Custom Products for the Digital Radio Amateur Enthusiast

Background -
Applications like VARA FM and SoundModem have been modified / upgraded to support PTT (radio keying) from the C-Media CM119A that we use to build our radio adapters from.
PTT is derived by toggling GPIO3 on the C-Media chip, and that turns on a transistor that keys the radio.

You may be interested in a specific guide for configuring SoundModem for use with DRA interfaces. Otherwise simple instructions follow below.
Click here to get the Guide

Unlike VARA FM, some extra stuff needs to be done to SoundModem to make the PTT work. The following instructions will help with that.

For PTT control on UZ7HO Soundmodem, you must download the PTT-dll.zip file from their website. Unzip this file and save it in the same folder where you saved SoundModem.

Then start SoundModem and select settings -> devices, under the PTT Port, select EXT.

The PTT-dll will check the system for DRA devices and allow you to select them. You may have to restart SoundModem, then back in the devices settings, you can select the Advanced PTT settings and the PTT.DLL panel will come up.

If you have more than one RA / DRA attached, you can select which one to use, and also test the device (causes it to transmit briefly).

All of this is also documented in the SoundModem user guide.

Email Kevin Custer for additional support.