HF BACKGROUND NOISE MEASUREMENT IN HF ENVIRONMENTS.

摘要

PCT No. PCT/AU92/00197 Sec. 371 Date Dec. 8, 1993 Sec. 102(e) Date Dec. 8, 1993 PCT Filed May 1, 1992 PCT Pub. No. WO92/19981 PCT Pub. Date Nov. 12, 1992.A frequency surveillance method for monitoring background atmospheric noise levels in unoccupied channels in an operating frequency band of a high frequency communication system. In the method, the unoccupied channels are scanned a number of times to obtain analogue signals. The obtained signals are transformed to a digital form and averaged. The averaged digital signals are filtered to remove substantially all radio frequency interference. Absolute signals are then produced by scaling or comparing the filtered signals with a known noise level. The background noise levels are obtained by further averaging the absolute signals. A visual display unit is used to display the background noise levels as a function of frequencies. A frequency surveillance apparatus is also disclosed.