[Elecraft] K3S PTT using DTR/DTS issue

[Lyle Johnson]

That won't work.  Nothing will be damaged.

The input signal group TO the radio from the outside world (RTS, DTR, 
serial data) are physically switched as a group between the RS232 buffer 
chip and the USB<-> serial chip.

In USB mode, data to the radio, along with RTS and DTR, will only be 
recognized from the USB port.  Data FROM the radio will be available on 
both the USB port and the RS232 port.  This allows you to use USB to a 
computer, for example, while having an antenna tuner or SteppIR antenna 
or other external devices "listen" to the radio data.

In the RS232 mode, all three signals are switched as a group to the 
RS232 buffers.  Again, serial date FROM the radio is simultaneously 
present on the USB and RS232 ports, though in this case the data on the 
USB port will only be meaningful if the RS232 port is set to 38,400 bps 
because the internal USB<->serial chip is set to communicate internally 
for 38,400 bps at all times.

The USB mode or RS2323 mode are selected from the RS232 menu.  If a data 
rate is displayed (4800, 9600, 19200 or 38400) then the RS232 mode is in 
effect.  If the display is "USb" then the USB mode is selected.

Similarly, LINE OUT audio (from the radio) is always sent to both the 
USB port AND the analog LINE OUT jack on the rear of the radio. if 
nothing is plugged into the LINE IN jack, then audio in LINE mode will 
be taken from the USB port.  If a plug is detected at the LIEN IN analog 
jack, then USB audio will be ignored and audio will be expected from the 
analog LINE IN jack.

I'm sorry if the documentation in the manual was not clear on these points.

73,

Lyle KK7P

> What I'm trying to do:
> 1. USB for audio and serial control.
> 2. RS232 for PTT keying.