Radio Broadcast (Nov. 1925-Apr 1926)

376 RADIO BROADCAST ADVERTISER TONE Full, sweet, mellow and natural, without the slightest indication of distortion, is another achievement that is making the APEX SUPER FIVE the most popular of all receiving sets. A VOLUME That supplies dance music or entertainment without any loss, is a feature f orwhich the APEX SUPER FIVE is world famed. DISTANCE Lends added enjoyment to radio with an indescribable fascination of tuning-in far away stations, which is always possible with the APEX SUPER FIVE. Ask your dealer for a demonstration. Your eyes and your ears will tell you that APEX stands at the high point of perfection in both performance and appearance. $80 without accessories. Quality Radio Apparatus SUPER 5 APEX ELECTRIC MFG. CO. 1410 W. 59th Street Dept. 104 CHICAGO THE GRID A Department Devoted to Solv mt our QUERIES ANSWERED i. what are the values of the condensers, resistances, and ballasts etc., for the Radio Broadcast "aristocrat"? T. J. L. Lansing, Michigan. 2. WHAT ARE THE CAUSES OF SOME OF THE NOISES PRODUCED IN MY RADIO SET? CAN THESE ORIGINATE AT THE STUDIO? A. W. T. — Pompton Lakes, New Jersey. What is the theory of operation of impedance AUDIO AMPLIFIERS? W. S. Burlington, Vermont. "aristocrat values" THE following values apply to the "Aristocrat" receiver which is shown diagramatically in Fig. i: Ci and C2, .0005 mfd.; C3, .002 mfd.; C4, .0005 to .002 mfd.; C6, .00025 mfd.; C7, C8, and Co, not less than .01 mfd. C5 is a midget variable condenser and its capacity approximates .000032 mfd. The values for the various resistances shown in the diagram, are as follows: Ri, R2, R3, R4, and R5 are filament ballasts, and their size will vary with the different types of tubes employed. Thus, for tubes consuming .25 amperes, \ amp. ballasts are necessary, etc.; R6, 2 to 4 megohms; R7, Rq, and R11, 100,000 ohms each; R8, approximately 1 megohm; R,ioJ megohm; Ri2,J megohm. The use of condenser C10 often improves the results but its use may not be essential. Its capacity will be in the neighborhood of .002 to .004 mfd. A large capacity condenser of about half a microfarad will often improve the tone if connected across the B battery binding posts. In the original Radio Broadcast "Aristocrat," single broadcasting, are often excessively noisy by induction from neighboring wires. A steady rushing sound, especially noticeable when the receiver is tuned to resonance, is often caused by the generator which supplies the plate potential to the transmitter tubes. This noise is more or less pronounced on all stations and continues until the broadcasting is finished and the stations sign off. Noise contributed by the ether medium may be defined as those sounds which are caused by electrical disturbances between the broadcasting station and the receiver itself. In this group are found the disturbing influences of high tension power lines, violet and X-ray machines, leaky transformers, electrically operated elevators, sparking motors and generators, trolley and elevated systems, railway systems and telephone and telegraph wires, and a host of other electrical contrivances. Electrical impulses from those undesirable sources usually occur at short wavelengths and are picked up by sensitive receivers. Static also comes in this class and is Enclosed Herein Comprises Resistance Coupled \ Amplifier which may be Obtained as a Complete Uni) Separate Resistor Units may be Employed inthe AudioAmplifier ' where the Complete Manufactured Amplifier is not used ' FIG. I units consisting of two resistances and a coupling condenser all in one piece were, among other arrangements, tried out. It is for this reason that the two resistances and coupling condenser preceding each audio amplifier tube are surrounded by dotted lines. noises and their causes IT IS possible that various noises heard through one's loud speaker can .have originated at the transmitting station, but generally speaking the trouble can be traced to either the receiving equipment or the intermediate medium — the ether. Noisy microphones cause a steady hiss which often blurs the voice of the artist, while programs picked up outside of the studio and carried overland by wire for if Tested and approved by Radio Broadcast -At more prevalent throughout the summer months. Many satisfactory programs are suddenly broken up by a series of unfamiliar clicks, and in many cases are interrupted entirely for short periods Those may be caused by key clicks from continuous wave transmitters and by improperly operated regenerative and super-heterodyne receivers. In another class are the noises which are caused by the receiver itself or by the equipment which is used in connection with it. Discharged B batteries become noisy and are usually the cause of a high pitched squeal when the receiver is operating on the second audio stage. These batteries should be discarded when their voltage drops below about thirty-four. Storage B batteries often cause the same trouble