T 1<\/code> drives Arduino pin 8 high, turning on the LED and enabling transmission. The command T 0<\/code> brings the pin back low, turning off the LED and returning the transceiver to receive mode.<\/p>\n![\"Schema](\"https:\/\/www.i8zse.it\/wp-content\/uploads\/2025\/02\/cat-ptt-1024x429.png\")
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If your shack mixes modern rigs with a few glorious vintage pieces, you already know how integrating them into modern digital workflows can turn into an exercise in patience. PTT control, in particular, is often the most delicate point: recent radios expose full CAT interfaces, while older ones offer no remote control mechanism at all. In these cases, relying on VOX is almost always a fragile solution, especially in fast-paced operating environments where switching must be precise and immediate-not to mention the constant risk of accidental transmission if a program outputs unexpected audio signals.<\/p>\n
The traditional method for handling PTT on vintage radios is to use control lines from old serial interfaces. It\u2019s a common, simple, and seemingly effective technique, but it comes with a well-known issue: during computer boot, those lines can enter unpredictable states, triggering transmission without any explicit command. This is dangerous, especially in shared operating environments or crowded bands, and it\u2019s one of the main reasons I eventually abandoned this approach.<\/p>\n
The solution I adopted instead is based on CAT emulation. I programmed an Arduino Nano to respond to a small subset of TS-850 protocol commands, limiting myself strictly to those needed to avoid conflicts with Hamlib, which I tested in version 4.3 on both Linux and Windows. In this setup, the radio only goes into transmit when the software sends an explicit command, eliminating any risk of spurious activation during system startup or abnormal conditions.<\/p>\n