How it works
The MC1496 multiplies the carrier and message signals together, producing sum and difference frequency components at fc+fm and fc−fm with the carrier suppressed below −50 dBc. A crystal filter centred at 455 kHz then passes only one sideband. The Phase method alternatively uses two 90° phase-shifted paths — Hilbert transform of the baseband signal — and cancels the unwanted sideband by subtraction. Bandwidth is strictly fm(max), so a 3 kHz voice signal occupies exactly 3 kHz of spectrum. Power efficiency is maximum because all transmitted power carries information.
Key points to remember
SSB requires exactly half the bandwidth of DSB and no carrier power is wasted, so the power saving compared to conventional AM can exceed 83% for a single tone. Suppressed carrier level should be at least 40 dB below peak sideband power. Two generation methods appear in every syllabus: the Filter Method using a 455 kHz IF crystal filter, and the Phase Cancellation Method. Demodulation needs carrier reinsertion — a BFO at the receiver adds back the missing carrier. Figure of merit for SSB is 1, the best among all analog modulation schemes.
Exam tip
The examiner always asks you to compare SSB power efficiency with AM and DSB-SC — memorise that SSB saves 83% power for a single-tone message and be ready to derive it from the AM power equation.