dison Nicholson spent part of his considerable creative energies in the development of methods for generating signals having selec- table frequency deviation from a reference frequency. Nicholson achieved this goal with notable accuracy by creating an artificial Doppler effect using a tapped delay line. Even though patent searches uncovered similar frequency-synthesis claims by the Hammond Organ Company, the resulting inventions [120], [121] were a breakthrough for Sylvania engineers working on SS systems. In addition to being used to slew the time base in the Hush-Up receiver, Nicholson's "linear modulator" (or "cycle adder") was an essential part of another system which Jim Green named the Buffalo Laboratories Application of Digitally Exact Spectra, or BLADES for short. Initiated with company funds in 1955, and headed by Green and Nicholson, the BLADES effort was originally intended to fill Admiral Raeburn's Polaris submarine communications requirements. Perhaps concern for the serious distortions that multipath could produce in long-range HF communication caused the ARC-50 DS configuration to 2It is convenient to recount this Sylvania system next, even though chronologically it would belong toward the end of this chapter. 0.2 usec PULSED AMPLIFIER 500 cps 200 cps 200 mc 200 cps OSCILL ATOR MODULATING 200 mc SIGNAL -200 cps +200 cps 500 cps 200 cps 200 mc P W 0.2usec BAL ANCED MODULATOR 2047 DIGITS= 2047 = ~ 500 cps 2047 DIGITS CARRIER FIRST PERFECT WORD WORD REPEATED PULSE DISPERSAL GENERATOR PATTERN GENERATOR CLOCK Figure 2.13(a). Green and Nicholson's SS transmitter contains an m-sequence generator, shown here as a "carrier-dispersal-pattern" gener- ator. Data is keyed onto this SS carrier by means of a 200 Hz oscillator. The lower of the two displayed output amplitude spectra corresponds to PSK suppressed carrier modulation by the 1 MHz-clocked m-sequence. The upper spectrum shows the effect of further spreading by mod- ulating the same carrier dispersal pattern onto .2 usec pulses. This latter technique fo