Fig. 9From: Software-defined radio-based HF doppler receiving system(Left) The Dynamic spectrum of the radio wave at the frequency of 5006Â kHz (JG2XA). The spectrum were observed on 18 January 2021 using the a digital and b analog receivers in Awaji. (Right) the signal intensities obtained by c digital and d analog receivers at 12 JST on 18 January 2021Back to article page