Jim, I can't speak for sure about CH because I don't have one to look at. However, I have three ignition system boxes right here. They are Yy Ti (Victor engines), CRRC, and XYZ. On all three, a continuity check between the braid and the battery ground reads zero ohmsgrounded. Thus, as I have said, the return path should be thru the shroud-to-the-braid-to the ignition box. No engine should be necessary to test the sensor as long as the plug is correctly stuffed into the receptacle (with a braid). Many old time ignition sites sell systems with a single wire and clip going to the plug. In such a case, obviously a seperate ground wire would be necessary.

Look at the ignition housings for all these systems. Mostly, they're plastic. And if the braid were not connected at the box end, then the mfg'er would provide a ground lug, or wire to go to the engine. I don't see that on any of my systems. The plug wouldn't fire if the braid wasn't connected at the box.

As for the RF shielding theory, I've heard it both ways. Ground one end, ground both. But most antenna aren't connected to the same conductor source at both ends, right?

Now, an update on the Saito's misbehaving ignition box. More careful observation on my part has revealed that when I plug in the 6V battery to the ign box, clicking (sparking) comes from BOTH the plug and the ign box too. They come rapidly at first, and then the sparking slows down until it stops completely after about, say, 1 minute max. It reminds me of a camera flash strobe whining as it's capacitor charges. Then stops when fully charged. Same kind of rate. After the sparking stops, running the magnet by the sensor causes the plug to spark and also gives that same click from the ign. box. I've never heard ANYTHING like that from any other ign box before. This seems odd, though the engine seems to run.

I swapped this Saito's sensor for a known good one, from a Victor engine (a Yi Ta ign box). The misbehaving ign box from the Saito behaves the same way with this new good sensor. So I preliminarily conclude the sensor is good, and the ign box is at least suspect. Perhaps, as I said earlier, damaged from having been run when the plug wasn't connected all the time. We ALL agree this is bad I think.

Here's a picture of an RCEXL box, with the same electrical leads as all the other kinds have. I don't see any independend means of connecting a ground to an engine.