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Transmission Modes WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
THROB and THROBX
THROB and THROBX are two MFSK modes, created by Lionel Sear, G3PPT. THROBX is an evolution of
THROB.
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 sup-
ported 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.
TWINPLEX
TWINPLEX (F7B) is a FSK modulation technique with four modulation frequencies. Two transmission chan-
nels V1 and V2 are obtained through a combination of the modulation frequencies.
SITOR-TWINPLEX systems employ the second channel to double the data transmission rate from the
equivalent of 50 Bd to 100 Bd. The V1 and V2 channels each contain 3 telegraph characters from the SI-
TOR alphabet.