An instrument for determining the direction of maximum response to a received radio signal, or selecting the direction of maximum radiation of a transmitted radio signal; consists of two fixed perpendicular coils, each attached to one of a pair of loop antennas which are also perpendicular, and a rotatable coil which bears the same space relationship to the coils as the direction of the signal to the antennas.

1. An instrument used to measure the angles between crystal faces.

2. An instrument which uses x-ray diffraction to measure the angular positions of the axes of a crystal.

3. Any instrument for measuring angles.