The ATS-20 and its upgraded sibling, the ATS-20X, have become ubiquitous in the world of amateur radio and shortwave listening. As incredibly affordable, portable HF (High Frequency) receivers, they offer a lot of functionality for the price. However, many users find the out-of-box experience lacking—quirky menus, limited frequency steps, or a user interface that feels unfinished.
Many ATS20 units use the Si4732 chip, but the stock firmware sometimes misidentifies it as an Si4735. This causes band limits to be incorrect. Custom firmware correctly identifies the hardware. ats20 firmware
Conclusion
Choose a firmware version based on your needs. The ATS-20 typically comes with PU2CLR V1.1.5 pre-installed. The Unofficial User’s Guide to ATS20 Firmware: Unlocking
Flashing third-party firmware on the ATS-20 carries risks. USBasp Programmer (or an Arduino Uno configured as an ISP)