If you want to use some shielded cable for the glow plug wire, you can use either coaxial cable for tv's or shielded A/V cable. This cable has one of the conducting wires wrapped around the inner one to cancel out any EMF. It sounds like your panel is the cause of the problem, as well as maybe the RX. If your panel uses pulse frequency modulation than it is sending a DC voltage at adjustable intervals to "create" the desired voltage. this would for sure create pulsed EMF's instead of a constant one, which would mimick an AC current. The whine i was referring to with high voltages is that buzz that you hear on things like neon lights, and crappy computer monitors. The sparking shouldn't cause a continued radio jitter but a momentary one. Anyways, hopefully this all gets fixed, I am surprised that if the manufacturer of the panel is using IC controlled PMF that they don't use a shielded cable as well. Goodluck!