Communication has from the first been a major priority of humans. From the early days of travelling Minstrels that oft times use the major news of the day in their repertoire. To the printing press and the first “Newspapers.” But until the early 19th century and the advent of the telegraph, one could hardly call this news. It could take days, weeks even months for any information the travel any distance.
Which more appropriately puts it under the heading of recent history. There were various attempts at signalling devices but most were limited in distance, cumbersome to use, complicated, unreliable and therefore of little improvement over just carrying the message there by Pony Express. By the mid 1800s a number of electromagnetic methods of sending messages were being developed.
The one adopted here was one that Samuel B. Morse designed. Initially limited in distance — only about 10 miles — with the addition of relay stations, it eventually crossed the contentment and even the Atlantic and Pacific Oceans. Using a special code to represent the letters and numbers and punctuation necessary by sending pulses down a wire: the Morse code. The code, if not the mechanics, was quickly adopted world wide.
But this “land line” telegraphy was not with out it’s problems. The greatest being it’s vulnerability to intentional sabotage by Native Americans, train robbers, bank robbers and opposing military forces.
But still you might hear what’s going in in Chicago but Poplar Bluff, MO? Forgetaboutit.
In the late 1800s Heinrich Hertz did experiments with electromagnetism. Discovering the principal of electromagnetic waves IE Hertzian or radio waves. It was not long before a number of people started to experiment with these new found magnetic waves. Of course there was a big push to use them to send information.
One cannot really say who first got the idea of using electro magnetic waves to send and receive messages but Gugleilmo Marconi was the first to make a commercial success of it. And it became a big hit I can tell you. By the early 20th century it seemed like everyone was building radio sets and trying out this new technology.
Unlike wired telegraphy where all messages went through a telegraph office, anyone could put together a wireless set and have at it. But early wireless was crude to say the least.
There was absolutely no way to tune or separate wireless transmissions. Either sending or receiving. The receiving set was not at all sensitive and the transmissions themselves, even from the most sophisticated apparatus sounded like noise. Keyed on and off buzzing sounds. Like this or this or this. Now imagine 4 or more stations on at the same time all trying to contact you or them selves or somebody else. It would get very chaotic to say the least.
Well after the Titanic sank and other lessor disasters, it was obvious this new wireless thing needed regulation big time. And so it was. It was Edison who saved the day, though he did not know it at the time. He was trying to figure out why his light bulbs were getting this coating on the inside and the filaments burning out at the same time. Edison did not understand alternating current and was not the least bit interested in wireless. Sill he want to know what was going on and made a special bulb with a wire attached to a plate in it. What he noticed was when he put a meter between the plate and one of the filaments, it showed an electric current flowing. He called it the Edison Effect, wrote it up and gave a few demonstrations and that was it.
Fortunately Sir John Ambrose Fleming who was interested in wireless attended one of those demonstrations and got very curious. Would this detect radio waves? And indeed it did. What he discovered was the first practical application of Thermionic emission. Essentially meaning that when you heat a metal of any kind up really hot, it givers off electrons. In the air these electrons just go into the air and if enough are given off can combine with the oxygen and create ozone. But in a vacuum, like a light bulb, they have nothing to combine with, so they collect somewhere. Like on the metal plate.
If you connect this plate to a positive electrical voltage, the the electrons will flow from the filament to the plate. If you put a negative voltage on the plate, no electrons flowed. Fleming called this his valve or oscillation valve. Another engineer named Lee DeForest then discovered that if you put a wire grid in between the plate and the filament, a very small electric voltage on this “grid” made a large change in the electron flow from the filament to the plate. He called his new “tube” the Audion. DeForest found that not only could it amplify but could also be easily made to oscillate and produce a nice pure radio wave and its frequency could be easily set.