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TGXL Interconnection with a K3 using RS-232 for CAT Frequency Info

It is my understanding that the K3 can interface with the TGXL using Kenwood protocols. That said, it appears that the K3 has a contention issue with TXD. As I understand it, the TGXL tuner requires the TGXL TXD line (TGXL CAT Pin 3) to be connected to the rig's RS232 port, so that the TGXL can send commands to the rig. It will not be able to do that when connected to a K3. 

It can work for Kenwood radios because the USB and CAT connectors operate independently, so only one device (a PC) can connect to the rig's TXD pin, not two devices like PC and TGXL. 

Is the TGXL designed to track a rig's frequency using RS232 "listen only" mode (just monitoring the RXD line, Pin 2) like other products do? If not, then I assume there is no way to make the TGXL track a K3 via CAT. (This assumes that PC software like WSJT-X or a logging program is connected to the K3. 

Is this why the TGXL manual shows using BCD for Elecraft rigs instead of RS232.

Can the TGXL track in listen only or AutoInfo mode, with no polling commands sent to the rig, no connection via TXD pin 3?

Any help would be appreciated.


Rick N0YY


  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    The amp needs both RXD and TXD. It will not work with splitting the RS232 using a Y cable or SBox. The amp polls the radio by sending a command to the radio, requesting frequency. It can also poll radio using MD; CAT command to get mode to set MeFFA automatically (AB vs AAB).

    Using BCD will work but it will not set bias mode of amp automatically (AB vs AAB).

    There are ways to split the RS232 by feeding it to the computer then use a program from Eterlogic called Virtual Serial Port Emulator (VSPE). You would also need a USB to serial cable The program creates a bridge between the USB from radio and the USB to serial adapter from PC to amp. Then the program can create a virtual serial port for use by all your programs, including being able to use your logbook, Win4K3 Suite, and WSJT-X at same time.

    The limitation of serial protocol is why Flex has decided to go with LAN based equipment in all Flex/4O3A configuration.

    So, two choices. Add a USB to serial cable from PC to amp and buy VSPE or use BCD.


    Dave wo2x

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    I just noticed you are talking about the tuner. Sorry about that. It still requires TXD as far as I know.

    I have a K4D and use the VSPE solution I mentioned above. Takes USB serial from radio and then I have two USB to serial cables to amp and tuner. I also created the new virtual com port in VSPE that is connected to the bridge.


    Dave wo2x

  • Rick N0YY
    Rick N0YY Member ✭✭


    Thanks for your reply. My issue is a K3 (the K4/K4D works direct from the RS-232 port on the radio to the TGXL.)

    I need to do a bit more research to see if the VSPE will work for my situation. I have an SO2R station consisting of two K3 radios (one to be replaced with a K4D.) I also have the PGXL and the TGXL. I am not really concerned about mode setting for MeFFA, so for me using BCD from the K3 to the PGXL is OK. I can do BCD to the TGXL, but I lose the tune memories since I only have band info. As I understand it, the TGXL only establishes tune memories for CAT frequency exchange. I will admit I am not sure why polling would be required because any frequency change would be broadcast.

    Hmmmm.... still more info is required.

    Thanks again for your response. It provides a potential solution.

    Rick N0YY

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    Hi Rick.

    Contact me direct if you like. I have a white paper I wrote on using VSPE as I described. It was written for a Yaesu to share com port out of radio with an external PalStar tuner and multiple software programs. The concept would work for your K3 USB to PC with additional of a USB to serial cable from PC to TG XL. The white paper will give you an idea on what is involved.

    73 Dave wo2x

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