1. A system ( 100 ) for detecting the presence of a narrowband signal having a bandwidth ΔF2 in a wideband frequency channel having a bandwidth ΔF1>Δ2, the system comprising: a receiver front-end section ( 110 ) adapted to receive a received signal in a selected frequency channel having a bandwidth ΔF1, to digitize the received signal, and to output a digitized signal; a time domain to frequency domain transformer ( 120 ) adapted to transform the digitized signal output by the receiver front-end section into N digital frequency domain components spanning the frequency channel; a spectral averager ( 130 ) adapted to average the power spectrum of the N digital frequency domain components over a plurality of samples, K; a filter ( 140 ) adapted to filter the averaged power spectrum of the N digital frequency domain components with a filter having M non-zero values spanning a bandwidth, ΔF3, where N>M and ΔF1>ΔF3; a statistics calculator ( 150 ) computing a mean, μ k , a modified standard deviation, β k , and a peak value, P MAX of the filtered, averaged power spectrum of the N digital frequency domain components; and a detector ( 160 ) adapted to detect the presence in the frequency channel of a narrowband signal having a bandwidth ΔF2 whenever P MAX >(k 1 * μ k )+(k 2 * β k ), where k 1 and k 2 are selected to provide a probability of detection, a probability of missed detection, and a probability of false alarm.