Thursday, May 13, 2010

An Univeral Radio Interface

All of the various digital modes out there require some sort of interface to your soundcard. Most of these interfaces use the serial port (RS-232) for keying, or some of the newer "Rig-blaster" interfaces can do provide that over a USB connection in the absence of traditional com ports on the newer computers.

There is still one thing lacking. Their own dedicated sound card. There is nothing more embarrassing than forgetting to disable your computers system sounds. And on the same token having to mess with the mixer settings each time is also annoying.

Thanks to the hard work of Steven Henke, W9SH and Jim Dixon, WB6NIL, they have ground work for a Univeral Radio Interface.

You can build your own using inexpensive USB sound FOB's/sticks. Or you can buy a pre-manufactured interface from DMK Engineering.

The basis of it all is the C-Media electronics CM-108, CM-108AH, or CM-119 USB interface chips.

PTT and optional Carrier Detect are accomplished using unused general purpose I/O lines of the USB sound devices chipset. Just plug this into a USB port of your computer, no other connections to the PC are necessary!

If you build your own, the sound fob will require some modifications to bring out PTT, block DC on the audio outputs, and attenuate the receive audio to match the microphone levels.

Unfortunately the number of programs that support this type of interface are presently limited. The good news is any one coding a program like ham radio deluxe or the like can easily adopt support for this interface. The channel driver is open and authored by Jim Dixon, WB6NIL and Steve Henke, W9SH.

If you an author of such a program you can find the definition in file chan_usbradio.c. I encourage you to add support for this inexpensive to build interface.

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