A quadrifilar antenna is comprised of four radiators which, in the preferred embodiment, are etched onto a radiator portion of a microstrip substrate. The microstrip substrate is formed into a cylindrical shape such that the radiators are helically wound. Also etched onto the microstrip substrate is a feed network that provides 0°, 90°, 180° and 270° signals to the antenna radiators. The feed network utilizes a combination of one or more branch line couplers and one or more power dividers to accept an input signal from a transmitter and to provide therefrom the 0°, 90°, 180° and 270° signals needed to drive the antenna. For receive operations, the feed network utilizes these same components to receive the 0°, 90°, 180° and 270° signals from the antenna radiators and to provide a single output signal to a communications receiver. The power divider accepts an input signal and provides therefrom two output signals differing from each other in phase by 180°. The branch line coupler accepts an input signal and provides therefrom two output signals differing from one another in phase by 90°.