Well, the high "lowest output power" issue is a consequence of the limited
hardware capabilities (there is no fancy programmable attenuator, period).
For a work-around, you need a dirty trick:
Scale down the IQ samples. To make this work with PureSignal, you have to
scale up the TX DAC feedback samples by the same factor. This essentially
solves the problem but it remains to be seen whether the reduced
resolution affects PureSignal.
Of course, scaling down the IQ samples can be combined with the hardware
attenuator. So for a given drive slider, chose the largest attenuation such
that the signal is stronger than desired, and scale down IQ samples for the
rest (and scale up feedback with that factor)
@Reid: Is it this which you have in mind?