Radio Broadcast (Nov 1926-Apr 1927)

RADIO BROADCAST ADVERTISER 423 B-POWER SUPPLY KITS ^^^POWER AMPLIFIER KITS □ □ NATIONAL Equipment for B-Eliminators and Power Amplifiers NATIONAL Power Transformer This Transformer, for the construction of Power Units, is designed for use with either Raytheon or Rectron Tubes. The secondary carries sufficient voltage to operate the new Raytheon BH 8o-mil Tube and the wire is of sufficient size to permit continuous operation for long periods without heating or damage. The transformer has center-tapped 7.5 volt and 5.5 volt secondaries, for heating the filaments of rectifier tubes or of power tubes, whether of the UX-210, UX-112, or UX-171 type. This makes the transformer adaptable without change to a number of different rectifier and amplifier circuits. The unit is cased in a heavy pressed metal box, attractively finished in black crackle. The terminal panel is of Bakelite with special NATIONAL screw-type terminals. Dimensions: 45" wide x 4" deep x 4}" high. Built to JvJATIOAJAL standards. Price — with Raytheon BH Tube $2.2.50 each Price — without Raytheon BH Tube 16.50 each NATIONAL Filter Chokes (Types No. 35 and No. 80) These Filter Chokes are made for use in Filter Circuits of plate-supply units. Type No. 35 contains two iron core inductances and is designed for a maximum con' tinuous output of 35 mils. This is sufficient for the average 5 tube set, with or without one power'tube. Dimensions: l\" x 4" x 35", finish and type of case to match the l^ATIOT^AL Power Transformer. Price — Type No. 35 $7.00 The NATIONAL Filter Choke Type No. 80 is a larger unit containing two iron core inductances wound with larger wire than the Type No. 35 and with larger cores, and capable of handling up to 80 mils continuously, as with the new Raytheon BH Tube. Dimension: 45" x 4" x 4!" '. Cased to match the A[ATIO>{AL Power Transformer. Price— NATIONAL Filter Choke No. 80 $10.00 Tobe Special B Block built for use with NATIONAL B Eliminators and Amplifiers This Special TOBE B BLOCK, designed expressly for the NATIONAL B Eliminators and Amplifiers, contains TOBE HighVoltage short-path Type Condensers, suitable for working voltages up to 400-volts D.C. It is not guaranteed for use with UX-216-B tube when more than 400 volts is being rectified with it (a higher voltage condenser bloc\ is required for this purpose; prices sent on request). Dimensions: RATIONAL 4I" x 4" X4j". Price— TOBE SPECIAL B BLOCK $17.50 each NATIONAL Tone Filter The plate voltages now required with either the UX-171, UX-112 or UX-210 Power Tubes, for fine quality of reproduction, range from 180 volts upward. The makers of the tubes recommend passing the output to the loud speaker through a Tone Filter. The NATIONAL Tone Filter is designed for this purpose. It contains an impedance of the proper value through which the plate of the Power Tube is supplied, a 2 Mfd. TOBE Filter Condenser, through which the A. C. com ponent of the power tube output passes to the speaker. With this NATIONAL Tone Filter all D.C. is kept out of the speaker windings, thus preventing them from burning out, and at the same time the quality of the output is greatly improved, because no force is exerted on the speaker armature, except that due to the signal. Cased to match the other NATIONAL B-Power units, supplied with 5-foot phone cord, for instant attachment to any existing set. To install put the tips on the end of the phone-cord plug in speaker jac\ on the set and insert speaker cord into the two tip-jac\s mar\ed LS on the panel of the Tone Filter. Dimensions: 2!" x 4" x 3 \" high. Price— NATIONAL Tone Filter $8.00 each NATIONAL products are built to engineering standards of excellence. Anyone who has ever built a set using NATIONAL BROWNING-DRAKE Coils and Transformers knows what that means. Send for Bulletin 116-RB. National Co., Inc., Engineers and Manufacturers— W. A. Ready, Pres., Cambridge, Mass., Makers of NATIONAL BROWNING-DRAKE Coils and R. F. Transformers, Impedaformers, Condensers, Power Transformers, etc., for Radio. ■ — ~> NATIONAL Power Transformer NATIONAL Filter-Chokes NATIONAL Special Tobe B Block NATIONAL Tone Filter B-POWER and AMPLIFIER UNITS