PSKAM

The interleaved PSKAM50 mode derives from PSK10 mode for the modulation and for AMTOR FEC for the repetition of the characters (time diversity). The speed is 50 bauds but each character is transmitted twice at an interval of five characters (example: A X B Y C A D B…). The speed is about 31 wpm. This mode permits to lower appreciably the number of errors due to HF radio conditions (without transmitting random characters). The bandwidth is about 180 Hz. The lowest S/N is -11.5 dB (for a PC at 166 MHz or higher).

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

Created by : Patrick Lindecker F6CTE (2002/2003)
Description :
Baud rate : 10 (PSKAM10) , 31.25 (PSKAM31), 50 (PSKAM50)
Speed : 6 wpm (PSKAM10), 20 wpm (PSKAM31), 31 wpm (PSKAM50),
Modulation : DBPSK
Reception mode : indifferent (LSB or USB)
Character set : 56 « fixed length » characters A..Z 0..9 <CR> <SPACE> . , : - = + ? $ ’ ( ) ! / @ % 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 : for PSKAM10 and PSKAM50: rectangular but the transition between 2 successive different bits is done by a decreasing sine then by an increasing sine (each one during a quarter of period)
for PSKAM31: raised cosine
Bandwidth : about 50 Hz (PSKAM10), 80 Hz (PSKAM31), 260 Hz (PSKAM50),
Demodulation : coherent,
Synchronization : automatic using the signal
Correction code : no
Convolution code : no
Interleaving : no
Repetition : each character is repeated 5 positions later (0.8 s in PSKAM50, 1,28 s in PSKAM31 or 4 s in PSKAM10) between 2 transmissions of the same character) (example: A X B Y C A D B…). This time diversity allows the correction of an erroneous character. Its detection is easy due to the particular content of a character (5 « space » and 3 « mark »).
Automatic Frequency Correction : from +/-3 Hz to +/- 10 Hz depending on signal level,
Drift tolerance : 60 Hz/mn for PSKAM31 and PSKAM50 and 40 Hz/mn for PSKAM10 (depending on signal-to-noise ratio)
Pmean/Ppeak : 0.86 for PSKAM10 and 50, 0,79 for PSKAM31
Lowest S/N : -11.5 dB for PSKAM50, -14 dB for PSKAM31 and -19.5 dB for PSKAM10

For precise specifications about PSKAM modes, see the PSKAM.DOC file de Patrick F6CTE.

Recommanded frequencies for PSKAM10/31/50 (USB)

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

A CW prefix, at 12 or 20 wpm, indicating mode, software and power used, for example: "VVV DE F6CTE / MODE PSKAMXX / 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 "PSKAMXX" , it will be sent automatically "PSKAMXX" in CMT Hell. The other Ham will see "PSKAMXX" displaying on his "waterfall" and will switch immediately to PSKAMXX.