EESDR3 have a nice feature for working with the SPE Expert 1.3k-FA amplifier. I have both, the amp is EU version, second series.
This is a intersting setup to have the amplifier control the driving power of the SunSDR2 DX radio as it does not have a working ALC.
The idea is to use CAT for driving power control.

I am using CAT setup for Flexradio in the amplifier and EESDR3 RadioSync app for radio CAT using Kenwood TS-480 protokol
With the SPE CAT setup for Flexradio, each power mode LOW,MID,MAX for each band, you have to define the driving power to be programmed into the SPE amp.
This is explained in detail in the SPE manual and it is a MUST to study.

The amplifier is controlling the radio driving power when you have defined the power level in the SPE amp by mode and band.
When amplifier is in STANDBY the Drive can be 100% and 100W out. By activating SPE amp to OPERATE OP (Yellow indicator) the SUNradio Dive power is reduced to the preset level. It is fun to watch the Drive slider moving!

In summary: The SPE Amp can automatically control SDR radio driving power by using Flexradio CAT protocol in the amplifier and Kenwood TS-480 protocol in a radio not having ALC with a properly setup by using CAT.
It turns out that it is only the SPE amplifier CAT protocol for Flexradio that will enable power control settings in this way. And it can talk to radio Kenwood TS-480 CAT. NICE!!!
73 de Erik SM0JCA