^J^-^7>^^^'X!T~':t-^3^ : .~---'>, 



r^^ 



Overcoming Troubles 



in a 200-Meter 



Wave Outfit 



By R. H. G. Mathews 



The following article won the second prize of Fifteen Dollars in the POPULAR 

 Science Monthly's Radio Article Contest. We would call it to the attention of 

 wireless amateurs because it shows how, with a little ingenuity, a wireless amateur 

 can overcome discouraging obstacles. We want more articles of this type. — EDITOR. 



WHEN the radio law of 1912 went 

 into effect, many of the amateur 

 operators of the United States 

 dismantled their apparatus and gave up 

 experimentation with wireless teleg- 

 raphy, thinking that a station which 

 complied with that law could not do 

 successful work. "Successful work" at 

 that time in the amateur field meant 

 transmitting 30 miles, with an input of 

 2 to 3 Kilowatts. Many amateurs whose 

 stations comply with the present law, 

 are now able to work over distances of 

 from 800 to 1,000 miles with less than 

 one Kilowatt input. To do this long 

 distance work, using a short wave and 

 low power, requires specially designed 

 apparatus. A minimum of condenser 

 with a maximum of inductance must be 

 used in the closed oscillating circuit. 



In order to obtain this condition, I 

 designed and built a 43,000-voIt, i-Kilo- 

 watt, closed core transformer. Because 

 of the use of this extremely high \-oltagc, 

 a condenser consisting of only 358 sc]. in. 

 of conducting surface, on opposite sides 

 of \i-\n. plate glass sheets, is used. With 

 this small condenser capacity, the prim- 

 ary inductance which may be used on a 

 short wave is quite large, and con- 

 sequently an easy transfer of energy 

 from the closed to the open circuit is 

 obtained. 



At first, I made my condenser of the 

 usual packed type, suspended in a tank 

 of oil. I found, however, that my plates 

 were continually puncturing, due, I 

 thought, to my excessive voltage. I 

 eventualh- discovered that the breakage 

 was caused, not by direct puncturing, 

 but by what appeared to be a crushing 

 of the glass by a force exerted on it by 

 the attraction of the charges of opposite 

 polarity on opposite sides of each glass 

 plate. When the plates were clamped 



GLASS- 

 PLATES 



i^^^^^P 



fP 



CONTACT 

 STRIP 



TANK CON- 

 TAINING OIL 



RACKTOHOIO 

 PLAItSAMRI 



Fig. 1. Method of spacing plate glass 

 sheets to eliminate breakage when im- 

 mersed in tank of transformer oil 



together the crushing strain exerted in- 

 this force was tremendous. I entirely 

 eliminated this breakage by spacing 



623 



