HF noise measurements - The Jindalee surveillance system

The HF surveillance system incorporated in the Jindalee frequency management system and operating over the frequency range from 4 to 30 MHz is described. The system is based on spectral analysis of the digitized output of a 20-kHz bandwidth receiver. There are two modes of operation: the spectrum surveillance mode measures the signal level on an omnidirectional antenna in all 13,000 2-kHz channels between 4 and 30 MHz; the background noise mode measures atmospheric noised levels on occupied channels at approximately 1 MHz over the same frequency range. Both modes of operation are discussed and representative plots of results are illustrated. The difficulty of comparing the measurements with the CCIR model is noted.