What is meant by fundamental overload in reference to a receiver?

Fundamental overload in the context of a receiver refers to interference caused by very strong signals. When a receiver is subjected to signals that are significantly stronger than its intended operating range, it can become overwhelmed, leading to distortion or inability to properly demodulate the intended signals. This phenomenon is particularly noticeable when dealing with nearby powerful transmitters or when a receiver is in close proximity to a big signal, which can saturate the front end of the receiver. This results in reduced sensitivity and selectivity, degrading overall reception quality. Understanding this concept is essential for effective operation in the amateur radio spectrum, where signal strength can significantly vary across different environments and conditions.