Page:Popular Science Monthly Volume 88.djvu/487

 Popular Science Monthly

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��of the ringing musical tone which is so desirable. At one time it was tliought that the increase in damping of spark signals, as compared to those of sus- tained-wave transmitters, was responsible for this change of note, but more recent- ly it has been found that the difficulty arose through the constant changes of phase from group to group. If the train of waves produced by a single spark dis- charge continued until the next spark passed, and if the second spark occurred at just the right instant and in the right direction to keep its waves in exact phase (or so to speak, hand in hand) with those which were dying away, the beats- receiver would pro- duce a musical tone instead of a hiss. The method of the present pat- ent is directed to- w a r d producing this result.

Referring to the figure, the closed primary circuit /, including the con- denser / and quenched spark- gap 2, coupled to the antenna circuit

���Fig. 7.

��//, is charged by power from the alternator I2 through lead wires 4 and 5. A portion of the spark-gap is shunted by the closed cir- cuit ///, which comprises the secondary of transformer 8, condenser 7, and spark-gap p, with shunting-switch ij. Transformer 8 serves to couple the con- trolling circuit IV with the ignition cir- cuit ///; IV includes one coil of trans- former i^, coupling it to the antenna. Primary and secondary of 75 may be short-circuited by switches 16 and //. Associated with the antenna is a closed pick-up circuit VI, which has coupled to it a rectifying-detector combination VIII and a local high-frequency-generator circuit VII.

The operation of circuits / and // is in accordance with the ordinary quenched spark-gap practice. Controlling circuit IV, however, acting through ignition cir- cuit ///, (and being of high persistence compared to the antenna), tends to reg- ulate the recurrence of si)ark in the main gap 2. With transformer 75 in

��operation, by opening switches 16 and //, the antenna // reacts upon and gov- erns the controlling circuit IV; the con- joint operation of these various systems keeps the successive wave groups of the same phase and therefore, by continual reinforcement of the oscillations in the persistent receiver-circuit, results in a pure signal note in the heterodyne tele- phone. Thus it becomes possible to take advantage of the musical note for read- ing through static, in addition to the am- plifying properties of the beats-receiv- er and the compar- ative simplicity of quenched-gap op- eration. The cir- c u i t s VI, VII, VIII, form a beats-receiver used as a tone-tester at the transmitting station ; when the outgoing wave- trains are held ex- actly in step by the controlling circuits, the telephone of VIII gives off a musical tone of the distant receiving

��A modified form of quenched-gap sender

the

��sort heard station.

��at

��ANNOUNCEMENT

The time which must neces- sarily elapse before the pub- lication in a monthly maga- zine of neics of any sort has forced us to discontinue the department of "Radio Club Neivs.'* The editor will, hoivever, be interested to re- ceive communications from Radio Club secretaries, and suggestions from them con- cerning the magazine and future articles.

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