Radio Broadcast (May 1928-Apr 1929)

OUR Readers Suggest. . ." is a regular feature of Radio Broadcast, made up of contributions from our readers dealing with their experiences in the use of radio apparatus. Little "kinks," the result of experience, which give improved operation, will be described here. Regular space rates will be paid for contributions accepted, and these should be addressed to "Our Readers Suggest Editor," Radio Broadcast, Garden City, New York. — The Editor Remote Volume Control THE operation of a receiver by remote control is an interesting possibility, and one that has intrigued many engineering minds. The mechanical and electrical complications of existing systems are such, however, as to preclude their general use. It is, nevertheless, a relatively simple matter to control the volume of a receiver from your easy chair, which, though only partially solving the problem, is really a great convenience. The radio fan is, I think, inherently a lazy individual. Writing from personal experience I may say that there is nothing more annoying than finding it necessary to rise from a comfortable chair or sofa to tone down or bring up volume on a receiver that a few minutes before was apparently correctly adjusted. Fans indisposed to labor have undoubtedly noted that the volume of a receiver is anything but constant. An original adjustment made when the broadcaster was using the soft pedal, proves entirely off on a fortissimo passage. Also, in congested radio districts, the intensity of signals, I have found, varies considerably with the number of receivers tuned to the same program in the immediate neighborhood. This is not due to an absorption effect upon the field strength, but rather to a parallel wave trap effect. Regardless of the reason, the condition exists and can be made more tolerable by providing a means of volume control from wherever the indolent listener may be reclining. The writer uses a variable zero to five-thousand ohm resistor connected between the antenna and ground posts of the receiver by means of a long flexible telephone cord. This is employed as an auxiliary volume control to the adjustment provided on the receiver itself. The original volume control is set for a degree of volume quite a bit in excess of comfortable listening, and is toned down by the external control. I have found that practically any variable resistor, covering a range of from five to at least five-hundred ohms, is satisfactory for the purpose described. It is apparently immaterial whether or not the resistor is inductive. James Montague, Newark, New Jersey. STAFF COMMENT pLECTRAD, Clarostat, Yaxley and others are ' manufacturing remote volume controls of the type described by our contributor. Their use in the antenna circuit, where, of course, signal A NEW CLAROSTAT It is the remote vo'ume control type. Electrad Yaxley and others have similar controls intensity is reduced before the signal is impressed on the audio-frequency circuits, precludes the possibility of overloading, with resulting distortion. Devices of this nature can be made to serve a utilitarian purpose other than Mr. Montague's commendable moral support to laziness. Such a volume control installed near the telephone is a logical arrangement of genuine utility, and will be greatly appreciated by persons who have endeavored to converse over the 'phone in competition with the radio. Improving Your B Device CEVERAL articles have appeared in "Our ^ Readers Suggest" department on the improvement of socket power devices. These articles have considered, singly, the stabilizing possibility of the glow tube, the use of additional resistors to obtain desired plate potentials, and the use of C biasing resistors. It is the purpose of this article to describe a simple arrangement which takes care in one unit of these various desirable possibilities. The starting point in improving the existing B device is in the rectifier tube. In this connection it is necessary first to clarify a misunderstanding which has gained ground of late, namely, that a rectifier tube, when renewed, must be replaced bv one of identically the same type. With virtually any good Raytheon B socket power outfit heretofore provided with the Raytheon B type rectifier, an increase in voltage output may be obtained by substituting the present Raytheon type BH tube for the old B type. The voltage, providing it was adequate for the requirements of the output tube used before this substitution, now is of sufficient value to take care of the grid biasing requirements of the power tube as well as its plate supply demands. Other improvements for B devices have taken the form of better voltage regulation at the output end. Reliable potentiometer resistances, together with a voltage regulator tube, will maintain fixed voltages across two or more terminals. The photographs on page 34 present an adapter which may be connected to many of the better quality B power units so as to incorporate the advantages of a potentiometer resistance network and a regulator tube, while increased voltage output is obtained for use as grid bias by replacing the B type with the BH type Raytheon, as mentioned above. It will be noted from Fig. 2 that the adapter comprises a tapped potentiometer resistance, two bypass condensers, a socket for the R (regulator) tube, and a special current-limiting resistor for use in the third element circuit of the regulator tube. These few parts, along with the necessary binding posts, may be mounted in almost any desirable manner. Fig. 1 shows a typical B unit circuit, with the original resistors supplying the potential requirements of last year's receivers. Fig. 21 shows a "wiring diagram of the additional unit described by the author. Point "A" is connected to point "A" in Fig. 1 and point "B" to point "B" in Fig. 1. The center choke tap runs through the Raytheon X — -^-^ 1 /^rX fit oAmp, VA,*/ ™"mfd. "mfd. ~ 8 mfd. J— !I!ho Det. — ' f T 1 1 i J — I i 1 1—oB Raytheon -WW Type R -OB+Max. -OB+lst. A.F( -O B+R.F. *4 C,J=10 -OB+DeL mfd. oc FIG. I FIG. 2 33