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Amateur Extra · FCC ELEMENT 4

E2E03

Amateur Extra · FCC Element 4 · answer reveals automatically

EXTRAE2 · Operating Procedures
E2E03

To what does the "4" in FT4 refer?

AnswerFour-tone continuous-phase frequency shift keying

The '4' in FT4 refers to its four-tone continuous-phase frequency-shift keying modulation.