(dB) PB-FBC PB-FBC PB-FBC 1,250 Wideband Energy Restating, then, the basic strategy that should be employed by the commu- nicator: 1. He should choose FH or FH/PN parameters SO that any channelized detector requires larger SIN than that for the wideband radiometer, or 2. He should choose FH or FH/PN parameters SO that, if any channelized detector requires lower SIN than that for the wideband radiometer, it is uneconomical to build because of the large minimum number of chan- nels needed. No channelized detector can be expected to be used against pure FH pro- vided that the hop cell bandwidth is set equal to the hop rate and all possi- ble hop frequencies are employed (i.e., can be synthesized). 1.3.2 Anti-Jam Measures The basis for good AJ performance was covered in Parts 1 to 3. It was established there that both spread-spectrum modulation and error-cor- rection coding must generally be used jointly in order to maximize jam- ming immunity. Table 1.8 tabulates for two different hop rates the maximum J/S ratios that may be tolerated for some typical cases of inter- est. 12 Each J/S entry has been calculated against the most effective jam- mer type and, therefore, represents the worst case jamming environment. As large a J/S ratio as possible is the desired condition that will, in turn, foster the most favorable LPI state. Without coding, it is clear that FH/PN at the lower hop rate Rh1 gives the best results. With coding, either FH or FH/PN at Rh1 emerges the winner. Since, with error-correction coding, the highest levels of performance are attained for all conceivable jamming situations, it should be preferred. Whether or not PN spreading is employed is unimportant as it gains noth- ing when the hop rate is low. Superscript(2)The numerical entries for this table may be calculated from the theoretical results presented in Chapter 2, Part 2. Table 1.8 Maximum J/S ratios as a function of modulation and coding methods. Modulation Maximum J/S = = (N /3R) 3 (R,/R)//E,/No) Technique for Pb = 1024 FH/8-ary MFSK FH/PN/8-a