their use is limited to low signal amplitudes to avoid obvious distortions as the capacitance would be affected by the change of signal voltage, precluding their use in the input stages of high-quality rf communications receivers, where they would add unacceptable levels of intermodulation. at vhf/uhf frequencies, e.g. in fm radio or tv tuners, dynamic range is limited by noise rather than large signal handling requirements, and varicaps are commonly used in the signal path.