The coherent CW is a pure digital mode because it is only done for computers (although it is readable by a human being). The keying produced by the computer is perfect so as to allow synchronization and correct evaluation of the bit (dot or dot abscence).

The description done hereafter corresponds to the CCW of Multipsk, which has introduced some modifications (F6CTE/DK5KE) and new modifications in the Multipsk version 3.10.

Created by: Raymond Petit (W7GHM) in 1975

Description :

Speed : 12 wpm in standard. Here 12, 24 or 48 wpm respectively corresponding to a dot length of 100, 50 and 25 ms

Modulation : On-Off keying of an audio tone,

Receive mode: indifferent (LSB or USB)

Character set : A..Z 0..9 ? = / + and some others signs more or less used (“ Varicode ” characters type). The waiting character (-_---) is used as idling character. It is specific to the CCW (of Multipsk) to keep the synchronization in case of absence of characters to send. The line feed character is transformed in a "message start" signal (_-_-_). The removal of a character is done with the transmission of an error character (--------), correction which is taken into account by the receiver.

Shape of pulse : rectangular

Bandwidth : up to about 100 Hz according to speed,

Demodulation : coherent,

Synchronization: automatic using the signal

Correction code: no

Convolution code: no

Interleaving : no

Drift tolerance : 15 to 25 Hz/min (depending on the CCW speed and on the signal-to-noise ratio)

Pmean/Ppeak: 0.5 but very variable

Lowest S/N : the slower is the CCW speed, the better is the decoding.

The minimum S/N ratio depends on the speed and the letters sent. For the standard speed (12 wpm) the minimum S/N is about -12 dB (-8 dB at 24 wpm and -5 dB at 48 wpm).

Note 1: at the beginning of transmission, "CCW", a space and a waiting character (-_---) are transmitted. The user, to win time, can supress the prefix CCW and its space but the opposite operator will ignore that it is CCW.

Note 2: in order not to lose the synchronization, it is not possible to type more than one space between two words.

Created by : Patrick Lindecker (F6CTE) in 2005

Description :

This mode derives from the Multipsk CCW mode. It permits a more efficient decoding and a better Pmean/Ppeak ratio than in classical CCW (OOK). The Morse sound can be built digitally, which strongly reduces radio noise and allows the selection of the only one signal clicked on the waterfall.

The essential difference is the transmission of a complementary morse signal, on a carrier situated at a 240 Hz distance, for example:

* morse signal at 1000 Hz,

* complementary morse signal at 760 Hz.

This "shift" of 240 Hz is sufficient to separate the 2 signals for a human decoding .

The 2 signals form a FSK modulation.

Note: the program can decode either the 2 carriers in FSK or both carriers in OOK, or one of the two carriers in OOK, according to the link conditions. The normal decoding is done in FSK.

All the characteristics are the ones of CCW Multipsk, except the following:

Receive mode: USB only

Pmean/Ppeak 1

Lowest S/N : -14 dB at 12 wpm, -10.5 dB at 24 wpm and -8 dB at 48 wpm.

As CW, QRSS is a digital mode because it can be easily decoded by a computer but it can be also decoded visually by Hams from the signal trace on the waterfall. The human visual decoding is moreover better that the decoding done by the software.

Description :

Speed : currently dot of 1, 3 and 10 seconds (or respectively 1.2 , 0.4 and 0.12 wpm) (standard QRSS dot: 3 seconds)

Modulation : On-Off keying of an audio tone (800 Hz currently) or of a HF simple carrier.

Receive mode: indifferent (LSB or USB), but prefer USB

Character set : A..Z 0..9 ? = / + and some others signs more or less used (“ Varicode ” characters type)

A carriage return is transformed in space

Shape of pulse : rectangular

Bandwidth : from about 10 Hz to less than 1 Hz according to the Morse speed,

Demodulation : non coherent,

Automatic Frequency Correction (without noise): +/-5 Hz/mn in QRSS1, +/- 1.6 Hz/mn in QRSS3 and +/-0.5 Hz/mn in QRSS10. In presence of noise, the maximum supportable drift  is inferior to these values,

Pmean/Ppeak: 0.5 but variable

Lowest S/N : the following values are approximative and depend on the soft (Multipsk) or the visual (by SWL or Ham) decoding:

QRSS1:     soft: -18 dB     visual: -22 dB
QRSS3:     soft: -21 dB     visual: -26 dB
QRSS10:   soft: -24 dB     visual: -28 dB

Mapping of Morse characters into ANSI characters

It will be refered to the same paragraph written for CW.