Brian, I had the same problem and found out the AH4 wanted the length of coax that came with it 16' 4" for it to work with the 706 I had it working with. I had a shorter piece of coax as I did not need the length to reach between the rig and the tuner. It would start to tune and then shut down ( 706 would quit tuning mode). Hope this helps. 73 Van WD6FGB