184 



ANNUAL KEPORT _SMITHSONIAN INSTITUTION, 1908. 



Transmitting Circuits. 



Figure 2 "■ shows a type of arc circuit. 



Figure 3 ^ shows a suitable type of connection for use with a high- 



frequenc}^ alternator. 

 Figure 4 ^ shows a 

 type of circuit for 

 use with the condenser 

 transmitter. 



Figure 5 '" shows a 

 type of circuit in 

 which the modulation 

 is accomplished by 

 changing the induc- 

 tance of one of the 

 oscillating circuits. 



As a matter of fact 

 the transmitter may 

 be placed almost anywhere in the circuit between the arc or dynamo 

 and the antenna, or between the arc or dynamo and ground, or in the 

 transformer circuit, or in shunt to an inductance or capacitj^, the 

 results obtained in all cases being indistinguishable. 

 The sole criterion of success seems to be that the trans- 

 mitter should be capable of handling the energy and 

 the circuit should be properly adjusted. Some success 

 has also been attained by placing the transmitter in the 

 field of the dynamo,** but this method requires very care- 

 ful designing of the field circuit. 



Receivers. — The receiver which the writer has found 

 most satisfactory for general purposes is the liquid 

 barretter. Plate 15, figure 2, and plate 16, figure 1, 

 show this receiver. It consists of a fine platinum wire, 

 about a ten-thousandth of an inch in diameter, immersed 

 in nitric acid. Tests made with this receiver show that 

 it responds without apparent loss of efficiency to notes 

 as high as 5,000 per second. Some very careful meas- 

 urements recently made by my assistants, Messrs. 

 Glaubitz and Stein, give the following results: 



Voltage of high frequency circuit necessary to produce readable 

 signals, 15 X 10~^ volts. 



Fig. 2. — Type of arc circuit. 



P 



Fig. 

 of 



—Type 

 connec- 

 tion with 

 b i g li - f r e - 

 quency a 1 - 

 ternator. 



« United States patents Nos. 706742, June 6, 1902, and 730753, April 9, 1903. 



& United States patent No. 706742, June 6, 1902. 



" United States patent No. 706747, September 28, 1901. 



•^ United States patent No. 793649, March 30, 1905. 



