Long Distance Wireless Telegraphy 1 



By J. B. Woolsey 



THE casual "listener-in" on a long 

 distance radio set at the present date 

 is apt to he impressed with the fact that 

 the use of undamped oscillations for 

 long distance radio telegraphy may soon 

 become more or less universal. While it 

 is true that no definite decision has been 

 arrived at as to the relative merits or 

 demerits of the damped and undamped 

 .systems, still, the general trend of prac- 

 tice seems to be toward the latter. This 

 is probably augmented by the fact that 

 there has been developed of late a certain 

 type of receiving apparatus peculiarly 

 suited to the reception of undamped os- 

 cillations, giving at the same time ex- 

 treme sensitivity. 



There are a number of long distance 

 radio telegraphic circuits used more or 

 less commercially, but largely experi- 

 mentally, concerning which the general 

 amateur field is not at all informed. One 

 of the most successful of these is that 

 of the Marconi Company between Glace 

 Bay, Nova Scotia (WSS), and Clifden, 

 Ireland (MFT). These stations work 

 twenty-four hours per day with practi- 

 cally no interruptions, handling an enor- 

 mous volume of commercial and war 

 traffic. The dispatch of traffic at these 

 stations is facilitated by the fact that 

 the circuit is duplex, allowing the opera- 

 tors to interrupt each other during the 

 transmission of a message, permitting 

 the immediate correction of an error. 

 These stations, although fitted with spark 

 gaps of the rotary type, produce oscilla- 

 tions of feeble damping which possess 

 characteristics similar to the stations em- 

 ploying genuine undamped oscillations. 



There are five methods in use to-day 

 for the generation of undamped oscilla- 

 tions, viz. (i) the Poulsen arc; (2) the 

 Goldschmidt high-frequency alternator; 

 (3) the high-speed, high-frequency alter- 

 nator ; (4) the Count Arco step-up trans- 

 former system for the generation of un- 



*Owing to the*inordinate length of this article, it has 

 been found necessary to publish it in two parts. The 

 secojid and concluding part will appear in the August 

 issue. (Photos. International News Service.) 



damped oscillations; (5) the General 

 Electric Kenotron. 



The Poulsen arc does not, as is gen- 

 erally supposed, generate pure undamped 

 oscillations; as a matter of fact these 

 oscillations are produced in a series of 

 groups, the groups taking place at a rate 

 above the limits of audibility. Due to 

 slight irregularities in the action of the 

 arc, this type of transmitter possesses 

 slightly damped characteristics, so much 

 so, in fact, that the signals may often be 

 read on the ordinary crystalline detector 

 at a distance of 10 to 50 miles from the 

 station. 



The arc system is employed exclusively 

 by the Federal Telegraph Company of 

 San Francisco, Cal. The company op- 

 erates a few long distance stations at 

 various points. The arcs at these stations 

 are employed in a simple manner; one 

 of the electrodes being connected direct 

 to the earth and the other to the aerial 

 system. The wave length of the antenna 

 system is then increased or decreased as 

 desired by the simple addition or sub- 

 traction of the turns of a tuning induc- 

 tance connected in series with the aerial 

 circuit. Signalling is accomplished by 

 short-circuiting a few turns of this in- 

 ductance with an ordinary transmitting 

 key. 



Thus, the aerial system is rapidly 

 changed from one wave length to an- 

 other, and if the distant transmitting sta- 

 tion is tuned to the wave emitted when 

 the wave is depressed, the wave emitted 

 when the key is raised will be inaudible. 

 The arc at these stations is enclosed in a 

 chamber and supplied with either hydro- 

 gen or ordinary illuminating gas or per- 

 haps alcoholic vapor. It is likewise 

 burned in a strong magnetic field at right 

 angles, which increases the steadiness of 

 the arc and its effectiveness as a whole. 



The receiving apparatus at these arc 

 stations generally consists of a sliding 

 wire tikker which comprises a simple 

 piece of flexible wire in loose contact 

 with a rotating wheel. It is connected in 



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