q Amateur • 

 Electrician 



o\nd Wireless Operator 



An Easily Adjusted Ball-and-Socket 

 Detector-Stand 



A' DETECTOR-STAND capable of es- 

 pecially easy adjustment, on account 

 of the ball-and-socket arrangement of the 

 movable arm, is illustrated herewith. The 

 ball was taken from a butt-hinge; a bind- 



The ball-and-socket joint makes an easily 

 adjusted detector for wireless apparatus 



ing-post was re-threaded to fit the stud 

 attached to the ball, as shown. The 

 socket is made from spring brass, and holes 

 slightly smaller than the ball are drilled 

 very near the ends. A tension-screw is 

 fitted to the socket, which is three-quarters 

 of an inch long with a knurled nut for easy 

 turning. 



The mineral holder is a U-shaped piece of 

 quarter-inch brass rod flattened at the 

 bottom. Near the end of one leg a hole is 

 tapped with an 8/32 tap and an 8/32 thread 

 is also tapped in the bottom of the clamp so 

 that it may be fastened to the base. 



The base may be taken from an old spark- 

 gap or cut out of fiber or hard rubber and 

 drilled to suit. It should be about 2 in. by 

 4 in. The arm is made of Hs-in. brass rod 

 3 in. long; threaded 8/32 at each end. A 

 binding-post may be mounted on it to 

 carry the "cat-whisker" wire or mandolin- 

 string, or nuts may be used on the arm 

 end for clamping the same as a binding 

 post. — Francis W. Nunenmacher. 



A High Tension Audion Battery 

 Made of Medicine Vials 



WHEN using audion or similar tubes, a 

 battery giving from 30 to 40 volts is 

 necessary. Such a battery made up of 

 small flashlight dry-cells is most convenient 

 but costs as much or more than the tube 

 itself. Dry-cells also have what is known 

 as "shelf life." This means that they de- 

 teriorate even when standing idle (on the 

 shelf evidently). In a year's time, more or 

 less, they will have lost their strength and 

 their voltage and current will be near zero. 

 As the high tension current consumed by 

 the audion tube is extremely small, a bat- 

 tery may be madr >ip of very small storage 

 cells, when a direct or alternating lighting 

 current is available for charging them. 

 With alternating current, however, a suit- 

 able rectifier must be used. The battery 

 cells may consist of small medicine vials 

 with strips of roughened lead for plates. 

 Such a battery is shown in the illustration, 

 mounted directly back of the panel holding 

 the tube and voltage-regulating switch. 

 The vials are conveniently mounted in a 

 row between two wooden cleats so that they 

 will not topple over. Small wires are led 

 from the switchpoints and soldered to the 

 tops of the lead strips. The lead strips 



Cells of battery made up of small medicine 

 bottles with strips of lead for the plates 



should not reach to the bottom of the vials. 

 A drop or two of light oil on top of the 

 electrolyte will tend to prevent acid fumes 

 from arising and tarnishing parts of the 

 apparatus. When charging with no- volt 



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