Serial communication with a Kenwood TS-570D

I am setting up an amateur radio station at my local maker space, Decatur Makers.  Our transceiver is a Kenwood TS-570D.

I have spent a lot of time debugging how to get serial communications working between the Kenwood and a computer. Here is what I have learned. I have duplicated these results with two different computers (a Mac and a Linux box).

• The Kenwood connector is male.  Odd but true.  You need a straight through female-female DB9 cable to connect to a typical 9 pin serial port.   Some gender adapters and female-female cables are configured as null modem cables, so be sure.
• No handshaking or hardware/software flow control; BUT
• The RTS (request to send) pin must be set high on the computer for the Kenwood to respond.  It will still receive commands if the RTS is not set, but not send responses.
• The maximum baud rate that works is 4800 (8-N-1 or 8-N-2). Nothing faster worked.  Online forums confirm similar results.

When I do all the above, I can successfully open a terminal window and send CAT control commands to the radio.  If  you have never done this, these commands are the basis of amateur radio – computer communication for control.  Examples:

• Send FA; The radio will return FA00007123456; — where the long number is the radio frequency in Hz.
• Send FA00007121321; and the front panel of the radio will switch to 7.12132 MHz (radio does not display last digit, but it is stored)