Radio age (Jan-Dec 1925)

RADIO AGE for January, 1925 How To Construct A Station Finder The Magazine of the Hour 23 By FELIX ANDERSON C.A Novel Unit That will Cut out Guesswork in Tuning and Help Reduce The Annoying Set "Squeals" THIS radio pastime is at last getting to a point where enthusiasts no longer are satisfied with the old haphazard methods of tuning, and the out-of-date system of radio "fishing" is resorted to only as a means of entertainment nowadays. The up-to-date listener seeks to go after the long distance stations in a more accurate and sure-fire way; he endeavors to get the results he wants by employing the right methods of tuning. The recent transatlantic broadcasting tests prove conclusively that there is a pressing need for a unit which will eliminate the guesswork variety of tuning, insure more certain results, and at the same time reduce the nuisance of radiation which broke up more than one reception of the foreign stations. You will no doubt recall the pandemonium of squeals and howls which prevailed in the air during that memorable week. And no doubt you more than once "cussed" some neighbor softly when you found that you had been trying to tune in his radiation. There were times when we gave up in disgust, loudly voicing our disrespect for those bugs who couldn't keep their hands off the controls, and who constantly interfered with the incoming long distance signals with their malicious squeals. The underlying reason for all the trouble and the real cause for the ceaseless search for the carrier waves or signals of the European stations, can be directly attributed to one main and grand reason. Listeners in general are not so fortunate as to have sets that are calibrated; that is, they do not possess a receiver that tells them where to set the dials for definite wavelengths. So the logical way to get the much sought receptions was to guess — fish, in other words, until you struck something that sounded promising, and then listen until the announcement was made; or until some other bug spoiled it all by squealing you out. The Right Way to Do It. TT WOULD be impossible to set down -* specified rules for the calibration of every receiver now in use. It is a fact that there are some sets which cannot be calibrated because of their circuit peculiarities. What we can do, fortunately, is make a separate unit and calibrate that instrument, and then tune our receivers to it instead of fishing. The result is that we make only one operation of the job, and then we know that we are accurate and that we are listening on the right wave. Therefore, the purpose of this article is to describe a unit of this type. For purposes of reference, we will call the unit about to be described and discussed a "Station Finder." Its technical name is wavemeter, or probably more correctly a driver — but that matters only little. What we are after is a unit that is going to tell us where to set our dials In the circle is a three-quarters view of Air. Anderson's station-finder, giving an unusual angle of the buzzer and the switch. At the left is a top view, showing the dial with its valuable hair-line indicator. when we want to listen for a certain station, the wave of which we are informed. The preceding paragraph probably sounds a little imposing, and no doubt you have visions of a mighty piece of apparatus with all the embellishments that usually go with a measuring device; but that is not the case. The station finder is a simple affair, and not in the least bit expensive. The Bill of Materials TF YOU have the parts listed below — -I all well and good; if not, a visit to the local radio store will be necessary. 1 Cabinet 7 inches long, 6 inches wide and 6 inches deep. Get a neat one, and make the job a good looking one. 1 Composition panel 7x6x>6 inches, Bakelite, Celeron, Formica, Spaulding or other. 1 low Loss Straightline condenser. Eleven plate 250 MMF. (0.00025 Mfd). The straightline plates are advised for the purpose of making calibration easier. See text of article. 1 Cardboard tube 3}4 inches long and i^i inches in diameter. 2 pieces of brass 2% inches long and }4 inches wide. Any fairly heavy gauge will do. j| pound No. 22 Double Green Silk Covered wire. 2 Binding posts. 1 Dial reading 0 to 100°. A metal dial with well etched divisions that . are easy to read is suggested, since the readings on it are hair line in cases. 1 High frequency buzzer. One that will operate on flashlight or C batteries, and give a steady clear note. 1 Switch lever. (Turn the page)