Kenwood TS-890S, Подробное руководство

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07 DSP
● FM Mode
Similar to the SSB and AM modes, after processing by the TX equalizer and other filters, filtering by the pre-emphasis
filter and 3 kHz low-pass filter for band limitation are applied and the sub-tone signal is superimposed. Next, modulation
with the 36 kHz center frequency is performed to generate the FM modulated wave.
Microphone Gain Control
Microphone gain can be adjusted by turning the [MIC/PITCH] knob.
Audio from the microphone is converted by the A/D converter to a digital signal, which will be sent to the DSP. The TX
audio signal input to the DSP is subject to band limitation by the TX filter, and its level is adjusted by the MIC-AGC so
that it does not exceed the reference level configured for the DSP.
If the signal level exceeds the reference level, for instance, when the configured value of the microphone gain is higher
than the audio signal level for transmission, the audio gain level for transmission will be lowered. The reference level
is equivalent to the level that fully deflects the ALC meter needle in the SSB mode, and equivalent to the maximum
modulation factor in the AM and FM modes.
The TS-890S supports modulation by mixing signal input from either the ACC 2 connector, USB audio or VoIP with input
from the microphone. In other words, MIC-AGC can be used for mixed audio signals.
Microphone gain for audio that is not from a microphone can be adjusted independently using “Audio Input Level” on the
menu screen.
MIC
ANI (ACC2)
USB Audio ANI/USB/VoIP
Gain
MIC Gain
VoIP
AGC
MOD TX IF TX Filter EQ ADC
ADC
Fig. 57 Microphone, ACC 2 Connector, USB Audio Input, VoIP Input and Amplifier Processing
Speech Processors
The TS-890S is equipped with a speech processor in the IF stage in the SSB mode (hereinafter referred to as “IF speech
processor”) and a speech processor in the AF stage in the AM and FM modes (hereinafter referred to as the “AF speech
processor”).
The speech processor is a feature that amplifies the average power of the modulated wave within the maximum power
limit to enhance the intelligibility of the receiving stations. The speech processor is intended as a function to amplify the
average power of the modulated wave in the SSB mode, but it also increases the average power of the audio in the AM
and FM modes, thereby enhancing the intelligibility of the receiving station.
The IF speech processor compresses the modulated wave in the IF stage. Unlike the compression in the AF stage,
harmonics generated by distortion due to compression are outside the audio band. The bandpass filter eliminates
distorted components outside the audio band from the compressed signal to achieve a high average power (talk power)
with less distortion than that of the AF speech processor.
To pursue a dynamic sound quality to be called back during pileup, select “Hard” on the Speech Processor Effect
screen. In comparison with “Soft”, this causes more compression of the modulated wave. The TS-890S is designed not
to alter the frequency characteristics even when the Speech Processor Effect is toggled between “Hard” and “Soft”.
By monitoring the transmitting audio signal and visually checking the COMP meter deflection, you can adjust Input Level
of Speech Processor to an appropriate compression level, and by visually checking the ALC meter deflection, you can
adjust Output Level to an appropriate level.