Radio Broadcast (May 1928-Apr 1929)

150 RADIO BROADCAST JULY, 1928 TESTS FOR TUBES AFTER making certain that filament, plate and grid circuits are correct, you are ready to test the tubes. Insert the plug of the tester into a socket in the set having a relatively high plate voltage (90 volts is best) and adjust filament and plate voltages to proper values. Now insert the tube to be tested in the socket of the tester, using one of the adapters provided, if necessary. With switch, S2, on "TEST" and Si on "C — ," read milliammeterand make noteof plate current. Throw Si to "C+" and make note of the plate current. The difference in the two readings shows the worth of the tube when compared with a known good tube. Suppose the good tube (a 20I-a) gives a reading of 8 mils with switch, Si, on "C+," and a readingof 4! mils with switch, Si, on "C — ," the difference is 8 — 45 or 3 '. mils, a very good reading at 90 volts plate potential. If the tube being tested gives a reading of 75 mils with switch, Si,on"C+"and 4 mils with switch, Si, on "C — ," the difference would still be 35 mils showing the tube to be at least almost as good as the sample tube. If the difference was only 3 mils the tube could be rated as only fair and should be reactivated. These sample readings are given only to make the method of testing clear and not to indicate readings which should always be found. Test each tube in turn, replacing or reactivating all those not up to the proper standard of performance. Gaseous detector tubes are very deceptive when tested in this manner, a tube of very poor quality often giving a good reading. This is due to the high conductivity of the gas in the tube. The only sure test is to replace the tube with a new one and note results. A shorted tube, that is, one with either of the three elements touching either one of the other elements in the tube, will cause the pointer of the milliammeter to be deflected off or nearly off the scale, and must be removed from tester at once to prevent damage to the meters. The method of using the tester on a.c. sets is the same as for d.c. sets except that switch, S3, should be on "AC" and the switch, S4, is not used because a.c. meters have no polarity. The rules for testing apply to a.c. tubes as well as d.c. tubes. Many other uses will be found for this tester by the practical radiotrician, such as testing the filament voltage applied to rectifier tubes in B-power units. Used correctly this instrument will prove its worth many times over and will save many a weary hour over a shop bench. The manufacturer's name and model of the various parts listed below are given merely as a guide, and not because they must be used. The experienced constructor will of course use his own judgment as to the make and model of parts he prefers. The Weston No. 506 voltmeter has an internal resistance of about 125 ohms per volt. I prefer such an instrument, rather than the more expensive 1000-ohm models, for testing B-power units because the milliampere drain more nearly matches that of a tube, giving, in my estimation, a more accurate reading for my purpose. A valuable accessory would be a Weston No. 528 a.c. voltmeter, although this is not a necessity. PARTS EMPLOYED THE parts and instruments used in the model described are comparatively inexpensive, and are listed as follows: Mi 1 a.c. voltmeter 0-10 volts, Weston No. 476 M2 1 d.c. voltmeter 0-8-200 volts, Weston No. 506 with 3 studs and push button. M3 1 d.c. Millimeter 0-50 mils, Weston No. 301. Si, S6 2 — Double-pole double-throw panel switches, Yaxley No. 60. Si, S2, S3 3 — Single-pole double-throw panel switches, Yaxley No. 30. 1 — ux socket, Benjamin. 4 — Tip jacks or binding posts. 1 — Cabinet from old Radiola m. 1 — Bakelite panel to fit cabinet. 1 — 25-ft. roll flexible Celatsite. 1 — 45-volt C battery. 1 — 4-wire cable 4 ft. long. The cable used by the writer came from an old Radiola balanced amplifier. 1 — Piece wood i-inch diameter and 3 inches long for handle of plug. I — UX-199 tube base with bakelite and prongs intact for base of plug. 1 — UY-227 tube base with bakelite and prongs intact for adapter. 2 — Rubber-covered flexible wire leads about 5 ft. long. 6 — Phone tips. 2 — ux-to-uv-199 adapters. 1 — ux-to-uv standard adapter. 1 — UY-227-to-uv adapter. 1 — ux-to-wD-n adapter. 1 wd-i i-to-uv standard adapter. Broadcast Station Calls With a Past By WILLIAM FENWICK THROUGH the years that broadcasting has been with us, the listener has interested himself, among a multitude of other things connected with a station, in the biography of practically every member of the personnel and the contributing performers. Occasionally, in the beginning of radio the former roles the transmitter and other instruments had played elsewhere were disclosed and eagerly absorbed by the radio devotee, but this ceased as the practice came into being of making the radio broadcasting equipment to order. Few, though, have ever paused to think of what might have been the past of their favorite station's call letters, a reflection, as will be seen, that revives the memory of many heroic deeds and horrible occurrences. WSB TWICE WRECKED A SEARCH through old records will bring to light several calls now popular in broadcasting that once were well known in shipping circles, the original owners of many of which have met with disaster. The reason the greater number of these were not reassigned to other vessels is due mainly to a seamen's superstition that is at variance with the idea, wgr, as an instance, was at one time a familiar steamship.call all along the Pacific coast when it was being used by the passenger steamer Governor previous to its allocation to the widely known Buffalo broadcasting station of the Federal Radio Corporation. The Governor sank following its collision with the freighter West Hartland in April of 1921, resulting in the loss of eight lives. Another quite famous call and one which has twice Seen the central factor in perilous episodes of th. eep, is wsb, now of the Atlanta, Georgia, Jourr The S. S. Francis H. Leggett was the first po '.essor and, after foundering off the Oregon coa.t on September 18, 1914, taking a toll of two of the 67 lives aboard, it was reassigned to the Firewood, the name of which forms a grim coincidence with its fate, it being burned off Peru on December 18, 1919, with 28 persons on board, all of whom were saved. klz of the Reynolds Radio Company of Denver, Colorado, presents an even more exciting life story. It belonged to the Speedwell in 1920 when the vessel on September 29 of that year found itself suddenly amidst the sweep of a tropieal hurricane in the Gulf of Mexico. An idea of the severity of the storm may be had from the report that upon the flashing of the SOS and the ship's position, the engine room became flooded, disabling the dynamo, and the only other source of power for the station, storage batteries, became useless when the whole afterdeck was torn off and swept away by the sea. Nine of the 25 people on board were lost in this tragedy. The most sorrowful memories, however, lie behind the letters kre now of the Berkeley, Cali fornia, Ga;ette and formerly of the Florence H. which was wrecked by an internal explosion on April 17, 1 9 1 8, in Quiberon Bay, taking a toll of 45 lives of the 77 present in the catastrophe. The greatest monetary waste to the sea of those mentioned was in the case of the Princess Anne, carrying the call kob, subsequently given to the radio station of the State College of New Mexico. The Princess stranded on February 2, 1920, on Rockaway Shoals, Long Island, and though she broke in two and all of the 106 passengers and crew were saved, the cargo valued at $500,000 was practically a total loss. Another call sign which has its past marred with tragedy is the now familiar whn of New York City. This call was at one time assigned to the ill-fated steamer Hanalei. Later it was passed to the steamer Santa Isabel, which vessel was subsequently sold to Chile. In cases of this sort, where a ship is bought by a foreign country, the letters are changed to those given by the government having jurisdiction over the purchaser. A few other examples of this where the calls are now in use in broadcasting are: wwj, well known as the Detroit News, was formerly of the steamer Peru which was sold to France, kls, familiar now as the Oakland, California, station of WarTier Bros., was once possessed by the steamer Kermanshah, transferred to Hungary. Likewise, knx of the Los Angeles Express was the signal of the vessel Susana, which was later purchased by an Italian company.