. QST . is taken from the60-cycle line. The frequency marker contains itsown power supply, consisting of a 1-am-pere filament transformer, and a half-waveselenium rectifier and resistance-capacitancesmoothing filter comprised of Ci. d, and against short circuits to ground isprovided by the ground coupling capacitor, C12,in the output circuit. The crystal oscillator uses a 6AK5 pentode inan electron-coupled Pierce oscillator circuit, withthe screen of the pentode serving as the plate ofan equivalent triode while output to the multi-vibrator is taken from the plate of the
. QST . is taken from the60-cycle line. The frequency marker contains itsown power supply, consisting of a 1-am-pere filament transformer, and a half-waveselenium rectifier and resistance-capacitancesmoothing filter comprised of Ci. d, and against short circuits to ground isprovided by the ground coupling capacitor, C12,in the output circuit. The crystal oscillator uses a 6AK5 pentode inan electron-coupled Pierce oscillator circuit, withthe screen of the pentode serving as the plate ofan equivalent triode while output to the multi-vibrator is taken from the plate of the frequency of oscillation can be adjusted overa small range by means of the variable capacitorsCs and d. Capacitor d is used to raise the fre-quency, whereas C3 lowers the frequency of these capacitors are mounted on a singleceramic base as a double trimmer, and each hasa capacitance range of from 10 to 170 /x^f- Aseries capacitor, C5, was used to reduce the 50-Kc. MULTIVIBRATOR. Fig. I — Circuit of the 50-kc. frequency marker. Resistors are 3^-watt composition unless otherwise in nfii. except where specified otherwise. Ci, C2 — Electrolytic. Ce, C7, Cs, C12 — Ceramic or paper. Cs, C4 — Dual ceramic-mounted trimmer. CRi — 75-ma. selenium rectifier. Cs, C9, Cio, Cii, Ci3 — Mica. Si — slide. Except for the 115-volt source of power, it isentirely self-contained in a standard metal case,3 by 4 by 5 inches in size. It uses a low-frequencycrystal, such as are now readily available on thesurplus market in FT-241 or FT-243 holders fortwo dollars or less. Circuit As the wiring diagram. Fig. 1, shows, themarker comprises a OAKS crystal-controlledoscillator, followed by a ()U8 triode-pentodefrequency-controlled multivil)rator adjusted toprovide marker frequencies at intervals of 50 is ample for communication-type receiv-ers up to 30 Mc. * 22 Temple Street, Belmont 78, Mass. maximum capacitance of C4 to a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
