Good low cost spectrum analyzer. I purchased one (with Tracking Generator) as a floor diagnostic tool for RF_LINAC problems.

These machines use 10 or more high power RF amplifiers to accelerate ions. On one machine there was a strange audio modulation signal on the beam current that needed a root cause and fix.

Normal beam trace.

On each RF section there is a RF tap for adjusting the phasing and to monitor signal quality.

The normal spectrum should look like this below

but one RF amp of 10 had an internal modulation signal like this at high power that was causing the
signal on the beam when it should be a DC signal.

It's very easy to see this ~1KHz modulation signal on the 13.56MHz carrier signal with the RIGOL at 30Hz resolution and it's very hard to see that same modulation signal with a older low cost CRT based unit at the highest RBW resolution.

A latest software update to the RIGOL gives 10Hz RBW instead of 100 Hz and lower noise floor.
https://www.rigolna.com/products/spectrum-analyzers/dsa800/

Tracking Generator

 

@nsaspook
Where did you get this image? From a text book/manual or did you make this yourself?

 

@nsaspook
Where did you get this image? From a text book/manual or did you make this yourself?

View attachment 137629

It's from a google search for linac. Now that I look at it closely its not very good. Don't use for for an exact explanation because I used it just to provide a general visual reference of RF acceleration. The linac type used in my example was a different type below where each resonator has a separate RF generator, matching and phase control.