On my 857D I use it in DIGI mode. Menu 38 is PSK31-U. Try that setting. I don't remember where but I read that the radio should be in PSK31-U mode vs. USER-U. It might have been written in the manual. I would recommend one more thing. Try operating JT65 into a dummy load. This way you can play around with power levels and other things without causing willful interference. If you have a receiver, turn to your operating frequency and listen to what your radio is doing.