Thor Modes

THOR Modes

Thor-4 Spectrum Sound	Thor-8 Spectrum Sound	Thor-16 Spectrum Sound
Thor-5 Spectrum Sound	Thor-11 Spectrum Sound	Thor-22 Spectrum Sound

all signals shown in x2 waterfall mode, tick marks at 100 Hz intervals, waterfall palette is "blue-2"

General Description

THOR is a family of offset incremental multi-frequency shift keyed modes with low symbol rate, closely related to DominoEX. A single carrier of constant amplitude is stepped between 18 tone frequencies in a constant phase manner. As a result, no unwanted sidebands are generated, and no special amplifier linearity requirements are necessary. The tones change according to an offset algorithm which ensures that no sequential tones are the same or adjacent in frequency, considerably enhancing the inter-symbol interference resistance to multi-path and Doppler effects.

The mode has full-time Forward Error Correction, so is extremely robust. The default speed (11 baud) was designed for NVIS conditions (80m at night), and other speeds suit weak signal LF, and high speed HF use. The use of incremental keying gives the mode complete immunity to transmitter-receiver frequency offset, drift and excellent rejection of propagation induced Doppler.

Protocol

These are unconnected, manually controlled message asynchronous simplex chat modes, using binary convolutional Forward Error Correction. The default calling mode is THOR11.

Coding and Character Set

A binary varicode with ASCII-256 user interface (same as MFSK16) is used. Lower case characters are sent faster. An ASCII-128 secondary character set extension allows a fixed (typically ID) message to be sent whenever the transmitter is idle. Modulation uses two dibit pairs, symbol synchronous, differential.

The FEC system uses binary convolution to generate two dibits per varicode bit, and halves the corrected data rate compared to the equivalent DominoEX mode. Rate R=1/2, Constraint length K=7, Interleaver L=10 (40 bits).

**Operating Parameters**
Mode	Symbol Rate	Typing Speed¹	Duty Cycle²	Bandwidth³	ITU Designation⁴
THOR4⁵	3.90625 baud	14 wpm	100%	173 Hz	173HF1B
THOR5⁵	5.3833 baud	22 wpm	100%	244 Hz	244HF1B
THOR8⁵	7.8125 baud	28 wpm	100%	346 Hz	346HF1B
THOR11⁶	10.766 baud	40 wpm	100%	262 Hz	262HF1B
THOR16	15.625 baud	58 wpm	100%	355 Hz	355HF1B
THOR22	21.533 baud	78 wpm	100%	524 Hz	524HF1B

Notes:

1. WPM is based on an average 5 characters per word, plus word space. Values based on sending 100 "paris " words.
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
5. Double spaced mode.
6. Default and normal calling mode.