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QRP Labs QMX SSB beta firmware relased
qrp-labs.com
If CESSB is not switched on, in QMX (and in other transceivers), Automatic Level Control (ALC) will act to reduce the gain of the transmitter, to prevent the overshooting peaks of the amplitude envelope from driving the PA into highly non-linear clipping. In QMX, when CESSB is switched off, a simple ALC action is implemented which prevents peaks from causing RF clipping and temporarily reduces gain, which is held at the lower value and gradually recovers; in very much the same way as the Microphone AGC described above. For a long time I stuck with 32 but in the end I reduced it to 28, which does not detectably alter performance, because 28 works out with integer divisions from the system clock rate of 168 MHz whereas 32 didn't (and led to discontinuities in the audio sample stream).
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