Traduction anglaise.

    In the software MULTIPSK by Patrick F6CTE, an experimental new mode called PSKFEC31 is introduced. This mode is derived from PSK10 mode for the set of characters and from PSK31 for the speed (31.25 bauds). Each bit (and not each character as in PSKAM) is transmitted twice with an interval of 13 bits between the two transmissions of the bit. The speed is about 28 wpm. This mode permits to lower appreciably the number of errors due to HF propagation conditions. The bandwidth is about 110 Hz. The lowest S/N is -14.5 dB (for a PC at 166 MHz or higher).

    This mode is included into the software MULTIPSK by Patrick F6CTE, there is the description of this mode and its variants as well as the specifications coming from his software :


Click on the copy of the screen in order to listen to the corresponding audio signal.

Created by : Patrick Lindecker F6CTE (06/2003)
Description :
Baud rate : 31.25
Speed : 28 wpm
Modulation : DBPSK
Reception mode : indifferent (LSB or USB)
Character set : 56 "Varicode" characters " A..Z 0..9  <CR> <ESPACE> . , " : - = + ? $ ' ( ) ! / @ & # * with an error reset character and an idle character (displayed by ">"). Small characters are transformed in capital characters and special characters as" é " are transformed in standard capital (in the example above: " E ").
Shape of pulse : rectangular but the transition between 2 successive different bits is done by a             decreasing sine then by an increasing sine (each of one during quarter of period)
Bandwidth : about 160 Hz
Demodulation : coherent,
Synchronization : automatic using the signal
Correction code : no
Convolution code : no
Interleaving : no
Repetition : each bit is repeated 13 positions later (so 0.42 s between 2 transmissions of the same bit). This time diversity allows the correction of an erroneous bit. The synchronization is easy.
Automatic Frequency Correction : from +/-3 Hz to +/- 10 Hz depending on signal level,
Drift tolerance : 60 Hz/mn for PSKFEC31 (depending on signal-to-noise ratio)
Pmean/Ppeak : 0.86
Lowest S/N : -14.5 dB
Due to the FEC process, this mode permits to reduce appreciably the number of errors due to HF propagation conditions, compared to BPSK31.

For precise specifications about PSKFEC31, see the PSKFEC31.DOC file.

Recommanded frequencies for PSKFEC31 (USB)

These modes (expect PSK220F) like  PSKFEC31 as well as PSK10, PSKFEC31, PSK63F +DIGISSTV "Run", PSKAM10/31/50 are QRP transmissions and they are used very little, Patrick F6CTE proposes to focus calls at the following frequencies and times :

*   14075 Khz USB (AF around 1000 Hz) at 17h00 UTC,

*   10148 kHz USB (AF around 1000 Hz) at 22h00 UTC.

* 144620 kHz USB (AF around 1000 Hz) at 20h00 UTC.

CW prefix, at 12 or 20 wpm,  indicating mode, software and power used, for example: "VVV DE F6CTE / MODE PSKFEC31 / SOFT MULTIPSK / PWR: 5 WATTS" could be transmitted before the CQ call itself. The  option of the video identifier of mode,  now included in MULTIPSK,  permits to specify visually in CMT Hell  the mode label (and/or other information) before the main transmission. This identifier will be visible in the "waterfall" of the other Ham. For example, just before the general call ("CQ") in PSKFEC31, it will be sent automatically  "PSK63F" in CMT Hell. The other Ham will see "PSK63F" displaying on his "waterfall" and will switch immediately to PSK10.
Back to the list of modes included in MULTIPSK