Avenues for improvement in the design and calibration of VHF-UHF noise and field strength meters

Abstract

Increased accuracy of measurement of VHF-UHF field strength may be obtained by improveing the impedance match of the antenna-balun assembly and by taking into account the measured gain of the antenna system, rather than by relying on the assumption that the antenna performance approximates that of the idealized half-wave dipole. The latter assumption appears to be the basis of present practice. Although the standard field method of calibration is theoretically available as an over-all calibration procedure, the present types of instruments depart from ideal in a manner so complex with respect to frequency that it becomes a prohibitive task to make detailed periodic calibrations by the standard field method, aside from the difficulties in the technique of the standard field method itself. A simple form of the reciprocity method is shown for measurement of the effective gain of the antenna-balun assembly under essentially free-space conditions. It is argued that the calibration of field strength meters should be carried out under conditions equivalent to free space.