The original multiturn potentiometer inside the rotator (PST61 by Prosistel) was substituted by a US Digital MA3 absolute encoder, the specification can be found at :
The encoder used is the 12bits digital version with a PWM encoding signal(MA3P12), the ration between OnTime/TotalPeriod gives the current position
A MEMSIC 2125 accelerometer (the same component of the famous "level meter") was housed in a small waterproof box and clamped to the antenna boom as Elevation sensor.
The MEMSIC 2125 delivers 2 PWM signal (X,Y axis) with which calculate the relative gravity
For both elevation and azimuth the precision is in the order of +-0.2 degrees
The control box is in common with 23cm solved by using a Raspberry PI 2 board.
Only for 70cm there is an Arduino 2 with the function of encoders front end by timing each status variation of the 3 PWM signals and passing the result to the Raspberry vith a USB connection.
The rate at which encoders values are passed to the Raspberry is about one every 70 msec
A more detailed description of the control box plus the tracking system can be found at: Control Box and tracking