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CESSB (Controlled Envelope SSB) increases the average-to-peak power ratio of transmitted SSB by typically 4dB without incressing distortion or bandwidth. CESSB is implemented on a few high end transceivers like Elecraft KX4, Flex SDR software and Apache Anan. Often the marketing says "double your talk power with CESSB!" or something similar. It's actually true. A CESSB transceiver running 5W PEP is equivalent to about 12W of standard SSB.

The details are that when you take baseband which is perfectly clean and non clipping, modulate to SSB, the Hilbert Transform (either explicit in DSP or inherent equivalently in the analog filter SSB generation process or any other how), causes overshoot of the amplitude envelope. Depending on the nature of the modulating signal it can be quite severe overshoot. In order to avoid RF clipping in the PA which causes splatter (adjacent channel interference) if is necessary to reduce the gain somewhere in the system; either the drive power, PA gain via Automatic Level Control (ALC) etc. A 100W PEP transmitter transmitting SSB will typically only have an average power of something like 15W, due to these sharp peaks which mustn't be able to cause clipping.?

CESSB prevents these overshoots occurring in the SSB Modulation process and therefore increases the average power.?

73 Hans G0UPL