The inexpensive D7DDC design ATU-100 100 watt autuners advertized on Ebay and Amazon work great. 

$73 fully assembled: https://www.ebay.com/itm/134226040446 

$30 kit, no enclosure: https://www.ebay.com/itm/154835157861 

 

These can be modified to connect to the 4 pin Icom TUNER port.  Operate from your transceiver TUNER button: 

 Solder a 560 ohm resistor to via "A6" on tuner.  Connect to Icom TUNER pin 1 (_KEY). 

 Solder a 560 ohm resistor to "B" header on tuner.  Connect to Icom TUNER pin 2 (_START). 

 Connect "+" header pin on tuner to  Icom TUNER pin 3 (+12v). 

 Connect "-" header pin on tuner to  Icom TUNER pin 4 (GND). 

The current limiting resistors protect the tuner micro I/O pins from an accidental connection to +12 volts or ground. 

Recommend strapping 100pF capacitors to ground on these pins to keep out stray RF. 

 

Wnen the Icom transceiver senses 2 volts or more on _KEY when _START goes low,  the Icom transceiver automatically limits power to 10 watts while tuning (when _KEY is then driven low by the tuner).  On other transceivers, the operator mustmanually limit power to 10 watts while tuning, to protect the tuner's relay contacts. 

 

Description of the _START and _KEY signals on the Icom and LDG antenna tuners: https://hamoperator.com/HF/AH-4_Design_and_Operation.pdf 

Description of the TUNER connector circuit on the IC-7000: https://www.eham.net/article/18466 

N7DDC ATU-100 Technical Description: https://github.com/Dfinitski/N7DDC-ATU-100-mini-and-extended-boards/blob/master/ATU_100_EXT_board/ATU-100_Extended_Board_User_Manual_eng.pdf