Controller is based on Arduino-mini and the multi-turn (1k, 10 rounds) potentiometer connected to it. There is also servo controlled with three standard lines (power + steering). Additionaly, I equipped controller with button (blue one) which allows to power off the servo (in my case it was necessary to swith the servo off during transmission, becouse servo was being unstable).
Capacitor used in ths project has range of 12 – 367pF. There are also two manual switches, which allows to jump into 80m (1st one adding extra cap of 450pF in parrallel) and 10m (2nd one adds 5pF in series). Antenna has length of c.ab. 3m and 1/5 part of small loop in diameter. It could be necessary to extend a diameter of small loop for better SWR on 80m. Dimensions of capacitor allows to transmitting even 100W on 80m.
Please find an Arduino code or visit My Github
LCD HD44780 2×16 is connected to standard Arduino PINs (12, 11, 5, 4, 3, 2). You can use I2C line by modyfing the arduino code. Potentiometer is connected to Arduino pin (A0).
The servo driving is done with pin 9.
Here you can find my another version of Magnetic Loop antenna for higher band and less transmitting power. In this case there is a simple(but very slow!, it’s important due to very high antenna magnification factor )DC engine which turns the capacitor
Thank to Cezary 161BD850 for hard soldering the capacitor with connection lines.
Jakub/SP5TOF