The mode has no Forward Error Correction, and is difficult to tune. It is fairly sensitive and moderately robust. Keyboard-to-keyboard QSOs are reasonably fast. Tuning must be very accurate, and the software will not tolerate differences between transmit and receive frequency.
The amplitude modulation component of THROB is a raised cosine AM modulation of each symbol. This combined with two tones transmitted at the same time, means that a very linear transmitter is required. It also gives the mode its very unique sound. You will never mistake Throb for any other mode.
For THROB, nine tones are used, spaced 8 or 16 Hz. For THROBX, 11 tones are used, spaced 7.8125 or 15.625 Hz.Mode | Symbol Rate | Typing Speed | Bandwidth |
THROB1 | 1.0 baud | 1.0 cps (10 wpm) | 72 Hz |
THROB25 | 2.0 baud | 2.0 cps (20 wpm) | 72 Hz |
THROB4 | 4.0 baud | 4.0 cps (40 wpm) | 144 Hz |
THROBX1 | 1.0 baud | 1.0 cps (10 wpm) | 94 Hz |
THROBX2 | 2.0 baud | 2.0 cps (20 wpm) | 94 Hz |
THROBX4 | 4.0 baud | 4.0 cps (40 wpm) | 188 Hz |