Satellite communication widely uses antennas with reflectors to achieve high gain for the long-distance signal transmission. This configuration mainly consists of a feeding antenna and a parabolic reflector that should be optimized to obtain the most optimum performance. This paper investigates some factors affecting the antenna performances, especially gain, for a C-band satellite ground station, such as losses contributed by materials, efficiencies, and distance between feeder and reflector. CST Microwaves Studio is used to simulated and investigates the gain performance of the proposed antenna model. The feeder antenna is a 4x4 microstrip array antenna, which has gain and bandwidth of 13.7 dB at frequency 4.148 GHz and 3.794-4.528 GHz, respectively. The parabolic reflector diameter is 2.4 m. The analyzed parameters include gain and directivity generated by theoretical calculations and simulations. Theoretically, the maximum directivity is 39.85 dB. However, the simulated antenna gain is 31.1 dB. This reduced value is coming from the effect of efficiency, material losses, and unexpected radiation pattern from the feeding antenna. The proposed design has successfully increased the gain of 17.4 dB by combining a reflector antenna. This result still has a niche to be further improved by considering the affecting factors.