Functional requirements of transmitting and receiving antenna have markedly different but directional characteristics apply equally to both antenna. A single antenna may be, and frequently be used for transmitting and receiving the signal simultaneously.
One of the biggest differences between a low earth satellite and a geosynchronous satellite is in their antennas. Transmitting antenna for low earth satellite requires less power (approximately 9,000 times less) in compression to geosynchronous satellite transmitting antenna. Transmitting antenna transmits the energy in one direction for reducing the loss and this characteristic will decide the gain of antenna. Gain simply tells us how much more power will fall on 1 square meter (or square centimeter) with this antenna than would fall on that same square meter (or square centimeter) if the transmitter power were spread uniformly (isotropically) over all directions.