Radio mirror (Jan-Oct 1923)

Jun 1 y * J R A D I O D I G E S T 13 Characteristics of Some New Vacuum Tubes Part II— Tube Advice; UV-199, DV-6 and Philips Tube ■VIM nt-*un TVCt'i > ,3 1 J^„ |_j^_ Figure 5 clearest and best in tone value ever heard. But I have the rheostats barely turned on. If I increase the current, the reception turns to howls and growls. Undoubtedly there is even greater volume in the set but I can't get it." This statement clearly indicates that the source of trouble lies in the tubes, inasmuch as the same experience was encountered by the author. Tubes on Keflex Circuit Especially in the reflex type — there is required a certain percentage of operating efficiency, if this is lacking in the tubes used, no amount of development or alteration of the circuit will remedy the situation. Reflexing with but a single tube does not present the difficulties that multitube reflex circuits do. The demand on that single tube is usually within the functioning limits. Portable Set Tabes The question of portability of receiving sets has developed a decided demand for a good dry cell tube. Unfortunately most dry cell tubes are either too microphonic, sensitive to mechanical vibrations of any sort, or their efficiency is doubtful. If it was not for the cost the best solution would be to purchase ten tubes of the type decided on and then test them for the selection of the three best. Dry cell tubes should always be cushion mounted, that is supported on either a rubber or felt pad to take up any shocks, bumps, or knocks, as much as possible. Sockets and Rheostats In order to be on the safe side it is best to use standard sockets and if neces c S-' y MC&ATiVt PCTO. *t WCT1 ( Figure 6 sary use adapters — then if a better tube is produced the chances are no socket changes will be necessary. The subject of rheostats can also be easily taken care of. Manufacturers are now producing small unit resistances that can be added in series in the filament cir By H. J. Marx AMONG the multitude of letters received from fans working with the Reflex De Luxe is one that states: •'Have constructed your Reflex De Luxe. The reception on a loud speaker is the cuit, building up to any particular resistance value best adapted for the tube used, and enabling the use of the popular 6-ohm type of rheostat with which most sets are equipped. Rheostats are also being produced now that have a total of 30 ohms resistance but are so constructed that they can be used in the same way as that of the 6-ohm type. UV-199 Characteristics This tube is rated at a filament voltage of three. The current consumption is exceptionally low, only .06 amperes. This permits its use with dry cells. A special socket is required, with a standard type of socket an adapter is necessary. The variable resistance in series in the filament circuit is recommended as 30 ohms. If a 6-ohm rheostat is used, a 25-ohm resistance unit should be added in series. The plate-grid potential curves taken on three of these tubes were so far different from what was taken that more were tested, the two extreme sets of curves as taken are given in Figures 5 and 6. Curves A are taken at a plate voltage of 21, Bat 45 and C at 80 volts. It is easily seen, that as the plate volt OEfORC OV-6 T / / y / <■ / / / % y -" <> 1 / :< 1 1> / VOtTS »*E«ATIVC POTENTIAL WOtTS .OVTiVi VOTfTlAfc Figure 7 age is increased a more negative grid potential is required. In the De Forest DV-6 tube considerable variation was found, but due to lack IF COMPARE. IT WITH WHAT YOU ARE NOW USING OURS IS BETTER MAIL US 3 0 CENTS NOT Return it at Our Expense ZOBEL-STEIN LABORATORIES 322 9™ ST. BR00KLYN.N.Y. South 2650 Jewell Pattern No. 95 Complete Radio Test Set The only complete radio test set made. All curves on vacuum tubes may be taken, the only other equipment necessary being batteries. The instrument is enclosed in a handsome case and includes five instruments, a standard vacuum tube socket, a filament rheostat and grid potentiometer, an instruction book and special cross-section paper for plotting curves. The instruments are a filament voltmeter reading to 6 volts, a filament ammeter reading to 1.2 amperes, a plate voltmeter reading to 120 volts, a plate milliammeter reading to 10 milliamperes and a center zero grid voltmeter reading to 10-0-10 volts. Voltage tests of "A" and "B" batteries and resistance tests of telephone receivers, grid leaks, amplifying: transformers and similar apparatus may also be made. The most important use of this instrument, however, is in taking the characteristic curve of a vacuum tube, from which all of its constants may be determined and the relative value of any tube measured. This instrument is absolutely invaluable to serious experimenters, to dealers handling large quantities of tubes and to anyone who wishes to ?*> beyond the mere fundamentals in the radio game. PRICE, $65.00 Jewell Electrical Instrument Co. 1650 Walnut St., CHICAGO of space only the average set of curves are given (Figure 7.) On a few of these tubes exceptionally good values were discovered while others didn't come up to the standards shown. The tube "is rated at 3 to 5 volts. Results at three volts were negligible so only the curves at 4 and 5 volts filament are shown. Although rated at 5 amperes the current consumption at 4 volts was found to run from .7 to .75 amperes while at 5 volts it varied between .8 to .85 amperes. The tube has a standard socket base. The usual 6-ohm rheostat can be used. The curves, although indicating no exceptional values, are fairly consistent. In fact, they are more so than many tubes that indicate relatively higher efficiency. The tube is small and saves space for compact arrangements. The rated plate voltage recommended Is 40 to 60. In Figure 7 the curves A and C are taken at 4 volts filament and 45 and 67% volts on the plate, respectively, while B and D are taken with 5 volts filament and the same respective potential on the plate. Philips Detector Type IV For the purpose of comparing a few of the foreign type of tubes with American manufacture, tests were made on a few of these also. Many of the foreign tubes that are made for the American market are rather poor in quality due to the necessity of keeping costs low in order to overcome the rather high duty imposed on this type of apparatus. Where this cheaper production method has been avoided some very high efficiency values have resulted. Due to a lack of some of these higher grade tubes, the tests made were very limited in number. One of these, the curves of which are given in Figure 8, is a Dutch tube known as the Philips Detector Type TV. This tube has a standard base and can be used on either dry cells or a storage battery in conjunction with the standard 6-ohm rheostat. The filament voltage recommende-1 is 3.5 while the current consumption is .51 amperes. The curve A, Figure 8, was developed with the plate potential at 16 y2 volts, when this was increased to 22% the curve shown as B was developed. Curve C shows the variation when the plate was PHiLiPilDcrtatertPt a TIL V-3S 5'ATVPS A 7— *< 1 i 1 1 ■j i 1 J 1 J 1 Figure 8 changed to 25% volts. It is evident that this tube will give a very high efficiency value, but the adjustment of a proper grid potential is necessary. For this reason the use of a potentiometer connected across the A battery, with the grid return connected to the center terminal of the potentiometer, is advisable. (TO BE CONCLUDED) A steady hum in the headset isn't always caused by alternating current lines. It is often due to an open circuit somewhere. 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