Rf Power Amplifier Circuit (Tx Section); Rx Amplifier And Mixer Circuit (Rx Section); Diagram For Rf Power Amplifier Circuit; Rx Amplifier (Lna) And Rf Bandpass Network (Bpf) - HYT TC-610 Service Manual

level, causing Q653 to be off and Q101 to operate. The output from Q100 and Q101 is amplified by
Q102 and sent to the buffer amplifier for process.
If PLL is unlocked, the LD pin of U202 outputs low level. When this situation is detected by the
microprocessor, transmit/receive operations are inhibited and a warning tone is heard.

RF Power Amplifier Circuit (Tx Section)

Diagram for RF Power Amplifier Circuit

3 Amplifier
Q104
1
2SC5108 1
To obtain the required RF power, the output RF signal from VCO is amplified by driver amplifiers Q400
and Q401 after passing through buffer Q104. The amplified RF signal enters driver Q402, which
performs power pre-amplification on the input signal, to derive a certain power to drive the final-stage
power amplifier. Then the final-stage power amplifier Q403 performs power amplification again on the
input RF signal to derive the required power. Finally, the amplified RF signal passes through Tx-Rx
switching diode D401 followed by the LC low-pass filter circuit (LPF). The signal is transmitted through
the antenna after ultraharmonic is removed by the LPF.

Rx Amplifier and Mixer Circuit (Rx Section)

1. Rx Amplifier (LNA) and RF Bandpass Network (BPF)

To obtain better frequency band selectivity, the Rx bandpass utilizes multi-level electrically tunable circuit.
The diagram is shown below:
The Rx signal input from the antenna is filtered to remove the out-of-band signal at the electrically
tunable bandpass network (D503, D504, L501, L502, C503, C505 and 507) and then amplified by
low-noise amplifier (LNA) Q500 to obtain a certain level required for receiving. The signal passes
through the three-level bandpass network (mainly consisting of D505, D506, D507 and periphery
components) to effectively restrain the out-of-band interference and to derive pure Rx RF signal, which
Q402
2SK3475
Q400
2SC5108
1
Q401
2
2SC4988
TUNE FROM MCU
C521
C524
D505
D507 D506
C526
C523
C519
L508 L507
L506
TUNE BPF
RF PA
Q403
RQA0002
MATCH
2
APC
Figure 3
LNA
Q500
1
C505
D504
C506
L502
TUNE BPF
Figure 4
13
TC-610/620 Service Manual
LPF
R/TSW
RX
TUNE FROM MCU
D503
C504
L501
ANTENNA
L453
1u
0