“The software only runs on MS DOS, not Windows... Due to the way files are accessed, you're unlikely able to run the RSS software and load/save files in Windows.” Radiotronics UK
The following methodology has been identified as the most stable for programming the GM300 on Windows 10.
Buy a $50 vintage laptop on eBay—something like a Dell Latitude with Windows 98 and a real physical COM port (DB-9 connector). This is the 100% guaranteed bulletproof solution. No USB, no drivers, no fuss.
The most reliable method remains using an old "slow" PC (e.g., Pentium 1 or 2) running native MS-DOS. Community Feedback
are recommended for Windows 10 as they have reliable driver support. Radio Interface Box (RIB)