Abstract: In order to complete the upgrade of the BPM broadcasting system, it needs to monitor the field strength of BPM signal in far field. Therefore, it is necessary to research the transmission loss of the radio channel and construct an appropriate model. On the basis of analyzing the transmission loss model, both the influences of sky wave and ground wave on BPM signal are taken into account. The software developed in Labwindows/CVI is designed to calculate the field strength of BPM signal in remote field. The comparison between the measured and predicted value of field strength indicate the availability and accuracy of the software. And it can be applied to monitor the field strength of BPM signal in far field.

Key words: Transmission loss, BPM, Sky wave, Ground wave, Labwindows/CVI