The ANF (Automatic Notch Filter) removes constant tones from the audio.

title bar area RUN button Display button KEYPAD button QSIR button SERV button CMD button MODE button FILT button AGC button BAND button NB1 button Receiver buttons MRKS button NB2 button Spare button NR button VLOCK button ANF button Wheel button Centre button Memory button RX EQ button reserved button MODE button 2 AGC button 2 FILT button 2 VLOCK button 2 Frequency panel Frequency panel Step DOWN button Step panel Step UP button SQ button BIN button MUTE button S meter panel Volume control Panadapter left Panadapter filter area Panadapter right Frequency bar position adjuster Frequency bar Waterfall display panel Status bar ANF control panel

Double click the button to show the ANF settings dialog.