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Vintage Radio
WSHU Chief Engineer Paul Litwinovich explores aspects of vintage radio, from the radio sets themselves to the people and technology that made it all possible.

So What Did Marconi Hear?

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Wikipedia
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It is December, and for any die-hard radio enthusiast that brings Guglielmo Marconi to mind. It was on Dec. 12, 1901 that Marconi claims to have received the first transatlantic Morse code transmission. I can envision the hairs bristling on the necks of Marconi fans already. Most articles that I write in this column are not controversial. None the less, there are a few subjects that will stir up some hot debate, mostly over who invented what, or who came up with the concept first. Get a bunch of techies in the same room, particularly if some are from Europe and some from the U.S., and start a discussion as to who invented the vacuum tube. It will quickly turn into heated DeForest vs. Flemming argument. That issue though, is nothing compared to the tempers that flare when you mention Marconi vs. Tesla, and many consider it blasphemy to question whether or not Marconi actually heard anything.

The story though, goes back a few years earlier, and involves other notable players. It starts with James Clerk Maxwell's mathematical theory of 1873. He predicted that electromagnetic disturbances should travel as waves through space at the speed of light, similar to light itself.

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Credit Date and photographer unknown, first appeared in German publication “Grosse Naturforscher” in 1930.
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Heinrich Hertz.

German-born Heinrich Hertz was a professor of physics at Karlsruhe Polytechnic. In 1883, he was working in his laboratory trying to confirm Maxwell’s theory and prove the existence of these electromagnetic waves. In his experiment, he discharged a Leyden jar ( an early form of capacitor used to store a charge of electricity) into a large coil of wire hoping to create a magnetic field that he could measure to determine if it created such waves. Using the concept of electrical resonance, the charge oscillated back and forth between the coil and the capacitor at a specific frequency. To determine if any of this oscillating energy was radiated, he placed a similar coil a few feet away, its ends connected to a small spark gap.  Whenever he discharged his capacitor into the coil, a spark would jump across the nearby coil. In proving that what we now call radio waves did exist, he had also created the world's first transmitter and receiver. For his achievements he would be recognized by naming the measurement of frequency after him. This is where we get Hertz, kilohertz and megahertz etc, when discussing frequency. Beyond this he missed the boat. He saw it as a scientific curiosity to be studied in the lab. He did not recognize its potential as a means for communication.

Others though, would take note of what he had discovered.

Guglielmo Marconi was born in Bologna Italy on April 25, 1874, son of Italian nobleman Giuseppe Marconi and his Scottish/Irish wife, Annie Jameson. Money not being a problem for his family, the young Marconi received much of his early education privately, including time spent in the laboratory of noted Italian physicist Augusto Righi. Although his academic performance was less than stellar, his instructors recognized him as an intuitive genius. Righi introduced Marconi to the works of Maxwell and Hertz, which as a student he found fascinating. While others, including Nikola Tesla, were experimenting with the new phenomenon, Marconi recognized the potential of using it for wireless communication if he could find a way to get these strange new waves to travel far enough and a way to detect them. There are many comparisons between Marconi’s methods and those of the Wright brothers. Both were trying to accomplish something that had never been done before. Both had very crude technology to work with. Most importantly, both took a careful and scientific approach to the matter, studying and analyzing everything that they discovered experimentally until they understood, as best they could, the physics behind it.

When it came to detecting weak radio signals, several others were already working on the problem, most notably Englishman Sir Oliver Lodge. It was discovered that in the presence of radio waves metal or carbon filings would stick together (cohere) and become conductive. Lodge himself did not discover this, but, in 1890, he published the results of his refined device with the Institute of Electrical Engineers. He named the device a “coherer.” In 1896, he developed a point contact device where a steel or brass spring would gently touch an aluminum plate, the dissimilar metals forming a primitive crystal diode. This device would prove more sensitive than the coherer. Marconi was unable to generate much investor support for his radio experiments in Italy and by 1896 had moved to England, where he was introduced to Lodge. From here on he used the coherer as his radio signal detector.

Prior to the invention of the vacuum tube in 1906, there was no device that could amplify a weak signal. Marconi chose to put his efforts into designing more powerful transmitters and better antennas in an attempt to present stronger signals to the coherer detector.

Marconi had success at sending his signals for short to moderate distances, and established a business sending messages across the English Channel and to ships immediately off the coast. He set his sights on the larger goal of bridging the Atlantic.

On Dec. 12, 1901 he claimed to have achieved this, sending a signal from his high power transmitter in Poldhu, Cornwall, England to his receiving station on what is now known as Signal Hill, in St. John's, Newfoundland, Canada. This represented a distance of 2200 miles.

For the greater part of the last century, it was generally accepted as fact that Gugielmo Marconi did successfully receive at least some Morse code transmissions on that day. Recently though, several studies and an objective look at conditions at the time shed serious doubt on his claim. Before we look at those studies and what they represent, keep the following in mind. Mr. Marconi was the only one wearing the headphones that day, although he did hand the headphones to his assistant briefly. Otherwise he had no "ear witnesses" to verify and backup his claim. He had a lot riding on the experiment, most important raising capital from investors to advance his work and build a wireless communications company. Some sources put the amount at the equivalent of $3.5 million in today’s dollars. Mr. Marconi, having proven that sending such signals over shorter distances was possible, already had a high degree of credibility, to the point that few at the time would question his results. His transmit station was repeatedly sending the letter “s,” three dots in Morse code. A more scientific method would have been to send a series of letters unknown to him, and then compare what he had received at a given time. He claims to have heard the letter “s” only once or twice during the entire period of monitoring.

From whence comes the doubt?

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Layers of the Ionosphere that affect radio waves.

First let's look at the way low frequency radio waves behave. There was no way at the time to measure the exact frequency that he was using, but it would have been in the lower half of what is now the AM broadcast band, probably around 850 kHz. So just how do radio waves propagate at these frequencies? If you are an avid radio listener, you may have noticed that AM stations have a range of about 20 to 300 miles during the day, depending on how much power they operate. At night though, they can go great distances. Why is this? It has to do with the behavior of the upper part of the earth's atmosphere, known as the ionosphere. It consists of several different layers, each having different properties. For convenience scientists use letters to identify these different layers. The ones that typically affect radio wave are (in order from bottom to top) D, E, F1, and F2. The upper E and F layers are kept ionized (electrically charged) by particles from the sun, day or night, and they reflect lower frequency radio waves back to earth. The D layer is charged by more intense solar bombardment during the day. It shrinks, or even goes away completely, at night. Because the D layer is lower and, hence, in thicker, denser atmosphere, it absorbs low frequency radio waves during the day. As such, these waves never reach the E or F layers to be reflected back to earth.

Marconi’s experiment took place during the day (on three consecutive days), when the entire path was in daylight. He had no way to know at the time, but he had chosen the worst possible time to conduct his test. Atmospheric conditions would have made propagation at this frequency nearly impossible even using today’s sensitive receivers and modern transmitters of far greater power than Marconi’s station produced.

Dr. John Belrose, of the Communications Research Centre in Canada, has published several papers regarding the probability (or lack thereof) of Marconi’s success, including a rather extensive technical analysis of Marconi’s equipment published with the IEEE in 1995 in which he concludes that the success would have been “impossible.”

So what did Marconi hear? Marconi had several other strikes against him. His original receive antenna destroyed by a storm, he was using a long wire supported by a kite in the wind. Such a moving antenna would have been somewhat unstable so far as signal reception was concerned. He had been listening to three days of atmospheric noise and static, and what we now know as “listener fatigue” would have taken its toll. Common atmospheric discharges such as lightning could have easily mimicked three dots. I would also question the possibility of man-made noise, such as that radiated by long, land based telegraph wires in use at the time, could have produce three dots. In all likelihood, Marconi either misinterpreted atmospheric noise, or, as Dr. Belrose and others claim, faked it altogether.

Ok, so I have blasphemed. But does it matter? Marconi had already conclusively proven the viability of radio telegraph over shorter distances. He intuitively knew that his idea for transatlantic communication would work. Within a few years , backed by investor’s money, with improved technology and better understanding of propagation, he would be successfully sending traffic across the Atlantic, and even greater distances, on a regular basis. The result would be financial success as well. I certainly would not revoke Gugielmo Marconi’s title as “The Father of Radio” nor deny him the Nobel Prize awarded in 1909 for his achievements. Oops, now the Tesla fans will be after me. I’ll have to save him for a future article.

Enjoy the holiday season.