High Frequency Calibration of the 41 Inch (1.04 m) Receiving Monopole with and Without Connecting Counterpoises and with Different Sources

The 41 inch (1.04 m) monopole antenna is used from 10 kHz to 30 MHz at a distance of 1m from the Equipment Under Test (EUT) and its associated cables and so the antenna is invariably used in the near field. Many commercially available 1.04m monopoles are not calibrated but rely on a purely theoretical far field value based on antenna and buffer input capacitances. This paper shows that the antenna factor measured in the near field is different from that predicted for the far field and depends on the source of radiation (monopole or transmission line). Also the antenna factor of the receiving monopole and the E field incident on it, from a standard source of radiation, both change when the counterpoise of the monopole is either isolated from ground, connected to a ground plane on a table or to an underlying floor ground plane. Even more so when no counterpoise is used.