What is an effect of excessive phase noise in an SDR receiver’s master clock oscillator?

Phase noise occurs when an oscillator's signal spreads out slightly, creating 'skirts' of noise around the desired frequency. In a Software Defined Radio (SDR), the master clock oscillator drives the analog-to-digital converters or mixers. If this clock has excessive phase noise, the noise can mix with strong adjacent-channel signals. This process, known as reciprocal mixing, brings the noise of those strong nearby signals directly into your receiver's passband, raising the noise floor and burying weak signals. Other options are incorrect because phase noise does not primarily affect the third-order intercept point (which is a measure of amplifier linearity) or frequency calibration (which relies on the oscillator's stability, not its noise).