Contestia Modes


General Description

Contestia is a family of MFSK modes with a high redundancy Forward Error Correction system similar to Olivia.  The mode works well on poor HF paths and has good sensitivity.  It is a mode designed to be used for contesting and keyboard to keyboard contacts.

The most widely used versions have a symbol rate of 31.25 baud. The typing speed is varied by changing the number of tones used, but can also be changed by change of baud rate.  The MFSK is constant phase, and the transmission constant amplitude, so transmitter linearity is inimportant. The modes are moderately tolerant of mis-tuning. The typing rate is very modest, given the high bandwidth used.

The mode was designed by UT2UZ.

Protocol

These are unconnected, manually controlled message asynchronous symbol synchronous simplex chat modes, with full-time Forward Error Correction. The tones are spaced the same as the baud rate, for example 31.25Hz for the 31.25 baud modes. The default mode has 8 tones and is 500 Hz wide.

Coding and Character Set

The ASCII-128 user interface is converted to upper case and control codes are either dropped or mapped to a fixed set.  This results in a smaller character block which is then mapped to a block of sequential MFSK tones via a Walsh-Hadamard function. Tones are deployed via a gray coder.

There are three popular modes, which have 8-FSK, 16-FSK and 32-FSK, thus having three, four or five bits per symbol. The combination of a reduced character set with a reduced number of bits per character provides approximately a 2 to 1 speed advantage over the equivalent set of tones in the mode Olivia. 

Operating Parameters

Mode
Symbol Rate
Typing Speed1
Lowest S/N
Duty Cycle2
Modulation
Bandwidth3
ITU Designation4
4-250
62.5 baud
~40 wpm
-10 dB
100%
4-FSK
250 Hz
250HF1B
8-250
31.25 baud
~30 wpm
-13 dB
100% 8-FSK
250 Hz
250HF1B
4-500
125 baud
~ 78 wpm
-8 dB
100% 4-FSK
500 Hz
500HF1B
8-500
62.5 baud
~ 60 wpm
-10 dB
100% 8-FSK
500 Hz
500HF1B
16-500
31.25 baud
~ 30 wpm
-12 dB
100% 16-FSK
500 Hz
500HF1B
8-1000
125 baud
~ 117 wpm
-5 dB
100% 8-FSK
1000 Hz
1K00F1B
16-1000
62.5 baud
~ 78 wpm
-9 dB
100% 16-FSK
1000 Hz
1K00F1B
32-1000
31.25 baud
~ 48 wpm
-12 dB
100% 32-FSK
1000 Hz
1K00F1B

Notes:
1. WPM is based on an average 5 characters per word, plus word space.
2. Transmitter average power output relative to a constant carrier of the same PEP value.
3. This is the "Necessary Bandwidth" as defined by the ITU.
4. A summary of the ITU Designation system can be found at  http://en.wikipedia.org/wiki/Types_of_radio_emissions