and another one...
https://youtu.be/9nBShoROJb0
Why do people love this weird way of displaying a waveform?
It seems to be the default amongst YouTubers but in my experience, is not really something which is used in practice.
The signal input is conventional AM as is shown on the signal generator display & the normal way to display it on a 'scope would be triggered by the modulation, showing several cycles of the RF envelope at the modulation frequency.
Such a display allows a rough measurement of modulation percentage & linearity, which are things which would be important to someone using AM.
The display which is commonly used in YouTube videos is triggered at carrier rate, showing several cycles at that frequency, with the waveform amplitude variation shown as in the above video, which may disclose some information, but just seems to be used for a "pretty" display.
Magnova are at least using it to obtain the time interval between zero crossings, although my old HP22s calculator disagrees a bit as to frequency for that time interval, but why not just use a CW carrier?
On reflection, the weird display may be useful for obtaining a
very approximate measure for Incidental Carrier Phase Modulation,
The only time I have ever tested for ICPM was with an analog TV transmitter, & that was just because NEC showed how to do it in their handbook.