3807 D S P● AM and FM ModesIn the AM mode, the AF filter is placed after demodulation.It adopts a mechanism that switches the IF filter bandwidth when the high-cut frequency is switched. Meanwhile,switching the low-cut frequency alters only the AF filter setting. In the AM mode, extending the bandwidth only with theIF filter may cause the audio to sound distorted. Combining the use of the AF filter in this case allows the audio to standout.In the FM mode, it is possible to configure the low-cut or high-cut frequency of the AF filter for the audio afterdemodulation without affecting the IF filter setting. When the CTCSS feature is turned on, the high-pass filter is insertedin addition to the low-cut frequency filter to prevent the sub-tone signals from standing out.As with the SSB and CW modes, it is also possible to select “Narrow”, “Medium” or “Wide” on the RX Filter screen in theAM and FM modes.Audio Peak FilterThe audio peak filter is applicable in the CW and FSK modes.In the CW mode, it is a peak filter with the pitch frequency as the center frequency which helps to enhance theintelligibility by highlighting the desired signal when it lacks intelligibility due to noise.The passband width can be configured to one of the three levels ("Narrow", "Medium" and "Wide") to provide amaximum peak gain of +6 dB. The peak frequency can be shifted within the range of ±200 Hz with respect to the pitchfrequency.Fig. 45 CW Audio Peak Filter Characteristics (Medium)
