The TTL circuit needs a common ground.
To unlock the full potential of the KT8900 (adding repeaters, setting squelch levels, and naming channels), you need a and the CHIRP or QYT OEM software . qyt kt8900 programming cable pinout
Here is the for the radio’s 2-pin K1 connector : The TTL circuit needs a common ground
This article provides the definitive pinout diagram, explains the wiring standard, troubleshooting steps for driver issues, and how to build your own cable. : Most cables use the Prolific PL2303 or CH340 chipset
: Most cables use the Prolific PL2303 or CH340 chipset. Ensure the correct drivers are installed to avoid "Interface not found" errors in CHIRP or the QYT software.
The radio’s TXD (transmit data) connects to the PC’s RXD (receive data). The radio’s RXD is actually carried on a separate logic line within the radio’s CPU, but in practice, the programming cable only needs the radio’s TXD and GND, because the PC sends data via the same pin (tip) when the radio is in programming mode? No — that’s a common confusion.