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PTT when using USB microphone for PC voice into Flex transmit

k4rgn Member
The only way to trigger PTT when using a USB microphone is to manually click the MOX button in SSDR. The PTT port on the radio is ignored. Radio firmware should be modified to recognize the PTT port regardless of the source of transmit audio.
3 votes

Active · Last Updated


  • Neil D Friedman N3DF
    Neil D Friedman N3DF Member ✭✭✭✭

    If the radio’s PTT port is convenient, why not use the radio’s mic jack?

  • Gord-VA7GP
    Gord-VA7GP Member ✭✭

    I use an XLR mic, with a Distribution Amp to several radios. In this case, the mic doesn't have PTT, and even if it did, I would have to switch it among the radios. So my solution is to have separate PTT solutions for each radio. This may work for you in your case.

    I can understand if your USB mic includes a PTT switch - I'd want that to work in the "expected manner" also.

    Among my various PTT devices: footswitches, and hand-switches. I tried the SmartSDR MOX button and that was going to drive me InSaNe !

    Summary: While I agree with your desire to have PTT recognizable from USB port, the reality may require a PTT switch workaround. Fortunately, my FlexRadio 6400 (and quite like your model also) includes an easy-to-use PTT input.

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    @k4rgn , there is another way, but it involves a USB to RS232 adapter and a switch.

    Set up a PTT port in SmartSDR CAT (click the Add... button)

    Give it a name that is meaningful to you. It will pick an open serial port (mine happens to be COM16). At the RS232 end, put a switch from RTS to ground. Now you have a PTT button or footswitch that will work regardless of the source of audio.

    This solution does not speak to your assertion that the rig should always be able to key from the back panel, but it does provide a work-around if you really need it.

  • n8wrl
    n8wrl Member ✭✭

    Hey Ken!

    I'm looking at using this to trigger PTT via software. Am I correct in my assumption that I can connect a serial object (like .NET's SerialPort class) and **** with RTS/DTR programmatically?

    Not sure what else "PTT" as "Port Protocol" means.

    HNY and thanks for all you do!


    -Brian n8wrl

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Brian, I suppose that might work but if you are going to do it programatically, I would suggest the Flex API. There are a couple of routes that you can take.

    One is Node Red. Dave, WO2X and Alan WA9WUD have laid a lot of the groundwork to make that pretty easy.

    Another is C# and .net with the FlexLib library. I have some sample code on GitHub that will get you started if you choose this route.

    Finally, you can use your language of choice and use the API natively. It is text based and pretty straightforward to use. The other solutions take care of discovery and that kind of thing so that you don't have to reinvent that particular wheel.

    PTT in the port protocol box just means that CAT will interpret a switch closure (RTS or DTR) as PTT and send the appropriate API command to the rig.

    Good luck with your project!

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