Medium Wave Drive Test Antenna

The development of new standard such Digital Radio Mondiale (D.R.M.) on medium wave, requires to perform specific drive test in order to guarantee network quality in accordance to the international norms. Field measurements on travelling veichules, are not easy at this frequencies especially when done with electrical field antennas (eg. rods), because they ten to change the pattern depending from the ground distance and from the metal surface of the chassis, typically non ideal due the small dimensions.
The use of crossed magnetic loops antennas, avoids this issues because less sensitive to the ground capacitive effect and the reflection plane size. Due to this charapteristics, they have been largely used for years with MF and HF receivers and direction finders installed on ships and aircrafts.
MIL MFDL 0517 is an active crossed loop antenna, designed to measure the field coverage and propagation of medium wave networks (AM - DRM) and compatible to the ITU RECOMM. N° ITU-R 8S.703 (Annex 1 to Appendix 1).
The antenna consists of a couple of crossed shielded loops for HF, two independent pass band filters, two low noise amplifiers and one 90° hybrid combiner, to achieve the omni directional radiation pattern (see block diagram). The size of the loops has been calculated to achieve the necessary gain over the noise and to permit an easy installation of the assembly onto cars and vans, allowing measurements when travelling.