Hi Group,
I am a fan of the AH-4 antenna tuner as it works well mounted remotely for the long wire antennas I drape over trees. But it is no longer manufactured. I recently purchased a AH-705 antenna tuner:
It turns out to use the same protocol as the AH-4. This link was very helpful to set it up:
I have been quite happy with the AH-705. I am "old school" and use 5W QRP and the interface on the back panel:
but I suspect it should work just as well with any AH-4 support provided by the IO board.
I have played with the atu-10 and atu-100, but found the tuning range more limited and lacked an easy weather proof assembly.
73,
Steve
kf7o