And how can I get it sounding perfect? Back off modulation or more amc?
Actually for being new to the scope you actually got it pretty good.
You might want to play with the slope/level/filter settings on the scope to get a more consistent stable triggering of the waveform.
Maybe you could tell me what model scope you have and what is the 'rd sampler' built into the dummy load that you speak of.
Also, Robbs' advice of using a constant tone is really good.
I use a 'tone box' as I call it.
Just a box with a speaker and a tone generator with enough power to drive the speaker to a moderate to low level. (something you can fabricate from misc electronic devices or assemblies)
And then just hold the microphone near the speaker on the box and press the PTT and then your waveform on the scope will be stable (once you get the triggering settings adjusted to suit you) and easier to interpret (and more meaningful).
But, utimately, you can only tell so much from looking at the waveform on the scope; Tonal quality, sound quality are not embedded into the waveform on the scope; Ultimately the sound quality of your transmission will have to be judged by other people listening to their radios while you are transmitting.