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Signal Generator - Output Generating Circuits
.. Electronics

Signal Generator

Oscillators generate wireless signals or high frequency signals on their outputs (radio oscillation). It is worth noting that the low-power signal generator has a good ability to tune with any signal, regardless of its oscillation.

Figure (222) includes a signal generator circuit consisting of a transistor and two resistors M1, M2 whose task is to find the most suitable conditions for operating its base through a resonant circuit consisting of the coil L1 and the variable capacitor Sm connected to the base Q by a connecting coil L2 that plays the role of feedback. The output resulting from the arrangement of the components of the circuit shown in Figure (222) is an unmodulated radio frequency signal. If it is tuned to a normal receiver, it is not possible to hear any sound, so it is called an "unmodulated" or "carrier signal" output signal. When we need a wave modulated by an audio frequency signal, an audio oscillator (223) must be added to modify the carrier signal. In this case, the audio signal can be heard from the receiver after tuning it to the modulated signal.

222 - Tunable radio frequency signal generator.
223 - Audio wave modulator

The signal generator can be used to adjust the alignment of the intermediate frequency transformers in the receivers (224). Most intermediate frequency transformers include two tuning circuits whose coils contain adjustable cores. These transformers can also be equipped with trimming capacitors. In addition, the signal generator is tuned so that its output is about 470 kilocycles per second, and this output is then directed to the receiver at a point directly preceding the intermediate frequency transformer circuits. The cores or trimming capacitors are then turned and adjusted so that the frequencies are tuned to obtain the optimum output of the receiver at the appropriate tuning.

The antenna and all the tuning circuits in the receiver can be tuned in the same way. This is done by tuning the generator to the appropriate frequencies, then by adjusting the cores of the coils or trimming capacitors so that the frequencies or wavelengths are tuned to the correct positions corresponding to the positions on the plate included in the receiver.

We see in Figure (225) the section dedicated to radio signals in a signal generator that falls in the range between 10 and 300 megacycles. This generator is used in testing operations or in the alignment operations of very high frequency transformers.

224 - Using the signal generator to adjust the receiver alignment.

225 - Circuit for obtaining the very high frequency range.