The Electrical experimenter

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74 THE ELECTRICAL EXPERIMENTER May, 1917 THE WORLD IS OPEN to the wireless man. Travel, good poaitioos, rapid promotions, attractive salaries are waiting for our licensed operators. Full course 6 months. Only Radio School in Nfw England. Fine equipment. Officially endorsed by U.S. Government and Marconi Co. Easy payments if desired; day and evening classe?. Send stamp for prospectus EASTERN RADIO INSTITUTE 899-B Boylston Street Boston, Ma^3. Learn Wireless Under Marconi's Chief Instructor SRECIAL, EVEIVIISG COURSES for amateurs or beginners now in session. Outof-town men should write for Inlormation about temporary riay employment and li\'in£: conditions while studying Our students may enter the Marconi service direct. Radio Operators are now in Great Demand Great stress is laid on laboratory experiments, with complete commercial appar;itus. Special training given on advances types of Trans-Oceanic Equipment. Course under the personal supervision of the instructing Engineer ol the Marconi Co. Send today for our folder E. EASTERN DISTRICT Y. M. C. A. Marcy Ave., near Broadway Brooklyn, N. T. 13 minuies ftom New Yoik City Hall. 18 minutes Irom Hudson Tefminals_ EXPERIMENTS FOR EVERY STUDENT That's how we teach you cleztricity in One Year, by actually training you to handle, use and install electrical instruments and apparatus of every kind and style. Our equipment is absolutely perfect and includes instruments and machines so expensive you will hesitate to touch them. Yet we require you to use them till you know electricity thoroughly. Enter at any time. Our FREE illustrated Book E will give you full details. Send for it to-day. SCHOOL of ENGINEERING 0/ MILWAUKEE 313 Stroh Building MILWAUKEE. WIS. electrical; men with training are always in Having trained over ' 2
May, 1917 THE ELECTRICAL EXPERIMENTER 75 the clftct was due to the action of diffracted waves on the receiver was further -liown by the fact tliat witli the rotating screen in t'le position to allow no transmission a wire reflector back of the receiver at varying distances clearly indicated the presence of nodes and loops at distances apart wliich showed the wave-length to be that of the original wave. The average distance from node to node was found to be slightly more than 50 cm., making the wavelength approximately 10() cm. l-'inal observations were made with the receiver in the horizontal position at a distance of 225 cin. from the fixt screen, and with the oscillator at distances from the >creen ranging from 120 cm. to 230 cm. The Law of the Silicon Detector Since for the final curves obtained the -jeceiver was so adjusted as to respond only 10 the horizontal component of the transmitted wave, it seemed possible to use the (lata to determine the law of response of the silicon detector with a variation in the intensity of the incident wave. The data already obtained showed the response of the receiver for each position of the rotating screen. Since ojily the component of the wave at right angles to the wires of the screen could be transmitted, the am- I)litnde of the transmitted wave varied as the cosine of the angle between the wires and the vertical. As the receiver was capable of responding only to horizontal waves, the transmitted component suffered a second resolution at the receiver, which again cut down its amplitude by the cosine of the same angle. Hence the amj>litude of the component of the wave to which ic receiver responded was proportional to the stpiare of the cosine of the angle between the vertical and the wires of the screen. Presumably the ainplitude of the oscillations set up in the receiver for different I)ositions of the screen was proportional to the amplitude of this received component, and hence to the square of the same angle. In determining the law only those data were considered in which the values of the current obtained without the resonator were small, l-'or each set of readings two curves were plotted, with the galvanometer dellections as abscissae and in one case the second, in the other the fourth powers of the cosines of the angles as ordinates. I'rom these results it seems safe to conclude that the rectified current is proportional to the fourth power of the cosine of the angle between the vertical and the wires of the rotating screen. Since the amplitude of the oscillations in the receiver is presumably proportional to the square of the cosine, this result indicates that the rectihed current thru the silicon detector is proportional to the square of the oscillating current in the receiver. .\ustin, in his study of the silicon detector, reached the conclusion that for alternating currents of ordinary frequencies and for ciscillating currents of a frequency of 140,- 000 the rectified currents are approximately proportional to the square of the alternating currents. The results of the investigation of the writers confirm this law for a frequency of approximately 3X10'- 1 IVliiy Learn Theory, Code and Laws of RatlU) nmunication in Our School or at Your Home fitting you for positions paying goo
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