PSK31, in my opinion, is one of the neatest new modes to come out of the 1990's. Consider some of it's features. The bandwidth is as narrow as CW so it gets through in the toughest of band conditions ( just like CW). It's cost is very low due to the fact that an existing PC will probably work fine along with free downloadable software. The only hardware needed may be available from your junk box, or from Radio Shack at low cost. You can even go mobile with PSK: PSK Mobile-In-Motion. But the real charm of PSK31 is the ability to ragchew. Ragchew endlessly keyboard-to-keyboard to anywhere in the world.

Fig. 1. This is a snapshot of the screen from my favorite downloadable free software, Digipan: I have just had a very quick QSO with Carlos in Portugal during the 2001 TARA PSK Rumble contest.

This short QSO is very unusual on PSK. Typically it is a ragchew mode where a QSO can last 45 minutes easily. That's a lot of fun when you're talking to someone in another country. And it's something that is very hard to do these days on SSB. I put this short QSO in to show that it can be used as a contesting mode, too.

Those yellow lines coming down are the signals. Each vertical line is a PSK station.

There are several other excellent free software packages available besides Digipan. Take a look at MixW32, Logger and Hamscope.

What kind of equipment does PSK31 require? I have used very simple antennas like verticals and small wire loops very successfully. PSK lends itself to antenna restrictions. How much power is necessary? During the QSO to Portugal above I was running 45 watts! But that is high power on PSK. I have a QRP rig that is a lot of fun to use which only runs 1.5 watts. I have worked 17 states so far with that QRP rig and that's after only a month of having it. So you don't need big rigs or big antennas for PSK. What a blast!

The Best Links

"Official" PSK31 Home Page


K4ABT's PSK31 Page




W2MU's PSK31 Page


PODXS 070 Club


ARRL(Steve Ford)'s PSK31 Page


Fig. 2. Here's a snapshot of the little 1.5 watt rig I mentioned. I made it from a kit that is sold by a great company called "Small Wonder Labs", Model PSK20. I paid less than $100. It is a full transceiver, complete with a builtin interface designed for PSK.

To my amazement this kit worked the first time. It is sensitive and selective, a required combination for a good receiver.

PSK31 works by modulating a single tone. The tone is wiggled back and forth like a warble. That warble contains bits of information that make up characters slightly similar to Morse code but much more elegant. "PSK" stands for "Phase Shift Keying" which means the tone changes phase to impart the information. It just sounds like warbling when you hear it.
Fig. 3. A look at the back of the Small Wonders Labs PSK20

I first heard about PSK31 from an article in the Denver Radio Club newsletter, The Roundtable, in March of 1999. PSK exploded on the American ham scene right after that. There was a tremendous article in the May, 1999 QST magazine, PSK31--Has RTTY's Replacement Arrived? by Steve Ford. This article is a MUST READ.

I also attended a talk at the Dayton Hamvention that month in 1999. About 25 people attended and the moderator was surprised that most of us weren't there for the "tor" talks. In 2001 the attendance was 400.

Like many hams getting on PSK31 for the first time, I had clipstrapped together an interface just to see if this mode really works. Well, I have news for you. It not only really works but it is extremely popular by now and if you haven't tried it you're missing out. If you are already on PSK then you should find someone who isn't and help them get on.

The interface is very simple. It consists of three sections. The first section conducts the audio signal from the PC soundcard to the radio. Section two conducts the audio the opposite way, from the radio to the PC soundcard. And section three switches the Push-to-talk on the radio.

Better Mousetrap

I have invented a circuit for the PTT section that I think is superior. The QST articles and others discuss the interface thoroughly but every source uses a transistor in their design. Instead I use a relay. I believe a relay to be easier to get working because you don't have issues like polarity, voltage, current to jinx the circuit. Besides my circuit uses fewer components 2 vs. 4) and is simpler! Let me blow my own horn some more: I have been using my circuit since before PSK and it has NEVER failed. Here is what it looks like:

You can go the commercial route, too. Probably the biggest selling interface is made by West Mountain Radio called the RIGblaster. It works excellently on all types of rigs. It's strong point for me is that it has lower distortion than I have been able to attain with the homebrew circuits. I also have a Rascal interface which was much cheaper and works fine. MFJ offers one and other new interface products are appearing on the market each month.

2008 Update: I have recently purchased a RigBlaster Plug and Play Plus and like it a lot. It uses a USB connection instead of a com port, and it gets it's power from the USB port. This unit is easier to hook up, especially since my new laptop doesn't have a com port.

"Small Wonder Labs"

So, that's it for my little PSK31 Web Page for now. The bottom line, GET ON and HAVE FUN!!!

73, Mark
w0ql -at- hotmail.com