5.4 TX/RX Board (05P0733)
5-30
Receiving circuit
Fig.5.4.7 shows the block diagram of the receiver on TX/RX board, 05P0753. The
signal from PRESEL board is supplied to IF (72.455 kHz) trap circuit consisting of
C211 and L21 via 30 MHz LPF (Low Pass Filter). Q1 and Q2 are RF amplifiers, gain of
10 dB. The signal is down-converted, amplified and demodulated. AF signal is output
from TX/RX board as “AF OUT” signal.
Fig.5.4.7 Block diagram of TX/RX circuit
In J3E mode, received signal is frequency-converted as shown in Table 5.4.5.
Table 5.4.5 Frequency converter and Receiver IF frequency (J3E)
Frequency converter Local frequency Converted signal
1st mixer Q3, 4 (PMBFJ310) F0+72.455 kHz+1.5 MHz (3rd Lo) 72.455 MHz
2nd mixer U14 (NJM1496V) 72 MHz (2nd Lo) 455 kHz
3rd mixer U30 (NJM1496V) 456.5 kHz (3rd Lo) 1.5 kHz
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