Radio Broadcast (May-Oct 1926)

OCTOBER, 1926 THE NEW SEASON SHOWS PARTS OF HIGH QUALITY 525 years. Better construct ion in much larger units give longer life and ample current capacity for economical sets which require up to 155 volts plate potential. Some of these larger batteries power such receivers for as much as nine months to even a year without renewal. The most novel advance in the B battery field is the National Carbon Company's Layerbilt battery, constructed of flat cell units somewhat on the order of the Voltaic pile. The French Battery Company also has a fine new radio battery, classed as "pitchless," for which very long life is promised. Another concern new to the radio field, is announcing the "Tab" rechargeable B battery for the chemically inclined who may renew the mix in the battery when the first batch is exhausted. BETTER AUDIO AMPLIFICATION THOSE desiring better quality of reproduction from their receiving sets, as well as those building new receivers, have at their disposal a choice of amplifier systems by which this objective may be attained. Among those in the resistance amplifier field are the Allen Bradley, Daven, Dejur, and Heath each making three-stage units with or without filament rheostats. Some of these are designed for power tubes in the last stage, having provision for the installation of a C battery. The resistance amplifier finds rivalling it, various combinations of impedanceand transformer-amplification. The wellknown Thordarson line includes the essential parts for a high grade, impedance amplifier, while Rauland-Lyric calls attention to its "trio," consisting of one transformer stage and two impedance stages. And then there is the Na-Ald Trufonic amplifier, a three stage device, built after the design of H. P. Donle. The National Company supplies "Impedaformers" for those desiring to build an impedance amplifier. In the field of power amplification are various units which may be plugged-in the detector or first amplifier stage of receiving sets, subjecting its output to one stage of THORDARSON S AMPLIFIER AND B POWER SUPPLY power amplification as well as furnishing A and B power for the amplifier tube and also supplying the radio set itself with the necessary plate potential. Thus we have the combination of B battery substitute and power amplifier converting the usual receiving set into one capable of delivering substantial undistorted volume to the loud speaker. These cover a wide price range and furnish B voltage of various ranges, beginning with the neat Radio Receptor device and ranging in price up to models by such experienced makers as Pacent, Farrand, Timmons, and General Radio. The last named, for instance, offers three B battery voltages and one stage of power amplification, using the ux-171 tube. NEW LOUD SPEAKERS TO MENTION by name the numerous types of loud speakers available to the public would be almost a hopeless task. They range in size from the little Tower cone at a price within range of the most modest buyer to the Pacent auditorium volume 36-inch cone. Magnavox has announced a new and neat model, while Acme, already well known in this field, has produced a new type cone with a base so shaped that the cone may be placed within a cabinet. A newcomer in the field is the Sparton, automobile horn maker, with several types of free-edge cones, while the Utah h'ne combines a variety of unique shapes and styles for those preferring something not along the conventional lines. Owners of receiving sets, having high grade power amplifiers, may, by using a Bristol electric tone-arm, play phonograph records and use their radio amplifying system to reproduce them. This device performs a function just the reverse of a phonograph adaptor. Another method of improving a set is to eliminate unsightly accessories. Console cabinets, combined with loud speakers and having an ample battery compartment are exhibited in numerous styles by such makers as Pooley, Detroit Woodcraft, and others. An economy measure and an essential in checking the condition of A and B batteries are various meters manufactured by Weston, Roller Smith, Hoyt, and Jewell. The first concern is exhibiting a dual range voltmeter with pin jacks, provision for the installation of which is made on such well known manufactured sets as the Radiola super-heterodyne and some of the receivers in the Bosch line. The set constructor who has examined some of the latest manufactured receiving sets is likely to feel that he can no longer hope to make a radio receiver which approaches the precision and quality of some of the more expensive manufactured sets. Of course, this cannot be literally true, because every manufactured set had its hand-made predecessor which served as a model. Some parts manufacturers have gone a long way to help the constructor in making a receiver at least comparable to some of the better manufactured sets. SPECIAL NEW PARTS FOR THE SET BUILDER THE Alden localized control gang condensers, for example, offer the convenience of one control for two, three or four tuned circuits. The condenser shafts are mounted parallel instead of at right angles to the panel and are separately controlled by closely adjacent, knurled knobs, all of which may be moved simultaneously with the aid of two fingers of one hand, or separately at the will of the user. The Bruno device, built along the same lines, controls two condensers and may be purchased with inductances attached, covering the broadcast band. The Bruno NEW UNITS FOR SUPPLYING B POWER The Valley B Power, using Raytheon tube; the Balkite Combination Radio Power Unit, which, when connected to the A battery furnishes power both to A and B circuits. It is controlled by the filament switch on the set and is automatic. Price $59.50. Next is the General Radio Power Amplifier and B supply. Finally, the All-American "Constant B" using a Raytheon tube, which sells for $37.50