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DarwinPsk - PSK31 for amateur radio on the Macintosh

DarwinPsk is a version of LinPsk, written by Volker Schroer/ DL1KSV for Linux and ported by him to the Macintosh OSX operating system with the help of Tom Dove / K3ORC.
DarwinPsk allows a Mac to receive and transmit with PSK31 (Phase Shift Keying 31 Hz), a narrow-band digital mode which allows efficient keyboard communications even with low power or in poor propagation conditions.

PSK31 enables real-time "chat" over ham radio, with one operator typing a message on a computer, which is then transmitted and displayed on the screen of the other. It has become quite popular on the 20-meter amateur band, with activity centered around 14.070.15 mHz.

Besides the software, you need an amateur transceiver (and government license to transmit) capable of Single Sideband operation and an interface that will send the audio output of your Mac to the microphone input of the radio and send the received audio from the radio to the external microphone input or Line In jack of your Mac. For receiving, this interface can be as simple as a set of headphones resting on the Mac's internal speaker, although a hard-wired connection will be much better.

DarwinPsk was ported from LinPsk using a 500mHz iMac (2001 model) with 320mB of RAM. It also builds and runs reliably on a 366 mHz iBook (2000 Blueberry) with 192 mB of RAM, but that machine has no sound I/O to test it fully at this time.

I believe that DarwinPsk is the first amateur radio application to be ported from UNIX/Linux to Macintosh OSX.

System Requirements
  1. A Macintosh running OSX, preferably version 10.1.3 or later
  2. OSX Developer Tools, version December 2001 or later, available on the OSX CD or by free download from the Apple Web site at www.apple.com.
  3. A working X-Windows environment. The Fink project with XDarwin at is an excellent source, and it is free.
  4. The Qt libraries for XDarwin, version 2.3 or later.
  5. The Esound sound daemon.

Installation

These instructions assume a standard installation of XDarwin with Fink. If you have used Tenon XTools or other method of installing X-Windows, the directory holding your local files will have a different name from /sw, which is the Fink standard.

  1. Start XDarwin in the usual way and open your favorite terminal program. You can also work in the Mac OSX Aqua environment, but XDarwin must be running to provide the necessary libraries and compilers for building DarwinPsk.
  2. Move to the /sw directory, create a new subdirectory for DarwinPsk and move into it
    cd /sw
    mkdir ham
    cd ham
  3. Copy the tarball into this directory from wherever you saved it and untar it.
    cp /SOURCEDIRECTORY/xdarwinpsk.tar.gz .
    tar -zxvf xdarwinpsk.tar.gz
  4. The /sw/ham directory should now look something like this linpsk-0.6.2 xdarwinpsk.tar.gz
  5. Move into the /linpsk subdirectory of the linpsk-0.6.x directory and build the program. On a 500 mHz iMac, this takes about five minutes. Your mileage may vary.
    cd linpsk-0.6.2
    cd linpsk
    make -f Makefile.mac
  6. Take a test drive.
    ./linpsk
  7. You should see the DarwinPsk window, with no activity in either of the white display screens. Click on the Settings menu and choose the Settings submenu. Click on the DemoMode button to turn it off, as DemoMode does not work in this Alpha version. You can set other options in this window, including your amateur callsign, your timezone as an offset from UTC, and the sound OutputLevel. The default OutputLevel is 50, which will be much too high for most Macs, so the sound will be distorted. Try 1 as a starting point. Click OK to return to the main screen.

    Click on the RX button. This should produce a display in the lower left window, showing the Spectrum input to the microphone of your Mac. Click on Input to change to that window, tap the microphone and look for a change in the display. If there is no change in the display, the sound input of your Mac is not activated.

  8. Activate the microphone input by going to the Mac OSX Aqua interface and opening the System Preferences control panel. Click on Speech Recognition to open the sound input window. In a few seconds, the display in that window should indicate the sound source as Internal Microphone. This means that the sound input is activated.
  9. Go back to XDarwin and DarwinPsk. Tapping the microphone should now produce a visible change in the Input display window. If so, the sound input is working properly. Try the Spectrum and Waterfall windows to see the difference in the display. In Waterfall, there should be a dark blue background with yellow dots that indicate noise. Whistle a single note and a yellow line should appear on the waterfall. This resembles the display of a signal tone from an incoming PSK31 station.
  10. Tune your receiver to 14.070.15 mHz, Upper Sideband. You should hear a variety of warbling tones from the radio speaker, each one representing a ham using PSK31. Turn up the volume until DarwinPsk "hears" the audio through the Mac microphone, as shown on the display. Adjust the volume so the Waterfall shows a dark blue background with white or yellow lines streaking down it. Click on one of these lines. In a moment, the ham's message should appear in the Rx window as he types. If not, click on the Squelch bar and lower it until the signal breaks through the squelch. Noise will show up as random letters on the Rx display.
  11. With receive working, click on TX. A clean-sounding warbling tone should come from the speakers. If the tone is raspy, the OutputLevel is too high. Type some words in the window to the right of the TX/RX button. The warbling sound should vary as your typed words appear in the Rx window above. Click on the TX/RX button to return to receive mode.
  12. Once everything works satisfactorily, make it easier to start by creating a symbolic link in a location that XDarwin can locate. After this, you will be able to start DarwinPsk by typing "psk31" from any terminal prompt, or include it in menus.

    cd /sw/bin
    ln -s /sw/ham/linpsk-0.6.2/linpsk/linpsk psk31
  13. Wire up an interface between the Mac and the transceiver. The exact setup will vary with your radio and the specific Mac model you have and is beyond the scope of this document. Many hams use a commercial interface, such as a RigBlaster, for PSK31 operation. Others find a simple cable connection is sufficient. Some Mac portables do not have sound I/O and will require a USB audio adapter, such as the one made by Keyspan, to interface with the radio. It may be necessary to put a variable potentiometer in the sound input to drop the audio level and prevent overdriving DarwinPsk.

Please send comments and bug reports Tom, K3ORC so we can continue to improve DarwinPsk.

73 es BCNU on PSK31!

-- Tom Dove / K3ORC