I agree with RCIGN1, PCM is not necessary. You can get by very well with PPM if you take proper precautions. Even if you use PCM you should take those same precautions as PCM does not ignore interferance, it just masks some of the interferance some of the time and; if you have the fails safes set up properly, will sometimes save a plane which experiences interferance problems by retarding the engine or stopping it thus ending the interferance if it is caused by the engine or vibration from the engine.