wer SIN threshold than a wideband energy radiometer of a mere 0.5 dB. Considering the complexity of a 125-channel PB-FBC relative to that of the one-channel wideband detector, the gain is clearly not worth the cost. Thus, the interceptor will opt to use the wideband radiometer. There is another pure-FH entry in Table 1.5 that warrants some view, namely, the minimum channel PB-FBC requiring 12,500 channels with Rh chosen to give NT = 107. The 10.2 dB performance advantage over the wide- band energy detector is very significant, and some form of implementation is therefore tempting. Postulating that mechanization of 12,500 channels is out of the question, even for a 10.2 dB S/N advantage, it may be logically asked: Is there some implementable realization that can attain some of the gain? Since it is mandatory that 12,500 channels be equivalently manifest, the only choice is to construct a PB-FBC with fewer real channels, say, by a fac- Table 1.5 A comparison detector performance as a function of hop rate and FH versus FH/PN (WssTM = 8 X 10°). RJR = 1000 R IR = 100 RJR = 10 Detector Type Rh1 (NT = 107) Rh2 (NT = 106) R (NT = 105) No. of No. of No. of Channels Channels Channels Optimum -17.5 Multichannel FH/PH FB-FBC -11.6 FH/PN Minimum Channel 12,500 -10.2 PB-FBC (f=1.25x10-3) = FH/PN +10.4 Wideband Energy FH/PN (Includes Average Time and Frequency Asynchronous Losses) Low Probability of Intercept Communications Table 1.6 Hopped-channel PB-FBC performance. Detector No. of Channels AS/N° (dB) PB-FBC 12,500 -10.2 PB-FBC 1,250 PB-FBC Wideband Energy tor of 1/K, and further reduce the integration time in each channel by the same factor SO that the 12,500/K channels may be "hopped" to different (unique) sub-band locations K times per hop pulse inteval. Table 1.6 sum- marizes the results of such a strategy. As can be seen, a reduction of the num- ber of channels by a factor of 10 (to 1250 channels) decreases the gain from 10.2 dB to 2.4 dB, while another factor of 10 decrease (to 125 channels) causes worse performance tha