ICOM IC-F3022S ユーザーズマニュアル

5 - 1

The antenna switching circuit toggles the receive (RX) line and 
transmit (TX) line.

The received signals from the antenna are passed through the 
low-pass filter (ANT UNIT; L801, L802, C802, C803, C807) 
and antenna switch (D701, D704, D706).

While transmitting, the voltage on the T5V line is applied to 
D701, D704 and D706, and these are ON. Thus the TX line 
is connected to the antenna. Simultaneously, the RX line is 
connected to the ground (GND) to prevent transmit signal 
entering.

While receiving, no voltage is applied to the D701, D704 and 
D706, and these are OFF. Thus the TX line and the antenna 
are disconnected to prevent received signals entering. 
Simultaneously, the RX line is disconnected from the GND and 
the received signals are passed through the low-pass filter 
(L712, L714, C750, C751). The fi ltered signals are applied to 
the RF circuits.

RF circuits filter and amplify the received signals within the 
frequency coverage.

The received signals from the antenna switching circuit are 
passed though the two-staged bandpass filter (BPF; D19, 
D24, L7, L8, C22, C25, C27–C29, C369) to fi lter-out unwanted 
signals, and the fi ltered signals are applied to the RF amplifi er 
(Q5). The amplifi ed received signals are then applied to the 1st 
mixer (Q6) via another BPF (L47–L49, C19, C40, C437–C439, 
C443).

The received signals are converted into the 1st IF signal, 
fi ltered and amplifi ed at the 1st IF circuits.

The received signals from the BPF (L47–L49, C19, C40, C437
–C439, C443) are applied to the 1st mixer (Q6) and converted 
into the 46.35 MHz 1st IF signal by being mixed with the local 
oscillator (LO) signal from the RX VCO (Q17, D9, D11, D33).

The converted 1st IF signal is passed through the 1st IF fi lter 
(FI1) to filter-out adjacent signals, then applied to the 1st IF 
amplifi er (Q7). The amplifi ed 1st IF signal is then applied to the 
FM IF IC (IC9, pin 16).

The 1st IF signal is converted into the 2nd IF signal, and 
demodulated.

The 1st IF signal from the 1st IF amplifi er is applied to the 2nd 
mixer in the FM IF IC (IC9, pin 16), and converted into the 
450 kHz 2nd IF signal by being mixed with the 45.9 MHz 2nd 
LO signal from the reference frequency oscillator (X2) via the 
tripler (Q22) and BPF (L33, C163, C164, C166). The converted 
2nd IF signal is output from pin 3, and passed through the 2nd 
IF fi lters to remove sideband noise.

The 2nd IF signal is passed through the 2nd IF fi lter (FI2) and 
applied to the FM IF IC (IC9, pin 5) again. The fi ltered 2nd IF 
signal is amplifi ed at the limiter amplifi er, and FM-demodulated 
by the quadrature detector (IC9, pins 10, 11, X1). The 
demodulated AF signals are output from pin 9, then applied to 
the AF amplifi er circuits.

The demodulated AF signals from the FM IF IC are amplifi ed 
and fi ltered at AF circuits.

The demodulated AF signals from the FM IF IC (IC9, pin 9) are 
passed through high-pass fi lter (HPF; IC5, pins 2, 1) to remove 
tone signals. The filtered AF signals are passed through the 
de-emphasis circuit (R142, C249) to obtain the 6 dB/oct of 
frequency characteristic. The de-emphasized AF signals are 
passed through the RX mute switch (Q32, Q33), AF switch 
(Q36, Q37), HPF (IC5, pins 13, 14), analog switch (IC3, pins 1, 
2), AF mixer (IC5, pins 6, 7) and analog switch (IC3, pins 10, 
11) in sequence.

D/A converter 

(IC12) 

Mixer 

RSSI 

Quadrature   

detector 

24 

23 

1st IF signal from the 1st IF amplifier (Q7) 

16 

Noise  

detector 

R5V 

X1 

11 

10 

Filter 
amp. 

Noise 

amp. 

Limiter 
amp. 

Demodulated signals  
to the AF circuits  

9 

“NOIS” signal to the CPU (IC22: pin 75) 

“RSSI” signal to the CPU (IC22: pin 50) 

13 

12 

Q22 

X2 

15.3 MHz 

45.9 MHz 

BPF 

2 

3 

8 

7 3 

5 

FI2 

TCXO