Engineering Performance Measures. 3.5.1 Maintenance Limits for VHF FM Transmitters Frequency Deviation 75 KHz (Mod. capability: 100 KHz) Pre-emphasis 50S Audio Frequency Response (Mono) 0.5 dB between 30Hz – 15 KHz. Total Harmonic Distortion (Mono) -50 dB or better, 30 Hz-15 KHz. Noise (Unweighted) @ 75 KHz dev. -70 dB or better. (Stereo /Mono) (Weighted)* -68 dB or better. (Stereo/Mono) Audio Frequency Response (Stereo) 0.5 dB between 30Hz – 15 KHz. Total Harmonic Distortion: (@ 75 KHz) -50 dB or better, 00 Xx-00 XXx (@000 XXx) -00 dB or better, 30 Hz-15 KHz Intermodulation Distortion (2-tone) -55 dB or better, second order. -50 dB or better, third order. * In accordance with CCIR Rec 468-4 specification.