Transmission; Modulation - Kenwood TS-890S In-Depth Manual

07 DSP
On the TS-890S, the processing block has been modified to enable more accurate decoding.
RX IF IF Filter
Envelope detection is performed with Morse codes controlled at a constant level via AGC processing. The level
assessment by AGC are then synchronized with the threshold assessment of envelope detection to enhance the
decoding rate. At the same time, we have also optimized the settings to deliver a better user experience.

Transmission

Modulation

● SSB Mode
Audio signal input from a microphone or an external input terminal is processed by the TX equalizer, microphone gain
control and TX filter before it is being modulated. SSB modulation employs the PSN system, a well-established method
among conventional transceivers that uses a 24 kHz carrier for modulation.
Unlike demodulation, modulation requires sufficient sideband suppression to be secured for the input bandwidth. This
characteristic of PSN is designed to deliver sufficient suppression according to the characteristics of the TX filter, which
is the bandwidth-limiting filter for transmission.
Fig. 55 Opposite Sideband Suppression Characteristics of PSN for SSB Modulation
In the SSB mode, the TX filter is made up of a high-pass filter (high-cut) and a low-pass filter (low-cut), which allows the
high-cut and low-cut frequencies to be altered.
A high-cut frequency can be selected 2.5 kHz to 3 kHz, 3.5 kHz, and 4 kHz.
44
AGC Limitter
Fig. 54 Detection Block of Morse Code Decoder on TS-890S
Envelope
Delay
Detection
Frequency (Hz)
Threshold
CPU
Judge