Anyone have a problem where the voltage will drop randomly and fairly often?

I am having a problem where the voltage will drop causing the rpms to drop. It does it at idle and while cruising, but not really above 3k rpms. I am leaning towards the alternator, but opinions are welcomed.
Thanks.
Josh

 

Check the volt drop from the alternator charge cable to the + terminal on the battery. (engine not running)
If thats ok use your volt meter at the battery (engine running) and see if the voltage really is dropping.