When I first got my Zero II I could not get it to respond to UART, I2C or be recognized as a USB device. It seemed like the device was dead. I found this video by Ed March, aka Professor Vector that ...

reasonably cheap but very functional antenna analyzer that is a handful tool for tuning coax-fed shortwave ham radio and CB antennas. Parameters are similar to known RigExpert AA-170, but color TFT ...