[Test-Equipment] FS: Heath IM4180 FM deviation meter

[James Duffer]

> > How arcane. Yes, the math works, but try looking at it with just an> RF power instrument: FM envelope amplitude is constant, and that's why> one can use a non-linear PA, like Class C.> 73 de Mike W5VSI>  I was under the impression that the reason a FM signal applied to a Class C amplifier (a non-linear device) was not distorted, was that any instant of time only one frequency was applied, while in AM more than one frequency was applied at an instant of time resulting in a mixing action producing distortion.
 
I am sure there may be a better way to explain this. but when a single sinusoidal frequency is applied to a class C amplfier no distortion, but apply two sinusoidal or a non-sinusoidal frequency (contains more than one frequency) you will have intermodulation (distortion).  This seems to indicate that in FM you would have only one frequency at any instant of timel.....right?
 
73, Jim wd4air