. QST . Fig. 4 — firing diagram of the amplifier. Ci-Ce — See text. Cm — See text. Li-Le — See text. L m— See text. L? — 143 mh., Q of 20 to 30. Ti — 5000-ohms-to-line output transformer. April 1955 33 the and signals at the grid ofthe first audio amplifier. The is tuned to thehigh side of the signal frequency. An octal socket. Fig. 5 — Equivalent circuit of an amplifier stage. is wired so that a Selectoject can be used with theamplifier. When the Selectoject is not in use, anoctal plug must be used to jump Pins 6 and t\-pes of audio filters
. QST . Fig. 4 — firing diagram of the amplifier. Ci-Ce — See text. Cm — See text. Li-Le — See text. L m— See text. L? — 143 mh., Q of 20 to 30. Ti — 5000-ohms-to-line output transformer. April 1955 33 the and signals at the grid ofthe first audio amplifier. The is tuned to thehigh side of the signal frequency. An octal socket. Fig. 5 — Equivalent circuit of an amplifier stage. is wired so that a Selectoject can be used with theamplifier. When the Selectoject is not in use, anoctal plug must be used to jump Pins 6 and t\-pes of audio filters could also be used. (Adouble-tuned critically-coupled selective ampli-fier tuned to 1 kc, with a bandwidth of 30 cycles,has been experimentally used by the author withvery results.) The decoupling l)etweenstages may look elaborate, but adequate by-passing is quite difficult at 20 kc, where a looks like 80 ohms. After some experi-mentation the decoupling shown was adopted asa means of completely isolating the stages so theresponse curves are as calculated and not asmodified by the regeneration inti-oduced l)y thewiring. Design of the 20-Kc. Tuned Circuits The gain of an amplifier at resonance is where r/m = transconductance of the valve inmhos, andZ = load impedance in double-tuned critically-coupled circuits. Z = ,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
