Abstract: A planar near-field antenna measurement and diagnostic system is described which collects data on a bi-polar grid. The planar scanning is accomplished using rotary positioners and a mechanical arm. The test antenna is mounted to a rotary positioner such that it can spin about its axis. The arm is mounted to another rotary positioner such that it can rotate about a second axis. A field probe, attached to the end of the arm, scribes an are which passes through the antenna rotation axis. By rotating the two positioners, the near-field of the antenna can be measured on a bi-polar sampling grid comprising concentric circles and radial arcs. The mechanical simplicity afforded by rotational motion rather than the linear motion of most planar near-field scanners provides for an elegant and cost-effective design.