KH6TY Sound card interface

It took a few hours at the workbench, but here’s the result of my attempt to build the digital VOX sound card interface by KH6TY.

KH6TY sound card interface v0.1
KH6TY sound card interface v0.1

Only one of the transformers and the perfboard I built it on were new. Some of the components were generously donated to me by Jason/NT7S, and the rest came out of my parts bins. The PS2 cable was harvested from an old Microsoft mouse, and I decided to reuse the connector on the board to make things easier. I also avoid having to deal with those thin wires.

Based on a comment left over on WB5RMG‘s blog entry about the interface, I used a 22μF capacitor instead of the 47μF capacitor in the original schematic.

It’s not the prettiest build (especially the back side where the connections are).

KH6TY sound card interface back
KH6TY sound card interface back

That blue wire at the top right and black wire at the bottom right don’t go anywhere. they’re just extra wires off the transformers. The ugly clump in the middle is where most of the connections to ground ended up.

Much to my surprise, it worked the first time! At least for listening anyway. I connected the PS2 cable to the radio, plugged in the USB sound card I got from Jason/NT7S and connected the interface to the sound card. Turned on the radio, tuned to the digital portion of 20m and when I fired up fldigi, I got stuff on the waterfall! I could click around to some signals and see them getting decoded. Most of what I saw was PSK.

Transmit also seems to work. I tried sending out a CQ and some test text and the radio went into transmit mode. I don’t now how well or if I’m getting out, or if my signal levels are adjusted properly. I could be splattering all over the place as far as I know.

One problem I was having with fldigi was that it would keep hanging. Not sure what was going on.

I’m quite excited about this, especially the fact that it appears to be working on the first attempt. Will need to spend some more time playing with it and trying to figure out how to get the sound settings on the laptop adjusted properly. This opens up some more ways to play radio!