KENWOOD TS480HX
Manual de Servicio

TS-480HX/480SAT
CIRCUIT DESCRIPTION
3) Recording a message
The signal sent from the microphone is output from pin 11 to pin 10 of the analog switch (IC219), where it enters into the CODEC (IC217). The signal sent from the CODEC enters pin 13 of the DAC (IC212), and is then sent from pin 14 to the optional unit (VGS-1) to be recorded.

2) Playback
The output signal (VOI) sent from the optional unit (VGS-1) passes from pin 1 to pin 2 of the DAC. The signal passes from pin 8 to pin 9 of the analog switch (IC219), and is then mixed with the input signal of the AF amplifier (IC734). The DAC (IC212) controls the volume.

� Constant received audio recording function 1) Recording
A part of the received audio signal is sent from the CODEC (IC217) to pin 13 of the DAC (IC212), and is then sent from pin 14 of the DAC to the optional unit (VGS-1) to be recorded. The recording level is automatically compensated to become constant and you cannot randomly change the level.

� Other functions 1) Playing a message (monitor)
The output signal (VOI) sent from the optional unit (VGS-1) passes from pin 1 to pin 2 of the DAC. The signal passes from pin 8 to pin 9 of the analog switch (IC219), and is then mixed with the input signal of the AF amplifier (IC734). The DAC (IC212) controls the volume.

2) Playing a pre-recorded voice message
The above-mentioned signal path is also used for playing a pre-recorded voice message.
IC218 (A/2) DET IC219 Anolog SW 12 11 10 21 2 IC220 DSP 3 6 VOS VOO 8 9 VOAF VOO 2 1 VOI 13 14 DRM Option VGS-1 24 16 IC734 AF AMP IC212 DAC 22 23 15 FMOD SMOD ANO AF OUT IC217 CODEC

MIC MIC

PKD 13 1 ANI 5 DRO 4 DRO

TX-RX unit (A/2)

Fig. 8 Signal path before/after the CODEC

Modulation Circuit
The modulation signal processed at the DSP is sent to the modulation circuit. The circuit receiving the modulation signal is different between FM mode and SSB/ AM/ FSK mode. ceiver generates the FSK signal by changing the single tone (AF) generated at the DSP. The balanced modulator performs the same operation as SSB mode. � CW/FM mode The necessary carrier wave is obtained by making the balanced modulator lose balance.
Q625 (1/2) DC for AM/FSK TX-RX unit (A/2) DSB OUT 10.695MHz

1) SSB/ AM/ FSK mode
The modulation signal sent from the DAC (IC212) enters the balanced modulator (IC621) after inverting the phase at Q625. The 10.695MHz transmission signal sent from the balanced modulator is amplified at Q621 and is then sent to the next stage. � AM mode The DC voltage is applied to the pin 1 of the balanced modulator via D624. With the DC voltage, the AM carrier is generated since the balanced modulator becomes unbalanced. � FSK mode In conventional FSK mode, the frequency of the carrier was changed with the external keying signal. This trans-

SSB/AM/FSK Mod. IN

IC621 Balanced Mod. Differential Q625 input (2/2)

CAR 10.695MHz

Fig. 9 SSB/AM/FSK mode modulation circuit 9