PSK31 – A HF Digital Ham Radio Mode

Abstract:
PSK31 allows worldwide “text messaging” communication with high frequency (HF) radio with low power (~5 watts) and narrow bandwidth. It combines amateur radio with digital signal processing on a laptop computer.

This webpage was derived from the Powerpoint slides by Everett Palmer.

• What does it do? What was it designed to do?
  • Design goals for PSK31
  • History ... other digital modes ...
• What is required for a PSK31 station?
  • What equipment is needed?
  • What software is available?
  • How do you hook it up
• How does it work? ... some theory
• How do I operate a PSK31 station?
• Demonstration

• Live contacts
• Responsive
  • No error correcting process because all error correction adds delay
• Social
  • Does not require a one to one link
  • You can listen in and then join in
• Quality of radio link is apparent in the quality of the information received
• Improve on RTTY

  See Peter Martinez (G3PLX), “PSK31: A New Radio – Teletype Mode,” QEX, July/Aug. 1999.

• Character rate sufficient for typing
  • 31.25 bits/sec = ~ 50 words/minute
• Narrow bandwidth
  • 31 Hz
  • many signals in the bandwidth of a SSB signal
• Long distance contacts possible with low power
  • great for QRP
• Full ASCII character set – “Varicode”
• Self-synchronizing
  • The character separator – “00” – never occurs inside a character
• Uses Binary Phase Shift Keying ... B-PSK
  • Uses two phases 180 degrees apart

  “PSK31” = Phase Shift Keying with 31 Hz bandwidth

The codes are transmitted left bit first, with “0” representing a phase reversal on BPSK and “1” representing a steady carrier. A minimum of two zeros is inserted between characters. Some implementations may not handle all the codes below 32.

1          space
11        e
101      t
111      o
1011    a
1111    n
......
1010101101    Z

 

No “00” used.

Lower case are shorter than upper case.

What does it sound like?

These sights have numerous soundfiles, scroll down to PSK31.

http://www.kb9ukd.com/digital/

http://www.wunclub.com/sounds/

• High Frequency (HF) Transceiver capable of SSB ... FT 990
• PC Computer with a sound card
• Radio to PC link
  • audio
  • push-to-talk
• PSK31 Software
  • DigiPan
  • HamScope

  To just listen in you don’t really need the Radio to PC link.

Screen snapshot of DigiPan: The spectral lines show various PSK31 signals, table in upper right has corresponding text to the lines, and the text on the left is the text from the selected line.

Screen snapshot of HamScope:

• Live contact modes ... responsive but not error free
  CW, RTTY, Hellschreiber, PSK31, PSK63, QPSK31, MFSK16, ...

• Data transfer modes ... error free ... pocketized
  Packet, PACTOR, AMPTOM, ...

  see http://www.arrl.org/tis/info/digital.html

• Peter Martinez (G3PLX), “PSK31: A New Radio – Teletype Mode,” QEX, July/Aug. 1999.
  http://www.arrl.org/tis/info/pdf/x9907003.pdf

• Software
  Digipan http://www.digipan.net

  Hamscope http://www.qsl.net/hamscope/HamScope.html

• PC to radio links
  “EZ-PSK” http://www.saratogaham.com

• Best frequency 14.070 MHz on 20 meters
• Panoramic display
• Macros

  HF Frequencies • 160 m @ 1838 KHz • 80 m @ 3.580 MHz • 40 m @ 7.035 MHz • 30 m @ 10.140 MHz • 20 m @ 14.070 MHz • 17 m @ 18.100 MHz • 15 m @ 21.080 MHz • 10 m @ 28.120 MHz

  VHF Frequencies • 6 m @ 50.290 MHz • 2 m @ 144.144 MHz • 1.25 m @ 222.07 MHz • 70 cm @ 432.2 MHz • 33 cm @ 909 MHz

Screen snapshot of QSO with N5EFS during PSK31 demonstration:

Screen snapshot of QSO with N5EFS during PSK31 demonstration:

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