Tell us about yourself!
your ORC photos and the DSO captures inside the PDF are not congruent, the waveforms and delays are totally different.¿why is there a delay between TX pulse and collector output?, the moment the TX pulse is sent to the coil, the RX pulse will also appear and make TX transistor stop conducting and put the collector to +V, yet in your ORC captures, the collector goes up after several mS.¿Is the 47nF value for the RX cap based on some time constant?, ¿what's the theory behind that value?(because the RC constant with the 1M R gives me 47mS)¿why use the transistor at all when you can also use the comparator as a negative peak detector directly?.
i see that in your coil variation photos there's one which has a large diameter(the entire plate) ¿how was it's performance?.Also, are you triggering the receive transistor on a negative pulse of the receive coil, ¿is that correct?(i'm really rusty on my electronics!).i'll see if i can get a single coil/no screen version based on this one too, with a FET drive(i'll also think on using a larger Vcc for the coil drive, maybe with a dc-dc converter, but the issue is that it needs a lot of power)