Radio broadcast .. (1922-30)

314 RADIO BROADCAST ADVERTISER CME r Celatsite iattery Cable A rayon-covered cable of 5, 6, 7, 8 or 9 vari-colored Flexible Celatsite wires for connecting batteries or eliminator to set. Plainly tabbed; easy to connect. Gives set an orderly ap- pearance. Stranded Enameled Antenna Best outdoor an- tenna you can buy. Seven strands of enam- eled copper wire. &^^P Presents maximum surface for reception, resists corrosion; this greatly improves the signal. Outside diameters equal to sizes 14 and 16. (We also offer solid and stranded bare, and stranded tinned antenna.) Loop Antenna Wire Sixty strands of No. 38 bare copper wire for flexibility, 5 strands of No. 36 phosphor bronze to prevent stretching. Green or brown silk covering; best loop wire possibje to make. Flexible Celatsite for sub-panel wiring A cable of fine, tinned copper wires with non- inflammable Celatsite in- sulation. Ideal for sub-panel or point - to - point wiring. Strips easily, solders readily. Nine beauti- ful colors; told only in 2S ft. coili. In carton* colored to match contents. Acme Celatsite Wire Tinned copper bus bar hook- up wire with non-inflam- mable Celatsite insulation, in 9 beautiful colors. Strips easily, solders readily, won't crack at bends. Sizes 14, 16, 18, 19; 30 inch lengths. Spaghetti Tubing Oil, moisture, acid proof; highly dielectric — used by leading engi- neers. Nine colors, for wire sizes 12 to 18; 30 inch lengths. (We also make tinned bus bar, round and square, in 2 and 2}£ ft. lengths.) Send for folder THE ACME WIRE CO., Dept. B New Haven, Conn. ACM IRE MAKES BETTER RADIO The Radio Broadcast SHEETS "TpHE RADIO BROADCAST Laboratory Information Sheets are a regular feature of this *• magazine and have appeared since our June, 1926, issue. They cover a wide range of information of value to the experimenter and to the technical radio man. It is not our purpose always to include new information but to present concise and accurate facts in the most convenient form. The sheets are arranged so that they may be cut from the magazine and preserved for constant reference, and we suggest that each sheet be cut out with a razor blade and pasted on 4" x 6" filing cards, or in a notebook. The cards should be arranged in numerical order. In July, 1927, an index to all Sheets appearing up to that time was printed. All of the 1926 issues of RADIO BROADCAST are out of print. A complete set of Sheets, Nos. i to 88, can be secured from the Circulation Department, Doubleday, Doran & Company, Inc., Garden City, New York, for $1.00. Some readers have asked what provision is made to rectify possible errors in these Sheets. In the unfor- tunate event that any such errors do occur, a new Laboratory Sheet with the old number will appear. — THE EDITOR. No. 161 RADIO BROADCAST Laboratory Information Sheet February, 1928 Comparing the 112, 171, and 210 Type Tubes THEIR RESPECTIVE OUTPUTS r\N LABORATORY SHEET No. 162 are shown *"* three aurves that indicate an interesting re- lation between the three most common types of power tubes, i.e., the 112, 171, and 210 types. The curves indicate the relation between the power out- put of the tubes and the value of the signal voltage impressed on the grid. The plate impedance and amplification constants of the 112 and 210 type tubes are practically identical and, therefore, the curves for these two tubes coincide from zero up to that point corresponding to the maximum output power of the 112, which is approximately 195 milli- watts, or 0.195 watts. If a vertical line is drawn at any point on the curve, for example, at A, the points at which this line crosses the various curves will indicate the power output obtained from the particular tube associated with the curve being examined. In this particular case, line A, drawn at the point corre- sponding to a signal voltage on the grid of 15 volts indicates that, with this value of signal voltage, the power output of a 210 tube with 425 volts on the plate is approximately 0.34 watts. The power output of a 171 at the same point is approximately 0.1 'watts. The maximum grid voltage that can be impressed on a 112 without resultant output dis- tortion is about 10.5 volts and, therefore, a 112 tube cannot be used if the signal input voltage is greater than this value. At B we have drawn another line corresponding to a signal on the grid of 8 volts. Here we find that the power output of a 112 is approximately 0.1 watts and the power out- put of a 171 about 0.04 watts. It is therefore evident that at low values of input voltage a 112 tube is capable of putting more power into the loud speaker than is a 171. If the signal voltage, however, is in excess of 10} volts, the 112 cannot be used and the chbice then lies between the 210 and the 171. The curves indicate that the 210 will give much more power output than a 171 but it should be realized that much greater plate voltages are necessary on the 210 than on the 171. With 180 volts on the plate the 171 can deliver approximately 740 milliwatts of power, but 250 volts on the plate of the 210 will only permit this tube to handle signal voltages up to 18 volts and the maximum output power will be only 460 milliwatts. From these data the follow- ing conclusions can be arrived at: (1.) For input signals on the grid of the power tube of 10 volts or less the 112 tube will deliver the most power to the loud speaker. (2.) When more power output is required and only moderate plate voltages are available (not in excess of 200 volts) a 171 is capable of giving greater output than can be obtained from a 210 under simi- lar conditions of plate voltage. (3.) Where high plate voltages around 400 volts are available the 210 should be used and under the same input signal it will give approximately 2J times as much power as can be obtained from a 171.