Radio Broadcast (May-Oct 1922)

How to Begin to Enjoy Radio CAPTAIN LEON H. RICHMOND, SIGNAL CORPS, U. S. A. Editor, Technical Training Literature, Office Chief Signal Officer Captain Richmond, who was Professor of Physics at Western Maryland College before the war, was commissioned in the Signal Corps at the outbreak of the war. After passing through various instruction camps, he was assigned to the Royal Navy (British) Flying Field at Crsnwall, England, where he worked with L.t. Commander J. M. Robinson (British Navy) in developing a radio direction finder and other radio apparatus for airplanes. Upon the completion of this duty, and after a short time at an American Flying Field, he was assigned to duty at the Army Signal School, Langres, France, where he was in charge of the Radio Department at the signing of the Armistice. For the past year and a half. Captain Richmond has been on duty in the Office of the Chief Signal Officer at Washington. — ^The Editor. THE main topic of discussion at the International Radio Convention at Paris was radio wave lengths. The main topic of discussion at the "Hoover Radio Convention" held recently in Washington was radio wave lengths. It is the purpose of this first of a series of elementary discussions on radio to explain what is meant by wave length and to show why the subject is such an important one in the radio world. Every one is familiar with some kinds of waves, especially with those that appear on the surface of water. Let us study these water waves. We can represent them by a line as in figure i, where the curving line represents riG. 1. the surface of the water with waves on it and the straight line, AB, represents the surface of the water when there are no waves. The first thing we notice about a wave is its height. The stronger the breeze the higher the waves. The correct way to measure the height of a wave is to measure from the crest of the wave to the surface of the water when it is smooth. In figure i this would be represented by the line cd. A better term for this measurement is amplitude of the wave. Hereafter we will refer to the amplitude of the wave and not to the height. The reader should realize that in learning a new art, the learning of new words or new meaning of old words is probably the most important factor. So through this series a term of particular application in radio will be italicized when it first appears. If we have been in a boat or in swimming when there were waves, we are familiar with the fact that the waves have energy. In other words, they have power to move objects that are in the water or which they may strike. It is seen that the bigger the waves the more energy they have. Another way of saying this same thing is to say that the energy of a wave increases as its amplitude increases — a large amplitude gives a large amount of energy — a small amplitude gives a small amount of energy. In radio we use the energy of the radio wave. If we watched water waves we would soon notice that besides height, the waves have length also. There would be a certain distance from one wave to the next. This distance can be measured from the highest part of one wave (called the crest) to the highest part of the next wave. This distance is the length of the wave. In figure i it is represented by the line ce. Also jj shows the length of the wave. The wave length, then, is the distance from any part of one wave to the corresponding part of the next wave. A short way of writing the word wave length is, "X" pronounced" Lambda." This symbol means wave length. (Write several of these symbols so as to become familiar with them.) If we stood on the shore and watched waves go by we would notice that waves, besides having amplitude and length, passed us at regular intervals of time. Count the number of waves passing per second. You have counted the frequency of the waves. Frequency, then, is the number of waves passing