Icom ID-880H Service Manual

• TX AMPLIFIER AND APC CIRCUITS
4 - 5
PWR
DET
LPF
APC
CTRL
HPF
PWR
AM P
ATT
ATTLPF LPF
TX/RX
SW
DRIVE
AMP
HPFLPF
DRIVE
AMP
PWR
DET
LPF
TX/RX
SW
PWR
AM P
DRIVE
PRE
Q25
D59,68,75,77
D42,52,1006
LIMITER
T
LIMITER
D39,D47,D1005
Q22
D25
IC4
D30,53,61,62,177
To UHF RX circuitsTo VHF RX circuits
IC3
Q26
PCON_U PCON_V
D29
IC2
From the frequency synthesizer
circuits
D155
LO SW
LO SW
D103
VHF band TX signal ->
UHF TX signal ->
TX AMPLIFIER CIRCUITS (VHF BAND)
The output signal of VHF VCO (Q111, D145–148) is passed
through the LO SW (D155), LPF and ATT, then applied to
the drive AMP (Q25) via the limiter (D29), to obtain adequate
input level for the power AMP (power MOS-FET module;
IC3).
The amplifi ed TX signal is power-amplifi ed to 50 W (approx.;
25 W for [TPE] ver.) of output power (max.) by the power
AMP (IC3).
The power-amplified TX signal is passed through the LPF
which attenuates harmonic components to prescribed level,
then applied to the antenna connector via the power detector
(D39, 47, 1005), TX/RX SW (D59, 68, 75, 77) and two LPFs.
APC CIRCUITS (VHF BAND)
A portion of the TX signal from IC3 is rectifi ed at the power
detector (D39, 47, 1005), and converted into the DC voltage
which is in proportion to the RF power, and applied to the
operational amplifi er (IC4, pin 6). IC4 is an APC amplifi er for
both of V/UHF bands. The TX power setting voltage “PCON_
V” from the D/A converter (IC1) is applied to the pin 5 as
a reference. IC4 is rolled as a differential amplifier which
outputs voltage in inverse proportion to rectifi ed one.
When the TX power increased, the rectified voltage also
increased, that causes the decrease of output voltage of
differential amplifier. The decrease of output voltage of
differential amplifi er causes the drop of the gate voltage of
IC3, Thus the TX power maintained to keep stable level.
TX AMPLIFIERS (UHF BAND)
The output signal of UHF VCO (Q73, D87, 91, 92) is passed
through the LO SW (D103), HPF and ATT, then applied to
the pre-drive AMP (Q22). The amplifi ed TX signal is applied
to the drive AMP (Q26) via the limiter (D25) and amplifi ed to
obtain adequate input level for the power AMP (power MOS-
FET module; IC2).
The amplifi ed TX signal is power-amplifi ed to 50 W (approx.;
25 W for [TPE] ver.) of output power by the power AMP (IC2).
The power-amplified TX signal is passed through the LPF
which attenuates harmonic components to prescribed level,
then applied to the antenna connector via the power detector
(D42, 52, 1006), TX/RX SW (D30, 53, 61, 62, 177), HPF and
LPF.
APC CIRCUITS (UHF BAND)
A portion of the TX signal from IC2 is rectifi ed at the power
detector (D42, 52, 1006), and converted into the DC voltage
which is in proportion to the RF power, and applied to the
operational amplifi er (IC4, pin 2). IC4 is an APC amplifi er for
both of V/UHF bands. The TX power setting voltage “PCON_
U” from the D/A converter (IC1) is applied to the pin 3 as
a reference. IC4 is rolled as a differential amplifier which
outputs voltage in inverse proportion to rectifi ed one.
When the TX power increased, the rectified voltage also
increased, that causes the decrease of output voltage of
differential amplifier. The decrease of output voltage of
differential amplifi er causes the drop of the gate voltage of
IC2, Thus the TX power maintained to keep stable level.

Icom ID-880H Specifications

General

Input voltage	13.8 V
Mounting kit	Yes
Product type	Portable CB radio
Product color	Black
Housing material	-
Frequency range	10 - 20000 MHz
Channels quantity	1052 channels

Weight and Dimensions

Depth	198.12 mm
Width	149.86 mm
Height	40.64 mm