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Problems with PTT via SmartSDR CAT (foot switch)


My setup: Flexradio 6500, SmartSDR 3.2.39, Windows 10 21H2

I connected a foot switch for PTT to a serial port via SmartSDR CAT.

Sometimes the radio doesn't go on the air. There is no transmission power out.

But I can see the audio control and TX flag. See picture below.

If I then release PTT and press again, it usually works but not always.

Pressing MOX with mouse within SmartSDR does alway work.

Any idea?

Best Answers

  • Hardy
    Hardy Member ✭✭
    Answer ✓

    Update: This must be a timing bug within SmartSDR CAT.

    As soon as I enable "logging" the failure disapears. Disable logging reenables the failure.

  • Hardy
    Hardy Member ✭✭
    Answer ✓

    I got the answer from the help desk which solved the issue:

    >The CAT COM Port PTT was not originally designed for use with an external footswitch, though many have done this.

    >The most common cause of the issue you report is "keybounce" on the footswitch causing inconsistent operation.

    I put a 470 nF capacitor between the contact of the foot switch and got success.


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