Kenwood TS-890S In-Depth Manual page 49

DSP 07
Frequency (Hz)
Fig. 56 Characteristics of the SSB TX Filter
TX monitoring audio is generated by detecting the IF signal in the final stage of DSP. This enables monitoring of audio
signals that are close to those to be output as radio signals.
● CW Mode
The rising and falling waveforms of a CW keying signal is shaped to optimize the amplitude change to prevent the
occupied bandwidth from expanding. The rise time can be configured to one of the four levels (1, 2, 4 or 6 ms) in the rise
time setting. A smaller value represents a steeper rise and more dynamic sound quality, while a larger value represents
a more gradual rise and softer sound. Using the waveform-shaped keying signal as the baseband signal, a modulated
wave in the IF stage is generated through multiplication with the 24 kHz carrier.
Additionally, through multiplication with a carrier with an accurate tone frequency linking with the CW pitch frequency, a
sidetone is generated. The rising and falling waveforms become the same shape as those of the modulated wave in the
IF stage.
● FSK Mode
After baseband filtering, frequency modulation of the FSK keying signal is performed with the 24 kHz center frequency
and preconfigured FSK Spacing (FSK shift frequency) to generate the FSK modulated wave.
Also, the frequency is shifted based on the audio mark frequency to generate the FSK modulated wave for monitoring.
For operation using the RTTY encoder, ASCII codes transferred from a USB keyboard or message memory are
converted to Baudot (5-bit) codes. The start bit and stop bit are then added to generate the keying signal which is
modulated in the same way as described above. FSK Spacing is fixed at 170 Hz when the RTTY encode is used.
● PSK Mode
In the PSK mode, a modulated wave is sent out only when the PSK31/63 encoder is active. No modulated wave is output
when it is turned off.
BPSK or QPSK can be selected for the PSK31 encoder, and BPSK can be used for PSK63.
The ASCII code from a USB keyboard or message memory is converted to Varicode. Convolutional encoding is also
performed in the QPSK mode. After baseband filtering is performed, quadrature modulation with a 24 kHz carrier is
applied to generate a PSK modulated wave.
A separate PSK modulated wave for monitoring is also generated.
● AM Mode
As with the SSB mode, processing by the TX equalizer, microphone gain control and TX filter is applied before the signal
is being modulated. A DC signal is added according to the AM modulated wave and modulation factor, and modulation
is applied with the 24 kHz carrier.
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