HF BACKGROUND NOISE MEASUREMENT IN HF ENVIRONMENTS

摘要

2102200 9219981 PCTABS00017 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 functions of frequencies. A frequency surveillance apparatus is also disclosed.