After some chat with Charles i've made a plot of power curve of the combined RD06 and RD15 device...

gnuradio was used to ramp the output amplitude of a cw signal from the DATV Express.
A coupled output from the RD15 amp stage was fed into an rtlsdr dongle, the amplitude measured and plotted, the result is below.
The power is swept from very low o/p up to 9Watts.

Amplifier plot

In GNUradio right or wrong i've used the function probe to feed back the sawtooth signal from a signal source to a variable which is the value of the multiply const block.

GNURadio power sweep setup