It is very important that the oscillators contained in a superheterodyne receiver are:

In a superheterodyne receiver, local oscillators are used to mix with incoming RF signals to produce a fixed Intermediate Frequency (IF). It is critical that these oscillators are both stable and spectrally pure. High stability prevents the receiver from drifting off frequency over time or with temperature changes. Spectral purity means the oscillator produces a clean signal without unwanted phase noise or spurious harmonics. If the oscillator has high phase noise, strong adjacent signals can mix with the noise and mask weak desired signals (a phenomenon called reciprocal mixing). Attributes like 'sensitivity' and 'selectivity' apply to amplifier or filter stages, not oscillators.