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4-5
4-3 FREQUENCY SYNTHESIZER CIRCUIT
(MAIN UNIT)
VCOs
The ID-5100A/E has total of fi ve VCOs: three VCOs for Band
A and another two for Band B.
• Band A
VHF VCO #1
(Used when the Heterodyne function is set to "Normal")
The VHF VCO #1 (Q211, D204, D206 and D228) generates
both 1st LO signal (for receiving a VHF signal on Band A)
and the VHF TX signal. The output of buffer (Q215) is ampli-
fi ed by the LO AMP (IC203), and then used as the VHF TX/
RX LO signal.
While receiving, the LO signal is applied to the 1st IF mixer
(IC125) for receiving a signal on the VHF band, through the
RX LO SW (D212 and D217) and LPF (L314, L316, C986,
C992 and C997).
While transmitting, the LO signal is applied to the TX AMP
circuits, through the LO SW (D50).
VHF VCO #2
(Used when the Heterodyne function is set to "Reverse")
The VHF VCO #2 (Q237, D238 and D239) generates the 1st
LO signal (for receiving a VHF signal on Band A). The output
of buffer (Q215) is amplifi ed by the LO AMP (IC203), and
then applied to the 1st IF mixer (IC125) for receiving a signal
on the VHF band, through the RX LO SW (D212 and D217)
and LPF (L314, L316, C986, C992 and C997).
UHF VCO
The UHF VCO (Q205, Q210, D201, D202 and D205) gener-
ates the 1st LO signal (for receiving a UHF signal on Band
A). The output of buffer (Q214) is amplifi ed by the LO AMP
(IC203), and then applied to the 1st IF mixer (IC125), through
the RX LO SW (D213 and D216) and LPF (L315, C988 and
C995).
• Band B
VHF VCO
The VHF VCO (Q228, Q233, D225, D226 and D230) gener-
ates the 1st LO signal (for receiving a UHF signal on Band
A). The output of buffer (Q236) is amplifi ed by the LO AMP
(IC208), and then applied to the 1st IF mixer (IC124), through
the RX LO SW (D235 and D237) and LPF (L338, L339,
C1103, C1105 and C1106).
UHF VCO
The UHF VCO (Q232, Q227, D223, D224, D227 and D229)
generates both 1st LO signal (for receiving a UHF signal on
Band B) and the UHF TX signal. The output of buffer (Q235)
is amplifi ed by the LO AMP (IC208), and then used as the
UHF TX/RX LO signal.
While receiving, the LO signal is applied to the 1st IF mixer
(IC124) for receiving a signal on the UHF band, through the
RX LO SW (D234 and D236) and LPF (L337, C1102 and
C1104).
While transmitting, the LO signal is applied to the TX AMP
circuits, through the LO SW (D52).
PLL
•
Band A
A portion of VHF and UHF VCOs output signal is amplifi ed by
the buffer (Q213), and then fed back to the PLL IC (IC201).
The PLL IC (IC201) phase-compares the output of reference
frequency oscillator (TCXO: X200) and VCO, and the phase
difference is output as the charge pump current. The current
is passed though the loop fi lter (R715, R717, R719, R722,
C924, C926 to C928 and C930) to be converted into the lock
voltage, which controls the oscillating frequency of VCO.
When the oscillation frequency drifts, its phase changes from
that of the reference frequency, causing a lock voltage change
to compensate for the drift in the VCO oscillating frequency.
• Band B
A portion of VHF and UHF VCOs output signal is amplifi ed by
the buffer (Q234), and then fed back to the PLL IC (IC206).
The PLL IC (IC206) phase-compares the output of reference
frequency oscillator (TCXO: X201) and VCO, and the phase
difference is output as the charge pump current. The current
is passed though the loop fi lter (R797, R799, R802, R805,
C1041, C1043 to C1045 and C1048) to be converted into the
lock voltage, which controls the oscillating frequency of VCO.
When the oscillation frequency drifts, its phase changes from
that of the reference frequency, causing a lock voltage change
to compensate for the drift in the VCO oscillating frequency.
TX/RX
SW
AMP
AMP
FIL
LOOP
BUFF
BUFF
BUFF
BUFF
BUFF
BUFF
PLL
IC
LPF
LPF
X3
TX/RX
SW
X3
FIL
LOOP
PLL
IC
RX
SW
IF IC
IF IC
15.3 MHz
38.4 MHz
45.9 MHz
12.8 MHz
R_UHF
R_VHF
L_UHF
L_VHF
IC207/Q222
X201
IC206
Q220
IC202/Q202
X200
IC201
Q200
Q213
Q215
Q211
Q210
Q214
IC203
Q234
Q236
Q233
Q232
Q235
IC208
D52/D234/D235
D50
D212/D213
D236
D237
D216
D217
2nd LO
1st LO
1st LO
2nd LO
IC121
A band
B band
IC120
IC125
1st mixer
1st mixer
IC124
LPF
LPF
RX
SW
D223,D224,
D227,D227
D225,D226,D230
D201,D202,D205
D203,D204,
D206,D228
Q237
D238,D239
TX:400-470 MHz
RX:353.65-516.35 MHz
RX:164.35-220.35 MHz
RX:361.15-511.15 MHz
137-174 MHz
RX:79.15-135.15 MHz
TX:
RX:
156.85-212.85 MHz
• FREQUENCY SYNTHESIZER CIRCUIT