Kenwood TS-590S manual Transmission, Kenwood Traditional Transmitting Circuitry, IF Circuits

2 TRANSMISSION

2.1 Kenwood Traditional Transmitting Circuitry

The tradition of high quality audio technology that users rely on Kenwood to deliver is produced by combining analog and digital technologies that Kenwood has nurtured thus far. The DSP controls modulation and determines the sound quality and analog circuits convey and amplify the signal cleanly.

2.1.1 IF Circuits

The first IF transmit signal that is output at 24 kHz from the DSP and the DA converter is converted to 10.695 MHz in a dedicated IC for the mixer. The second IF signal at 10.695 MHz passes an IF filter of 6 kHz bandwidth at which undesired frequency components outside the pass bandwidth are attenuated before the signal is amplified. Then, the second IF signal passes to the ALC circuit that controls the output power to a stable level. After that, the signal goes through the gain control circuit that corrects the minutely small differences in gain from band to band, and the signal enters the mixer that is commonly used in TX and RX, and is converted to the third IF of 73.095 MHz. The signal passes the gain control circuit that adjusts the signal to the necessary gain level according to the specified power level. Then, the signal passes the filter that eliminates spurious components before going into the mixer circuit that converts the signal to the desired transmit frequency. Also, delicate gain control is done, such as decreasing the gain of the amplifier while the key is not depressed in CW mode. By means of these processes, a high-quality transmit signal with low noise can be acquired. The signal converted to the desired transmit frequency passes the BPF for removing spurious signals to prevent from generating interfering signals outside of the transmit bandwidth, and is amplified to a prescribed level before being sent to the final circuit. The drive signal produced here can be extracted from the DRV terminal. (While the output from DRV is selected.)

2.1.2 FET Final Circuit

The final amplifier of the TS-590S is a push-pull amplifier using two pieces of RD100HHF1 MOSFET from Mitsubishi Electric Semiconductor (Pch 176.5 W). The drive amplifier also uses an RD100HHF1 MOSFET and the pre-drive amplifier employs an RD06HHF1 MOSFET and they, despite being 13.8V final circuits, amplify the signal reasonably in a stable and continuous manner with low distortion. Figure 2-1 shows the graph of IMD characteristics and Figure 2-2 shows the graph of harmonic spurious characteristics. Superior distortion characteristics and clean signals are acquired in this way.

TS-590S

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