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4-6
HPF
LPF
PWR
AMP
TX/RX
SW
LPF
DRIVE
AMP
PWR
AMP
LPF
ANTENNA
DRIVE
PRE
ATT
LPF
DRIVE
AMP
HPF
TX/RX
SW
DRIVE
PRE
ATT
APC
CTRL
PWR
DET
PWR
DET
ATT
ATT
LPF
LPF
HPF
LO
AMP
LIMITER
118-550MHz
118-174MHz
375-550MHz
PCON(V/U)
LIMITER
UHF BAND
UHF RX CIRCUIT
VHF RX CIRCUIT
VHF BAND
Q38
D55
Q41
IC4
D62/D67
D68/D73/
D84/D75
Q36
D53
Q40
IC3
D59/D63
D66/D69
IC2
Q37
D70/D71/D77
UHF band
VHF band
TX AMP CIRCUITS (MAIN UNIT)
VHF BAND
The TX signal from the VHF band modulation circuit is passed
through the LPF (L50, L51, C215, C220 and C225) and ATT
(R146, R147 and R151), and then sequentially amplifi ed by
the pre-drive AMP (Q36), drive AMP (Q40) and power AMP
(IC3).
The amplifi ed TX signal is passed through the LPF (L67, L68,
C291, C297, C301, C302, C326, C331 and C332), TX output
power detector (D59 and D63), ANT SW (D66) and two LPFs:
(L79, L83, L87, C378, C386, C394 and L90, L94, L96, C409,
C418, C428), before being applied to the antenna.
UHF BAND
The TX signal from the UHF band modulation circuit is ampli-
fi ed by the LO AMP (Q37), passed through the HPF (L52 and
C232), ATT (R155, R156 and R162), and then sequentially
amplifi ed by the pre-drive AMP (Q38), drive AMP (Q41) and
power AMP (IC4).
The amplifi ed TX signal is passed through the LPF (L69, L73,
C310, C319, C322, C323, C350, C358 and C359), TX output
power detector (D62 and D67), ANT SW (D68 and D84) and
HPF (L84, L88, C391, C392, C395, C402, C429 and C430)
and LPF (L90, L94, L96, C409, C418 and C428), before be-
ing applied to the antenna.
APC CIRCUITS
VHF BAND
A portion of RF signal is rectifi ed by the power detector di-
odes (D59 and D63) at the LPF (L67, L68, C291, C297,
C301, C302, C326, C331 and C332), and the produced DC
voltage, which represents the TX power level, is used as the
TX power sensing voltage.
The TX power sensing voltage is applied to the APC AMP
(IC2, pin 2), and the power setting voltage from the D/A con-
verter (IC102, pin 8) is also applied to the AMP from pin 3,
resulting in the output voltage which is inversely proportional
to the TX power sensing voltage.
When the TX power sensing voltage increases, the output
voltage, which controls the gain of the power AMP (IC3), de-
creases to control the TX power constant.
UHF BAND
A portion of RF signal is rectifi ed by the power detector di-
odes (D62 and D67) at the LPF (L69, L73, C310, C319,
C322, C323, C350, C358 and C359), and the produced DC
voltage, which represents the TX power level, is used as the
TX power sensing voltage.
The TX power sensing voltage is applied to the APC AMP
(IC2, pin 6), and the power setting voltage from the D/A con-
verter (IC102, pin 7) is also applied to the AMP from pin 5,
resulting in the output voltage which is inversely proportional
to the TX power sensing voltage.
When the TX power sensing voltage increases, the output
voltage, which controls the gain of the power AMP (IC4), de-
creases to control the TX power constant.
TX AMP CIRCUITS