I measured the open loop gain of the FSS (as usual, I have multiplied the whole OLG by 10dB to account for the forward loop gain in the box). I used a source level of -20 dBm and made sure this was not saturating by changing the level.
Its clear that the BW is limited by the resonance at ~1.7 MHz. Does anyone know what that is?
EO resonance in the RC path?