When evaluating a spectrum analyzer, the most critical technical parameter is the Frequency Range, which must cover your specific application (e.g., 9 kHz to 6.5 GHz for general RF testing). You must also prioritize Resolution Bandwidth (RBW); a narrower RBW allows for better separation of closely spaced signals. Additionally, check the Displayed Average Noise Level (DANL)—a lower DANL (e.g., -160 dBm) indicates higher sensitivity for detecting weak signals. For high-speed digital communications, ensure the device has a high Real-time Bandwidth (RTBW) to capture transient or hopping signals.