ATU is based on a PI Network. This design uses two Miniature Tuning Capacitor-AM from Rapid electronics . 1 pole 12 way rotary switch from Rapid electronics. One T68-2 Toroid core from Sycom  20 swg wire and two BNC sockets. The ATU work from 7mhz to 50 mhz. The Toroid coil is made up of 33 turns of 20 swg wire. The coil is taped every 3 turns. This sits on the back of the 12 way switch. The tuning capacitors have both oscillator and antenna connected together to give about 0-200 pf
Parts List

2 MINIATURE TUNING CAPACITOR-AM (RC) 12-0255 Rapidelectronics
1 1 POLE 12 WAY ROTARY SWITCH (RC) 79-0100 Rapidelectronics
1 T68-2 Toroid core Sycom
2 BNC Sockets
1 Box
1 20 swg wire