“When building HF radio kits, one of the final steps before going on the air is to connect a 50-Ohm load and measure the RF power output. I used to do this by taking measurements with an oscilloscope and then calculating the power using formulas and a calculator. I built this project to automate this step by using an Arduino to measure the RF voltage, calculate the RF power and display the results.
The circuit is relatively straightforward and it could be built using point-to-point wiring, but I decided to make the build easier by designing a circuit board. Referring to the schematic the circuit consists of a 50-Ohm load (made up of 8x 100-Ohm resistors) followed by a rectify/sample circuit which is then connected to an ADC (analog to digital) input pin of an Arduino Nano. The Nano is also connected via an I2C serial bus to an OLED display.”