Sanity Check - Play back audio files

While waiting for my cable to arrive, I wanted to share my plan with the group and solicit feedback.

I need to start playing pre-recorded audio for a local net (amateur radio newsline). I looked at doing this with my FT-991a, but a couple of dead ends led me to look at how I might use my digirig and an old FT-7900R to solve the problem. Once the radio arrives, I suspect that my biggest challenge will be toggling of PTT on the radio (which doesn’t have intrinsic vox support).

My thought is that I can toggle RTS enabled of the digirig to “on” before playing back to the digirig audio device and back to “off” to stop transmitting. To avoid unnecessary troubleshooting, I play to approach with the following steps:

  1. with the cable plugged only into the radio side (rj12), short the TRRS connector to verify that PTT is activated
  2. With everything connected as it should be, use the Windows “mode” command to observe PTT being turned on and off when RTS is toggled
  3. On simplex frequency with a receiving station set up, use the Windows “mode” command to turn on RTS, play an audio file to validate that the audio is heard on the receiving station, and then use the Windows “mode” command to turn off RTS
  4. Write a small Windows application to provide more convenient way to toggle the RTS bit

Does that approach track or does someone have more directly applicable experience that would make some of the steps unnecessary?


KB9KMB - Kyle

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I do exactly what you want to do - I am net control sometimes for a net that transmits AR Newsline, and I use a Yaesu FT-7800 (pretty much the same as the 7900). I have a digirig connected between my computer and the rig. With the setup I have, it is very easy to transmit Newsline:

I use the Echolink program (free to download from and set it up in Sysop mode. The program allows you to play MP3 files and will trigger the PTT directly via the digirig when you start playback, and release it when playback ends. This works perfectly for me.

One other note - the FT-7800 I have seems to be a bit picky about the level of audio coming into the Data connector on the back. Most times, the volume settings I have are fine, but every few weeks, the AR Newsline is mastered to have maximum volume (waveform is fully compressed), and those editions overdrive the rig, leading to almost no volume heard by the others on the net. To solve this, I download the audio file from AR Newsline, and then open it up in Audacity for Windows (you can probably use any number of audio file editors for this). I check the file to see if the tops and bottoms of the waveform are flat (file is fully compressed) and if they are, I lower the volume level so that the peak is hitting around -6dB on the Audacity VU meter. Then, I have a pre-recorded short MP3 file I recorded for a station ID - I paste this short file into where the 5 beeps are in the middle of the AR Newsline file, and now I never have to play with the volume settings that are in place for my Echolink node, and I don’t have to stop the playback to key the mic to ID at the 10-minute break; I just sit back and listen. Oh, and the Echolink program will play its output through your computer speakers, so you can listen along with the audio that you are transmitting.

When you set up the Echolink program in sysop mode, you will need to setup the sound settings: choose the digirig “microphone” as the input device, the digirig output as the output device, your computer microphone as the local mic (optional), and your computer speakers as the monitor out. You will also have to go into the sysop settings menu, the TX Ctrl tab, and click on the RTS radio button for the type of TX control, and choose the com port associated with your digirig in the box below.

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Thanks for this excellent explanation.

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Not to dissuade you from using a Digirig for this, but I use a 991A and play (and capture) files regularly.