Wanting to get into packet on VHF

Discussion in 'Ham Radio Discussions' started by KE0CPH, Sep 28, 2018.

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  1. KE0CPH

    KE0CPH Ham Member QRZ Page

    I have a Yaesu FTM-350AR and I know it can do some APRS stuff but I'm wanting to hook up my laptop to it.

    I have an easydigi that I can use to interface with it.

    I've been taking a look at some of the mic pinouts for my radio and had some questions. Before that, I know I can interface the easydigi to the mic by hooking up the PTT, audio in, and GND.

    Here's the question. Can I connect audio going from the radio to my computer via the mic connection? I'm doubtful and thinking I'll have to connect my laptop to the ext. speaker connection on the actual radio unit.

    Here's what I've found with the mic pinout:
  2. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I don't have time to research the answer, but most radios today use a mini-DIN connector to support external TNCs and external soundcard devices. My FTM400 does, but it uses a bizarro mini-DIN, and you need a special cable to convert from mini-DIN to bizarro mini-DIN. But it works fine with my external soundcard interface. I am not sure what your FTM350 has. Look in the manual for back panel drawing to see what it is. If it's a normal one, you can cut a PS2 mouse extension cable in half to get a usable mini-DIN.
  3. WF7A

    WF7A Subscriber QRZ Page

    If I understand correctly, you probably could but you'd most likely need a pad/attenuator to bring the voltage down so you don't overdrive the mic input in the computer.
  4. KE0CPH

    KE0CPH Ham Member QRZ Page

    I could just use a variable resistor, couldn't I?
  5. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I downloaded the manuals for the FTM350, and I found what I needed at the back of the APRS manual. It's an 8 pin DIN connector. To get from a normal 6 pin DIN to the 8 pin, you need the CT-140 cable. Where it says packet data, it's expecting audio from a TNC or soundcard adapter like the Easydigi. You probably want to use the 1200 baud packet receive line for audio from the computer. Of course, you would hook up the PTT and ground lines, too.

    I don't think you can use the Easydigi. At least the ones I saw relied on the VOX circuit in the radio to provide PTT. Most VHF/UHF rigs don't have VOX capabillity. You could make an outboard PTT circuit as explained here - https://www.soundcardpacket.org/7cableptt.aspx but the easy, if not real cheap option would be to buy an interface with the function built in. This one is inexpensive and provides the functionality, but you'll still need to make up a cable.
  6. KE0CPH

    KE0CPH Ham Member QRZ Page

    I've got a fairly old Easydigi so it does have dedicated PTT circuitry. IIRC, the FTM-350 does have VOX anyway.

    I've ordered a mini din 8 male connector to solder to some Cat 6 cable. I'm thinking about buying an ethernet wall jack to install under the dash on the passenger side of my car as well. That way I can just hookup my Easydigi into the ethernet jack with a single cable.
  7. WF7A

    WF7A Subscriber QRZ Page

    KK5JY likes this.
  8. KK5JY

    KK5JY Ham Member QRZ Page

    You probably want a DC blocking capacitor on both MIC connections, with the (+) terminal pointed at each device's MIC pin. Most soundcard mic connections, and radio mic connections, have DC bias voltage present to drive condenser microphones.

    As for levels, every external TNC that I saw had an internal pad, and instructions on how to adjust it for your radio. For your computer, you could use a variable resistor, or just adjust the output volume of the PC using software.
  9. K8JD

    K8JD Ham Member QRZ Page

    I tried 2M FM packet about 20 years ago,
    The only thing that was going on was hams exchanging video game software files on the air.
    I made ONE contact (sorry, CONNECTION) with another op about 7 miles from me.
    Then my TS700a all mode rig quit working, I think I fried a relay somehow.
  10. KE0CPH

    KE0CPH Ham Member QRZ Page

    I'm fairly sure the Easydigi has that. Otherwise I wouldn't know what the caps are doing on the mic in and audio out.

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