> For slower modes (taking more then 12 hours), could it be
> useful to insert non-keyed sections to make a phase check
> each 2 hours or so?
> Maybe, but it would spoil the Eb/N0 capability of the mode.
Our way of generating the PSK signal already generates a very weak carrier component: At each bit transition, the phase takes a couple of seconds to swing around from -90 through 0 to +90 degrees (or vice versa). This creates short blips on the 0° real axis, on average a one second pulse every 80 seconds, equivalent to a -38 dB carrier. These blips are also causing the other spectral lines at clockrate multiples which are visible in the „6000“ window from the tree.
If you want you could create a stronger carrier component by slightly unbalancing the PSK phases. For example, switching from -80 to +80 degrees would create a sin(10°)=-15.3 dB in-phase carrier, while weakening the modulated quadrature component by only cos(10°)=-0.133 dB.
All the best,