The resistor in the cap is not what stops the radiation..The metal cap and shielded wire alone do this..NGK makes a bakelite resistor cap to use with the CM6 spark plug..A properly set airplane doesn't need a shielded wire..Look at all the thousands of Zenoah and US engines flying around out there with the stock rubber cap and no shield at all..I fly with a 20 year old Proline AM transmitter/Ace receiver and have no problems..It can be done....