Primary standards for antenna factor calibration in the frequency range of (30 to 1000) MHz

There are two established methods for antenna calibration in the frequency range of 30-1000 MHz: The standard site method assumes ideal, calculable wave propagation conditions on an open-area test site with large metal groundplane. The reference antenna method uses a tuned half-wave dipole as a standard with calculable voltage at the feedpoint when exposed to a certain electric field-strength. The aim of our work was to minimize and precisely evaluate uncertainties involved in antenna calibrations using the two methods. In order to establish an accredited antenna calibration laboratory we took the following steps to obtain precision primary standards: We constructed an open-area test site that should exhibit wave-propagation conditions as ideal as possible. We constructed a set of precision, tuned, half-wave dipoles. We calculated site attenuation on an ideal open-area test site for our primary standard dipoles using the NEC-code. We finally measured site attenuation at 10 m distance in horizontal and vertical polarization. In the comparison of measured and calculated data we achieved an agreement of /spl plusmn/0.1 dB between 30 and 80 MHz, /spl plusmn/0.3 dB between 80 and 400 MHz, and /spl plusmn/0.5 dB between 400 and 1000 MHz for horizontal polarization. For vertical polarization agreement was within /spl plusmn/1 dB. We carefully analyzed the residual uncertainty and could dearly identify standing waves on the site by probing the field distribution along longitudinal and transversal axes. This influence can be taken into account by careful selection of antenna positions for the calibrations.