Weak input signals can be displayed only if the RF Gain control is set to the minimum. If the RF gain step is set too high, weak signals are superposed by amplified noise of the RF stage. A measurement of FM signals recorded at lowest gain step is depicted in Figure: FM Spectrum High Reference Level. Every carrier is received with a 30 dB signal to noise ratio. If the reference level is set too high, the signal to noise ratio is significantly reduced. Figure 2-2 is also an example of the reference level setting being set too high for the signal displayed.