Modulation Circuits (Main Unit); Tx Amp Circuits (Main Unit); Apc Circuits (Main Unit); Vhf And Uhf Bands - Icom ID-5100E Service Manual

MODULATION CIRCUITS (MAIN UNIT)

The MIC signal from the TX AF circuits is applied to the VCO
as the GMSK (For the DV mode) or Frequency Modulation
(For the FM mode) modulation signal.
VHF BAND
The modulation signal is applied to the VHF VCO (Q211,
D203, D204 and D228).
The modulated VCO output signal is amplifi ed by the buffer
(Q215) and LO AMP (IC203), and then applied to the TX AMP
circuits as the TX signal, through the LO SW (D50).
UHF BAND
The modulation signal is applied to the UHF VCO (Q232,
D223, D224 and D227) as a modulation signal.
The modulated VCO output signal is amplifi ed by the buffer
(Q235) and LO AMP (IC208), and then applied to the TX AMP
circuits as the TX signal, through the LO SW (D52).
• TX AMP AND APC CIRCUITS
Q232
Q235
Q227
UHF TX VCO BUFF
Q211
Q215
Q207
BUFF
IC205
VCOMOD MOD
MUTE
VHF TX VCO
IC208 D52 Q38
TX/RX
LO
HPF ATT YGR
AMP SW
Q36
IC203 D50
TX/RX
LO LPF ATT
YGR
AMP SW

TX AMP CIRCUITS (MAIN UNIT)

VHF BAND
The TX signal is passed through the LPF (L50, L51, C215,
C220 and C225) and ATT (R146, R147 and R151), and then
sequentially amplifi ed by the YGR (Q36), drive AMP (Q40)
and power AMP (IC3).
The amplifi ed TX signal is passed through the LPF (L67,
C291 and C297), TX output power detector (D59 and D63),
ANT SW (D66) and two LPFs (L90, L94, L96, C409, C418
and L79, L83, L87, C378, C386, C394), before being applied
to the antenna.
UHF BAND
The TX signal is passed through the HPF (L52 and C232) and
ATT (R155, R156 and R162), and then sequentially amplifi ed
by the YGR (Q38), drive AMP (Q41) and power AMP (IC4).
The amplifi ed TX signal is passed through the LPF (L69,
C310 and C319), TX output power detector (D62 and D67),
ANT SW (D68 and D84), HPF (L84, L88, C391, C395 and
C402) and LPF (L90, L94, L96, C409, C418), before being
applied to the antenna.

APC CIRCUITS (MAIN UNIT)

At the TX output power detector, the RF signal at the LPFs
(VHF band: L68, C301, C302 and C326/UHF band: L73,
C322, C323 and C350) is rectifi ed by the diodes (VHF band:
D59 and D63, UHF band: D62 and D67), and it is used as the
TX power sensing voltage.
The voltage is applied to the APC AMP (IC2), and the output
voltage controls the bias voltages of the power AMP (VHF
band: IC3, UHF band: IC4) to keep the TX output power con-
stant.
UHF band
Q41 IC4
PWR
DRIVE
HPF LPF LPF
AMP
AMP
Q40 IC3
PWR
DRIVE LPF
AMP
AMP
IC2
VHF band
APC
CTRL
4-4
D84
375-550MHz
D62/D67 D68/D73/D75
PWR TX/RX
HPF
DET SW
D66/D69/
118-174MHz
D59/D63 D70/D77
PWR TX/RX
LPF
DET SW
VHF RX circuit
UHF RX circuit
ANTENNA
118-550MHz
LPF