The ARC-190 is a military HF radio that operates between 2-30 MHz and transmits at 300+ watts. It features a dual heterodyne receiver/transmitter that uses IF frequencies of 97.8 and 1.8 MHz, an antenna coupler that is pressurized to 7±1 PSI with dry nitrogen (air) which (1) prevents high voltage arcing, (2) prevents corrosion, (3) provides a uniform cooling medium, and one of various controls which provide access to 30 preset channels, 30,000 normal channels, 280,000 channels when using SSB, test functions, squelch, power on/off, and one of 8 modes of operation: UV (Upper Voice), LV (Lower Voice), UD (Upper Data), LD (Lower Data), CW (Continuous Wave), AME (Amplitude Modulated Equivalent), P (Preset) and A (not used).