Sound Card Interface for Amateur Radio Stations:

As discussed above, PC's sound card is nothing but a modem, a term defined as "modulator" and "Demodulator". In short, it converts digital zeros & ones to sound tones and again, sound tones to digital levels. The soundcard interface detailed here is not different from many made by amateurs and available commercially. However, I have made it simple to construct and easy to use. On this interface, you have a 5pin DIN connector where you can connect your microphone and use a shielded cable to connect Mic, Mic ground & PTT to your radio's Mic Connector. A push switch is provided to change over from digital mode to microphone. And another push switch is provided to monitor Rig (Radio) Speaker output. (requires a speaker connected on this switch, not included in kit) You have choice to use this interface with or without DC Power. It will work equally well in both situations. Great for your Portable Rigs. Since most people do not require a PTT relay, Reed Relay may be ordered as an option. Two reed relay options are available: 5V and 12V. 5V reed relay is required where supply voltages are below 12V. 12V Reed Relay is standard with most desktop supply source of 12-13.8VDC. If 5V reed relay is used, a series resistor would be required, which may be placed instead of Diode D6 (1N4001). A new sound card interface, SC2, is under development. New design will be using RJ45 sockets and smaller SMT Transformers.

Picture of the Assembled Sound Card Interface:

Click the photo to enlarge

read more...