A noise generator with a wideband output signal is always handy to have around when you're adjusting receivers and other types of HF equipment.
Simple RF Noise Source Circuit Diagram:
The noise generator circuit described here uses the base-emitter junction of a transistor (in this case a 8Fl99) operating under reverse bias. As a result, it acts as a Zener diode and generates a wideband noise signal. The noise signal passes through a 1-nF capacitor to the
output connector (female BNC), which means that its low-frequency components do not appear at the output. The 47-Q resistor gives the noise generator an output impedance of nearly 50 Q. You can easily fit the entire noise generator in a small metal enclosure equipped with a BNC connector. The supply voltage is not critical; anything in the range of 8 to 15 V will do.
Author : Fred Brand - Copyright : Elektor
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