Sound card interface troubleshooting

A little more troubleshooting on the sound card interface moved the problem from the radio settings (which I think I have set properly…blog post about my radio settings to follow) to the interface board.

If I use fldigi to transmit, nothing happens on the radio. PTT was being triggered, but I think that was flrig triggering the PTT over the serial port, and the radio would have been listening on the mic jack instead of the data port.

If I ground the collector lead of the transistor on the board to trigger PTT on the data port and then tell fldigi to transmit, then I hear transmitted sounds on the radio and there’s activity on the signal meter.

For some reason, the audio signal going out into the PTT part of the circuit isn’t enough to make the transistor switch and ground the collector pin.

I’ll have to go through that part of the circuit to make sure i have all the components right and wired up properly. Worst case scenario I’ll just wire in a button switch to manually ground the collector pin for manual PTT.

Messing with the sound card interface.

Still don’t know if any of my signals are making it out of the radio.

Using headphones, I can hear the sounds fldigi generates in response to the text I “transmit”, so I know there’s stuff coming out of the laptop. The radio goes into transmit mode, but there’s no activity on any of the meters so I can’t tell if anything is actually being transmitted.

Matthew/W2MDW suggested using pskreporter.info to see if I get spotted. After sending out a bunch of CQs, test messages and trying to respond to someone’s PSK31 signal, it didn’t appear that any of the listening stations heard my signal as far as I could see.

The data port pinout for the TS-480 has pin 2 as the audio signal ground, which is unconnected in the PS2 cable I’m using. I wonder if that could be messing up the audio that’s going into the radio.

Update: I can see there’s about 70 mVAC of signal going out of the interface into the radio, so at least there’s something getting to the radio. Not sure how much needs to be going into the data port to make the radio send stuff.

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!

Sound card interface project

The next project on the workbench is this digital VOX sound card interface by Skip Teller/KH6TY from the March 2011 QST.

It’s a simple enough looking project, and I’m pretty sure that between what I had before and what Jason/NT7S sent me, I’ll have all the parts that I need. I might need to go shopping for a connector for the radio end of the interface though.

My plan is to build it on a piece of the perfboard I picked up at Radio Shack the other day. I’ll have to take the schematic and translate that into a circuit layout for the perfboard. Should be a fun exercise.

Heathkit IG-102 capacitor

The Heathkit IG-102 signal generator has this big 20 μF 150VDC electrolyic capacitor that has 2 leads on the positive side and one lead on the negative side. It looks like an axial capacitor, but I’ve never seen one with two leads on one side before.

20 uF capacitor
20 μF capacitor
20 uF capacitor
20 μF capacitor

Although it doesn’t seem to be showing any signs of failing, given the unknown age of the signal generator I thought it might be a good idea to replace it with something new. I’m thinking I should replace it with two caps, one for each lead on the positive side. Don’t have any axial caps in the parts bin, but there are plenty of 20 and 22 μF radial electrolytic caps. No new 20 μF caps though.

Might have to go shopping.