Olaf,dk2lo wrote: ↑17 Feb 2021, 19:20 Nolan,
thanks for reply. I use a K3s with the USB-connection for digital modes and the serial port for CAT.
I tried already different CAT connections. Direct via RS232 port at my desktop and via USB to serial converter.
The problem only occurs in the "F8 window" and when mode is not changed. E. g. changing LSB on 40m to USB on 20m is working, but changing from CW to CW or from USB to USB does not work. No such problems in bandmap or cluster view.
So the question is, what is different in "F8 window" for my K3s configuration?
So you are using two cables from your PC to the K3S? One is via a USB cable from PC to the USB input port on the KIO3B and then you are also running an RS232 cable from your PC to the RS232/P3 input port on the KIO3B?
Both of those cables/ports are running the very same data into the K3S as they are copies of each other.
I've been digging into the Fred Cady book: The Elecraft K3S and P3.
One item Fred mentions is to be sure you match the baud rate in the PC setup to match what you have set up in the K3S at: CONFIG:RS232.
In light of your connections ... have you tried just the USB cable from your PC to the K3S?
Or as Terry has noted there might be some strange toggle that is causing "Murphy" to putz with things and that a fresh/clean installation might flush it out. Or course ... making sure you have backups.