Agilent offers oscilloscopes capable of capturing signals of 30+ GHz in real time. What are the applications that would require such a scope?
Developing systems like this.
Some of the fastest oscilloscopes were used for capturing data from nuclear test shots. These were analog scopes, and EG&G was a leader in the field.
In the fastest cases, it was not possible to deflect the beam fast enough, so the data channel was used to modulate the intensity of the beam instead of deflecting it vertically. This was known as a streak camera, the output being captured on film.