To get ready, he made a breakout board for 32-channel analog multiplexer device he wants to use. He put the project out on Hackaday.io and also has a video tutorial ... one output to 32 inputs.

The circuit will output about 0dBm into 50 ohms. The power detector is an Analog Devices AD8307 ... program to process the data from the Arduino. For example, here’s a plot of a 10 MHz crystal ...