DOMINOEX

This mode has some good speeds (default is 70wpm) to it and is pretty robust in many cases the FEC option is not needed but, it is there for ruff conditions , the lower baud should be used in the ruffest conditions w/FEC. This mode will resist multi path propagation effects a whole lot better than say a narrow PSK type of mode just because it is a MFSK type of mode. This mode is not used very much like oher exotic modes there has not been much education (to the masses) about this mode that is one reason it is not used all that much also the mode sounds and looks whole lot like some other modes such as mfsk, olivia etc.. which is another reason for it not being used all that much.

DominoEX works by sending short transmissions of 18 different tones (called symbols), one at a time, each carrying four bits of data. Two more tones than strictly needed for 4-bit MFSK are used, in order to accomodate IFK+ code rotation. So DominoEX is an MFSK mode, meaning it is naturally sensitive, resistant to interference and ionospheric effects. However, several new techniques are used.

DominoEX uses an Offset Incremental Frequency Keying incremental coding algorithm called 'IFK+', developed by Murray Greenman ZL1BPU, which avoids repeated tones (inter-symbol interference strategy) and gives strong sync.
IFK+ means that data is carried in frequency differences rather than absolute frequency, so also gives complete independence from tuning errors and frequency drift. The codes rotate around 18 tones.
DominoEX has an unusual and highly efficient 'Nibble Varicode'. It also has automatic nibble sync, a large character set, and secondary channel data transmitted when the keyboard is idle. These features are designed into the character set, and add no overhead to the sending speed.
With FEC activated, DominoEX uses the spreading effect of IFK+ to mitigate the effects of carrier interference, and soft decision receiver techniques to reduce the effects of burst noise and Doppler.
These features make the mode easy to use, easy to tune, convenient, and ideal for beginners.

- Fast typing
- Automatic ID
- Very quick to tune
- Needs no error correction
- Retune without losing data
- Faster sync than other modes
- Designed for slick QSO exchanges
- Full extended ASCII character set
- With FEC, perfect copy down into the noise
- European accented characters and simple graphics


Nibble Varicode
DominoEX is based on 'nibbles' of information (four bit data entities), and since exactly one nibble can be transmitted on each tone element (which we call a 'symbol'), the mode can be very efficient. The specially designed character set is defined in nibbles, marked with an identifier bit to ensure automatic nibble sync (initial nibbles have the MSB cleared, further nibbles in a character have it set). Each character transmitted consists of one, two or three nibbles (that is, one, two or three sequential tones), depending on whether the character is often or rarely used. The frequency of each symbol transmitted represents the mathematical difference between one nibble and the next (actually the increment from the last tone number to the next tone number represents the value of the next nibble).
At the receiver, the identifier bit in each nibble (which provides character synchronism) is automatically discovered because of the bit weighting, and used to decide the nibbles in the data stream to be used to decode each character. The Varicode almost doubles the text speed (compared to ASCII), and allows a very large character set (584 characters!) to be accommodated. Because of the way the character set is defined, no extra sync bits are required - they are built into the character set.

FEC Option
With FEC activated, the transmission changes to a bit-based system similar to MFSK16, and the MFSK16 varicode is used (identical except for the extension to provide secondary text). At present no practical convolutional decoder exists for four-bit data, so a bit-based system is used, the same as MFSK16. Robust convolutional coding and error correction result, although the typing speed is halved. IFK+ continues to provide the same advantages, and the combination of IFK+ and FEC working together (soft decisions, code puncturing, stuck code spreading) add further advantages.

Category:

Education

Tags:

• Ham Radio
• Sound card modes
• Digital Modes
• Domino
• DominoEX