This module is designed to help with setting up many different homebrew radio and audio projects, it will produce a strong white noise type signal starting at low audio frequencies and up to the VHF spectrum. The noise source can be used in a number of ways. It useful for testing audio and RF filters in Ham radio circuits, They can really be helpful when aligning homebrew radios filters and checking losses in LPF’s. The traditional approach which is tried and tested is very simple, a RF noise source is amplified and fed into the front end of the radio being tested, spectrum analyser software on a PC is then used to look at the filter response OK how do we get a noise source to amplify? Well many years ago some design engineer must have been asked to make a regulated voltage source but to do it has cheap as possible. They used a Zenner diode and resistor and to keep the cost down they didn’t put a capacitor across the Zenner, it saved a few pence BUT it was found that by using it this way a lot of noise was being produced, this noise was present right up to VHF frequencies, not what was wanted at that time but something that we can exploit in our circuit.
AF/RF Noise Source
Full Kit Instructions can be downloaded here (Use these to make your own if you wish