THROB and THROBX are two MFSK modes, created by Lionel Sear, G3PPT. THROBX is an evolution of THROB.
|
Parameter |
Value |
|
Frequency range |
HF |
|
Operation modes |
Simplex |
|
Modulation |
MFSK |
|
Symbol rate |
1, 2 or 4 Bd |
|
Receiver settings |
USB or LSB |
|
Input format(s) |
AF, IF |
|
Additional Info |
9 or 11 tones are used |
THROB uses 9 frequencies. 1 or 2 tones are sent at the same time. The frequencies are spaced 8 Hz at 1 and 2 baud, and 16 Hz at 4 baud. This allows for 45 characters. The THROB alphabet is slightly larger, so some characters are encoded using a shift character first.
THROBX uses 11 frequencies, spaced 7.8125 Hz apart. 2 tones are sent at the same time, which allows for 55 characters. W-CODE also supports THROBX with 4 baud, which is a non-standard mode, but is supported in the FLDIGI software.
Tuning
Since the spacing between two tones is only about 8 Hz, the tuning of the mode must be very exact. Put the middle tuning cursor to the center of the signal. The center of the MFSK signal can be measured by turning on the “Peak Hold” setting in the FFT tuning window.