Icom IC-746PRO Manual page 68

PREAMP/ATTENUATOR
• Push momentarily to toggle between preamp-1 and preamp-2.
– "P.AMP1" activates 10 dB preamp for HF all bands.
– "P.AMP2" activates 16 dB high-gain preamp for 24 MHz band and above.
• Push for 1 sec. to toggle the attenuator function ON and OFF.
– What is the preamp?
• The preamp amplifies received signals in the front end circuit to improve the
S/N ratio and sensitivity. Select "P.AMP1" or "P.AMP2" when receiving
weak signals.
– What is the attenuator?
• The attenuator prevents a desired signal from distorting when very strong
signals are near the desired frequency, or when very strong electric fields, such
as from a broadcasting station, are near your location.