ICOM IC-R20 Service Repair Manual

COMMUNICATIONS RECEIVER iC-r20 SERVICE MANUAL

INTRODUCTION DANGER This service manual describes the latest service information for the IC-R20 COMMUNICATIONS RECEIVER at the time of publication. This service manual covers each versions. MODEL IC-R20 VERSION [USA], [EXP-01], [CAN] [EUR], [EXP-02] [UK], [SEA] AC adapter BC-149A BC-149D – ORDERING PARTS Be sure to include the following four points when ordering replacement parts: 1. 10-digit order numbers 2. Component part number and name 3. Equipment model name and unit name 4. Quantity required <SAMPLE ORDER> 1110003200 S.IC TA31136FN IC-R20 RF UNIT 5 pieces 8930062430 Key 2699 Keyboard IC-R20 Chassis 12 pieces Addresses are provided on the inside back cover for your convenience. NEVER connect the receiver to an AC outlet or to an external DC power supply that uses more than 6.3 V. This will ruin the receiver. DO NOT expose the receiver to rain, snow or any liquids. DO NOT reverse the polarities of the power supply when connecting the receiver. DO NOT apply an RF signal of more than 20 dBm (100 mW) to the antenna connector. This could damage the receiver’s front end. REPAIR NOTES 1. Make sure a problem is internal before disassembling the receiver. 2. DO NOT open the receiver until the receiver is disconnected from its power source. 3. DO NOT force any of the variable components.Turn them slowly and smoothly. 4. DO NOT short any circuits or electronic parts. An insulated turning tool MUST be used for all adjustments. 5. DO NOT keep power ON for a long time when the receiver is defective. 6. READ the instructions of test equipment thoroughly before connecting equipment to the receiver. To upgrade quality, any electrical or mechanical parts and internal circuits are subject to change without notice or obligation. Icom, Icom Inc. and are registered trademarks of Icom Incorporated (Japan) in the United States, the United Kingdom, Germany, France, Spain, Russia and/or other countries.

SECTION 1 SPECIFICATIONS SECTION 2 INSIDE VIEWS SECTION 3 DISASSEMBLY INSTRUCTIONS SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1 4-2 PLL CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 7 4-3 OTHER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 10 4-4 POWER SUPPLY CIRCUITS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 11 4-5 PORT ALLOCATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 12 4-6 BC-156 CIRCUIT DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 14 SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1 5-2 SOFTWARE ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3 SECTION 6 PARTS LIST SECTION 7 MECHANICAL PARTS AND DISASSEMBLY SECTION 8 SEMI-CONDUCTOR INFORMATION SECTION 9 BOARD LAYOUTS 9-1 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 1 9-2 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3 9-3 REC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5 9-4 1STAVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7 9-5 1STBVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7 9-6 2NDCVCO BOARD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7 9-7 2NDDVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7 9-8 DOWNCONV BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7 SECTION 10 BLOCK DIAGRAM SECTION 11 VOLTAGE DIAGRAM 11-1 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 1 11-2 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 3 11-3 REC UNIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 4 11-4 1STAVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5 11-5 1STBVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5 11-6 2NDCVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 6 11-7 2NDDVCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 6 11-8 DOWNCONV BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 7 SECTION 12 BC-156 BATTERY CHARGER UNIT 12-1 DISASSEMBLY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 1 12-2 BC-156 BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 1 12-3 BC-156 VOLTAGE DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 2 12-4 BC-156 BOARD LAYOUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 3 TABLE OF CONTENTS

1 - 1 SECTION 1 SPECIFICATIONS • IC-R20 M GENERAL • Frequency coverage : • Mode : FM, WFM, AM, SSB, CW • No. of memory channel : 1250 channel (incl. scan edge and auto memory write ch.) • Frequency stability : ±6 ppm max. • Tuning steps : 0.01, 0.1, 1, 5, 6.25, 8.33*, 9*, 10, 12.5, 15, 20, 25, 30, 50 and 100 kHz *selectable depending on the operating frequency band. • Antenna Impedance : 50 Ω • Power supply requirement : 3 × AA(R6) alkaline cells, BP-206 or external power supply (BC-149/A/D, CP-18) • Polarity : Negative ground • Current drain (at 3.7 V, backlight is OFF) : Rated audio 150 mA typical Standby 100 mA typical Power saved 35 mA typical (Power save ratio is 1 : 4) • Usable temperature range : –10˚C to +60˚C ( –14˚F to +140˚F) • Dimensions : 60(W) × 142(H) × 34.8(D) mm; (projections not included) 2 3 /8 (W) × 5 19 /32 (H) × 1 3 /8(D) in • Weight (with antenna and BP-206) : Approx. 320 (g); 11 19 /32 (oz) • External SP connector : 3-conductor 3.5(d) mm ( 1 /8”) / 8Ω • Audio output power (at 3.7 V) : 100 mW typical at 10 % distortion with an 8 Ω load • BP-206 charging time : Approx. 8 hours • Charging current : 400 mA typical M RECEIVER • Receiver system : Triple super heterodyne and down convertor • Intermediate frequency : 1st 266.7 and 429.1 MHz 2nd 19.65 MHz 3rd 450 kHz • Sensitivity* : Single mode receiving; Except spurious point (Unit; μV) * FM and WFM is measured at 12 dB SINAD. AM, SSB and CW are measured at 10 dB S/N. • Squelch Sensitivity : (except spurious points) • Selectivity : SSB/CW More than 1.8 kHz / –6 dB AM / FM More than 12 kHz / –6 dB Less than 30 kHz / –60 dB WFM More than 150 kHz / –6 dB All stated specifications are subject to change without notice or obligation. Version [EUR], [UK], [SEA], [CAN] [EXP-01], [EXP-02] [USA] [FRA] Receive coverage (MHz) 0.150–3304.999 0.150–821.999, 851.000–866.999, 896.000–1304.999, 1305.000–3304.999 0.150–29.999, 50.200–51.200, 87.500–108.000, 144.000–146.000 430.000–440.000, 1240.000–1300.000 Frequency (MHz) 0.495 – 1.619 1.620 – 4.999 5.000 – 29.999 30.000 – 49.999 50.000 – 53.999 54.000 – 75.999 76.000 – 108.000 108.001 – 117.999 118.000 – 135.999 136.000 – 146.999 147.000 – 174.999 175.000 – 221.999 330.000 – 469.999 470.000 – 769.999 770.000 – 832.999 833.00 – 1304.999 1330.000 – 2304.999 2330.000 – 2999.999 FM — 0.56 0.4 0.56 0.71 5.6 18 WFM — 1.8 — 1.8 — 2.5 — AM 2.2 1.4 — 1.4 — SSB/CW 0.4 0.25 — 0.25 — 0.25 — 0.32 — Frequency (MHz) 0.495 – 1.619 1.620 – 4.999 5.000 – 29.999 30.000 – 75.999 76.000 – 108.000 108.001 – 117.999 118.000 – 135.999 136.000 – 174.999 175.000 – 221.999 330.000 – 469.999 470.000 – 769.999 770.000 – 832.999 833.000 – 1304.999 1330.000 – 2304.999 2333.000 – 2999.999 FM — 0.56 μV 0.4 μV 0.56 μV 0.71 μV 5.6 μV 18 μV WFM — 18 μV — 18 μV — 18 μV — AM 2.2 μV 1.4 μV — 1.4 μV —

1 - 2 • BC-156 • Input voltage : 8.0–16.0 V • Charging current : 0.96–1.44 A (Rapid charging) • Usable temperature : 0˚C to +35˚C (+32˚F to +95˚F) • Timer device : 192–288 minutes (Rapid charging) 12–18 minutes (Reserve charging) • Protect function : FUNCTION BP-206 CONDITION BC-156 ACTION LED CONDITION Over discharge Becomes 1.5 V Charging stop Blinking orange Over charge Becomes 4.5 V Charging stop Blinking orange Overcurrent Shorten BP-206 and GND Charging stop Blinking orange Full charge Becomes 4.2 V Charging stop Lighting green Normal charging Becomes 3.5 V Charging Lighting orange

2 - 1 SECTION 2 INSIDE VIEWS 2-1 RF UNIT • Top view • Bottom view Highpass filter circuit (C854, C856, C858) 470—833 MHz RF amplifier (Q24: 2SC5008) 1G RF amplifier (Q26: 2SC5624) B-BAND RF amplifier (IC18: PC2746TB) B-BAND 1st mixer (IC15: PC2757TB) B-BAND 1st IF filter (266.7 MHz) (FI1: EFCH266MKQP1) B-BAND 2nd mixer (IC16: PC2757TB) SSB AF amplifier (Q532: 2SK1069) SSB IF amplifier 450 kHz (Q531: 2SC4617) BFO mixer (D115, D116: RB876W) B-BAND 3rd Lo amplifier (Q555: 2SC5006) B-BAND 2nd IF amplifier (Q542: 2SC5006) A-BAND IF IC (IC2: TA31136FN) A-BAND 2nd IF amplifier (Q5: 2SC5006) A-BAND 3rd Lo amplifier (Q540: 2SC5006) A-BAND 2nd IF filter (19.65 MHz) (FI3: FL-293) A-BAND 2nd mixer (IC10: PC2757TB) A-BAND 1st IF filter (429.1 MHz) (FI4: EFCH429MKQP4) A-BAND 1st mixer (IC1: PC2757 TB) A-BAND RF amplifier (IC19: PC2757 TB) 30—300 MHz RF amplifier (Q36: 2SC5006) A-UHF RF amplifier (Q35: 2SC5006) B-UHF RF amplifier (Q548: 2SC5006) Lowpass filter circuit (L123—L125) A/B-UHF (pre-amplifier (Q551: PA805T) PLL reference oscillator circuit Oscilktes 19.200 MHz B-BAND FM IF IC (IC17: TA31136FN) X1: CR-593, D171: HVC350B Q556: 2SC4617 B-BAND AM detector and AGC amplifier (Q545: XP6501) A-BAND AM detector and AGC amplifier (Q4: XP6501) A/B-VHF pre-amplifier (Q550: FH102) A-VHF A-band RF amplifier (Q14: 2SC5006) MF/HF-L/HF-H RF amplifier circuit Q505: 2SC4226, D163, D164: MA2S728 B-BAND IF amplifier (Q544: XP6501) A-BAND IF amplifier (Q1: XP6501) DOWNCONV BOARD 1STBVCO BOARD 1STAVCO BOARD Bar antenna 2NDDVCO BOARD 2NDCVCO BOARD

2 - 2 2-2 LOGIC UNIT • Top view • Bottom view BFO circuit IC6: SN74AHC1GU04DBVR X2: CSBFB543K AF amplifier regulator (Q7: XP1501 Q9: 2SB1132) AF amplifier (IC15: TA31056F Q8: 2SA1588) AF pre-amplifiers (Q12, Q16: 2SC4617) +3 regulators (Q10, Q15: 2SA1362) Reset IC (IC2: BD5228G) Main CPU (IC3: M30620MCP-129GP [OTHER], M30620MCP-130GP [USA]) B-BAND AF circuit Q24: XP6501, Q27: 2SJ144, Q22: 2SC4617, IC7: SM6451B A-BAND AF circuit Q25: XP6501, Q26: 2SJ144, Q23: 2SC4617, IC7: SM6451B +3V reg. (Q17: 2SA1588) Battery daging regulators (Q30: 2SB1201, Q32: 2SC4617, Q33: 2SB1132) LCD (DS12: M3-0243TIY) +3SC reg. (Q13: XP6501) +3S reg. (Q14: 2SA1588) 3V reg. IC (IC8, IC9: R1111N321B) Recording/playback IC (IC7: ML2302TB) +3V regulator (IC1: BD5228G, IC10: R1111N321B) Mute (when SQL off) (IC8, IC9: SN74AHC1G66HDBVR) USB interface IC (IC3: FT245BM) Sub CPU (IC2: M30620FCPGP) Flash memory for recording/playback (IC6: K9F5608UOC-YCBO) 2-3 REC UNIT • Top view • Bottom view

SECTION 3 DISASSEMBLY INSTRUCTIONS (1) REMOVING THE REAR PANEL q Unscrew 4 screws, A (2 × 115 mm, black). w Unscrew 2 screws, B (2 × 8 mm, black). e Unplug W1 and J8 (LOGIC unit) to separate the front and the rear panels. (3) REMOVING THE REC UNIT q Unscrew 4 flat-head screws, H (2 × 4 mm, silver). w Unsolder 1 point, I. e Remove the REC unit in the direction of the arrow. (4) REMOVING THE RF UNIT q Unscrew 3 flat-head screws, J (2 × 4 mm, silver). w Unsolder 2 points, K. e Remove the RF unit in the direction of the arrow. Front panel Rear panel LOGIC unit Speaker W1 J8 A B H I REC unit RF unit J K K J1 LOGIC unit J5 C D E F G (2) REMOVING THE LOGIC UNIT q Remove 2 knobs, C, and unscrew 2 nuts, D. w Unscrew 2 flat-head screws, E (2 × 4 mm, silver), and 1 pan-head screw, F (2 × 4 mm, black). e Unsolder 10 points, G. r Unplug J5 (bottom side of LOGIC unit) and J1 (RF unit) to separate the LOGIC unit. t Remove the LOGIC unit in the direction of the arrow. 3 - 1

4 - 1 4-1 RECEIVER CIRCUITS 4-1-1 BAND SWITCHING CIRCUIT (RF UNIT) The RF signals from the antenna connector pass through the limiter (D68) and an attenuator* (D69). The signals are then applied to the antenna switching circuit (D3, D11, D13, D65, D66 and D73–D75 ). *Above 2 GHz RF signals do not pass through the attenuator. 4-1-2 RF CIRCUIT (RF UNIT) The RF circuit amplifies the received signals within the range of frequency coverage and filters out-of-band signals. • A-BAND CIRCUIT (1) MF (above 0.15 MHz, below 1.9 MHz) signals RF signals (0.15–1.9 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), band switch (D66) and another low-pass filter (L88, L89, C533–C535, C657, C658). The filtered signals pass through another band switch (D67), and are then amplified at an RF amplifier (Q505). The amplified signals are applied to the next band switch (D72). (2) HF-L (above 1.9 MHz, below 15 MHz) signals RF signals (1.9–15 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), band switch (D65) and bandpass filter (L85–L87, L91, C522–C531 and C891). The filtered signals pass through another band switch (D70), and are then amplified at an RF amplifier (Q505). The amplified signals are applied to the next band switch (D72). SECTION 4 CIRCUIT DESCRIPTION RF RF BPF BPF BPF RF BPF BPF Pre Amp Pre Amp HF-L (1.9 15 MHz) MF (15 30 MHz) A-VHF (118 175 MHz) B-VHF (118 175 MHz) 30 300M (30 300 MHz except A-VHF range) A-UHF (300 470 MHz) 800M (470 833 MHz) 1G (833 1305 MHz) B-UHF (300 470 MHz) MF (0.15 1.9 MHz) from the bar antenna HPF HPF LPF LPF LPF LIMITER BAND SW BAND SW BAND SW BAND SW BAND SW BAND SW BAND SW ANTENNA ATT ANT SW to 2nd mixer circuit RF-A circuit RF-B circuit 1st mixer 1st mixer to 2nd mixer circuit LO (1001 or 2002MHz) RF IC2 IC3 mixer 1305 3305 MHz RF RF BPF RF BPF RF BPF RF RF RF BPF BPF HPF Q505 Q36 Q550 Q14 Q549 Q551 Q35 Q548 Q24 Q25 IC18 IC15 IC1 IC19 • RF CIRCUITS

4 - 2 (3) HF-H (above 15 MHz, below 30 MHz) signals RF signals (15–30 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), band switch (D73) and bandpass filter (L81–L84 and C511–C520). The filtered signals pass through another band switch (D64), and are then amplified at an RF amplifier (Q505). The amplified signals are applied to the next band switch (D72). (4) A-VHF (above 118 MHz, below 175 MHz) signals RF signals (118–175 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), band switch (D74), and are then applied to the pre-amplifier (Q550) which is controlled by “A_VHF3V” signal via the D148. The signals are amplified at the RF amplifier (Q14), and pass through the bandpass filter (D1, D2, L1 and C14–C16). The filtered signals are applied to the next band switch (D25). (5) 30–300M (above 30 MHz, below 300 MHz and except A-VHF signals) signals RF signals (118–175 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853) and band switch (D75). The filtered signals pass through the bandpass filter (L9, L10, L92, L133, C40–C43, C665 and C666), and are then amplified at an RF amplifier (Q36). The amplified signals are applied to the next band switch (D34). (6) A-UHF (above 300 MHz, below 470 MHz) signals RF signals (300–470 MHz) from an attenuator (D69) pass through the high-pass filter (L126, L127 and C854–C858) and band switch (D3). The filtered signals pass through the low-pass filter (L3, L4, C22, C23 and C218), and are then amplified at the pre-amplifier (Q551) which is controlled by “A_UHF3V” signal via the D150. The amplified signals are applied to the RF amplifier (Q35), and then pass through the bandpass filter (D4, D5, L60, C58 and C59). The signals are applied to the next band switch (D29). • B-BAND CIRCUIT (1) B-VHF (above 118 MHz, below 175 MHz) signals RF signals (118–175 MHz) from an attenuator (D69) pass through the low-pass filter (L123–L125 and C851–C853), band switch (D74), and are then applied to the pre-amplifier (Q550) which is controlled by “B_VHF3V” signal via the D149. The signals are amplified at the RF amplifier (Q549), and pass through the bandpass filter (D145, D146, L120, C833 and C834). The filtered signals are applied to the next band switch (D147). (2) B-UHF (above 330 MHz, below 470 MHz) signals RF signals (330–470 MHz) from an attenuator (D69) pass through the high-pass filter (L126, L127 and C854–C858) and band switch (D3). The filtered signals pass through the low-pass filter (L3, L4, C22 and C23), and are then amplified at the pre-amplifier (Q551) which is controlled by “A_VHF3V” signal via the D151. The amplified signals are applied to the RF amplifier (Q548), and then pass through the bandpass filter (D141, D142, L113, C814 and C816). The signals are applied to the next band switch (D143). (3) 800M (above 470 MHz, below 833 MHz) signals RF signals (470–833 MHz) from an attenuator (D69) pass through the high-pass filter (L126, L127 and C854–C858) and band switch (D11). The filtered signals pass through the bandpass filter (D173, D174, L129 and L130), and are then amplified at the RF amplifier (Q24). The amplified signals pass through the bandpass filter (D175, D176 and L132). The signals are applied to the next band switch (D32). (4) 1G (above 833 MHz, below 1305 MHz) signals RF signals (833–1305 MHz) from an attenuator (D69) pass through the high-pass filter (L126, L127 and C854–C858) and band switch (D13). The filtered signals pass through the bandpass filter (L11–L13, L43, C5, C45–C51), and are then amplified at the RF amplifier (Q26). The signals are applied to the next band switch (D36). 4-1-3 DOWN CONVERTER CIRCUIT (RF UNIT AND DOWNCONV BOARD) The down converter circuit converts the signals within 1305–3305 MHz into 0.15 MHz to 1305 MHz signals. The converted frequencies can calculate as follow. F(x)=X–1001 (X is above 1305 MHz, below 2306 MHz) F(x)=X–2002 (X is above 2306 MHz, below 3305 MHz) NOTE: F(x) is converted frequency X is receiving frequency (Calculate example) • Convert into 599 MHz when receiving 1600 MHz. • Convert into 798 MHz when receiving 2800 MHz. The RF signals from the limiter (D68) are applied to the DOWNCONV board via the J1, pin 8 on the DOWNCONV board. The signals pass through the band switch (DOWN- CONV board; D1) and high-pass filter (DOWNCONV board; L1, L2, C2–C4, C41 and C42), and are then amplified at the RF amplifier (DOWNCONV board; IC2, pin 1). The signals are mixed with 1001 MHz or 2002 MHz LO signal at the mixer (DOWNCONV board; IC3, pin 1). The converted signals output from pin 6, and pass through the band switch (DOWNCONV board; D2). The converted signals are applied to the RF unit via J1, pin 1 on the board. According to converted frequency, the signals are applied to the each matched RF circuit. 4-1-4 1ST MIXER AND 1ST IF CIRCUITS (RF UNIT) The 1st mixer circuit converts the received RF signals to a fixed frequency of the 1st IF signal with a PLL output frequency. By changing the PLL frequency, only the desired frequency will pass through the bandpass filters at the next stage of the 1st mixer. • A-BAND CIRCUIT The RF signals from the band switch (D25, D29, D34 and D72) are amplified at the RF amplifier (IC19, pins 1, 4), and are mixed with 1st LO signals at the 1st mixer circuit (IC1, pin 1) to produce a 429.1 MHz 1st IF signal. The 1st IF signal is output from pin 6, and passed through the bandpass filter (FI4) to suppress unwanted harmonic components. The filtered 1st IF signal is applied to the 2nd mixer circuit. The 1st LO signals are generated at the 1st A_VCO circuit and are applied to the 1st mixer (IC1, pin 3) directly.

ICOM IC-R20 Service Repair Manual

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