[G0HZU_JMR]

It's a neat and versatile little device to have in the workshop so I'd advise caution when testing it to reverse engineer what it can do. Maybe fit an external series+shunt current limiting resistor network at port B of maybe 1000R in series with the generator and 47R shunt (across port B) to allow you to safely connect a function generator and play with typical modulator waveforms of a few volts pkpk?

You could then (safely) drive it with various waveforms from the function generator to create AM or DSB SC or BPSK or OOK? This would limit the diode current to a few mA. If you try generating BPSK with it I think it will generate classic/crude BPSK but this will have phase discontinuities at the switching points. So best to limit the rise/fall time of the square wave. The same applies to the OOK square wave. You can think of BPSK as two OOK waveforms (180deg out of phase) that are interlaced together. Each phase is effectively being on/off keyed (to be replaced by the other phase) so there will be a classic key click issue just like with OOK or morse code unless the modulation rise/fall time is shaped to minimise interference to other users.