European intercomparison of antenna factors in the frequency range 30 MHz to 1 GHz

In January 1993 an intercomparison exercise began in which 15 laboratories from nine European countries participated in the measurement of six antennas. The antenna factor and reflection coefficient were measured at a selection of frequencies in the range 30 MHz to 1 GHz. The project was sponsored by the European Commission under its BCR programme, with NPL as the pilot laboratory. The main purpose of the intercomparison was to find out whether national laboratories could calibrate EMC antennas to an uncertainty of better than ±1 dB at a confidence level of ⩾95%. The results showed that an agreement of ±1 dB was a reasonable target. There were 38 mandatory antenna factor measurements. All of the results of four laboratories and 92% of the results of three more laboratories were within ±1 dB of the averages. More than 95% of the results of three other laboratories were within ±1.5 dB. With the experience and information gained from participation in this intercomparison most of the laboratories should be capable of meeting the target of ±1 dB. Uncertainties of better than ±0.5 dB have been achieved by the pilot laboratory. This is a realistic future target for laboratories that offer services for the calibration of EMC antennas