How does a rotating antenna direction finder compare to a fixed array for signal bearing estimation?

Rotating antenna and fixed array direction finders represent two fundamentally different approaches to bearing estimation, each with distinct trade-offs in speed, accuracy, and complexity: (1) Rotating antenna DF: a single directional antenna (or a small array) physically rotates to scan 360°. The signal amplitude varies as the antenna sweeps past the emitter direction. The bearing is estimated from the amplitude peak (or null) as a function of rotation angle. Types: rotating loop antenna (used at HF/VHF, provides a figure-of-eight pattern with two nulls per revolution), spinning parabolic dish (used at microwave frequencies, high gain but slow rotation), and mechanically scanned horn (moderate gain, moderate rotation speed). Advantages: simple hardware (one antenna, one receiver), high gain (a large directional antenna can be used), and inherently unambiguous (the mechanical angle directly maps to bearing). Disadvantages: slow update rate (limited by the rotation speed; typically 6-60 RPM = 0.1-1 full scans per second), cannot measure the bearing of short-duration signals (a pulse shorter than the scan dwell time may be missed), and mechanical wear and maintenance requirements (rotating joints, motors, slip rings). (2) Fixed array DF: multiple antennas are permanently mounted in known positions. The bearing is computed from the amplitude and/or phase differences between the antennas. Types: interferometer array (phase comparison between pairs), Watson-Watt array (crossed loops or dipoles with amplitude comparison), and digital beamforming array (forms multiple simultaneous beams electronically). Advantages: instantaneous measurement (the bearing is computed from a single snapshot of the signals at all antennas), no moving parts (high reliability, low maintenance), simultaneous multi-signal capability (multiple emitters at different bearings can be resolved simultaneously), and fast update rate (microseconds per measurement). Disadvantages: more complex hardware (multiple antennas, multiple receivers, digital processing), limited aperture (the array size determines the resolution; large arrays at low frequencies are impractical), and potential ambiguities (phase interferometers must resolve 2π ambiguities).