mikem wrote:
The digital Zeftronics
puts out continuous broadband RF (as opposed to the old mechanical
units that put out various pops and clicks at random times

The mechanical regulator operates like a buzzer. I have a
couple of sim setups here I use to teach the systems, and in a dark
room with the alternator operating you can see the small but constant
arcing between the regulator contact points. A capacitor across field
and ground kills most of the noise. The inductance of the field winding
and the resistors in the regulator maintain a semblance of constant
current flow even thought the points are bouncing, and the capacitor
reduces the arcing that makes noise and burns the contacts. Works
pretty well, even though it's primitive. I do like the constant-current
regulator idea, though failure is more likely to be instant and without
warning. Worn mechanical regulators will start dropping the output
voltage or might stick occasionally.

Dan