AUSTIN AND GRIMES: BEAT ElECEPTION 1 75 



regeneration, while, according to others, the sensitiveness is 

 inherent in the beat method. With the autodyne the two fac- 

 tors are impossible to separate, but with the heterodyne this can 

 be done. The experiment was made as follows: The regular 

 laboratory long wave set with magnetic back coupling and with- 

 out grid condenser was used, but with the back coupling much 

 too loose for local oscillations. Oscillations were then produced 

 by a separate heterodyne and audibilities taken on Nauen, the 

 heterodyne coupling being adjusted to give the best signal. 

 Then the back coupling of the regular set was increased to a 

 point just before autodyne oscillations were set up and where 

 with spark signals strong regeneration would be noted, but no 

 increase in Nauen signals was observed even with retuning. 

 The removal of the plate coil and bridging condenser from the 

 receiving set, thus reducing it to a primitive audion, also had no 

 effect. 



Next, with a heterodyne coupling too loose to give the best 

 signal, autodyne regeneration increased the strength of signal; 

 that is, it seems that the back coupling of the receiving set re- 

 generates the local oscillations so as to bring them up to optimum 

 value, but has no observable effect on the strength of received 

 signals. It may' be that the resultant increase in sensitiveness 

 due to regeneration and that due to oscillation is the sum rather 

 than the product of the two, so that when they are added, the 

 smaller increase due to regeneration is hidden by the great in- 

 crease due to the oscillations. 



Best Strength of Local Oscillations. — For the range 1-5000 

 audibility, the best signal is obtained with the same strength of 

 local oscillations for any given circuit and wave-length. The 

 optimum value varies with different vacuum tubes and with 

 different ratios of inductance to capacity, increasing with in- 

 creasing capacity. 



Law of Response and Autodyne and Heterodyne. — In 191 5, it 

 was discovered (Joum. Wash. Acad., 6: 81. 1916), that the law 

 of response of the oscillating tube (autodyne) within the Hmits 

 of obser\^ational error, was linear, that is, that the telephone 

 current was proportional to the first power of the radio frequenc 



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