Radio Broadcast (Nov 1926-Apr 1927)

192 RADIO BROADCAST ADVERTISER Why the Silencer Socket is essential to clean-cut reception ^ In many cases good clean-cut radio reception is decidedly hampered by the disturbing microphonic noises within the radio tubes — particularly the detector tube. These No. 481 XS disturbing noises are caused by shocks and jars —very often slight — which come from various vibrations such as the vibration of the loud speaker, tapping the radio set itself, walking in the room or even street traffic. These vibrations cause the grid and the plate of the tube to vibrate slightly in respect to one another. In order to shield the tube against these shocks the Alden Silencer Socket has been designed. With this socket the tube is "cushioned" and "floated" absorbing all shocks in all directions — sidewise, up, down and pivotally. The marvelously balanced phosphor bronze springs which accomplish the "cushioning," form also the contacts for the tube and for the outside connections. This important point, among others, is fully covered by patents. Contacts press firmly, strongly and flatly against the full length of the tube prongs. Special phospor bronze, triple-locked contacts are held in constant tension insuring permanent, quiet action. Solder lugs are provided for making connection either above or below the base panel. Or the lugs can be removed and the binding posts used. Round edge permits of mounting in any direction, and makes for a neat mounting on the base panel. The Silencer Socket (for UV 201A and all UX tubes) is a markedly superior socket which large production enables us to sell for 50^. At all dealers. Other Na-Ald Sockets No. 481 X The Na-Ald No. 481X soc ket is the popular priced universal socket for all UV 201A and all UX tubes. This socket is in great demand for amplifying tubes. The price is 35c. The Na-Ald De Luxe Socket is designed for heavy duty service with the big, high voltage, expensive tubes. Triple lamination, dual-wire contacts will carry the heavy current used. The tube prongs and socket contacts can be self cleaned simply by a hall turn rotation of the tube in the socket. Alden processed moulding assures the necessary mechanical and electrical strength. The De Luxe Socket is 75^ at your dealer's. No. 400 ALDEN MANUFACTURING Dept. B-20, Springfield, Mass. CO. 1 Radio Broadcast Laboratory Information Sheet December, 1926 Overtones (Harmonics) THEIR IMPORTANCE IN RADIO A GREAT many of the fundamental notes used in speech lie below a frequency of 1000 cycles, but it is the overtones (or harmonics) which determine the quality and timbre of the sound. In order to obtain perfect quality, the characteristics of all the amplifiers and reproducers used in a radio receiving system must be absolutely flat, i.e., they must transmit all frequencies with equal fidelity. The overtones which were mentioned above are harmonics which are produced by all instruments, including the human voice, and the correct transmission of the harmonic frequencies is essential if the characteristics of the original sound are to be maintained. In many cases it is the prominence of certain harmonics which distinguish the different instruments from others. Quite frequently overtones are confused with octaves. An example will distinguish the difference between these two units. The fundamental sound of, say, 500 cycles has an octave corresponding to 1000 cycles, another octave at 2000 cycles and another one at 4000 cycles, etc. — each octave being double in frequency to the one preceding it. If two octaves are sounded at the same time, it is rather difficult to distinguish between them. On the other hand, the fundamental note of 500 cycles has overtones, or harmonics, corresponding to 1000, 1500, 2000. 2500 cycles, etc. In this case, the various tones are separated by an amount equal to the fundamental frequency. Whereas the difference between two octaves is rather difficult to detect, it is quite easy to distinguish between various overtones. From the above, it is evident that some octaves are also overtones; for example, the octave at 1000 cycles corresponds to the 2nd overtone of the fundamental note of 500 cycles. However, the next overtone is 1500 cycles, but there is no octave corresponding to this pitch. It is evident that, starting with a certain note, all octaves correspond to certain overtones but that all overtones are not octaves. On Laboratory Sheet No. 52 there is reproduced a diagram showing the fundamental frequency range of various instruments. In the diagram given, it will be noted that an extra octave is shown at the high frequency end of the piano keyboard. As experience has shown that at least one harmonic must be provided for when amplifying a signal near the top of the audible frequency scale, to obtain true fidelity, the extra octave is included to indicate the frequency range requirements of an amplifier to successfully reproduce the highest note of the piano, which has a fundamental of 4096 cycles. No. 52 Radio Broadcast Laboratory Information Sheet December, 1926 Frequency Ranges of Musical Instruments _ _1_U J-lJ-lJ-J NOTE A,B,C, D,E3F3 G, A;B2C, D?E2f, G, A, B,C, 0t E, F, G, A 8 C D E F G a1 Ire" dV I'g' »"lft"dueu(,,gna,"lrWl1"emf °1gman'lr,c"d"e"i"r»*bV FREQUENCY WINDS Flnte Piccolo Oboe English Horn Clarinets Bassoon French Horn Trumpet Comet Trombone Bass Clarinet Bass Tuba STRINGS Violin Viola Cello Bass Viol ~ HUMAN VOICE Tenor Baritone Soprano Bass Alto No. 53 Radio Broadcast Laboratory Information Sheet December, 1926 Shunts DETERMINING THEIR VALUE SHUNTS, as used in an electrical laboratory, consist of an electrical conductor placed in parallel with an indicating meter so as to increase the range of currents that can be read with this meter. We might have a 10-milliampere meter and desire to read a current of, say, 50 milliamperes; with the aid of a shunt, this can easily be done. The method of calibrating a shunt is indicated in the diagram. Suppose we desire to calibrate a 10-milliampere meter so that it will read 50 milliamperes. We would connect a battery, B, as indicated on the diagram, in series with a variable resistance, V.R., so as to limit the current passing through the meter (without a shunt) to 10 milliamperes. The resistance would be varied until the meter read exactly 10 milliamperes and then the rheostat R (the shunt) would be switched across the meter and its resistance altered until the meter read two milliamperes. Under such conditions (with the shunt connected), a reading of 2 milliamperes on the meter would mean that 10 milliamperes were flowing through the circuit. Likewise, full scale deflection would indicate a 50-miIliampere flow although the needle pointed only to 10 milliamperes. The same procedure would be followed in shunting any instrument, i. e., setting up a circuit which will pass sufficient current to give a maximum deflection on the meter, then shunt the meter and reduce it a definite amount such as one half, one third, or one fifth, then, in order to determine the actual current flowing in the circuit with the shunt connected, it is merely necessary to mulfiply the meter reading by 2, 3, or 5, depending upon how much the original deflection of the meter was reduced by the shunt. •fa Examined and approved by Radio Broadcast