I have one. It works fine with the 817. I set the 817 to 2.5w output and that drives the amp fully to its max output. Set the 817 to 1w and you get 20 from the amp, or 0.5w at the 817 and get 10w from the amp.
Antenna cable as described by Andy. I wish they’d used BNC connectors.
PTT cable from the ACC socket on the radio - some suppliers provide that cable and others don’t. Look up the pin number on the DIN socket to provide for keying the amplifier from rx to tx. It is labelled PTT on the manual but it actually means “hook the Earth return line of the relay of the external amplifier to this pin; when the 817 goes to Tx that pin is grounded so the amplifier is keyed onto tx”.
Using ssb with a speech compressor (Sotabeams lists them) has a similar effect to amplifying the output of the 817. Using cw also provides benefits over ssb, as you will read here in many threads.
Using cw with the amplifier gives you a killer signal! And using a compressor with the amplifier also works very well, but makes the whole setup sensitive to RF feedback, so take care with end fed antennas which usually result in a “hot” microphone. (It’s not a fault in the amplifier, it’s a fault in the antenna system. )
73 Andrew VK1DA/VK2UH