The paper presents the concept, implementation, and test operation of a modernized solar\nradio spectrograph for an investigation of the solar emission and solar bursts in radio frequency\nbands. Besides having a strong diagnostic significance for studying the flare energy release, the solar\nradio bursts can also cause strong interference for radio communication and navigation systems. The\ncurrent spectrograph for the Ondrejov observatory (Astronomical Institute of Czech Academy of\nSciences) was modernized by using a direct-conversion receiver connected to a field-programmable\ngate array (FPGA) for the fast Fourier transform (FFT) spectrum estimation and put into the test\noperation. The higher time and frequency resolution and lower noise in comparison with the existing\nanalog instrument were reached by the implementation of the latest optimal signal processing\nmethods. To reduce the costs for such modernization, the operating frequency range was divided\ninto four sub-bands of bandwidth 250 MHz, which brings another benefit of greater scalability. The\nfirst observations obtained by the new spectrograph and their comparison with the analog device are\npresented in the paper with future steps to put the spectrograph into the regular operation.
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