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

[Mike Manes]

Well, it's arguable whether an FM signal presents just a single freq at
a time. Fact is, the freq varies continuously, even during the period
of a single RF cycle.  But if the peak deviation is a very small fraction
of the RF carrier freq, then for all practical purposes, the Class C PA
operates as if the drive freq is constant.  The PA output tank Q must
be low enough to pass the full bandwidth of the FM signal, however.

73 de Mike W5VSI

James Duffer wrote:
>>> 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______________________________________________________________
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-- 
Mike Manes    mrmanes at gmail.com     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."
A. Einstein