Antenna beamwidth considerations

An empirical investigation is described in which the author studied antenna beamwidth of radiation and how it contributes to errors in the measurement of radiated profiles due to the antenna´s directivity. These errors result because measurements are often taken using highly directional antennas that tend to mask the full measurement amplitude of the equipment under test (EUT) due to the antenna´s directivity. Errors from this oversight may cause units to appear within prescribed radiation limits when in fact they may be falling. The author suggests that either a variable test distance be used to accommodate the beamwidth of the given antenna or some fixed distance which would adequately include the narrowest beamwidth that would be used, thereby allowing the measurement antenna to illuminate the EUT fully. He further suggests that all measurements be conducted on bore sight with respect to the EUT as seen by the measurement antenna