Homebrew cable PTT issues

Hi all,

I am trying to get my Digirig (rev. 1.6) to work with a FTM-400XDE. The plan is to use VaraFM on 2m for Winlink.

I use the 10 to 6 pin DIN adapter from Yaesu and from there Digirig’s 6-pin DIN to TRS plug into the “Audio” connector of the Digirig device. Digirig is programmed (as per factory) to be able to PTT via the audio interface (COM+RTS) and not via CAT.

I can see both audio devices and the serial port (COM6) in the Windows device settings (running inside Parallels on a Macbook Pro). I have set these devices in VaraFM as soundcard and COM/RTS (COM6) for PTT. I have also renamed the audio devices in the sound settings and set the levels to the required values. I can hear the TRX audio coming from the FTM into the Digirig if I play it back via the Windows settings.

The problem: I am not getting the TRX to PTT (via Sound Card “Tune” or simply trying to connect in a VaraFM session). I have tried changing the FTM’s data speed, data band selections (using VFO B for all of this), switched off APRS etc. but the radio is not reacting at all.

In order to rule out problems with VaraFM I have also tried to set the rig to “none” in WSJT-X and selected RTS (COM6) as PTT method but nothing happened when I clicked “Test PTT”.

Does anyone have any info on how to set up the FTM-400 in order to work with the Digirig?

Thanks a lot and vy 73 de Leo (DL2COM)

In your case as well as in any other situation where PTT by RTS is not working as expected, the first thing I recommend is testing the cables by simulating Digirig’s PTT action. There is a quick and dirty method for that:

  1. plug the audio cable on the transceiver side
  2. unplug the other end of the cable on the Digirig’s side
  3. electrically connect sleeve to the nearest ring on the Digirig’s side


If radio keys up then the issue is on software/Digirig side. If radio doesn’t key up then the issue is with the cable or the connectivity between the cable and transceiver (incomplete insertion etc.).

Thanks Denis! I tried it and the radio does not key up when I short sleeve and ring. Note that the cable I got from your shop is TRS and not TRRS on the Digirig side. From there is goes into the Yaesu adapter and into the radio.


It sounds like you are using a cable that predates the PTT support. For hardware PTT support via audio socket you need Digirig 1.6 or later (check) and TRRS cables (nope?).

Ok it seems we have found the issue here. I will be in touch via email also about another cable I would like to order. Thanks again for your help!

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