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
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)
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
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
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)
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
* 10148 kHz USB (AF around 1000 Hz) at 22h00
* 144620 kHz USB (AF around 1000 Hz) at 20h00
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.