its not PWM, its digital (binary) data. when output is high, the oscillator will output 433MHz signal to antenna indicating binary "1", when output is low, oscillator will be off, no signal (carrier) indicating binary "0". if you want to probe the RF transmission, it maybe on the lowest via (after the white capacitor) which is i think the antenna below (or you should solder in one), but a 100MHz scope will show not much amplitude and you have to be very good at triggering the scope to capture those carrier stable on the monitor, ymmv.