289 

 NOTK OX AXTEX.XAE RKSISTAXCK. 



K. K. I{A\rsi;Y. 



Attention is called to tlio fact Ihal in the modern oscillating rccoivinji 

 circuits using toloplioncs as currciil iiidicMtcrs the "half deflection method" 

 (if resistance measurements will not ,i;ive (•oiTcct results. 



A LOX(; WAVE RECEIVER. 

 R. R. Ramsky. 



In wireless work all wave lengths are used fi-om 200 meters or less, 

 anialures. to 20,000 meters in transcontinental transmission. It is cus- 

 t(imar.v to limit the wave length range of reception of any receiver to a com- 

 parative small band of this range. This is due to the fact that in order to 

 keep the natural frequency of the coil high. Avhich involves the necessity of 

 the distributed capacity of the coil being low, it is usual to wind the coils 

 with one layer of wire. Single layer coils in order to have a high induc- 

 tance must be made of large dimentions of very fine wire which necessi- 

 tates a very large resistance. 



In the coil which I have made I have endeavored to avoid this ditficulty 

 by winding the coils of relatively large wire in banks or coils one inch in 

 width and five layers deep. The distributed capacity is kept to a low 

 value by separating each layer by means of heavy card board. The coils 

 are wound on card board tubes whose length is seven inches and whose 

 diameters are. primary coll 14 cm. and secondary coil 10 cm. Each coil con- 

 sists of six banks one inch wide, five layers deep. Each layer containing 

 twenty turns of No. 20 wire. The total number of turns per coil is 000. 

 The original design of the coil called for No. 24 wire 30 turns per inch or 

 about 1.000 turns in all. This would give an inductance of about .07 

 henrys or a wave length of about 20.000 meters using an ordinary .001 

 microfarad condensed. The smaller wire was not available so the larger 

 wire was used and the lack of inductance was made up by using a variable 

 conden.ser whose maximum capacity is .01 microfarads. 



On the secondary coil ten taps are brought out. The taps are arranged 

 as follows. Tap No. 1 contains 1 turn ; 2, 3 turns : 3, 7 turns ; 4, in turns : 

 5. 1 layer : 6. 2 layers ; 7, 1 bank : S, 2 banks ; 0. 4 banks ; 10. the entire 

 secondary coil. Cut out or dead, end switches are inserted between taps 

 No. and 7. and taps 8 and 0. The windings of the primary are arranged 

 after the same plan as that in the secondary except that ther(> are S taps 

 instead of 10. The coils are mounted so that the secondary will slide into 

 the primary coil according to the well known plan of the slide tuner. A 

 feed back or regenerative coil of 425 turns of No. 30 wire is mounted so as 

 to slide into the primary coil from the opiM)site end from the secondary coil. 

 This coil is seldom used as it is found tliat an "auto feed back" connection 

 on the .secondary gives better results. This consists of a switch by means 

 of which the filament of the tube can be connected to a point near tlie middle 

 of the secondary coil. The diagramatic connections are shown in figure 1. 



