To be certain I wasn't missing a end-transient, I reshot the 80 meter photo with the horizontal sweep at the same speed as Farhan had (5 usec per major division) -- and you still see nothing on the drain of the PA Mosfet.
I do not understand why Farhan's scope shows an incredibly fast transition of the TX line, whereas mine shows a discharge with a time constant of 5-6 microseconds.? ?
The TX line is being pulled down by the RPi output, pulling against mosfet gate capacitances mainly.? ? Not quite sure why mine looks slower than his.? But that could be partly why he saw oscillations??
Gordon?
