I have been searching already for a long time for a design of an automatic antenna tuner that can handle 100 Watts. It was a surprise for me that I only recently came across the N7DDC 7×7 ATU that was sold in all kind of combinations (PCB only, PCB with relays and torroids, completely assembled). It is a very compact design with different option to use an Oled display, adding buttons for Bypass and Auto tuning.
I ordered the PCB with torroids and some components via ebay. I had some questions and contacted the seller, named Yulia. The responses were always prompt and offered even to program the PIC 16F1938 and extra SMD high voltage capacitors.
The ATU is build around 7 coils and 7 capacitors that can be selected in different configurations depending on the antenna adjustment needed. Maximum inductance is 8.5 uH with 0.1 uH steps and maximum installed capacity is 1870 pF with minimal steps of 10 pF.
The building of the ATU was fun but soldering the SMD components may be a challenge. Still with normal tools it was possible to solder the tiny components. After the soldering was completed, I tested the ATU and worked correctly. I have chosen a nice aluminum case to cover the PCB and display.
Below are some pictures of the internal and external view.