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back” which is exactly what we illustrated by our experiment with the two violins. If two strings are in tune and one is caused to vibrate, the second will “sound back” and is in “resonance.” So, when a Radio receiver is “tuned” to a certain station, it is also said to be “in resonance” with that station.
     Coming back to Radio, let us imagine that the transmitting station is violin number 1 and the receiving set is violin number 2. If our set is in resonance “tuned” with the transmitting station, we will hear its signals--if we are not in resonance we naturally don't get the station.
     We know that to tune a receiver it is necessary to turn one or more dials on the panel of the set, but just what goes on in the set when the position of the dial is changed, and what principles make it possible to tune in one station and all others out, is a matter that must be kept until a little later. However, by this time you should have a clear idea of what is meant by “tuning” and have a clear understanding of simple waves--water, sound, and also--Radio waves--as far as possible in this first lesson, which after all is just an introduction to Radio. In later lessons we shall meet the acquaintances we made in this lesson and learn to know them much better. We shall see how we can vary the amplitudes of simple Radio waves and how this will allow us to combine sound waves with the Radio waves.

FROM TRANSMITTER TO RECEIVER
     Having considered the natural phenomena that make Radio possible, we are now ready to look at our receiving apparatus for a few moments. You may wonder why we don't start with the details of the transmitting apparatus, but there are several reasons why it is much better to start at the other end. In the first place, receiving apparatus is much simpler than that of transmitting. In the second place, there are many more receivers in operation than transmitters, and much more chance to see them and get on our road of repairing and servicing receivers. And last of all, after you understand the receiver it will be easy to start work on the transmitter and get a thorough understanding of it in short order.
     You know that the Radio wave is sent across, “transmitted” from the transmitter, to the receiver through the ether. Remember that ether forms a part of everything in nature--that is why Radio waves travel everywhere, through houses, through the earth, through the air.

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Content©1931, National Radio Institute
Webpage©1997, Nostalgia Air
Transcriber  Richard Lancaster