Frequency Calibration of Spectral Observation System of the TM65m Radio Telescope

In order to carry out the spectral observation with the TM65m radio telescope, the frequency calibration and test of DIBAS (Digital Backend System) are performed, it is found that it has a good performance. First, by injecting the PCAL signals, the frequency resolution, frequency drift and the stability of frequency interval between two spectral lines of the DIBAS backend are measured. It is found that in one hour, the maximum frequency drift of a single spike is 0.03 channel, the maximum fluctuation of spike interval is 0.05 channel. Then, by the observations on the H2CO maser and absorbtion lines of massive star formation regions, and the comparison with the results observed by the GBT (Robert C. Byrd Green Bank Telescope), it is shown that the results of frequency calibration are correct. Finally, by the OH maser observations in more than one hour toward W3(OH), and the methanol maser observations in more than 5 hours, it is found that the spectral profiles keep consistent, and the observational noise is consistent with the theoretical value, indicating the stability and reliability of the frequency calibration program.