In this application note, we’ll provide an overview of interference finding techniques and offer examples to help your next interference hunting efforts to be more successful. We’ll also look at why real-time spectrum analyzers (RTSAs) have emerged as the go-to tool for tracking down elusive signals in a crowded spectrum. Once expensive and desk-bound, a new class of affordable, battery-powered, USB-based RTSAs such as the Tektronix RSA500 make an RTSA a powerful tool for interference-hunting applications.
In looking at interference, it helps to understand how receivers filter out unwanted signals. As shown in the figure, the received or assigned channel is in blue. Interference can occur when there is energy inside the preselector of the victim receiver. This means if there is any energy falling under the preselector passband it could impact the performance of the receiver, by blocking the receiver directly or through a form of desensitisation. It occurs when there is RF energy not directly on channel.