noise generator

I Q noise generator Noise is normally defined as unwanted electrical signals spread over a rela- tively flat, wide frequency spectrum. In most equipment, great care is taken to reduce the amount of noise to a minimum, resulting in a low noise factor. None the less, noise is useful for measuring the behaviour of a circuit under varying input conditions. A noise generator is used, for instance, for measurements on coaxial cables, microwave links, and RTTY (radio teletype) and CW (continuous wave= radio telegraphy) decoders. The present circuit may also be used to imitate the sound of wind, mos- quitoes, bees, and other buzzing insects. The circuit consists of a relaxation oscillator, IC,, which is provided with positive and negative feedback via Pi-R, and P3- P2-R3-C1respectively. Zener diode D1functions as noise source. The amplification of the noise is determined by the setting of P3 (coarse) and P2 (fine). The setting of P1determines the noise bandwidth: a small effective value r...