PSK31 Getting Started

This information should get you started receiving PSK31. If you want to start transmitting, you'll probably have to build a small interface circuit, depending on your radio. That's beyond the scope of this short article, but soon I'll include some text and pictures on how to build an interface.

If you haven't yet connected your HF rig to your PC, it's trivial. To be able to decode (but not transmit) PSK31, (and depending on your radio), all you should need is a cable and an adapter. If you have a decent cable collection, you may have what you need on hand. Or, for about $7 at Radio Shack, you can get set up.

• The Cables

I have a Yaesu FT-847, which has a 1/8" stereo plug on the back that outputs a fixed level received audio, and accepts transmit audio and PTT. To connect the radio to the sound card, I used a 1/8" stereo cable (RS #42-2475, $4.49), and a RCA to 1/8" adapter (RS #274-378, $2.49). Plug the 1/8" stereo connector on the cord into the packet connector on the radio, plug the left (red) RCA of the cable into the adapter, and plug the adapter into the line-in jack on the soundcard, and with a little (free) software, you're ready to starting listening to PSK31!

• Initial Audio Levels

You'll probably need to set the line-in input level for best results. Double click the speaker icon in the lower right hand side of the screen. Under 'Options', select 'Properties'. In the 'Adjust volume for' box, select 'Recording', then click 'OK'. One of the sliders should be labeled 'Line-in'. Click the 'Select' box at the bottom so that there is a check-mark in the box. Adjust the slider to about the half-way point.

• Using The Software

Go to the "official" PSK31 homepage, and download and install either the MixW32 demo version from WA2VOS' page (I personally prefer MixW32, and it's what I'll be using below), or the P31SBW software by G3PLX.

Start the MixW32 program. Click the 'PSK' button in the lower right of the screen. Make sure the that the 'aut', 'afc' and 'spec' check boxes near the bottom are checked ('sq' will probably be checked automatically after 'aut' is checked. This is normal). The frequency displayed in the box on the right doesn't matter.

• Initial Tuning

On the HF rig, open the squelch fully, tune to 14.070.150 USB, and adjust the volume to a reasonable listening level. This is the place you're most likely to find PSK31 activity, as it's the calling frequency. If everything is connected correctly, and you've selected the sound card settings, you should see a "waterfall" display in the lower left corner of the MixW32 window.

The waterfall display is a spectrum display of the audio signal being received. It should look like random green and yellow colors. If you see a fairly solid looking vertical double yellow line, with the center possibly tinged with red, then it's quite probable that you're seeing a PSK31 signal. Position the mouse over the center of the double yellow lines, and click the left mouse button. What you're listening for is a sound like this (164 KB). The image below shows a good solid copy PSK31 signal.

This is from a QSO between VE1VVV and WA2RSX, on 14.070.150, around 21:34 UTC on 11/30/99. I was getting about a S1 indicated signal. VE1VVV was in eastern Canada, WA2RSX in New York. I was monitoring from north Georgia.

At this point, assuming you've found a signal, you should see text start appearing on the display. If not, check the items below. If you still can't get it going, consider asking your friendly computer geek or fellow ham for help. A call on the local repeater will probably get more offers to help than you can use.

• Fine Tuning The Audio Level

Once you've started receiving text, and know what the signal should sound and look like, use the line-in slider control to adjust the input level until there are just tinges of red in the signal. This should coincide with the bar-graph display next to the slider just barely showing a red bar occasionally. Anything more and you risk overdriving the sound card. While this won't do any damage, it doesn't help. With a distorted signal into the sound card, the program will have more trouble trying to decode the signals.

• Filtering

Now try tuning around. The majority of activity seems to be between 14.063 and 14.080. If you have a narrow CW filter, or DSP, experiment with that. On the FT-847 with the narrow CW filter and the CW sidetone set to 700Hz, I tune the desired signal to 700Hz on the waterfall display, enable the narrow CW filter (which knocks down everything outside about a 1000Hz bandwidth), then enable the DSP filtering. (Set menu #10 to 25 Hz for best results). With these options set, the waterfall displays a signal that's about 100hz wide, with total black on either side. I've decoded QSOs that I can't even hear! It's pretty amazing.

This is from the same QSO as the previous image, with the filtering set as mentioned above, and the spectrum display setup as mentioned below. Notice how the signal is centered around the CW sidetone frequency of 700Hz.

• Options

The program has a lot of options you can explore. Some are not very obvious at all (there is a 'manual.txt' file in the directory the program was installed into, but it's pretty lame). For instance, I prefer to see a wider spectrum display. This can be changed by clicking the butterfly icon in the upper left, and selecting 'Setup'. On the 'Spectrum' tab, set the 'Spectrum start' value to 0, and click the 'x1' button in the 'Zoom' box. Now click on the 'Misc' tab, and check the 'Large screen' check box. Click 'OK', and you should see a screen with a wider spectrum display.

Try exploring the other tabs. Once you're capable of transmitting, you can set your callsign, etc in the 'Personal data' tab (note that these will not be saved unless you have the registered version. One of my beefs with this program is that nowhere is it mentioned the difference between the demo and registered version.) If your rig is capable of computer control, MixW32 appears to be able to control a number of them (there is little support for Yaesu rigs, however). On the main window, try clicking various areas. There are a lot of options I've never tried, such as logging.

• Registered vs Unregistered Version

Regarding the unregistered deom version vs. the registered version: The demo version (as of 11/30/99) was 1.23. The available registered version is 1.28. There are quite a few changes listed on the WA2VOS page about what's new in 1.28. Nick seems to churn out new additions fairly often, so a version newer than 1.28 is most likely available. It's probably worth the $49.95 to register it, although I'd prefer to see a better demo version before I part with that much cash. It's also a nuisance to buy the program, since Jim doesn't take credit cards, or net cash. In this day of e-commerce, it's unusual to find a product where you actually have to mail something to get ahold of it. Because of this, I'm still running the demo version.

• What To Do Next

Now that you've got your PC decoding audio from your radio, you can experiment with a bunch of other modes. There are CW decoders, SSTV programs, WEFAX, HF-FAX, all sorts of stuff. Check back on the previous page for links to other resource pages, or click here for VA2SF's page with a large list of software links.

• Tips

Here are some tips in case you're having trouble:

• If the display remains black, it indicates either that audio is not getting from the radio to the soundcard (perhaps you need to switch the adapter to the other channel, or check your wiring), or that the sound card is not configured properly. Explore the configuration of the sound card, and check all the settings. If audio is coming into the sound card (even static), the bar graph next to the slider should be showing some activity. Be sure the Line-in input is selected.

• Remember that 14.070.150 is 20 meters, which pretty much closes down after sunset. There is supposedly activity on 1.838.150, 3.580.150, 7.035.150, 10.140.150, 14.070.150, 18.100.150, 21.080.150, 24.920.150, and 28.120.150, but I've had best success on 14.070.150.
• The software runs fine under Windows-NT. I've not experimented with it under Windows 95/98, but configuring the audio properties should be basically the same.
• While you're only receiving, remember that if your transmitting (i.e. tuning up, or whatever), operate only within your license class. While technically you should be able to operate PSK31 in any of the CW bands (since the rules say CW operation, NOT Morse code), most likely no one will be listening for PSK31 there.
• Once you're ready to transmit, you may want to work someone local. Many hams can operate 2m sideband, so consider setting up something local to experiment with (especially if you are a Novice or coded tech).