Radio Broadcast (May-Oct 1922)

RADIO BROADCAST 145 laboratory. The invention, an ingenious arrangement, consists of a differential voltmeter actuated by a small hand-driven 250 volt dynamo. The device measures resistance with remarkable accuracy up to ten megohms (10,000,000 ohms)! The second illustration shows a testing table in the radio lab of Charles P. Madsen, New York City, with the author measuring the resistance between the blades of an amplifying jack by means of the ohm-meter. The radio apparatus, shown partialh' completed, was constructed in the lab by Mr. .Madsen and myself. The result of the test indicated an unsteady resistance approximating ten thousand ohms (very low!) which was doubtless the cause of the microphonic rattling in the phones that we had been experiencing. When we wiped away a slight trace of soldering paste between the lugs, using a cloth moistened with methyl alcohol, the resistance rose to one megohm (1,000,000 ohms) with comparative quiet in the receivers and a noticeable increase in signal audibility. A slide-rule and a dozen lengths of wire with test clips complete the equipment: this last, not a negligible item, but a most useful and integral part of the efficient whole. Ill A laboratory such as the one described is, of course, beyond the means of many amateurs, that is in the sense of being the individual property of any one of them. But it is fully within the resources of a well-organized club. With voluntary contributions of tools and apparatus, the financial disbursement should not exceed a few hundred dollars, a sum well invested and bringing in untold dividends of better equipment and a more comprehensive insight into our art. But the determined enthusiast intent upon his own lab will not be discouraged by the expense of the layout described. A radio laboratory is not a thing collected or built in a day. It is rather the result of an extended series of purchases, the more complicated tools and instruments arriving year by year, with experience. After all, the implements themselves are but a secondary consideration, the ability of the experimenter always coming first. In the hands of a deft mechanic, wonders have been accomplished with a small hand drill, a set of six and eight thirty-two taps and dies, a light soldering iron (electric preferred) and a few household tools. Add to these a wavemeter, and the whole, exclusive of transmitting and receiving apparatus, will amount to some twenty-five or thirty dollars, and the amateur will have laid the cornerstone to the laboratory of his dreams. Above all, strive for neatness and orderliness in the lab. It is a virtue, and though consistent with many virtues in being often missing, it is also always its own reward! Mistakes to Avoid in Erecting Antennas By G. Y. ALLEN J. B. WILSON of Reading, Pennsylvania, was visiting his friend Jim Black at Newark, New Jersey. That evening, at the dinner table, the conversation drifted to the wonders of radio, particularly to the latest achievements in broadcasting. Jim told how he and Mrs. Black scanned the programme as published in the daily papers, and how they "listened in" on evenings when they wanted some entertainment in much the same way as they would attend the theatre. He also went on to tell how the children liked the "Man in the Moon" stories and as the company arose from the table, Mr. Black invited J. B. to come into the living room and "listen in" on the evening's entertainment. "It's about eight o'clock now," said Jim, glancing at his watch. "They ought to be going. Here, put these on and see if I can tune him in," he continued, as he handed a spare head set to J. B. Jim adjusted the crystal and moved the tuning handle over the scale, and soon J. B. heard Schubert's Ave Maria just as clearly as