Spark Plug electrical noise

Hey Bernard,

Wondering if you ever found a solution.  I'm going through the same.

Have new 33,000uF cap, new antenna and coax, grounded both ends of ignition wires (as specifically instructed by Rotax), have done extensive trouble-shooting and checked plugs are resistor, checked plug caps (and even covered plug caps with foil tape), etc, etc, etc.  

Turning ignition to one set of plugs or the other doesn't seem to vary radio noise.

Still tons of radio noise, varying with RPM, and interferring tremendously with even separate handheld, run on batteries with rubber-ducky antenna.

Holy cow this is hard to diagnose and fix.   

Do you have a noise suppressor in the radio line?

I am experiencing the same issues.  I have found it is highly directional.  Flying towards a fixed base station like ASOS/ATIS or TWR is the worst.  You can barely understand the transmission. Flying directly away from same station is perfectly clear.  Flying angles between varies the Intensity.  There is no doubt it is ignition noise.  I would think ROTAX would have a handle on this type issue by now.  Definitely not safe.  Not certifiable.