PSK31

Harvard Wireless Club > Activities > Projects > PSK31

The inspiration of Peter Martinez, G3PLX, PSK31 means "Phase Shift Keying, 31.25 bit rate." With the advent of this new mode, many have found renewed excitement in live keyboard to keyboard conversations. Until recently PSK31 was known only to a handful of individuals who dabbled in digital signal processing. However, an article in QST, along with the creation of an active discussion list, has caused interest to skyrocket among Amateurs worldwide.

PSK31 uses a combination of RTTY and Morse codes. Martinez dubbed it "Varicode" because it uses a varying number of bits for each character. For example, the popular letter "E" is assigned the code "11" whereas the less-used letter "Z" gets "111010101." PSK31 is comprised of two modes, "Binary Phase Shift Keying," and a "Quaternary Phase Shift Keying" that adds error correction. PSK31 gives very good copy under very low signal levels. And although it is not immune to interference many have reported superior results in noisy environments like 160 meters.

What does PSK31 sound like? Some have described it as a "warbling" sound. Others have mistaken PSK31 signals for computer-generated "spurs."

For further information about PSK31, and the latest version of the software, visit http://aintel.bi.ehu.es/psk31.html.

"I just had my first experience with PSK31 last night. I got my old 486 computer running with a soundblaster card in it, hooked it to my radio, and started listening. It didn't take long to find a couple QSOs in progress.

"I don't have anything set up for transmitting yet, but at least it was fun to see how the software operates. The mode uses a very narrow bandwidth, smaller even than CW, and that seems to be the principle secret to its success. That, of course, is a limitation on the speed of communications -- but it seems that most of the people using it can't type very fast anyway. When you type fast, it just puts it all in a buffer and sends it out slowly while you go off and get a snack, I guess."—KO1O

Proposed frequencies for PSK31 QSO

Since PSK31 started some three years ago, the plan has always been to concentrate activity starting from the bottom edge of the IARU RTTY bandplan, expanding upwards as activity increased. The exception is in the 10 meter band in order to accomodate hams without full privileges Keep in mind that all you need is about 100 Hz channel separation.

"I'm planning to start some experiments with W1AF in a few weeks. Is anyone interested in playing with psk31?"—Edson, N1VTN

"...contacts with JA, VE, VK, Russia, USA, SAmerica, Europe and Africa. Starting local tests in 160 meters (why not?) and, may be the lowfer range (160...190KHz) if I get a special licence to do it. Contacts range from 100W RMS to 250mW (CX and VE). That's it!—Marcus Ramos, PY3CRX/PY2PLL

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