CHINESE 4+4 PARALLEL TONE MODEM

(VFT system running at 8 x 75 Bd QPSK)

FFT-Spectrum versus time, frequency and signal intensity (idle condition)

FFT-Spectrum versus frequency and signal intensity (idle condition)

FFT-Spectrum versus time, frequency and signal intensity (tfc. condition)

FFT-Spectrum versus frequency and signal intensity (traffic condition)

The Chinese 4+4 modem is interleaved in time and frequency
Tones 2+5 / Tones 3+6 / Tones 4+7 / Tones 1+8

The Interleaving in time (about 300 msecs) and frequency
can clearly be seen on the image below:

Phase Plane Spectrum of a single 75 Bd QPSK-tone

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