Optional automatic antenna tuner, AT-140/AT-130, matches the radio to your antenna. 0.5 to 29.9999MHz wide band general coverage receive. Channel knob allows the user to tune specific frequencies around a memory channel. 2 DIN connectors for external equipment connection - linear amplifier, FSK terminal, e-mail modem, etc. 2-tone alarm built in. NMEA 0183 interface included.