I have a Yaesu FT-857D radio in my car. I wanted a tuner to go along with it. I thought that since both the FT-857D and the FT-897D were almost identical from all outward appearances, including menus and rear panel connectors, that the AT-897Plus tuner would work on either rig. Well, I ordered one from R & L Electronics and discovered on page 9 of the instruction manual that it will NOT WORK on the 857D. Fortunately, I did not attempt to transmit or tune the rig when I had it hooked up, so no damage was done. The red LED on the front of it kept blinking. I knew this to be a warning sign that something was amiss. So, I unhooked it and put it back in the box.
I am trading it back to R & L for the LDG YT100 tuner, which IS compatible with the FT-857D and costs a little less. It is a bare-bones tuner with only one LED on the front panel, but I do have a good SWR/PWR meter hooked up in-line, so I will have some indication of SWR.
By the way, I really love the FT-857D rig for mobile use! I keep getting consistently good signal and audio reports with it. My antenna is the Little Tarheel II screwdriver antenna (80 thru 6M). My controller is the MFJ-1924 memory controller. My farthest contacts so far via mobile were Chita, Siberia (north of western Mongolia) and Pretoria, South Africa! Think of how exciting it would be to chat with folks like that on your way home from work! Give HF mobile a try!