The radio dealer (Apr-Sept 1922)

September, 1922 THE RADIO DEALER 31 Testing Radio Receiving Sets Important Need in Trade for Tests That Will Give Better Information to Prospective Purchasers of Sets By PAUL G. WEILER Of Gregg and Company, Engineers, New York, N. Y. While numerous tests have been developed to determine electrical characteristics of condensers, coils and other individual parts going to make up radio receivers, very little has been done so far toward testing complete receivers. Most of the tests now in use are developed purely to serve the purposes of the technically trained. The results, expressed in highly scientific form, mean little or nothing to the average purchaser of radio equipment, whether he be an individual purchaser or a dealer. Experience has shown that radio sets may vary in design and in the quality of their constituent parts more than any other scientific instrument. There are radio sets on the market today retailing at $20.00 which will bring in broadcasting within a limited range quite well. Other sets costing as much as $250.00 will give the purchaser probably more value for every dollar spent than the $20.00 receiver. Yet, even a close inspection would reveal no difference in construction proportionate to the difference in price. Two receivers of similar design may vary tremendously in effectiveness according to details of construction which are not very conspicuous. Consequently, there is considerable confusion in the radio trade, and with the number of makes offered to the buyer increasing at a rapid pace, the situation is constantly becoming more bewildering. This condition makes the buyer suspect everything that is offered and creates a general impression that radio equipment is sold at any price the traffic will bear instead of being priced in accordance with cost of production and value given. There is, therefore, a crying need for methods and facilities of testing and comparing receivers offered to the trade. As most of these receivers are used for broadcast reception, the tests applied should take into consideration especially those features which are recognized as most desirable in a broadcasting receiver and the results should be expressed in such a way that even the less experienced might compare the testing certificates issued. These certificates could then be used as a basis for the valuation of different makes. If a larger number of manufacturers were to subscribe to such a service, it would give them a much more accurate idea of the comparative value of their own product. The public probably values loud signals in a receiver more than any other quality. A good receiver used in connection with a horn or loud speaker should be as loud as the average phonograph, or nearly so. Therefore, tests should furnish information as to the comparative signal strength of the receiver. It is entirely feasible to obtain such data. Curiosity on the part of the purchaser as to what distance he may be able to get should be satisfied so far as possible. A familiar question of the purchaser in the metropolitan district is : " Will this receiver get Pittsburgh ? " This question is difficult to answer definitely, as local conditions, the skill of the operator and certain conditions within the set which are not always under control may affect very considerably the range of a set. It is, however, entirely possible to ascertain the degree of sensitivity of any instrument in comparison with a given standard. This means, practically speaking, that if a set made by manufacturer " A " will bring in Pittsburgh in a certain location with some degree of reliability, any set rated better than " A " would give better results, and any set rated lower in sensitivity should not be relied upon to bring in far distant stations except under particularly favorable conditions. Possibly the feature next in importance may be sharpness of tuning. Within the New York territory the question " Can you tune out the Navy Yard?" is common. The sharpness of tuning can be fairly well expressed in figures. Another quality of sets is the trueness of reproduction or absence of distortion. While there is no way of expressing this condition accurately in figures, certain characteristics of amplifying transformers together with other factors, will give a fairly good indication of the amount of distortion to be expected. These characteristics, in connection with actual comparison of tone qualities with a well designed standard, will give sufficient information for a pretty close rating of sets on this point. There are some other points on which information would be desirable and may be had, but in the present status of the art, the four above mentioned are probably the most important and would give the trade necessary guidance in making purchases and fixing sales prices. A consistent application of standardized test methods would go very far toward bringing order out of the present chaos. SCHWAB'S CATALOGUE Six types of variable condensers ranging in prices from three to six dollars and featuring the new wire ring washer, giving perfect alignment, are listed under the Drisco line in the new catalogue recently issued by Harold M. Schwab, Inc., of 419 West 42nd Street, New York. This firm is the sole factory distributor for Drisco radio products. Other Drisco specialties are the Drisco Radiometer designed to efficiently take the place of the conventional variocoupler ; Drisco panel switches designed to eliminate the drilling of holes in the panel for contact points; potentiometers rheostats, series parallel switches, tuning coils, etc._ The Drisco laboratories are equipped both for the assembly of radio equipment and other class of manufacturing such as die making, stamping, winding, screw machine work, etc. Among other items listed in the Schwab catalogue are the Jenkins Vernier, Estru Lattice variometer and variocoupler, Planet loud speaker, and the Schwab brand of dials, sockets, switch levers and binding posts.