Wireless Work in Wartime 



VII. — Fundamental Principles of Radio Apparatus 

 By John L. Hogan, Jr. 



THE six preceding articles of this 

 series comprise a fairly complete set 

 of instructions in learning wireless 

 operating, from the simple viewpoint of 

 telegraphing. Memorizing the code, read- 

 ing Morse signals by sound, and practice in 

 overcoming the difficulties of "station" 

 and atmospheric interference have been 

 taken up in some detail. All of these 

 matters are essentials in the study of radio 

 telegraphy, and they must be completely 

 mastered if one is to become a first-rate 

 operator. To be of the greatest value in 

 radio work, however, and to advance in the 

 naval, military or civilian radio services, it 

 is important to be more than a skilled 

 telegrapher. In addition to the ability to 

 transmit and receive messages s\viftly and 

 accurately under even the most adverse 

 conditions, one should know how and why 

 his instruments work. Such technical 



knowledge is of the greatest use to the radio 

 man in war work, for without it he is likely 

 to be unable to make urgently needed re- 

 pairs and adjustments. This, and the suc- 

 ceeding articles will go into the simple 

 technology of radio telegraphy, and should 

 prove helpful in studying to qualify as one 

 of the expert radio workers who are and will 

 be so much needed in the Signal Corps and 

 the Naval Communication Service. 



The main purpose of these articles, then, 

 is to guide the student to a thorough under- 

 standing of the radio station, and to point 

 out the precautions which must be taken if 

 the best possible working is to be obtained. 

 This wdll involve both the discussion of 

 apparatus design, and the elementary 

 theory of radio telegraphy. These two 

 branches of the general art are so closely 

 interwoven, however, that it is scarcely 

 possible to tell where one stops and the 

 other begins. One cannot design and build 

 good radio apparatus, or operate it most 

 effectively, without having a genuine appre- 

 ciation of what it is to do and how it can 

 be made to do it. Neither can one under- 

 stand the theory in such a way that it will 

 prove really useful to him, unless he has also 

 a knowledge of the practical apparatus to 



which the theory applies. In these articles 

 the concrete elements of design and opera- 

 tion and the reasons for them will be carried 

 along side by side. The only theory used 

 will be working theory, and the only con- 

 structional points explained will be those 

 which have been found satisfactory in the 

 experience of radio engineers in the military 

 and commercial fields. 



The Elements of Signaling Systems 



To understand the radio transmitter 

 itself we should fully understand its 

 object. In the first place, then, let us 

 consider the essentials of any communica- 

 tion system. Just as the natural act of 



'// / / '•'T~-- \ \ \ •• \ ^ \ \ 



' ' ' / ' ' ' A % ^\ \ \ \ \ \ \ > \ 



/ ,' ; / ; / / ,'-i--^ N \ > I > > ', \ \ I 



Fig. 27: General form of radio waves as they 

 pass from the sender in direction of arrows 



speaking to another person in the same 

 room calls into play the three main ele- 

 ments of any system for the transmission of 

 intelligence, so does the sending of a wire- 

 less message involve these same three 

 things. We cannot convey ideas from one 

 point to another without having something 

 which can act as a transmitting medium 

 connecting the two points. In the wireless 

 telegraph, the connecting medium is the 

 so-called "ether" of space, which lies 

 between the two stations. In talking, the 

 medium of transmission is the air which lies 

 between the speaker's vocal cords and the 

 listener's ear. In both cases, the medium 

 is vibrated according to some pre-arranged 

 code, and the vibrations pass from the 

 sender to the receiver. 



Evidently, the two remaining elements 

 are the transmitter and the receiver. The 

 first of these is merely an apparatus which 



?n7 



