An anti-jamming subsystem for a jamming signal originating along the horizon includes an anti-jamming antenna with a horizontal reception pattern constrained to receive signals originating along the horizon. The subsystem receives the signals from the anti-jamming antenna and a reference antenna, which has a half hemispherical reception pattern looking skyward. The subsystem utilizes associated phase information to phase shift the signals received by the anti jamming antenna and produce an anti-jamming signal, and combines the anti jamming signal with the signals received by the reference antenna to produce signals in which the interference from the jamming signal originating along the horizon is actively cancelled and the phase and timing information of signals received by the reference antenna from at least higher elevation satellites is preserved. The horizontal reception pattern of the anti-jamming antenna may be circular or directional toward a known jammer positioned along the horizon.