Icom ID-51E User Manual page 12

2ND IF CIRCUITS
• Band A
The 1st IF signal from the 1st IF circuit is applied to the IF IC
(IC13, pin 16), which contains the 2nd IF AMP, 2nd mixer, FM
demodulator, and so on.
The 1st IF signal is mixed with the 45.9 MHz 2nd LO signal,
resulting in the 450 kHz 2nd IF signal. The converted sig-
nal is passed through the external 2nd IF fi lter (FM mode;
FI2, FM-N or DV mode; FI1) to remove sideband noise. The
fi ltered signal is amplifi ed by the 2nd IF AMP, and then de-
modulated by the quadrature detector (X2).
The demodulated signal is applied to the RX AF circuit (For
FM and FM-N modes) or digital demodulation circuit (For DV
mode).
• 2ND IF CIRCUITS
To the RX AF circuit (Band A).
To the RX AF circuit (Band B).
• Band B
The 1st IF signal from the 1st IF circuit is applied to the IF IC
(IC901, pin 16), which contains the 2nd IF AMP, 2nd mixer,
FM demodulator, and so on.
The 1st IF signal is mixed with the 61.2 MHz 2nd LO signal,
resulting in the 450 kHz 2nd IF signal. The converted signal
is passed through the external 2nd IF fi lter (FI900) to remove
sideband noise.
While receiving in the FM mode, the fi ltered signal is amplifi ed
by the 2nd IF AMP, and then demodulated by the quadrature
detector (X900). The demodulated signal is applied to the RX
AF circuit, through the AF SW (IC18, pins 6, 1).
While receiving in the AM mode, the fi ltered signal is demod-
ulated by Q904 and amplifi ed by the AGC AMP (Q903). The
demodulated signal is applied to the RX AF circuit, through
the AF SW (IC18, pins 7, 1).
X1
FM-N/DV
15.3MHz
Q38
CERAMIC
BPF
REF
X3
45.9MHz
BPF
Q900
Q904
REF
X4
AM
DET
61.2MHz
IC18
MODE
BPF
SW
4 - 3
FM
CERAMIC
BPF
-Band A:46.35MHz-
FI1 FI2
W/N
SW Q36,D15
D16,D18,D19
IC13
From the 1st IF circuit (Band A).
FM
DET
DISCRI
X2
FM
CERAMIC
BPF
FI900
-Band B:61.65MHz-
IC901
From the 1st IF circuit (Band A).
FM
DET
DISCRI
X900