Mike is exactly right.
This is the way it is done on the BITX20A, where there is place on the board for a connection to the relay outputs for TX and RX.
Using a bicolor led, the green will be lit when in RX and the red will be lit when in TX. Use a resistor to ground in the common lead
to limit current in the led, probably about 100 ohms (YRMV). Use the PTT relay, not the antenna switch relay (though it too could be used).
Any of the BITX rigs can be adapted to this mod in the same way. The V.3 series has the relay on the PA board. In all the versions PTT
activates this RX/TX relay. I am not sure why D7 is not across the coil; if it were a 14v zener (say), that would shunt the back emf to ground,
but it appears to be a 1N4148. Perhaps AF can explain further. It measures Vcc with or without PTT. Releasing PTT does give an
indication of voltage change, but it appears to be less than .1v.
Incidentally, adding a relay and a diode across the relay was one of the first mods to the BITX series. The original wasn't too specific.
john
AD5YE
