ses by 1/8. Against the wideband detector, then, the communicator may effectively employ a joint strategy of low data rate and TH to the point where he is no longer willing to stretch the total message transmission time beyond some limit (likely dictated by some other operational considerations). The com- municator is also frequency hopping over the entire RF band, W but employing further pulse spreading by direct-sequence PN modulation of the instantaneous hop frequencies has no performance effect on the wideband detector. As concerns the FBC, lowering the communicator's transmitter power as a result of decreasing the data rate (but without altering the hop parame- ters) can be seen from (1.24) to effectively lower the intercept per-hop detec- tion S/N by A. On the other hand, the use of TH by the communicator causes the interceptor to raise his nd because N increases, requiring a smaller P in order to maintain the specified per-message PFA. However, since nd is not very sensitive to the increase, the overall effectiveness of this technique is slight. the proper strategy, therefore, is to lower the data rate and corre- sponding transmitter power as much as possible, again subject to some total transmission time constraint. Since the PB-FBC operates on the per-hop parameters, the perfor- mance being dependent on VWh/Th, anything the communicator does to increase this quantity directly affects the required intercept S/N forc- ing it closer to that needed for the wideband detector and discouraging Low Probability of Intercept Communications PB-FBC use (especially because of its much higher cost). Now, with pure FH, the per-pulse bandwidth is fixed at Wh = 1/Th. If, for a given a wider hop pulse bandwidth is desired, it must be brought about by a means of additional modulation, namely, PN spreading of the instanta- neous hop frequency in accordance with (1.19). thus the interceptor's SIN requirement appears to increase by VN. But it must be remem- bered that NT decreases with increasing per-channel bandwidth to NPN 