It was in the 1800s that a host of scientific and amateur experimenters in the Old & the New World played with chemicals and metals in an effort to thrust an intelligible electrical signal into space and to pluck it out again, equally intelligible, at a distance. Many great men, and an equal number of lesser men too, whose names and achievements have been chronicled and re-chronicled by professional and amateur historians, participated in the the quest for adequate methods whereby meaningful signals could be transmitted through space.
However, not only was the development of wireless techniques dependent upon the inventive genius of many scientists and experimenters, but it was also dependent upon available technology.
In our regular series of topics under the title “Radio Panorama”, we come to the era of early experimentation in signaling through the air. In the year 1802, Italian philosopher Gian Domenico Romagnosi experimented with electricity and a compass needle. He discovered that a spark discharge from a voltaic pile caused a deflection in the needle of a nearby magnetic compass, and he published his findings in Italian newspapers.
Two decades later; the year is 1820, the month is April, and the country is Denmark. It was at this time that Hans Christian Oersted, professor of science at the University of Copenhagen, invited a group of students and friends into his home to observe a scientific experiment. He intended to show that an electric current passing through a wire produces heat, and that it also causes a change in the deflection of a magnetic compass needle. The compass was mounted on a wooden stand nearby.
Oersted demonstrated that the electricity flowing through the wire produced a change in the deflection of the compass needle, even though the compass was several feet way from the wire. He was surprised however, to discover that a change in the direction of the flow of the current also produced a change in the direction of the compass needle.
On September 3 of the following year, 1821, Michael Faraday in England made his initial experiments with a wire and a compass. A vertical wire, with an electrical current running through it, was moved near a magnetic compass needle, thus causing the needle to deflect.
Ten years later, Michael Faraday made another series of similar experiments and it happened to be at the same time as Joseph Henry was working independently along the same lines in the United States. Joseph Henry passed an electric current through a wire on the 2nd story of a house and discovered that the spark induced a similar current in a wire two floors below.
At this stage, Joseph Henry performed his experiments mostly in August 1830, and Michael Faraday performed his experiments a few months later. However, Faraday published the results of his experiments first and he is generally given the credit for this discovery of magnetic induction, which is an early fore-runner to wireless transmission.
It is stated that the Scottish physicist, James Clerk Maxwell, began his initial experiments with electro-magnetic waves in the year 1861. However, his greatest contribution to the introduction of wireless technology was not his experimentation, but rather the development of his mathematical and theoretical basis for the propagation of electro-magnetic waves.
Maxwell presented two major papers on his theories to the Royal Society in London, one in 1867 and the other in 1873. It was upon the Maxwell theories about the propagation of electro-magnetic waves, and his insightful predictions regarding their usage in wireless technology, that inspired subsequent experimenters to persevere in their onward search for practical realities in the transmission of electrical and electronic signals through space.
During the year 1879, David Edward Hughes in London began experimenting with the transmission of a wireless signal. A coil of wire and a battery served as the transmitter, and a coil of wire and a telephone acted as the receiver.
The initial experiments were conducted in his London home, and afterwards he went out into the nearby street. When the circuit in the transmitter coil of wire was broken, the spark could be heard in the telephone in his receiver circuit. He discovered that the strongest signal could be heard at about 180 ft, and the signal got weaker until it could not be detected at about a quarter mile.
During the two following years, David Hughes made public demonstrations before prominent people, though he never developed his experimentation any further.
Comes the year 1887, and the noted experimenter, Heinrich Rudolf Hertz, constructs a simple wireless transmitter and receiver. At the time, Hertz was Professor of Physics at the Karlsruhe Polytechnic in Germany.
As the transmitter, Hertz used a coil of wire and a battery connected to two polished brass knobs quite close together. As the receiver, Hertz used a coil of wire connected to two more small brass knobs. When a spark was induced across the knobs in the transmitter circuit, a similar though smaller spark was noted in the receiver circuit several feet away.
These experiments by Hertz were a major development that set the stage for the introduction of experimentation in the transmission of wireless signals.
(AWR Wavescan/ NWS 97 via Adrian Peterson)