Explanation: Modern VHF amateur radio receivers are highly sensitive, capable of detecting very weak signals approaching their inherent noise floor. To accurately test and characterize the *ultimate sensitivity* of such a receiver, a lab-type signal generator must be able to produce signals at levels comparable to, or even below, the receiver's practical detection limit. Many good quality VHF receivers can achieve a useable sensitivity (e.g., for 12 dB SINAD) of around 0.2 microvolt. Therefore, a signal generator that can reduce its output to 0.1 microvolt provides the necessary range to precisely measure and evaluate a receiver's performance at its weakest signal threshold. Outputs limited to higher values like 0.5 or 1.0 microvolt would be insufficient for comprehensive testing of a high-performance receiver's weak-signal capabilities.