DIO SECTION 



Devoted to the Encouragement of Amateurs 



and Experimenters in the Field of 



Radio Communication. 



A Multiple Receiving Tuner* 



By Chas. P. Seeger 



AFTER having accomplished the 

 work outlined in the first portion 

 of this article, the reader is prepared to 

 pursue the task as follows : 



DETECTORS: In the first detector to 

 be described the pillar is a piece of ^2" 

 brass rod cut to the dimensions indicated, 

 the springs being inserted on either side 

 of the central piece. The retaining bolt 

 should be made by drilling a hole in a 

 piece of ^" rod and "sweating in" a 

 piece of 5/32" rod, threaded at the end 

 to receive an 8-32 hexagonal nut. A 

 similar but shorter retaining bolt is used 

 in the free end of the detector. Before 

 cutting the rod into the desired lengths 

 for the pillars, it is suggested that a 3" 

 piece be taken to a machine shop in order 

 that the 5/32" hole necessary to receive 

 the retaining bolt may be drilled through 

 the center, otherwise it will be difficult 

 to assemble the parts into a neat appear- 

 ing unit. 



Instead of the designated contact point, 

 sharp pointed 8-32 fillister head machine 

 screws may be used, either of iron or 

 brass, depending on the crystal in use. 

 For the springs use 18 or 20 gauge 

 springy stock, cutting to the desired 

 length. Cups for the detector may be 

 purchased or made by soldering a plug 

 in a piece of %" tubing and fastening a 

 pivot to the plug. A base may be made 



*Continued from the July issue of THE WORLD'S 

 ADVANCE. 



of y 2 " round rod, 3/16" thick, soldering 

 a piece of 5/32" brass rod, threaded 8-32, 



Details of One of the Switches. 



to one side, and drilling the other to fit 

 the pivot. 



The second detector is truly a univer- 

 sal detector, for one in use at the pres- 

 ent has been converted into the well- 

 known cat-whisker type, by interchang- 

 ing the cup and the clamping screw, and 

 fastening a wire to the movable arm. 



Obtain a piece of tubing %" outside 



249 



