So that's what PSK sound like eh!.
Please print this article and use it as a hand out at Club talks and lectures

Based on an idea by SP9VRC and developed by Peter Martinez, G3PLX a new Amateur Mode called PSK31 is emerging. Instead of keying using Frequency Shift, FSK, this mode uses Phase Shift Keying, PSK. It uses an alphabet similar to Morse which gives a text speed of about 50 wpm. Our experience to date shows that even without an error correcting algorithm, copy is as good as any and better than most at low signal levels. It is a particularly attractive mode since it requires no lock condition or handshaking with a second radio station, and roundtable QSO's with more than two stations can be enjoyed.
ince the bandwidth is equal to the baud rate and the chosen baud rate is 31.25 we can now use a bandwidth of 31Hz and narrow CW filters can be employed. This is good news because it can work at much lower signal levels in the crowded digital bands. The normal bandwidth of other modes is in the order of 300-500Hz.
t uses the Sound card of the computer instead of a TNC. The following chart has links to most of the major software programs currently offered, including the original, psk31sbw, which can be downloaded from this site.

Download from here!

The original PSK31 program
written by Peter Martinez, G3PLX.
file name


ftp from PSK Home Page

from PSK Home Page

from Kender mirror site.

Digipan v:1.6dv:1.7v:1.8

by Skip, KH6TY

DigiPan 1.x

Digipan v:2.0

by Skip, KH6TY


DarwinPSK for MAC

by Volker, DL1KSV (linux)



by Steve, NR4M



by Christian, F6GQK



by Dave, W3KM


IMD Meter

by Clint, KK7UQ

IMD Meter


by Luc, LX2GT (Linux)



by Volker, DL1KSV (Linux)



by Chris, N3JLY (Macintosh)



by Nick, UT2UZ



by Patrick Lindecker , F6CTE


N1MM Logger

by Tom, N1MM



by Edson, N1VTN (Linux)



by Erik, VK7AAB



by Al, WD5GNR


PSK Meter

by George, KF6VSG

PSK Deluxe

by Simon, HB9DRV


by Walter, DL4RCK


by Christian, F6GQK



by Hansi, DL9RDZ (Linux)



by Sergei, UA9OSV



by Moe, AE4JY



by Dave, KA1DT



by Dave, AA6YQ



by Ron, K5DJ



by Joe, W1SQL



by Bob, K4CY


The simplest and quickest computer to radio interface is to connect the Line Output from the Sound Card to the transceiver audio input with a 100:1 voltage divider to reduce the voltage output, and the Sound Card Line Input to the audio output of the radio. You can use the VOX to switch from Receive to Transmit. To setup this arrangement, adjust the sound card output level using the computer 'mixer' control until maximum transmit power is reached, and the ALC is just starting to read. Then tune to a strong carrier and adjust the soundcard input gain until the red line goes away as observed on the spectrum display. waterfall (indicator) This procedure is covered in great detail in the PSK31 Help files under "setting up the sound card".
For SWL the fastest way to Rx is to simply let your Computer listen to the Radio. If you have a microphone connected to your pc, load the PSK software, (see above table) tune your rig to a PSK signal and ta-dah, PSK print on you pc screen. :)

The circuit below shows the method I used which isolates the Sound Card Line In and Line Out from the Radio using a couple of Radio Shack transformers, and a 2N2222 transistor to switch the PTT radio line triggered by the RTS line of the computer Com Port. All audio levels are equalized when running either the computer, the SSTV program or PSK31.  To adjust this circuit, tune to a strong carrier and adjust the Rig Volume until the red overload lines disappear. At this point simply tweak RV1 to give the required output power from the transmitter.
he author of this page, WM2U, would greatly appreciate any technical updates and or Interface Schematics sent via e-mail. This would ensure the most current information is available to the user, however there is more Radio to Computer interfacing help on the Hook-up page. Try this if you need more information.

Interface circuit

Interface circuit

Please Note: The transformers T1 and T2 are no longer available at Radio Shack. I recommend contacting Bux Comm at Warehouse 209;  Office 211;  Luenburg Drive; Evington,  VA 24550;  FAX 434 525 7818 or email Buck at [email protected] and tell him I sent ya! ... yea! he'll charge you double. :)   Take a look at Buck's web page for these items at


To completely isolate the computer from the radio the PTT line schematic shown above should be replaced by the following optically coupled circuit. I have this unit installed and it works great. The Opto Isolator is a 4N29, ECG 3084 or equivalent from Digi-Key, Newark or Radio Shack, part #901-1617.
Thanks to Ed Pearson, KF4JU. for the optical circuit.

Optically Coupled PTT circuit

An e-mail off Ken, W7LAR gives us a great tip by the way. If you want to get the Optoisolator from Radio Shack it will probably not be a store stocked item. You can get it direct mailed to your home by asking the shop clerk to order it for you from their warehouse. It is number 11305190 and costs about $3.00

It is strongly recommended that you download the file and install it. Then print off the help files. I will not repeat any of the details that can be found in these files since Peter, G3PLX has done an excellent job. As well as the setup instructions for the sound card and software there is an excellent section on the Modulation Theory, the new character set and a general overview of PSK31.
The calling frequencies that have been decided upon for the time being are:
1838.15kHz, 3580.15kHz, 7070.15kHz, 7035.15kHz, 14070.15kHz, 21080.15kHz, 28120.15kHz, 50.290mHz, 144.144mHz, 222.07mHz, 432.2mHz, 909mHz and
10137.15kHz, 18100.15kHz and 24925kHz suggested for the WARC Bands.
From the PSK31 help files Peter, G3PLX suggests using USB on all bands. Please read the help file section: PSK31 Operating > Sideband selection with PSK31. This has ALL the answers to the sideband discussion.
o get you going fast, check out...
WM2U's Tip List.

  • Set sound card sampling rate to 11025Hz
  • This must be at least a 16 bit sound card.
  • No Signal observed? Check your WAVE slider is not zero.

  • Set Rx and Tx frequencies to 1000Hz.
    NOTE: This value will get you up and running but if you plan on using a filter change it to the center frequency.
  • If using LSB check the "Inverted QPSK" box.
  • Too much noise! Try using a narrow CW filter.
  • Using a Word Processor, write your buffered messages and save them as .txt files, placing em! in a folder called 'buffers' created in the main PSK31 folder.
    NOTE: This is NOT a form of type ahead buffer. It is simply a method to pre write 'Standard' messages hence saving you keyboarding time.
    • Your sound card output must NOT overdrive your Mic Input.
    • Do not overdrive the sound card input from the Radio.
    • Get used to the Waterfall/Phase indicators for tuning.
    • Do not use your Speech Processor.
    • Be patient. This is a new mode. You will not find all the features you are used to yet!

These values work but since this is such a new mode things will probably change in the near future. Please e-mail me for any Requests for Change to the Interface or Tips. Your input is crucial to the free dissemination of information.
ark Erbaugh, N8ME runs a great PSK Net on Tuesday nights at 10:00pm EDT on 7.071 MHz. Their a good crew. Come and join us!

To Subscribe to the TARA PSK Reflector:
Subscribe at or send an e-mail to
[email protected] and put the following in the BODY of the message:      subscribe psk-tara your e-mail address
Wallpaper collector? Hey! check out these new PSK awards offered by the Troy ARA, (TARA). These digital mode awards are part of the All Seasons Contest package and they are very extensive. Check out this site for all the details.
Join in the Signal reporting debate. For PSK there is a lot of talk about the validity of using the standard RST report. One web site that is devoted to this topic is well worth visiting. Goto with an open mind and decide yourself what you think. :)
Pictures over PSK31?  Hey! it's been done! Skip, KH6TY has a web page dedicated to just that. Check out QuikPSK at, you'll see :)
One very last word but not by any means the least--- IMD!  It is essential that your signal is clean on the air otherwise you will probably be splattering all over the band. On all the software available you will see a waterfall indicator which shows all the PSK traces available to you to work, however yours is NOT one of them. So how can you see what your signal looks like so you can take corrective action if needed? Well the other station will help you adjust your station until you have a fb trace or would you believe, there are indeed devices available that will allow you to see your own trace. Check out PSK Meter by KF6VSG or IMD Meter by KK7UQ.
I hope the page gives you a taste of the excitement that this new mode is generating. If you need help please feel free to contact me, Ernie, WM2Uand get into the action. See you there, and
Enjoy! de Ernie (WM2U)