Xantech is in California (Southern I think). I would also check with Pioneer to verify that it is indeed high frequency that is the problem. I do also know that Philips engineering is aware of your problem and is considering the solutions, although I still think the question is what carrier frequency? Xantech may have the answer on this. I'm not sure but
www.xantech.com might be worth a go. I'll also check at my end.