Digital anti-jam apparatus includes a CPU; N spectrum analysis and band rejection (SABR) modules, each receiving a digital quadrature signal input, outputting a spectral data output, and outputting a quadrature output with interference band rejected; the CPU first places the SABR modules into a spectral analysis (SA) mode, and upon detection of interference, places the SABR modules into a band rejection (BR) mode while the interference continues; N N-to-1 multiplexers, whose quadrature outputs are connected to corresponding SABR modules, wherein the CPU controls whether to connect an input of each multiplexer either to the quadrature signal input or to the quadrature band-reject output of any other SABR module; a (N+1)-to-1 multiplexer, connected to the quadrature signal input or to the quadrature output of any SABR module; and a frequency conversion module, that receives output of the (N+1)-to-1 multiplexer and shifts a spectrum of the digital quadrature signal input.