, total message time (TM) or hop time (Th), and spread-spectrum bandwidth (Wss) or hop frequency spac- ing (Wh). (The reason for the choice between TM or Th and Wss or Wh is tied to the choice between the two basic approaches to detecting hopped signals, as will become apparent shortly.) Section 1.2.1 presents the most pertinent For simplicity, we have not included the MFSK data modulation in (1.2) or (1.3) since it does not affect the basic form of these expressions or alter their spectral properties. Interception Detectors aspects of these endeavors and weighs the merits of the basic detector con- figurations against some practical considerations. In Section 1.2.2, the suboptimum performance of the detector types is evaluated against the substantial problems of time and frequency synchro- nization. The results show how little real advantage is likely to be gained by sophisticated channelized detectors over the wideband radiometer type detector. Finally, Section 1.2.3 begins with a discussion of some implementation considerations associated with wideband single-channel detectors and concludes with a presentation of some potential alternative detection methods, along with an assessment of conditions required for their prob- able use. 1.2.1 Ideal and Realizable Detectors In the following subsections, perfect frequency and time synchronization to the received signal structure is assumed. However, no presumption is made with respect to knowledge about the pseudorandomness of the signal's SS states. 1.2.1.1 Detectability Criteria The interceptor's task is to detect the presence of the communicator's trans- mission and attempt to identify the communicator's location within a spec- ified geographic area. Since the communicator's message or transmission is not time-continuous and occupies only a briefly interval, the interceptor desires a reasonably high probability that such a short message will, in fact, be detected if he is anywhere within detectable range. Thus, the detection probability, PD, should be close to unit