Electromagnetic modeling and measurements of the 104 cm rod and biconical antenna for radiated emissions testing below 30 MHz

The purpose of this paper is to identify the optimum approach to grounding of the 104 cm rod antenna counterpoise in a radiated emissions test setup when testing below 30 MHz. Electromagnetic modeling is used to analyze various grounding approaches and empirical results are included to substantiate the analysis. Results of the analysis and measurements reveal a complete floating of the counterpoise to be the optimum approach for obtaining accurate measurements. Commercially available fiber optic isolators are demonstrated as an easy way to achieve isolation of the counterpoise. Additional results are included for the biconical antenna in the frequency range of 20 to 30 MHz.