I was playing around a lot with the ignition I made. With the ignition running on the bench I tried to put a Futaba FM Reciever (Dual Conversion) and a GWS Naro (Single Conversion) at any place, even at 3cm of the ignition box, the spark plug wire or the spark plug and there is no interference at all. I tried to put the antena in the spark, no interference. I have done these tests on the bench using R spark plug.
With convencional spark plugs I can't use my phone and the calculator near to the bench makes sounds and print some numbers! (maybe messages from other planet)