Hi,
just tested my zbitx with 9v ps and 2 w output and 20% rate in wspr.
Backplate got extremly hot that I was able to hold it in hands for less than 5 seconds, what means over70 degree c out of my personal experience.
Had to lower output to 1 w and 10% rate to give enough cooling down time. Will check with a temp probe later.
Best solution would be to change the backplate to a real heat sink I guess.
'73
