While working with the uBitx V3 I finally got annoyed enough by the pop to fix it.
Basically copied from uBITX V4 but it still popped some..
Parts count 4:
2 1n4148/914 diodes.
1 10K resistor (any value from 10 to 100K really)
1 2n7000 mosfet
Why the second diode? The TX line is relay switched 12V and relays are not instant
they take milliseconds to physically move contacts. So the second diode to the T/R line
form the Raduino its the fast acting audio kill as that the command to the relay. The
second diode resistor is the hold until the relay returns to RX position.
TX muting with no pop, no thump.