RTTY/AFSK Interface - Simulation in LTspice

Transmitting mode

With BJT (Q2=2N2222)

Voltage at rectifier's output

R_base sweep, values 1K, 4,7K 10K

With MOSFET (Q2=2N7002)

Vin, V_gate and voltage at the PTT pin of the FT-817

Voltage at rectifier's output

R_gate sweep, values 47K100K 220K 330K 470K 510K

Receiving mode

V_mic at 250Hz with maximum RX input level and RX level potentiometer in the central position.