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Thread: Ham Radio Serial Connection to Epson PX-8

  1. #1

    Default Ham Radio Serial Connection to Epson PX-8

    I have a Kenwood TH-D7A ( hand held ham radio that has a built in Terminal Node Connector (TNC).

    I want connect the serial output of the Kenwood TH-D7A to my Epson PX-8's RS-232c port and use the terminal program for simple packet communications.

    The TH-D7A has a very simple serial output:

    1 - TXD
    2 - RXD
    3 - GND

    So I should be able to connect it to the Epson RS-232C like this:

    Epson TH-D7A
    1 GND to GND 3
    2 TXD to RXD 2
    3 RXD to TXD 1

    What I'm trying to figure out is if I need to do anything with the other pins on the Epson so the serial communications will work with the PX-8's terminal program:

    4 RST (Request to Send)
    5 CTS (Clear to Send)
    6 DSR (Data Set Ready)
    7 DTR (Data Terminal Ready)
    8 CD Carrier Detect
    9 Chassis Ground

    Does anyone have any advice on this...

    Last edited by detnyre; February 15th, 2007 at 12:18 PM.
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  2. #2


    On the PX-8 side, I would short 4 - 5 - 6 together. Basically trick it into thinking that hardware flow control is working. I seem to recall that I had problems before I did that. Won't hurt anything to do it anyway.

  3. #3


    Thank you for the information!

    I will give it a try this evening and see if it works.

    Check out my blog at:

  4. #4


    Of course, think I would just try the 3 wire job first, works fine in most cases.

  5. #5


    I've been working with the cable for a few days and have not been having much luck.

    The PX-8 gives me a RS-232c communication error each time I attempt to the handy talk.

    I'm in the process of trying different cable combinations....

    Check out my blog at:

  6. #6


    Personally I'd connect dtr to dsr, and rts to cts, on the epson.

    does either the kenwood, or the epson, require software handshaking (x-on and x-off)? and have you got the baud rates, and data format correct. also are the levels from the kenwood rs232 or ttl?
    "Don't it always seem to go
    That you don't know what you’ve got ‘til it’s gone" (BANG )

  7. #7


    The Kenwood's TNC is setup with these settings:

    Transfer rate: 9600 pbs
    Data length: 8 bit
    Stop bit: 1 bit
    Parity: Non
    Flow Control: Xon/Xoff

    I'm able to set the RS232C port to the same settings in the PX-8's Config screen, except for the Flow Control.

    According to the Kenwood's manual, there is a command that I can send to the TNC to turn off the Flow Control, but I need a computer setup and communicating with it to set the command:

    XFLOW ON/OFF- Causes the TNC to perform software flow control when ON, or hardware flow control when OFF.

    I'm going to attempt to get the Kenwood working with one of my modern Windows laptops first, then turn off the Software Flow Control and try it again with the PX-8...

    I'm also going to see if I can find another communications program for the PX-8 that handles Flow Control....

    Check out my blog at:


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