A Source of Error in the Measurement of Radiated Harmonics

A source of error known to be present in vhf field-intensity meters employing broadband radio-frequency input circuits, has been briefly investigated. The error is caused by harmonic generation in the receiver resulting from insufficient selectivity, and nonlinearity of rf or mixer stages in the presence of a strong fundamental. The magnitudes of the second and third harmonics generated internally were determined as a function of the level of the applied rf fundamental for a receiver having one particular type of rf input circuit. Errors in the measurement of the fundamental, caused by intermodulation occurring in the presence of a stronger interfering carrier of different frequency, are also briefly discussed.