BPSK-31, imd = -18 db, about 6 dB of ALC Sound

BPSK-31, imd = -14 db, about 12 dB of ALC Sound

These are examples of what not to do on the ham bands.

In both cases the audio drive to the transmitter was set too high, either by mistake or because the operator thought that more power is better. When the audio stages of the transmitter are over driven with clipping then you might possibly see 3rd harmonic audio images of the psk signal. They will be 3x as wide.

Be careful when evaluating a received signal. The receiver might also be overdriven and result in similarly distorted waterfall signatures. You can always check your local signal path by inserting 20 dB of attenuation at the antenna. If things get better then the distortion is in the receiver and not in the transmitter.

You cannot achieve better communications by overdriving the audio on any of the digital modes that require linearity.  These include all of the modes that have an amplitude modulation component.  Some like Psk and Throb have both an amplitude and frequency or phase modulation component.  An overdriven signal may produce more decoder errors than a properly driven signal of lesser power. This is particularly true for all variants of PSK.

The only fldigi modes that are not subject to this are:  FSQ, IFKP, MFSK, DOMINOEX and THOR.