The Aaronia MDF50400X Active Broadband Magnetic Field Tracking Antenna 500 KHz-400 MHz is suitable for signal tracking and field strength measurements with directly attached 40dB preamplifier, which can be operated by an internal battery or by the included USB AC adapter. This antenna measures the frequency range 500 kHz - 400 MHz. The MDF 50400X can be combined with any spectrum analyzer or power meter to perform as a highly accurate field strength meter. The calibration data of the preamplifier is stored in the internal EEPROM and can be read out via USB. Thanks to the high directionality of the antenna, the MDF is ideally suited for signal direction finding. The MDF 50400X can be used as a radio direction finder or to locate illegal or unwanted interference.