it is BAV70 (without suffix S)
BAV70-S is also diode array but in 6pin SOT363 package

 

@crutschow
Where does one connect the scope’s or meter’s return or negative input? To earth ground like the image?

View attachment 371748

Just FYI, I built and tested the circuit as drawn above. The earth ground came from the scope probe.
The received signal is quite low and full of noise, but there is a distinct level change when the transmitter is toggled.