The testing that I have done is that if you use a mic/headset with a 4-contact plug the FM radio antenna works correctly. I have not had any problem with any headsets while jogging and have not modified the jack. The problem is finding good stereo earbuds with a microphone. I have been looking for an adaptor cable that has the microphone built-in, with a 3.5MM 4-contact plug and 3.5MM 3-contact jack, similar to what I had with the Sony Walkman Phone (with the buggy proprietary Sony plug & jack). That way I could plug in any headset, including noise-cancelling headsets that I use when mowing the lawn. I have searched several times and can only find it in the 2.5MM version.