Getting the best out of biconical antennas for emission measurements and test site evaluation

The biconical antenna has been adopted for EMC testing because of its broadband frequency coverage, 20 MHz to 300 MHz, and compact size. Potentially the antenna works very well, but some models have poor reproducibility resulting in perceptions of excessively large uncertainties for emission measurements and predicting pessimistic performances of test sites. The antenna can be accurately modelled, which enables normalised site attenuation (NSA) values to be based on more rigorous theoretical principles, and challenges the validity of the currently accepted practice of calibrating antennas at 3 m and 1 m distances. Antenna factor can be measured with uncertainties of /spl plusmn/0.2 dB, which together with calculability, make the biconical antenna a worthy reference antenna. The use of properly constructed collapsible elements is recommended for portability.