For the software to communicate with the radio without "Op Code" errors, you must slow down the emulation. In DOSBox, set the CPU cycles to exactly 191 using Ctrl+F11 or by editing the config file.
. He hit F2 to read the radio. A progress bar crawled across the screen, each percent accompanied by a rhythmic click-beep from the GM300’s internal speaker. 98%... 99%... Success.
This is the standard method used by amateur radio operators today.