The SATCOM QPSK Modem , Model No: ICS-SATCOM-DQMODEM-1109 receives data/digitized voice through RS422, encodes, modulates, up converts it to 70MHz IF and sends it through Radio. The received modulated signal at 70MHz IF is down converted, demodulated, decoded and sent through RS422 to the controller.For the design of the QPSK‐TDMA satellite communication system, analyses and experiments of modem systems have been made. When the burst‐mode QPSK signals with white Gaussian noise are input into the demodulation system, the demodulation system including the carrier recovery circuit, is influenced by noise. In this paper, the symbol error rate in the CPSK transmission, the code error rate in the DCPSK transmission, the unique word error rate (UWER) [for PSK transmission for both C and DC] which is important for the frame timing synchronization signal extraction, and occurrence probability of cycle slip in CR as well as its effect on the UWER, have been analyzed. Furthermore, experiments have been made and their results have been compared with the results of the analyses. Also, it has been shown by examples that the modem system of the QPSK‐TDMA system can easily be designed by using the results of the analyses.