To load firmware, the K3 RS-232 connector must be cabled to a computer serial port. If no serial port is available, a USB to Serial Adapter may be used instead.
A 9-pin "straight through" Male-to-Female DB-9 serial cable is recommended for firmware loading.
Do not use a "crossover" or "null modem" cable.
The cable must have a minimum of three wires: Transmit Data, Receive Data, and Signal Ground. Other RS-232 lines (Request To Send, Clear To Send, Data Set Ready, Data Terminal Ready) are not used to load firmware, but they may be useful during normal K3 operation for PTT or CW keying.
The female RS-232 connector on the K3 has jack nuts, so the male end of your serial cable should have screws.
If your computer does not have an available serial port, a USB to Serial Adapter such as the Elecraft KUSB may be used.
Choose a "real" RS-232 serial port if one is available on your computer.
