How to connect common DIN 6 pin radio data connector to USB serial converter

Discussion in 'Computers, Hardware, and Operating Systems' started by K4ZOT, Aug 22, 2019.

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  1. K4ZOT

    K4ZOT XML Subscriber QRZ Page

    I have an old TM-255A 2M radio that I would like to use on FT8. It has a common DIN 6 pin data connector on the rear that in the day was used for packet communications. See below DIN connector pin outs (tnx to WB1USN). I will be using WSJT-X FT8 software on my PC.

    #1 - PKD: TX Audio Signal
    #2 - DE: Signal Ground
    #3 - PKS: PTT to Key radio - connect to
    #4 - PR9: FM Demod out for 9600 bps (packet) at 500 Mv p-p
    #5 - PR1: Demod out for 1200 bps at 300 Mv p-p
    #6 - SQC: Squelch detect to prevent TX when frequency is busy - Ground when squelch is open, +5Vdc when squelch is closed.

    I need to match up the above pins to a "USB 2.0 to TTL UART 6 pin CP2101 module serial converter". See Amazon: https://www.amazon.com/gp/product/B075N82CDL/ref=ppx_od_dt_b_asin_title_s01?ie=UTF8&psc=1

    The serial converter pins are as below. See attachment below.

    Pin # - Pin Name - Type - Description

    1 - CTS - Input - Clear to send control input/handshake signal
    2 - RTS - Output - Request to send control output/handshake
    3 - RXD - Input - Receive Asynchronous data input
    4 - TXD - Output - Transmit Asynchronous data output
    5 - GND - GRD - Device ground supply pin
    6 - VCC - Output - +5V output

    Can someone inform me as to which data connector pins go to which serial converter pins. I do not want to mis-connect any pins and damage the radio. Any comments on this method are also appreciated. I believe this approach should work with WSJT-X, but I will probably have to install WSJT-X on a separate directory on my PC in that you can only direct FT8 to a single radio at a time. But, I probably will install the FT8 software on an old laptop.

    Thank you very much,

    Glenn
    K4ZOT
     

    Attached Files:

    Last edited: Aug 22, 2019
  2. AA4PB

    AA4PB Ham Member QRZ Page

    You won't be able to connect the USB/Serial converter to the radio's data connector. The data connector uses Tx and Rx audio tones while the USB/Serial converter uses +/- data voltage levels. What you need is a digital radio interface like the SignaLink-USB. It contains a sound card which converts between USB digital audio to/from the computer to analog audio tones to/from the radio. The SignaLink also contains a VOX circuit that grounds the PTT line when it detects transmit audio tones.

    You also need to check out a couple of other issues about that radio which I don't have the answer to. Will the radio send/receive audio to the data connector while in USB mode? The data connectors were typically used for a Packet TNC using the radio in FM mode. You need to be in USB mode in order to do FT8. You may need to route the audio to the speaker output and mike input in order to work FT8. The other issue is whether WSJT-x supports frequency control of that radio. While it is possible to set frequencies manually, it might not support such features as split/fake-it or automatically changing to the appropriate frequency when changing modes in WSJT-x.
     
  3. K4ZOT

    K4ZOT XML Subscriber QRZ Page

    Tnx for the response. So really the only solution to use FT8 with the radio is to buy a SignalLink.

    Glenn
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Normally you can use a USB sound dongle for audio. Or the sound card in the computer.
     
  5. AA4PB

    AA4PB Ham Member QRZ Page

    That's one option. There are several others that have a built-in sound card. You can also use the sound card in your computer and build or buy a simple interface to connect the sound card input/output to the radio and provide PTT control from an RS-232 port (or USB/RS-232 adapter). I just offered up the SignaLink-USB as a ready made one-box solution that is relatively simple to get up and running. Basically, the interface requirements for WSJT-x are the same as with other digital modes like PSK31.
     
  6. KK4NSF

    KK4NSF Ham Member QRZ Page

    Before I bought anything, I'd talk to Paul Jahnke from Jahnke Electronics. https://jahnkeelectronics.com/ He is The MAN when it comes to Kenwood Radios. If your radio will support CAT Control, he can probably provide the right cable to connect your radio to it. Even if it's not showing in his catalog, still ask him. He may be a ble to help you.

    As far as the Data Connection goes, I would agree that a SignaLink is the best way to go. While you can make your own cables, and just use your computer's sound card, that is a clunky way to go about it. Trust me, I've done it both ways, and would never recomment the direct cable method.
     
  7. K4ZOT

    K4ZOT XML Subscriber QRZ Page

    Thanks for your comments. I was going to acquire a Easy Digi interface card to install between the USB serial converter and the rear radio data terminal. Have you used this approach?
     
  8. K7MEM

    K7MEM Ham Member QRZ Page

    The USB to TTL converter that you have is good for Rig Control, but not very useful for audio connections. The only exception to that would be managing the PTT. On my interface, I use the CTS signal to toggle the PTT and the DTR signal for direct CW keying. These can usually be selected when you configure the software.

    The Easy Digi interface or the RigBlaster from West Mountain Radio could be used to get the audio to/from your radio and PC. But it is possible to wire directly from your PC to the rear connector. I made my digital mode interface, to my IC-735, before there were commercially available interfaces. I just control the audio levels directly on the PC. You can see it on my web page on ICOM IC-735 - Digital Modes. The PTT and CW Keying only requires a single transistor each. I built a RS-232 to CI-V interface as well, but I don't think you need it.

    Overall, interfacing a PC to a radio is pretty simple.
     
  9. AA4PB

    AA4PB Ham Member QRZ Page

    It's possible to feed audio into the ACC connectors on an IC-735 but that is a different radio than the TM255A. The connector on the TM255A was designed in the days of Packet Radio TNCs which operated in the FM mode. It is quite possible that the TM255A packet connector does not pass audio to/from the radio when in USB mode. You may need to use the mike and ext. speaker connections on the TM255A in order to pass audio in USB mode.
     
  10. K7MEM

    K7MEM Ham Member QRZ Page

    That will work fine too. On radios without accessory connectors that connect directly to the audio in/out, I use the microphone connector. I run my HTX-100 that way. You just have to be careful with the microphone input. Some radios use electret microphones which require power. To connect from a PC you need to isolate the microphone input with a capacitor.
     

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