of paper. Popov presented his radio receiver to the Russian Physical and Chemical Society on May 7, 1895 — the day has been celebrated in the Russian Federation as "Radio Day" and Popov is widely recognized in Eastern Europe as the inventor of radio. Popov published his work at the end of that year and in it, he became the first person to propose the idea of distant signaling using radio. But he did not patent the idea.

In 1898, Serbian-American inventor and certified nut case Nikola Tesla added cryptography to Popov’s idea to create a radio controlled boat. He called it a “teleautomaton” and hoped to sell it to the Navy as a guided torpedo. No invention story is complete without a Tesla moment, god help us.

Which brings us to Marconi. Beginning in 1894, he read about the experiments of Hertz, Tesla and Popov. At the time, spark-gap wireless telegraphy (essentially, using artificial lightning to send a pulse signal) was widely researched but Marconi is the one who went to the patent office. So, therefore, he is credited with its invention. The Marconi Company Ltd. Was established in 1897, and demonstrated spark gap telegraphy to the British Post Office by sending a message from Salisbury Plain to Bath, 34 miles away. Marconi did make one crucial contribution to the development of radio, Marconi’s Law, an empirical relationship showing that for simple vertical antennas of equal height, the working radio distance varied as the square of the height of the antenna. By 1904, Marconi had created a daily newspaper on the waves, the Cunard Daily Bulletin, so that people sailing between the US and Europe could keep up with developments.

Marconi shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun. Braun also created wireless telegraphy, and a lot more. He significantly improved the system by physically separating the tuning and transmitting parts of the transmitter, coupled to each other by electromagnetic induction, and later on introduced the use of resonant crystals, another step in the invention of the transistor, giving rise to generations of science projects and Eagle Scout badges.

Braun’s work was vital in practical use of radio. Connecting the spark gap directly to the antenna produced a heavily damped radio pulse. It only oscillated a few times and then quit. This severely limited transmission distance as well as the amount of information that could be transmitted. Braun’s decoupled circuit was able to transmit over much larger distances with much longer wave trains, a vital step in making radio as we know it today. But Marconi invented the radio.

Braun was also critical in the development of television, inventing the cathode ray tube (CRT, still known in German speaking countries as a Braun tube), and the phased array antenna, which allows a directional and electronically steerable radio wave by adjusting the phase relationship between a large number of antennas to achieve constructive and destructive interference. The phased array antenna is universally employed in modern radar as it can scan far faster than the old style rotating antennas. It is also incorporated in the design of wireless routers so that the connection with one computer is less likely to interfere with the connection to another. If your wifi router sprouts several antennas (or none at all as they are internal), then you’re using a phased array system. Marconi stole several of his ideas.

In 1900, American mathematician and physicist John Stone Stone (the man so nice . . .) patented a system of imposing oscillations on a radio transmitter, enabling the transmission of continuous waves of a predetermined wavelength. Being able to transmit at a fixed frequency rather than scattering radiation all across the radio band is the only reason you can have more than one radio station. Being able to produce a continuous signal instead of a bursty one is the only reason you can transmit speech or music.

But still the signal is a few hertz, and that is nowhere near the auditory spectrum of the human ear. In 1901, Canadian engineer Reginald Fessenden invented the heterodyne receiver. This device takes as input the oscillating signal from the radio wave and superimposes it on a separate signal of a different frequency produced by a local oscillator. This produces two new waves, one at a frequency that is the sum of the two original ones and one whose frequency is the difference. These are called beats, and if you've ever tuned a piano, you've heard the frequency difference one. The purpose of tuning is to make it go away. But for radio, by filtering out the difference and keeping the sum, you get a signal that is shifted to a higher frequency, in the auditory band.

The trouble was that the local oscillator was either expensive and stable or cheap and not stable at all. So heterodyning did not get much use until American inventor Lee de Forrest invented the triode vacuum tube oscillator in 1905. De Forrest styled himself the “father of radio” and went on to invent a way of optically encoding sound on film, giving birth to the talkie. The triode is a transistor in vacuum tube form. Two power electrodes are separated by a grid electrode. Applying a voltage to the grid weakens the power current, and varying it varies the power current in exactly the same way. Hence, an amplified.

But still there is only radio of a single frequency, and while that produces a pleasing hum, it does not convey information. De Forrest had been inspired to invent the three electrode triode, by the invention in 1904 of the two electrode vacuum tube diode by British physicist John Ambrose Fleming, which he called the Fleming Oscillation Valve. To this day, tubes are referred to as valves in Britain.

The diode is a rectifier. That is, it passes current in only one direction and so converts an alternating current (AC) into a direct one (DC). This is important because AM radio transmits audio by creating a carrier wave at a specific frequency, and varying its intensity (or amplitude, so Amplitude Modulation) using an audio signal. To filter the carrier frequency hum, the signal passes through a rectifier, which eliminates the alternating part, the carrier wave, leaving behind a DC wave which is only the amplitude modulation. So now sound, less the hum. 

And now radio has arrived. Obviously it was the work of Marconi, right? For more on why the Great Man Single Inventor history of technology you learned in grade school is grossly wrong, please refer to the 1980’s PBS TV show and associated book, Connections, by James Burke.

The problem with AM is that it receives and amplifies noise and electromagnetic interference in equal proportion to the signal you’re trying to hear. That’s why it sounds so shitty. You probably thought that was Limbaugh. FM modulates the frequency rather than the amplitude, having the effect of strongly reducing noise when the amplitude is jacked up. However, to reproduce speech and especially music requires a frequency bandwidth that comes close to the auditory spectrum, around 20,000 Hertz. That allows only about 100 AM channels to exist, split between however many countries are within broadcast range. FM is at a much higher frequency, about 60 times higher, enabling a  much larger number of stations to exist, and allowing them to occupy a much larger bandwidth, so higher fidelity.

The downside is that FM frequencies are not reflected by the ionosphere so they are line of sight. The lower AM frequencies are reflected from the ionosphere. The height of the ionosphere is strongly affected by sunlight and rises to a much higher altitude at night, enabling transmission at distances up to 2000 km (around 1200 miles).. This makes the 100 channel AM limit significantly worse as many more countries overlap, but the upside was enabling pirate radio from Mexico to reach most of the US. This is what made Wolfman Jack famous, as nearly everybody could hear him blaring out from Juarez, and he played things that were prohibited by the FCC on moral grounds.

So wait a minute. De Forrest contributed the last critical piece, which was patented on November 13, 1906. Why is today National Radio Day? Maybe it is the day the first radio station went on the air?

Well, sort of.

In 1920, the Detroit News, owned by newspaper magnate E. W. Scripps and also where my father used to work, created a commercial radio station known as Detroit News Radiophone. It was a bit of a patent swindle. Lee de Forrest had sold all his patents to AT&T in 1917, but he retained the right to produce radio equipment for amateur purposes. The News leased a 20 watt transmitter from de Forrest and licensed it under a standard amateur radio license with call sign 8MK. They did indeed transmit a signal on August 20, 1920 and what is now known as WWJ claims to be the world’s first radio station because of it, but please.

That was a short equipment test, not the beginning of operations, and nobody heard it except a few amateur radio enthusiasts with nothing better to do. The station did not actually go on the air until August 31, with primary election updates and a vocal performance by Lois Johnson.

In the meantime, down south of the equator, Enrique Telémaco Susini began regular broadcasting from Radio Argentina on August 27 with a 5 watt transmitter broadcasting Teatro Coliseo’s performance of Wagner’s Parsifal using a microphone from a hearing aid. His transmitter was on the roof of the theater, with an antenna that stretched across the street to the roof of a nearby building. The venture was a creation of Susini, his nephew Miguel Mugica, and two friends, Cesar Guerrico and Luis Romero Carranza, so they acquired the nickname Locos de la Azotea (“the crazy people from the roof”). That was not a test but the beginning of regular operations that would continue until the station’s demise on December 31, 1997.