propriate nonlinearity, the out- put signal then observed at the difference frequency through a narrow band- pass integrating filter, and the result envelope-detected to recover correlation magnitude. Basore's conclusion was that the effect of noise in the reference channel was to reduce the receiver's output SNR by the ratio of the signal power level to the signal-plus-noise power level in the refer- ence channel. While the advantages of TR systems have since dwindled as a result of the development of synchronization techniques for the SR system, the dis- advantages of TR systems are to a great extent fundamental. Considerable experimental work on TR-NOMAC systems was performed at M.I.T. in the 1950-1952 time frame. Davenport's Group 34 at Lincoln Laboratory devel- oped several TR-SS systems, including one called the P9D. An HF version of the P9D was tested between Lincoln Laboratory and a Signal Corps site in New Jersey and, according to Davenport, worked "reasonably well." This led to the development of a VHF version intended for an ionospheric scat- ter channel to a Distant Early Warning (DEW) radar complex near Point Barrow, AK. Since the need for LPI and AJ was marginal, SS modulation was not considered necessary and the DEW-Line link was eventually served by more conventional equipment. A TR system study also was carried out by U.S. Army Signal Corps Capt. Bernard Pankowski in a secret Master's degree thesis [136], under the direc- tion of Davenport. Published at the same time as Basore's thesis, Pankowski's work details several ideas concerning jamming, multiplexing, and CDMA operation of TR-NOMAC systems. In particular, it noted that jamming a TR system is accomplished simply by supplying the receiver with acceptable alternative reference and data signals, e.g., a pair of sine waves in the receiver's pass-bands at the appropriate frequency separation. Bernie Pankowski offered three possible solutions to the jamming prob- lem, namely, going to the MF or SR systems which others were studying at the time, o