Direction findings by radio comprises arraigning an array of antennas, to receive signals from emitters, selecting individual antenna signals using a first multipole switch and determining, antenna signal strengths. Individual antenna signals are also selected by mutipole switch, which routes a selected signal to a third multipole switch. The third switch switches a phase shifter into and out of an antenna signal path. An adder is employed to add an antenna signal in a first signal path extending via the first multipole switch to a different antenna signal in a second signal path extending via the second and third switches. This determines combined signal strengths between pairs of antenna signals, one of which either has or has not been relatively phase shifted depending on the third switch position. Covariance matrix elements are determined from signal strengths enabling emitter bearings to be derived.