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4-1 RECEIVER CIRCUITS

4-1-1 ANTENNA SWITCHING CIRCUIT

The antenna switching circuit functions as a low-pass filter
while receiving and a resonator circuit while transmitting.
This circuit does not allow transmit signals to enter the
receiver circuits.

Received signals enter the antenna connector (CHASSIS;
MP44) and pass through the low-pass filter (L1, L2, C1, C2,
C420). The filtered signals are passed through the 

λ

4

type

antenna switching circuit (D25, L39, D24) and then applied
to the RF circuit.

4-1-2 RF CIRCUIT

The RF circuit amplifies signals within the range of frequen-
cy coverage and filters out-of-band signals.

The signals from the antenna switching circuit pass through
the tunable bandpass filter (D21, L37). The filtered signals
are amplified at the RF amplifier (Q20) and then passed
through the another three-stage bandpass filters (D20–D18,
L36, L34, L33) to suppress unwanted signals. The filtered
signals are applied to the 1st mixer circuit.

D18–D21 employ varactor diodes, that are controlled by the
CPU via the D/A converter (IC27), to track the bandpass fil-
ter. These varactor diodes tune the center frequency of an
RF pass band for wide bandwidth receiving and good image
response rejection.

4-1-3 1ST MIXER AND 1ST IF CIRCUITS

The 1st mixer circuit converts the received signal into fixed
frequency of the 1st IF signal with the PLL output frequency.
By changing the PLL frequency, only the desired frequency
passes through a monolithic filter at the next stage of the 1st
mixer.

The RF signals from the bandpass filter are mixed with the
1st LO signals, where come from the RX VCO circuit via the
attenuator (R108–R106), at the 1st mixer circuit (Q19) to
produce a 47.25 MHz 1st IF signal. The 1st IF signal is
passed through a monolithic filter (FI1) in order to obtain
selection capability and to pass only the desired signals. The
filtered signal is applied to the 2nd IF circuit after being
amplified at the 1st IF amplifier (Q18).

4-1-4 2ND IF AND DEMODULATOR CIRCUITS

The 2nd mixer circuit converts the 1st IF signal into a 2nd IF
signal. The double-conversion superheterodyne system
(which convert receive signals twice) improves the image
rejection ratio and obtains stable receiver gain.

The 1st IF signal from the IF amplifier (Q18) is applied to the
2nd mixer section of the FM IF IC (IC3, pin 16), and is mixed
with the 2nd LO signal to be converted into a 450 kHz 2nd
IF signal.

The FM IF IC (IC3) contains the 2nd mixer, 2nd local oscil-
lator, limiter amplifier, quadrature detector, active filter and
noise amplifier circuits. A 2nd LO signal (46.8 MHz) is pro-
duced at the PLL circuit by tripling it’s reference frequency
(15.6 MHz).

The 2nd IF signal from the 2nd mixer (IC3, pin 3) passes
through the ceramic filters (FI2, FI3) during narrow channel
spacing selection or FI2 only (bypassing FI3) during wide
channel spacing selection to remove unwanted heterodyned
frequencies. It is then amplified at the limiter amplifier sec-
tion (IC3, pin 5) and applied to the quadrature detector sec-
tion (IC3, pins 10, 11) to demodulate the 2nd IF signal into
AF signals.

The demodulated AF signals are output from pin 9 (IC3) and
applied to the AF circuit via the receiver mute circuit.

4 - 1

SECTION 4

CIRCUIT DESCRIPTION

• 2nd IF and demodulator circuits

Mixer

16

Limiter
amp.

2nd IF filter
450 kHz

X1

15.6 MHz

46.8 MHz

IC3 TA31136FN

12

1st IF from the IF amplifier (Q18)

"RSSI" signal to the CPU (IC14, pin 50)

11

10

9

8

7

AF signal "DSIN"

R5

X2

Squelch level
controller IC13

2

Active
filter

Noise

detector

FM

detector

13

"NOIS" signal to the CPU (IC14, pin 75)

RSSI

Noise
comp.

×

3

Tripler

Q15

23

24

FI2

5

FI3

3

Summary of Contents for IC-F41GS

Page 1: ...UHF TRANSCEIVER iC f40gt iC f40gs iC f4 1 gt iC f4 1 gs iC f40gt ic f40gs iC f41gt ic f41gs including MT version...

Page 2: ...efore disassembling the transceiver 2 DO NOT open the transceiver until the transceiver is disconnected from its power source 3 DO NOT force any of the variable components Turn them slowly and smoothl...

Page 3: ...PLL CIRCUIT 4 3 4 4 POWER SUPPLY CIRCUITS 4 4 4 5 CPU PORT ALLOCATIONS 4 4 SECTION 5 ADJUSTMENT PROCEDURES 5 1 PREPARATION 5 1 5 2 PLL ADJUSTMENT 5 4 5 3 SOFTWARE ADJUSTMENT 5 5 SECTION 6 PARTS LIST...

Page 4: ...0 000 MHz ML band 440 000 480 000 MHz GEN EUR MH band 450 000 490 000 MHz USA GEN H band 480 000 512 000 MHz USA 480 000 520 000 MHz GEN 16K0F3E 25 kHz Wide 8K50F3E 12 5 kHz Narrow Max 256 ch 16 chann...

Page 5: ...ircuit 3 58 MHz crystal X4 CR 563 3 579545 MHz PTT MD1 switch IC28 TC7W53FK 2nd IF filter 450 kHz FI2 SFPCA450KE4A FI3 SFPCA450KG1A IF discreminator X2 CDBCB450KCAY24 450 kHz T5 regulator Q29 2SA1362...

Page 6: ...off the flexible cable in the direction of the arrow e Unscrew 10 screws F 2 3 mm black to separate the shield plate q Unsolder 1 point G at the antenna lead w Unscrew 2 nuts H e Unscrew 6 screws I 2...

Page 7: ...gnal The 1st IF signal is passed through a monolithic filter FI1 in order to obtain selection capability and to pass only the desired signals The filtered signal is applied to the 2nd IF circuit after...

Page 8: ...s even when noise squelch is open A portion of the AF signals from the FM IF IC IC3 pin 9 passes through the low pass filter IC20b a to remove AF voice signals and is applied to the CTCSS or DTCS deco...

Page 9: ...LL circuit provides stable oscillation of the transmit fre quency and receive 1st LO frequency The PLL output com pares the phase of the divided VCO frequency to the refer ence frequency The PLL outpu...

Page 10: ...O port for data signals from to EEPROMs IC16 IC24 Outputs beep audio signals Outputs clock signal to EEPROMs IC16 IC24 Outputs clock signal to the D A con verter IC27 SO DAST DTAC SENC CTDA SDEC RXDT...

Page 11: ...tment data as desired High power transmittion When you adjust the output power high power the battery type detector must be connected to GND see illustration at below Otherwise the transceiver does no...

Page 12: ...12 70h 2 20V MOD BAL 90 5Ah 1 76 V Dev 45 2Dh 0 88 V CTCSS 76 4Ch 1 49 V SQL Lev 0 00h 1 18 V CH No 01 RX Freq 450 000 TX Freq RF Power Low1 Mode Wide Transceiver s connection state Reload adjustment...

Page 13: ...T F40GS F41GT or F41GS s up to date condi tion t Set or modify adjustment data as desired High power transmittion When you adjust the output power high power the battery type detector must be connecte...

Page 14: ...112 70h 2 20V MOD BAL 90 5Ah 1 76 V Dev 45 2Dh 0 88 V CTCSS 76 4Ch 1 49 V SQL Lev 0 00h 1 18 V CH No 01 RX Freq 450 000 TX Freq RF Power Low1 Mode Wide Transceiver s connection state Reload adjustment...

Page 15: ...eaker 8 Audio generator Connection common to the antenna connector RF power meter 0 1 10 W 50 Frequency counter Attenuator 40 dB or 50 dB FM deviation meter Standard signal generator 0 1 V to 32 mV 12...

Page 16: ...520 000 MHz H Receiving Transmitting MAIN Connect a digital multi meter or an oscillo scope to the check point CP7 1 3 V 1 3 V 2 5 4 0 V L 3 0 4 5 V other 3 0 4 5 V MAIN C372 C373 Verify ADJUSTMENT A...

Page 17: ...MHz ML 450 000 MHz MH 480 000 MHz H Output power Low1 IF bandwidth Wide Set the FM deviation meter as HPF OFF LPF 20 kHz De emphasis OFF Detector P P 2 Connect the audio generator to the multi connect...

Page 18: ...000 MHz MH 480 000 MHz H IF bandwidth Wide Connect a standard signal generator to the antenna connector and set as Frequency 400 000 MHz L 440 000 MHz ML 450 000 MHz MH 480 000 MHz H Level 10 V 87 dBm...

Page 19: ...perating freq 400 000 MHz L 440 000 MHz ML 450 000 MHz MH 480 000 MHz H IF bandwidth Wide Connect an SSG to the antenna con nector and set as Frequency 400 000 MHz L 440 000 MHz ML 450 000 MHz MH 480...

Page 20: ...C9 4550006150 S TANTALUM ECST1CY105R C10 4550006150 S TANTALUM ECST1CY105R C11 4550006150 S TANTALUM ECST1CY105R C12 4030014180 S CERAMIC ECUE1H470JCQ C13 4030014180 S CERAMIC ECUE1H470JCQ C14 4030014...

Page 21: ...S DIODE DAN202U T106 D13 1160000050 S DIODE DAP202U T106 D14 1160000050 S DIODE DAP202U T106 D15 1160000060 S DIODE DAN202U T106 D16 1160000060 S DIODE DAN202U T106 D17 1790001210 S DIODE 1SS375 TL D1...

Page 22: ...S RESISTOR ERJ2GEJ 202 X 2 k R60 7030005090 S RESISTOR ERJ2GEJ 104 X 100 k R61 7030007060 S RESISTOR ERJ2GEJ 684X 680 k R62 7030007570 S RESISTOR ERJ2GEJ 122X 1 2 k R63 7030005580 S RESISTOR ERJ2GEJ...

Page 23: ...7410000770 S ARRAY EXB V4V 102JV 1 k R246 7410000950 S ARRAY EXB V8V 102JV R247 7410000950 S ARRAY EXB V8V 102JV R248 7030005120 S RESISTOR ERJ2GEJ 102 X 1 k R249 7410000950 S ARRAY EXB V8V 102JV R25...

Page 24: ...014050 S CERAMIC ECUE1H030BCQ M F41G 4030014080 S CERAMIC ECUE1H050BCQ other C47 4030014220 S CERAMIC ECUE1E471KBQ C48 4030014130 S CERAMIC ECUE1H120JCQ F40G 4030014080 S CERAMIC ECUE1H050BCQ L F41G 4...

Page 25: ...4030009820 S CERAMIC C1005 JB 1E 103K T A L F41G C176 4030013850 S CERAMIC ECUE1E102KBQ C177 4030014220 S CERAMIC ECUE1E471KBQ C178 4550006670 S TANTALUM ECST1AD107R C179 4030013960 S CERAMIC C1005 J...

Page 26: ...20JCQ MH 4030014140 S CERAMIC ECUE1H150JCQ H C362 4030017220 S CERAMIC ECUE1E122KBQ C364 4030014180 S CERAMIC ECUE1H470JCQ C365 4030014180 S CERAMIC ECUE1H470JCQ C366 4030014180 S CERAMIC ECUE1H470JCQ...

Page 27: ...only C471 4030014180 S CERAMIC ECUE1H470JCQ F41G only C472 4030014180 S CERAMIC ECUE1H470JCQ F41G only C473 4550006700 S TANTALUM ECST1AY106R F41G only C474 4030009520 S CERAMIC C1608 CH 1H 020B T H...

Page 28: ...I ZU 8 MP60 8930046000 1903 microphone sponge GS 1 MP61 8930053660 2337 side seal 1 MP63 8930053880 2337 key sheet GT 1 8930054010 2337 4 key sheet GS 1 MP64 8930051781 Insulation sheet GA 1 1 MP65 89...

Page 29: ...C MP19 C MP26 C MP20 C MP5 C MP57 C MP59 C MP41 C MP40 C MP40 C MP40 C MP1 F MP2 F MP3 F W1 F MC1 F MP60 C MP2 M MP6 M MP8 M MP49 C MP52 C MP59 C MP32 C MP33 C VR w SW CHANNEL SW MP7 M MP1 M MP59 C MP...

Page 30: ...B8 HVU350BTRF B0 A C MA6S121 M2D A1 A2 A3 C1 C2 C3 MA77 4B A C 2SK2974 K2974 G G D D S S TOP VIEW 2SK880 Y XY G S D 2SK2973 K1 G D S S B E C B E C XP6501 AB 5N E1 B2 E2 C1 C2 B1 B E C 3SK206 T1 U78 U...

Page 31: ...Under side 1 P0 P1 P2 P3 4 7 2 5 8 0 3 6 9 MICROPHONE 9 1 9 1 FRONT UNIT SECTION 9 BOARD LAYOUTS TOP VIEW The combination of this page and the next page shows the unit layout in the same configuratio...

Page 32: ...1 D2 D3 D4 D5 D7 OSC0 OSC1 VSS PMODE VDD VEE CAP CAP VEE2 1 5 10 15 20 25 30 35 40 VOUT VR2 SCL WRB RDB D0 M86 VS TE RESB CSB RS M S P S V1 V2 V3 NC NC V0 V4 LCD PTT F2 F3 F3 F0 to MAIN unit J3 SPEAKE...

Page 33: ...9 AFO VCC DETECT MICE RESET XRXD XTXD MIC PTT 3 1 8 7 2 4 5 6 9 3 1 1 2 3 4 5 6 INT SP SW AF VR POWER SW CH SELECT OPT2 OPT1 1 5 10 15 16 20 25 30 1 5 10 15 16 20 25 30 UNIVERSAL CONNECTOR MP6 OPC 96...

Page 34: ...6 9 3 1 1 2 3 4 5 6 INT SP SW AF VR POWER SW CH SELECT PTT MIC XTXD XRXD RESET MICE DETECT VCC AFO MP67 CHASSIS H band only F40G MAIN unit BOTTOM VIEW The combination of this page and the previous pag...

Page 35: ...T2 OPT1 1 5 10 15 16 20 25 30 1 5 10 15 16 20 25 30 UNIVERSAL CONNECTOR MP6 OPC 966 EM 80 AD 52 HS 93 GND SPCN D0 FRST PTT D5 D4 D3 D2 D1 RDB WRB RS GND RESB VCC KR0 KR1 KR2 KR3 MIC SP GND 5V D7 D6 to...

Page 36: ...1 8 7 2 4 5 6 9 3 1 1 2 3 4 5 6 INT SP SW AF VR POWER SW CH SELECT PTT MIC XTXD XRXD RESET MICE DETECT VCC AFO F41G MAIN unit BOTTOM VIEW The combination of this page and the previous page shows the u...

Page 37: ...Q9 DTC144EU CPU BATT POWER SW FUSE VOXT TA75S01F F1 IC13 DA2 IC15 BEP1 BEP2 TONE VCC BEEP SSOR MCIN X4 Q47 2SC4081 MCOT CR 563 3 58 MHz REM MSKE TRD DIN REGS1 REGS2 RTM RDT FCLR D A IC27 M62334 SCL S...

Page 38: ...0k C357 47 T5C R5C HV SENC DTMF DECODE C242 4 7 C257 0 1 C244 0 001 INPUT 1 NC 2 PD 3 OSCO 4 OSCI 5 NC 6 VSS 7 LOADB 8 SD 9 ACK 10 STD 11 EST 12 NC 13 VDD 14 IC17 LC73872M C246 0 001 C384 0 001 R201 2...

Page 39: ...MOD MIX R182 27k 1 3 4 5 2 IC8 TC75S51F Q26 DTC144EUA 1 3 4 5 2 IC7 TA75S01F R178 27k R181 27k C200 56p C362 0 0012 R161 68k R162 68k C400 0 001 R163 33k C202 270p R177 18k R176 47k R281 27k C410 0 1...

Page 40: ...81 12 288MHz R235 1k C437 47p OPT22 OPT21 OPT23 SDA R237 1k C287 47p R239 1k R236 1k C273 47p OPT13 OPT11 OPT12 AUX MSCK MSO PB3 A11 TIOCD3 25 PB4 A12 TIOCA4 26 PE5 D5 1 PE6 D6 2 PE7 D7 3 PD0 D8 4 PD1...

Page 41: ...dquarters 2380 116th Avenue N E Bellevue WA 98004 U S A Phone 425 454 8155 Fax 425 454 1509 URL http www icomamerica com Customer Service Phone 425 454 7619 Glenwood Centre 150 6165 Highway 17 Delta B...

Page 42: ...iC f40gt ic f40gs iC f41gt ic f41gs S 13803MZ C1 q 2001 Icom Inc 1 1 32 Kamiminami Hirano ku Osaka 547 0003 Japan...

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