Popular Science Monthly 



031 



Lieutenant H. C. Gawler, the cliicf 

 radio inspector of the New England 

 District, and Inspector Cheetham, the 

 Marconi expert, were even more sur- 

 prised when they began sending from 

 their improvised station, for the rephes 

 they received showed that they were 

 able to send a distance of 150 miles, or 

 six times as far as would have ordinarily 

 been the case. The normal record for 

 a governmiMit field set is 44 miles, but 

 it is probable that an ordinary field out- 

 fit can be made to send to a distance of 

 300 miles or more, when a kite-supported 

 aerial is employed and if all conditions 

 are favorable. It is possible to send up 

 the kites and the aerial when there is 

 very little breeze. 



In last summer's Plattsburgh ma- 

 neuvers the signal corps were shown 

 that they could increase the range of 

 their field set by about 200 miles if kite 

 aerials were used, and also that they 

 could do this almost any day. When it 

 is impossible to send up kites, it is 

 proposed to use a small hydrogen 

 balloon. A later test of the improved 

 pack set at Fort Leavenworth demon- 

 strated that it is now possible to send 

 even farther than was believed pos- 

 sible. — ^Stanley Y. Beach. 



A New Spark-Gap for Wireless 

 Telephony 



IN order to transmit speech by wireless 

 it is necessary to produce continuous 

 waves, or, as a substitute, groups of 

 electromagnetic waves at a very high 



, " II " '" ■ 



^ 



A special gap wich highly cooled sparking 

 surfaces inclosed in a gas-filled chamber 



frequency. The transmitter should be 

 uniform in operation, so that a practical- 

 ly continuous stream of radiant energy 



will flow out from the sending antenna. 

 The various forms of arc generators, 

 when very carefully adjusted, or now 

 familiar high-frequency alternators, can 

 be used in this way. It has been sugges- 

 ted by various inventors that sparks 

 occurring at very high frequencies might 



Fiaz 



A diagram showing how the telephonic 

 sparker may be interposed in the line 



also form a basis for radio-telephonic 

 power generation; many forms of 

 quenched and rotary-gaps for this pur- 

 pose have been proposed. 



In U. S. Patent 1,173,562 there is 

 shown a special gap having small 

 highly-cooled sparkling surfaces enclosed 

 in a chamber through which passes 

 carbon dioxide gas. The inventor, 

 W. T. Ditcham, points out that if large 

 electrodes are used the spark will not 

 remain sufficiently constant for the 

 transmitted speech to be clearly articu- 

 late. In his new gap, which is shown in 

 Fig. I, the spark is restricted to the ends 

 of the small plugs B, which are firmly 

 set in the shafts 5' and B-. These rods 

 carry cooling flanges D, and are secured 

 to the walls H of the gap chamber /•" by 

 the flanges G, I. Fresh carbonic acid 

 gas is fed through the tubes K^, K' and 

 serves to cool the gaps. 



Figure 2 shows one of the circuits in 

 which the new discharger may be used. 

 M represents a direct-current generator, 

 of about 1,000 volts, which is connected 

 through resistance A^ and choke-coils 

 O, O, to the terminals of the gap A. 

 The high-frequency circuit is compo.sed 

 of the gap, the condenser P and the 

 primary Q; to this last-named coil is 

 closely coupled the secondary R, which, 

 with the microphone V, is connected 

 between the antenna 5 and ground W. 

 The two oscillation-circuits are not tuned 

 to the same frequency as if measured 

 separately, for the best transfer of 



