When timer output (pin 3) is high, meter receives calibrated current through R e . When IC times out, meter current stops for re- mainder of duty cycle. High-Q circuit is tunable from 1.8 to 150 MHz for indicating frequency of fields produced by RF harmonic. Center tap of T1 (any small AF transformer) can be grounded. CR1 and CR2 are germanium diodes. The author index will often help find related circuits after one potentially useful circuit is found, because authors tend to specialize in certain circuits. Operating volt- age is supplied through coax feeder. R1 isolates signal energy from ground, and C2 keeps DC voltage out of receiver input.
Circuit serves as electronic switch that isolates points from heavy interrupt current and high-voltage back- swing of ignition coil, thereby almost com- pletely eliminating wear on points. When you write to a magazine publisher for prices of back issues or copies, give the complete citation, ex- actly as in the abstract. Set S1 at 1, feed peak output of transmitter to J1 (5 W maximum), and adjust R4 for full-scale reading of M1. Next, connect 50-ohm resistive load between CR1-R1 junction and ground. This same search would take weeks or even months, at a large engineering library, plus the time required to write for manufacturer literature and locate elusive sources. Pure sine-wave signal is applied to device under test, and out- put of device is fed to AF input of distortion meter.
Unmarked resistors are on IC. — D. DeMaw, Understanding Linear ICs, QST, Feb. 1977, p 19-23. STABILIZED BIAS— Simple voltage-feedback loop stabilizes bias on direct-coupled FET and bipolar transistor stages. Can be driven to within 1 mV of ground. Circuit uses two overdriven FET amplifier stages in cascade. Entire circuit must be duplicated for other stereo channel. Adjust R6 until oscillator out- put at TP1 is 10 V P-P. FET provides constant current through variable resistance of carbon microphone, to give audio input voltage. Sensor head is small enough to fit most distributors.