How to Become a Wireless Operator 



III. — The Construction of a One-Mile Receiver 



By T. M. Lewis 



IT IS most important for a student of 

 wireless telegraphy to learn all about 

 the operation of the various forms of 

 receiving apparatus. The best way to 

 become familiar with the instruments is 

 to build and operate them. The simple 

 buzzer-sender and microphone receiver 

 which were described in the first article 

 of this series served to illustrate the 

 principles which are followed in all 

 wireless apparatus, but were of such 

 small signaling range that they could 

 not demonstrate fully the details of 

 modern instruments. The one-mile 

 transmitter shown last month, however, 

 when used in connection with the 

 receiver now to be 

 explained, is of suf- 

 ficient size to ap- 

 proach the c o n - 

 ditions of opera- 

 tion existing i n 

 commercial radio 

 stations. By 

 studying its action 

 carefully the ex- 

 perimenter can 

 learn much which 

 will be of inestim- 

 able value to him 

 in his later prac- 

 tice of wireless telegraph operation. 



The student should remember that 

 the use of a transmitter as powerful as 

 that described in the second article, 

 even though it is a very small one when 

 compared to some of the great commer- 

 cial, plants, may cause interference at 

 nearby receiving stations. He should 

 therefore be very careful to observe all 

 of the regulations and courtesies as to 

 transmitting, and should send only 

 when he actually has a message which 

 he wishes delivered to his communicating 

 station. One of the first habits which a 

 successful wireless operator should cul- 

 tivate is to refrain from sending except 

 when it is absolutely necessary. Testing 

 of the spark-gap should be done with 



Fig. 1. A cross-sectional view of a crystal 

 detector stand that is easily constructed 



the aerial disconnected, and code prac- 

 tice should be carried on with buzzers. 

 There is never any objection to the 

 amateur who sends actual messages with 

 a wavelength of less than 200 meters 

 (the range assigned to amateur stations 

 by the Government) but the man who 

 keeps tapping his key and sending out 

 interfering waves which hold up legiti- 

 mate messages soon becomes extremely 

 unpopular with both the serious amateurs 

 and the professional operators. 



The Detector 



Probably the most important element 

 of any receiving outfit is the detector, 

 which is an instru- 

 ment for convert- 

 ing the received 

 high- frequency 

 current into pulsa- 

 tionswhich operate 

 the telephones. 

 The microphone 

 which was d e - 

 scribed in the first 

 article is a wave- 

 detector of a very 

 easily constructed 

 tj'pe, and is always 

 worth remember- 

 ing for use in an emergency. It is very 

 delicate, but is not so reliable nor so 

 sensitive as the crystal detector which 

 is illustrated in Fig. i. A well made 

 crystal detector is about the best instru- 

 ment for all around use that can be had. 

 Apparatus of this type is installed at 

 by far the greatest number of commer- 

 cial radio stations, and every operator 

 should be familiar with its adjustment 

 and use. 



A side view of a detector-stand, which 

 has been found very satisfactory- in 

 practical work, is shown in Fig. i. The 

 construction should be clear from the 

 drawings, and a brief description. Di- 

 mensions are not given, since it is usually 

 most convenient to modify them slightly 



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