Apologies for asking too many (silly) questions), but I am not an electrician, only having very basic knowledge of electrics.
First - the mention of voltage "spike" - is this a spike above the normal 28V or a spike as in non-cosistent or sudden jump in voltage, but not above 28V that is damaging to the radio?
Secondly - back EMF - correct me if I'm wrong - Back EMF occurs when the flow of current suddenly stops and that's when back EMF comes in? And this back EMF causes a sudden "spike" in voltage?
Third - As the starter is engaged, the carbon pile voltage regulator 'tries' to increase the voltage by reducing the regulators "resistance" (but to no avail since battery voltage is already low due to high demand by the starter). However, when the starter no longer needs the high current flow, the voltage from the battery will return to normal, but the voltage regulator did not regulate quickly enough, causing the voltage to actually be above the normal 28V momentarily. Is this possible?