Audio Signal Tracer Circuit

Ham Radio Audio Circuit

Fig, 57. Thïs signal tracer provides more than adequate audio output with only J00 microvolts of modulated rf at the input. It may also be used for tracing audio circuits, but don't depend on its fidelity. All the transistors are germanium types such as the 2N404, 2NI450, 2N2953, SK3004,, GE-2 or HEP-253; the diode in the probe is a IN34A or IN67A or similar.

i ier to t beck microphones and preamps and to detect noise and hum in amplifiers.

The signal tracer shown in Fig. 57 uses a push pull output stage which produces more than adequate audio output to a miniature speaker with only ¡00 microvolts input. The output from the probe is applied directly to the 250 kilohm pot, which serves as a gain control and as a diode load when an rf probe is being used. The signal is coupled to the base of the first transistor, amplified, and fed to the driver stage and transformer coupled push pull output.

Only a very small amount of audio signal is necessary to operate the signa! tracer as a straight through audio amplifier, However, don't use it to check fidelity because it is designed primarily for maximum sensitivity without regard to frequency response.

When using this signal tracer always start with the audio gain control turned all the way down because it is easy to overload the simple amplifier; the result is a highly distorted output signal. In some receivers the rf probe may load the mixer plate or if grid. If this happens, a tone modulated signal should be injected at the antenna terminals of the receiver to obtain a usable output from the signal tracer

Signal Injector Circuit

Fig. 58. This signal injector/tracer switches from the injection mode to a signal tracer by simply plugging in a pair of high impedance magnetic earphones* As a tracer is works from audio up to 432 MHz. Transistor QI is a 2NI70, 2N388A, 2NI605, SK30II or GE-7; Q2 is a 2NI88A, 2N404, 2N2953, SK3004 or HEP-253,

Fig. 58. This signal injector/tracer switches from the injection mode to a signal tracer by simply plugging in a pair of high impedance magnetic earphones* As a tracer is works from audio up to 432 MHz. Transistor QI is a 2NI70, 2N388A, 2NI605, SK30II or GE-7; Q2 is a 2NI88A, 2N404, 2N2953, SK3004 or HEP-253,

Signal injector/tracer

The circuit illustrated in lag. 58 functions as both a signal injector and signal tracer. Furthermore, no switching is required; it's all accomplished automatically when the headphones are plugged in for signal tracing, In the inject mode the circuit is a clamped multivibrator with extremely narrow pulses and high harmonic content- In fact, with this circuit, sufficient output is available for signal tracing from audio (750 Hz) to well above 40 MHz, This frequency range is more than adequate for most requirements.

The unit is switched to the signal tracer mode by simply plugging in a pair of high impedance magnetic headphones. In this mode

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Wood Working for Amateur Craftsman

Wood Working for Amateur Craftsman

THIS book is one of the series of Handbooks on industrial subjects being published by the Popular Mechanics Company. Like Popular Mechanics Magazine, and like the other books in this series, it is written so you can understand it. The purpose of Popular Mechanics Handbooks is to supply a growing demand for high-class, up-to-date and accurate text-books, suitable for home study as well as for class use, on all mechanical subjects. The textand illustrations, in each instance, have been prepared expressly for this series by well known experts, and revised by the editor of Popular Mechanics.

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