PSK31
PSK31 ( Phase Shift Keying , 31 Baud ) is an operating mode for digital wireless communication and is mainly used by radio amateurs on shortwave .
technology
The PSK31 method was developed by the British radio amateur Peter Martinez (callsign G3PLX). Martinez first called the operating mode " Varicode " because a variable length coding is used to encode the characters. Varicode is used to encode frequently occurring characters shorter and less common characters longer - similar to Morse code . Very little bandwidth is used. This enables extremely robust behavior under difficult transmission conditions. However, PSK31 does not have built-in forward error correction (FEC).
The resulting bandwidth with phase shift keying ( phase modulation ) is not much larger than the baud rate . The bandwidth of a PSK31 signal is very low at 31.25 Hz, which makes the mode ideal for transmissions with low power and for full shortwave bands. The 31.25 Hz bandwidth was chosen because Varicode generates about 32 bits per second at normal typing speed of about 50 words per minute. Another aspect was that 31.25 Hz can easily be generated with the 8 kHz sampling rate of DSP systems - also an advantage for sound cards: 31.25 Hz results when 8 kHz is divided by 256.
Today software is often used to (de) encode the received PSK31 audio signal. The software on the PC is not special - it can be flexibly exchanged. In addition, there are ready-made hardware solutions that (de) encode a PSK31 signal and are addressed by the PC as a modem .
With most programs you have to tune to a signal in the waterfall diagram . Then you can read the text sent there. However, if many stations are transmitting, this is quite time-consuming, which is why newer software can often display the texts from over 10 channels at the same time. You can then look for an interesting signal from it and adapt it to it.
PSK31 is a single tone process with 180 ° phase rotation . Since there are only two phase positions, this binary modulation method is also known as Binary Phase Shift Keying (BPSK) or BPSK31. PSK31 can also be operated with the Quadrature Phase Shift Keying (QPSK) process with four phase positions in combination with the Viterbi algorithm for forward error correction .
The digital operating mode PSK63 with 63 baud and PSK125 with 125 baud have also been in use for some time . This is useful because of the double or quadruple transmission rate compared to PSK31, especially when transmitting pre-prepared texts that are not entered directly via the keyboard (e.g. for amateur radio contests ). The disadvantage is the doubled bandwidth and the associated halved or quartered signal-to-noise ratio . PSK63 and PSK125 can also be operated like PSK31 in the QPSK process.
Other digital modes of operation are e.g. B. RTTY , AMTOR and PACTOR .
Frequencies
PSK should always take place in the 500 Hz digital range of the current band plan (see DARC band plans).
The following frequencies are always the starting frequencies of the digital ranges from which the digimode is operated.
The following simplex frequencies are available for PSK31 (all in USB):
| 160 meter tape | info |
|---|---|
| 1.838 MHz | |
| 80 meter tape | info |
| 3.580 MHz | increasing activity |
| 40 meter tape | info |
| 7.040 MHz | for regions 1 and 3 |
| 7.071 MHz | United States |
| 7.080 MHz | Rest of Region 2 |
| 30 meter tape | info |
| 10.142.15 MHz | |
| 20 meter tape | info |
| 14.070.15 MHz | Main activity |
| 17 meter tape | info |
| 18.100 MHz | |
| 15 meter tape | info |
| 21.080 MHz | usually 10 kHz lower |
| 12 meter tape | info |
| 24.920 MHz | |
| 11 meter tape | info |
| 27.245 MHz | CB radio, channel 25 |
| 10 meter tape | info |
| 28.070 MHz | |
| 28.120 MHz |
screen
The picture shows some texts that run sideways across the screen at the same time.
Here are a few explanations: The line number is at the front.
- 3 UW0ZM (Russia)
- 8 + 9 KB1RNX (USA)
- 12 K4LRK (USA)
- 13 ON4KBL (Belgium) de EA5DUF (Spain)
- 18 EA5FIF (Spain) CQ = general call
If you want to answer the call from EA5FIF, if you click on this line, only its text and your own answer text appear on the right in a dialog box.
Software for PSK31 operation in amateur radio
Free software for Linux
Freeware for Windows
- WinPSK
- Hamscope
- DigiPan
- TrueTTY
- Ham Radio Deluxe / Digital Master 780 (PSK31, Cat, satellite tracker, DX-Cluster, etc.)
- Fldigi
- MultiPSK
- UR5EQF_log
Software for Apple Mac OS X
literature
- Reinhard Krause-Rehberg: PSK 31 - the new teletype standard in amateur radio? In: Der Funkamateur , No. 3, 1999, pp. 308-310.
- ITU-R M.2034: Telegraphic Alphabet for Data Communication by Phase Shift Keying at 31 Baud in the Amateur and Amateur-Satellite Services . International Telecommunication Union. 2013. Retrieved October 14, 2013.
Web links
- introductory theoretical basics
- Introduction for practitioners (focus on Linux)
- PSK31 interface for the sound card + info / links