Pontecchio, Italy, December 8th 1895
A gunshot in the distance marked the beginning of the communication era based on electromagnetic waves.
A sunny springtime afternoon, a villa in the heart of Italy’s countryside. Guglielmo, son of the marquise Giuseppe Marconi and Annie Jameson (perhaps you tasted the famous whiskey brewed by her father) is a very talented young inventor. These days, he’s experimenting with the newly discovered electromagnetic waves. In fact, in 1864 James Clerck Maxwell published a paper called Electromagnetic Theory of Light in which he predicted the existence of oscillations of the EM field. Some years later, Heinrich Hertz developed a dipole transmitter and an antenna receiver to test Maxwell’s theory. The two devices were designed to work in pair:the receiver was conceived to emit an EM radiation with a certain frequency (now measured in…Hertz!), and the receiver was designed to resonate exactly at that frequency. As a matter of fact, Hertz saw a spark every time the transmitter was turned on.
A very interesting phenomenon, but what’s the use of it? They say that Faraday, when was asked the same question by the Prime Minister Gladstone, answered “One day, sir, you may tax it!”. It’s unlikely that he was thinking about the BBC, but he was right!
In the same years, Augusto Righi, an italian physicist, started to work on electromagnetic waves. He reproduced Hertz’s experiments and showed that the EM waves can be scattered, polarized and refracted just like ordinary visible light. In 19889 Augusto Righi started to give lectures at University of Bologna, where his instruments are on display in the hallways of the department of physics to feed your historical curiosity.
Notably, among his students was indeed Guglielmo Marconi. Back to Pontecchio, Guglielmo carried out a series of experiments with transmitters and receivers. Born into a family of high social class, he had both the opportunity to spend time learning these cutting edge science topics and to develop a talent as an entrepreneur. So, he tried to make something out of these EM waves. However, the main obstacle to wireless communication was in fact…his house. In fact, Hertz and Righi proved that it was possible to send waves across the open air, but what about walls and hills? On December 8th, 1985, he set up a simple experiment: he tried to send a wireless message to a receiver located on the other side of the hill inside his family’s villa. He was supposed to activate the transmitter, the butler had to fire a shot if the receiver ringed. And it really happened!
Some years later, Guglielmo Marconi obtained a patent for his invention and founded the Marconi Wireless Telegraph Company. He even managed to send a message from Cornwall to Newfoundland, thanks to the fact that EM waves are reflected by the ionosphere (a layer of Earth’s atmosphere). At length, he shared with Carl Ferdinand Braun the Nobel Prize for physics in 1909.
From Analog to Digital
Wireless transmission flourished in the first half of the 1900s, ideally from the SOS message sent from the Titanic in 1912 to the broadcast of Winston Churchill’s Finest Hour speech. However, there was a very annoying problem: noise. Radio communications were very often unclear, noisy and distorted, and to some extent they still are. One way to solve this problem is to change the way information is transmitted from analog to digital. This means that information is encoded upon a carrier EM wave. If you just listen to the wave, it would mean nothing to you, no words, no music. Actually, it just sounds like noise! The idea stems from typewriters, which encode a text in Morse code: a string of dots and dashes can be converted back and forth into letters.
A very important concept made its way into physics: information. What really matters here is that very different physical media such as air and EM waves can carry the same message encoded in different ways – pressure or EM field waves for example. But his still does not solve the problem. With a noisy communication you can still lose some dashes and dots, so in the end the message can be unreadable.