Question 3-90O4

Shipboard RADAR commonly operates in the Super High Frequency (SHF) band, which spans 3 to 30 GHz. The primary reason for using SHF frequencies is the ability to achieve a highly directional beam with a physically small antenna. RADAR systems require narrow beamwidths for good angular resolution, allowing them to precisely distinguish between nearby targets and accurately determine their bearing. At SHF frequencies, the wavelengths are short enough (centimeters) that a practical-sized antenna (e.g., a rotating parabolic dish or slotted waveguide array) can produce a very tight, focused beam. Lower frequency bands like VHF and UHF have longer wavelengths, which would require impractically large antennas to achieve the necessary narrow beamwidth for effective navigational RADAR. Conversely, extremely high frequencies (EHF) suffer from significantly greater atmospheric attenuation, especially from rain and water vapor, severely limiting their range and reliability in adverse weather conditions common at sea. SHF strikes an optimal balance between resolution, antenna size, and acceptable atmospheric attenuation.