From Mike Collins:
"You will need R58 for sure to Transmit, this is the bias for the TXPREAMP. The value should be 400 to 600 ohm or so, ideally near the 499 spec'ed."
750 Resistor R31, 1k Resistor R61, and 490 Resistors R57 and R58 (top)
R31, R61, R57, R58