[Elecraft] Any ideas on how to run serial (DB9) and USBserial at the same time?

[Joe Subich, W4TV]

On 1/19/2017 10:53 PM, David Orman wrote:
>>> I need an additional RS232 output in addition to the connection
>>> to the PC for an external device that needs to track the vfo
>>> frequency of the KX3. I'd like to have the PC able to track what
>>> frequency/control what frequency my radio is tuned to, and at the
>>> same time have my external device also tracking the frequency the
>>> KX3 is tuned to.

David,

What is the external device?  Does it need to poll the KX3 or is it
satisfied by seeing the IF; and/or FA; responses to the logging
software?

RS-232 is a point to point protocol and does not allow for multiple
active transmitters at the same time. However, in some cases one
can attach a second "receive only" device in parallel.  The typical
connection is shown in the SteppIR "Y cable" schematic that I have
sent to you directly (ignore the jumper between pins 7 and 9 as that
is SteppIR specific).

If both the computer and hardware device must poll independently,
you might be able to get away with a "Modem Data Splitter" like
one of these from B&B Electronics: 
http://www.bb-elec.com/Products/Serial-Connectivity/Serial-Data-Tools-Adapters/Port-Splitters.aspx>
but you need to be careful that both the logger and hardware device
do not send data to the KX3 at the same time since the modem data
splitter is passive (diode isolation) and the data will be corrupted
if both devices transmit at the same time.

73,

    ... Joe, W4TV