What causes a receiver to lose sensitivity over time and what components should I check first?

What causes a receiver to lose sensitivity over time includes several degradation mechanisms, and the components to check first are: the LNA (the front-end low-noise amplifier is the most common cause of sensitivity degradation because: ESD damage (cumulative electrostatic discharge events gradually degrade the LNA's semiconductor device, increasing noise figure; the LNA input is directly connected to the antenna and is exposed to static discharge events from cable connections). LNA bias drift (the DC bias point drifts over time due to component aging, resistor drift, or capacitor degradation; a shifted bias changes the LNA's gain and noise figure). LNA device degradation (hot-carrier degradation in GaAs or GaN FETs, or oxide degradation in CMOS; this increases the device's noise and reduces gain)), cable and connector degradation (connector corrosion (especially in outdoor installations): increases the insertion loss before the LNA, directly degrading sensitivity (1 dB of pre-LNA loss = 1 dB of sensitivity loss). Cable degradation: moisture ingress, UV degradation of the outer jacket (for outdoor cables), and mechanical fatigue increase cable loss), filter degradation (filter center frequency or bandwidth may shift due to: temperature cycling fatigue (mechanical stress on ceramic or acoustic resonators), humidity or contamination (changes the filter's resonant frequency), and aging of the filter's internal matching components)), and the reference oscillator (frequency drift of the local oscillator can move the receiver's tuning off the desired channel, effectively degrading sensitivity by misaligning the signal with the IF filter passband). Components to check first (in order): connectors and cables (visually inspect for corrosion, tightness, and physical damage; measure cable loss and connector return loss). LNA DC bias (measure the drain/collector voltage and current; compare to the original specification). LNA gain and noise figure (measure at the bench if accessible). Pre-LNA components (filters, switches, limiters: measure insertion loss and compare to baseline).